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Litchi, a tropical and subtropical fruit with substantial commercial value, is prone to browning after harvest. Phytosulfokine (PSK), a plant peptide hormone, plays a significant role in postharvest fruit preservation by affecting various biological processes. However, its specific effects on litchi browning have not been fully elucidated. This study demonstrates that PSK application effectively delays litchi pericarp browning, maintains a higher TSS/TA ratio, and reduces electrical conductivity. PSK treatment inhibits the degradation of anthocyanins, flavonoids, and phenolics, while also decreasing the accumulation of hydrogen peroxide (H₂O₂), malondialdehyde (MDA), and superoxide anions (O₂⁻). Additionally, PSK enhances the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR), while reducing the activities of ascorbate peroxidase (APX), polyphenol oxidase (PPO), and peroxidase (POD) compared to the control. Transcriptome analysis reveals that PSK upregulates genes involved in plant hormone signaling and biosynthesis of anthocyanins and flavonoids, while downregulating genes associated with glutathione metabolism and autophagy. RT-qPCR confirms that PSK treatment decreases the expression levels of APX , LAC7 , PPO , POD1 , POD5 , POD51 , and PODX , while increasing the expression of GPX4 , contributing to the delayed browning. These findings suggest that PSK mitigates litchi browning by modulating oxidative enzymatic reactions and suppressing the expression of browning-related genes. • PSK application delays senescence and reduces pericarp browning in litchi fruits. • PSK boosts SOD, CAT, and GR activities, but reduces APX, PPO, and POD activities. • PSK enhances hormone signaling and anthocyanin biosynthesis genes expression. • PSK downregulates genes linked to glutathione metabolism and autophagy. • PSK delays litchi browning by regulating antioxidant enzymes and browning genes. [ABSTRACT FROM AUTHOR]

Litchi fruit is extremely vulnerable to postharvest browning due to its perishable physiological characteristics, which seriously restricts the shelf-life and industrial development of products. Trehalose is a natural product with excellent biological activity and safety. In this work, the ability of trehalose to mitigate the browning of 'Feizixiao' litchi fruit stored at 25 °C and its physio-biochemical mechanisms were evaluated. The application of trehalose at 2.5 g L−1 to litchi fruit delayed browning and redness loss. Trehalose treatment alleviated oxidative stress-induced impairment of membrane system, as indicated by reduced generation of O 2 -., H 2 O 2 and malondialdehyde (MDA) and lowered relative electrolyte leakage (REL), which was a result of increased activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR). Compared to control fruit, repressed activities of polyphenol oxidase (PPO) and peroxidase (POD) coincident with higher contents of total phenolics, flavonoids, anthocyanins, procyanidin B2 and cyanidin-3-O-glucoside were observed in fruit receiving trehalose, indicating an amelioration of enzymatic browning by trehalose treatment. Furthermore, trehalose treatment stimulated the expression of anthocyanin biosynthetic genes (LcPAL , Lc4CL , LcCHS , LcCHI , LcANS , LcDFR and LcUFGT) and their transcriptional activator genes (LcMYB43435 , LcMYB18362 , LcMYB30086 and LcMYB2539), while suppressing the transcription of microRNAs (miR159 , miR319 , miR828 and miR858) that mediate MYB degradation. Additionally, trehalose treatment increased content of adenosine triphosphate (ATP) and expression of LcPGK and LcCa 2+ -ATPase , while repressing the transcription of miR2118 that can target and negatively regulate LcPGK and LcCa 2+ -ATPase , which facilitated the synthesis and utilization of energy. These findings suggest that trehalose could retard postharvest browning in litchi fruit by enhancing antioxidant capacity, promoting anthocyanin synthesis and maintaining energy homeostasis. • Trehalose (2.5 g L−1) delays browning in litchi fruit during ambient storage. • Trehalose reinforces antioxidant capacity in litchi fruit during storage. • Trehalose inhibits enzymatic browning in litchi fruit during storage. • Trehalose positively regulates anthocyanin synthetic pathway in stored litchi fruit. • Trehalose promotes energy production and utilization in litchi fruit during storage. [ABSTRACT FROM AUTHOR]

Enzymatic browning is a major problem that seriously impacts the quality of fresh-cut potatoes. Our previous study found that glutamic acid (Glu) treatment could repress the discoloration of fresh-cut potatoes, but the molecular mechanism was still unknown. Herein, it was found that the content of total phenolic, H 2 O 2 , O 2 .- and the activities of PPO, POD and PAL were repressed, but the activities of CAT, APX, SOD and GPX were improved by Glu treatment. Moreover, transcriptomic analysis showed that an abundant number of differentially expressed genes (DEGs) were selected from fresh-cut potatoes browning between Glu and control groups. A comprehensive functional enrichment analysis showed that the metabolic pathways of glutathione metabolism, flavonoid biosynthesis, phenylalanine metabolism, phenylpropanoid biosynthesis, starch and sucrose metabolism, and plant hormone signal transduction were markedly enriched, which transcriptional levels were markedly altered by Glu treatment. RT-qPCR confirmed the results of RNA-Seq that Glu repressed the transcription of StPPO2 , StPPO3 , StPPO7 , and StERF-BR1-like. More importantly, as a nuclear protein, StERF-BR1-like activated the transcription of StPPO2 by directly binding with its promoter. Overall, these data indicate that Glu could repress the browning of fresh-cut potatoes by regulating the pathways mentioned above, and StERF-BR1-like may involve this process by stimulating the expression of StPPO2. • Glutamic acid (Glu) treatment inhibits the activities of PPO, POD and PAL. • Plant hormone and antioxidant enzyme play an important role in fresh-cut potatoes. • Glu treatment severely affects the transcription level during browning in potatoes. • StERF-BR1-like4 mediates the browning of fresh-cut potatoes by regulating StPPO2. [ABSTRACT FROM AUTHOR]

Enzymatic browning occurs rapidly in fresh-cut apples and can lead to economic losses. Although various methods have been developed to prevent this browning, physical methods are costly, and chemical methods are controversial, suggesting the potential usefulness of an endogenous natural browning inhibitor. In this study, the effects of ursolic acid (UA), a natural endogenous compound, on apple browning were investigated. It was found that UA inhibited the activity of polyphenol oxidase through Cu2+ chelation. Molecular docking indicated that the inhibition was reversible and mixed-type. Moreover, UA treatment promoted the scavenging of reactive oxygen species in fresh-cut apple and reduced the proliferation of microorganisms on the apple surface. Similar effects were observed on the browning of chestnut, eggplant, potatoes, and pears. In conclusion, the findings demonstrate the efficacy of UA on inhibiting browning in fresh-cut apple, together with an analysis of the mechanism involved. • A new function of UA, delaying browning of fresh-cut apple, was discovered. • UA treatment inhibits PPO activity and enhances ROS scavenging. • UA reduces breeding of microorganisms in fresh-cut apple surface. • UA has broad-spectrum anti-browning property in fresh-cut vegetables and fruits. [ABSTRACT FROM AUTHOR]

Postharvest internal browning (PIB) in pineapple fruit is induced by low-temperature storage. The characteristic brown color associated with PIB is likely due to enzymes catalyzing substrates released from the cold-induced damage of organellar membranes. However, the regulation of these processes is unclear. To understand the mechanisms behind PIB in pineapple fruit, we compared browning-related genes, enzyme activities, calcium transporter genes, and cell structure in three cultivars: the susceptible 'Trat Sri Thong' (TST), the tolerant 'Pattavia' (PTV), and the resistant 'MD2'. In response to the initial chilling stress, PM-ATPase3 expression, which is responsible for pumping Ca²⁺ to the apoplast, increased in the tolerant PTV and resistant MD2 cultivars, but not in the susceptible TST cultivar. Additionally, V-type-(H⁺)-ATPase and CAX3-like , which transport Ca²⁺ to the vacuole, were upregulated in all three cultivars. As chilling stress progressed, an upregulation of polyphenol oxidase 1 (PPO1) expression and an increase of PPO activity were observed in all three cultivars. However, the lowest PPO1 expression and activity were observed in the tolerant PTV cultivar. The ascorbic acid/H₂O₂ ratio was highest in the MD2 cultivar across storage durations, coinciding with intact cell and tonoplast membranes in MD2 during chilling stress, as observed with transmission electron microscopy and electrolyte leakage analysis. Consequently, no PIB symptoms were observed in MD2 despite high PPO activity. These findings suggest that different cultivars undergo distinct regulatory mechanisms at the subcellular level in response to cold stress. The details of potential mechanisms are discussed. • Chilling caused membrane damage in 'Trat Sri Thong' and 'Pattavia', but not in 'MD2'. • Ascorbic acid was higher in 'MD2' but lower in 'Pattavia' and 'Trat Sri Thong'. • PPO1 expression and PPO activity increased in 'Trat Sri Thong' and 'MD2' during chilling stress. • Chilling induced PM-ATPase3 , CAX3-like and V-H + -ATPase only in 'Pattavia'. • Chilling induced V-H + -ATPase only in 'Trat Sri Thong'. [ABSTRACT FROM AUTHOR]

Diode laser irradiation is a novel approach applied to preserve the quality of fresh commodities and minimise oxidative processes, including browning in fresh-cut products. The objective of this study was to investigate the efficacy of diode laser treatment in enhancing the quality of celtuce slices during refrigerated storage at 4 °C. The celtuce slices were subjected to a 660 or 450 nm diode laser for 5 min and then stored for 10 d. Both laser treatments hindered the progression of weight loss and firmness increase in the celtuce slices. The use of a 450 nm diode laser effectively prevented the development of browning and preserved the surface colour by inhibiting the increase in a * and overall colour difference values, as compared to other treatments, during storage for 10 d. The diode laser treatment suppressed the increase in oxidative stress by lowering the levels of MDA, H 2 O 2 , and O- 2 while retaining a high level of DPPH scavenging activity, AsA, and antioxdant enzyme activities, including SOD, CAT, APX, and GR, in comparison to the untreated slices. The treatment enhanced chlorophylls content due to the up-regulation of LsHEMA1 gene and down-regulation of LsNYC1 gene. The treatment also inhibited factors involving enzymatic browning reaction by suppressing PAL activity, total phenols content, PPO activity and LsPPO gene expression. These suggest that the blue diode laser exposure at 450 nm for 5 min is an effective approach hindering oxidative stress and discoloration of celtuce slices during storage. [Display omitted] • Diode laser exposured at 450 nm for 5 min could maintain the quality of celtuce slices. • The treatment preserved the green colour and inhibited the browning of the slices. • The treatment improved antioxidants and inhibited oxidative responses of the slices. [ABSTRACT FROM AUTHOR]

Freshly cut potatoes tend to brown during processing and preservation, which is an important issue worldwide. Ultrasound (US) combined with L-cysteine (L-Cys) treatment (US-L-Cys) has been reported to inhibit the browning of fresh-cut potatoes in our laboratory. However, the underlying mechanism remains to be elucidated. Untargeted metabolomics, a popular high-throughput technique, has been used to investigate the biochemical changes that are closely associated with the browning of fresh-cut fruits and vegetables. The present study investigated the effect of US-L-Cys treatment on the browning index (BI), related enzyme activities, total phenolic content, antioxidant capacity, malondialdehyde (MDA) content, and relative electrical conductivity of fresh-cut potatoes during 6-d storage. Metabolomics was used to compare the metabolites of US-L-Cys-treated and control samples on days 0 and 6. The results showed that US-L-Cys treatment reduced BI; decreased polyphenol oxidase, peroxidase, and phenylalanine ammonia-lyase activities; maintained high total phenolic content; increased antioxidant capacity; and decreased MDA content and relative electrical conductivity in fresh-cut potatoes during storage. Metabolomic analysis revealed that tyrosine and amino acid metabolisms were enriched. Higher levels of alanine and lower levels of dopamine were observed in US-L-Cys-treated samples compared with control samples. Therefore, depressed tyrosine and activated alanine metabolisms may be involved in the mechanism through which US-L-Cys inhibits the enzymatic browning of fresh-cut potatoes during storage. • US-L-cys decreased PPO, POD, and PAL activities. • US-L-cys improved antioxidant capability and reduced the damage of cell membranes. • US-L-cys suppressed tyrosine metabolism and activated alanine metabolism. [ABSTRACT FROM AUTHOR]

Enzymatic browning is an important issue impacting the shelf life of fresh-cut potatoes. Using browning inhibitors is an effective method to solve the issue. This research aimed to identify novel and safe inhibitors of enzymatic browning. The research first investigated the inhibitory role of furan compounds in enzymatic browning, then explored the anti-browning effect of furaneol and the involved mechanism. Among the eight tested furan compounds classified as flavorings in food additives, seven showed anti-browning effects, of which three demonstrated superior efficacy in delaying browning compared to the others. Based on the efficacy and odor, furaneol as one natural flavor composition of fresh fruit was selected to be further investigated. At 4 °C, control potatoes browned on day 1. However, furaneol at concentrations of 4 and 8 mM prevented the fresh-cut potatoes from browning for up to 10 d, and their anti-browning efficacies reached that of sodium bisulfite. Sensory evaluation showed the treated fresh-cut potatoes exhibited a slight and acceptable sweet aroma, which quickly disappeared after heat cooking. Further research revealed furaneol reduced the activity of polyphenol oxidase (PPO), chelated Cu2+, and acted as a mixed-type inhibitor of PPO with competitive inhibition being the dominant. Circular dichroism analysis indicated furaneol decreased α-helix content, increased the β-fold content, and altered the secondary structure of PPO. Fluorescence quenching data showed furaneol can form complexes with PPO, quench the fluorescence produced by PPO and change its tertiary structure. Molecular docking suggested that furaneol could enter the active center region near copper ions and interact with surrounding amino residues through van der Waals force, pi-alkyl interactions and carbon-hydrogen bonds. Furaneol can also cause the brown pigment colorless to a certain extent. Moreover, furaneol addition also improved the antioxidant capacity of enzymatic browning reaction system. Our study first reported the inhibitory effect of furan compounds on enzymatic browning and furaneol has great potential as an anti-browning inhibitor for fresh-cut produce in future. • Our study first reported the inhibitory effect of furaneol on browning. • Furaneol reduced PPO activity by chelating Cu2+ and interacting with residues. • Furaneol acted as a mixed-type inhibitor of PPO. • Furaneol formed a complex with PPO, influencing the structure of PPO. • Furaneol improved the antioxidant capacity of enzymatic browning reaction system. [ABSTRACT FROM AUTHOR]

Manna is the sap extracted in summer from the phloem of the stem and the old branches of Fraxinus sp. trees. Its composition is characterized by a high content of D-mannitol, gallic acid, tyrosol and a great antioxidant activity. The aim of the present work was to compare the effect of a solution enriched with manna or calcium ascorbate, the latter widely used by researchers as an antioxidant agent on the control of browning of apple slices. After harvest, apple fruit were cut, treated with manna (MN), calcium ascorbate (CA) or with distilled water as a control (CTR), and packed in polylactic acid (PLA) packaging. Physical, chemical and sensory analyses were performed after 3, 5, 7 and 10 days of storage at 5±0.5 °C. After one week of storage, manna and calcium ascorbate-based treatment significantly inhibited apple fruit slices browning of cut surface, to the same extent, while no significant differences occurred in terms of weight loss, DPPH, total carotenoids and flavor score. On the whole, manna may inhibit apple slices water loss without affecting fruit flavour and providing the maintenance of their shelf-life. It seems that manna and calcium ascorbate mechanism and effect on browning inhibition are very similar and account for maintaining stored apple slices shelf-life up to 7 days. Therefore, our work lays the foundations for the use of manna as a natural antioxidant compound capable of reducing fresh-cut enzymatic browning • Manna composition is characterized by gallic acid, tyrosol and antioxidant activity. • Manna treatment reduced softening and weight loss. • Manna and calcium ascorbate effect on browning inhibition are very similar. • Manna treatment application didn't affect apple slices flavor. • The increases of phenols can promote browning on the cut surface of apple. [ABSTRACT FROM AUTHOR]

White mulberry (Morus alba L.) fruit is a rich source of bioactive compounds, but it is highly perishable and vulnerable to browning. In the current study, melatonin at concentrations of 0, 125, 250, 500, and 1000 µM was sprayed on mulberry fruit and stored at 1 °C for 12 d. Melatonin treatment yielded the lowest browning index during storage time. This reduction was accompanied by a significant decrease in malondialdehyde, H 2 O 2 and polyphenol oxidase enzyme activity. The results showed that melatonin reduced weight loss and maintained pH, as well as total soluble solids. Furthermore, the total phenol, total flavonoids and ascorbic acid contents in treated fruit were significantly higher than in an untreated fruit, which was accompanied by an increase in antioxidant capacity. With assuming 40 % browning would render the fruit unmarketable, melatonin treatments could extend mulberry storage life beyond 8 days. The 500 and 1000 μM melatonin treatments showed the most effective results. In conclusion, exogenous melatonin application can be considered a safe and promising procedure to maintain the quality of mulberry fruit during low-temperature storage. [Display omitted] • Melatonin (MT) reduced weight loss, browning, and retained mulberry fruit quality. • MT reduced oxidative stress in mulberry fruit by decreasing malondialdehyde and H 2 O 2. • MT suppressed polyphenol oxidase enzyme activity and reduced enzymatic browning. • 1000 μM of MT revealed the most significant effects on preserving fruit quality. [ABSTRACT FROM AUTHOR]

Enzymatic browning is a primary factor affecting the quality of fresh-cut potatoes. Our previous research demonstrated that warming the tubers after cold storage can alleviate the enzymatic browning of fresh-cut potatoes. In this research, we explored if some new endogenous compounds play roles in browning inhibitory effects. Utilizing a non-targeted metabolomics approach on tubers subjected to pre-cutting different temperature treatments, thirteen differential metabolites in potatoes were revealed, and five compounds with anti-browning effects were screened out. Among these five compounds, chenodeoxycholic acid (CDCA) exhibited the best inhibitory effect on browning and has not been reported in plants till now. The changes in CDCA content in tubers of pre-cutting different temperature treatments were further confirmed by LC-MS/MS. Subsequent experiments showed that the anti-browning effect of pre-cutting CDCA treatment was much better than post-cutting. Pre-cutting CDCA treatment only at a low concentration of 5 mg L−1 for a 10 min soaking and then standing for 6 h extended the shelf life of fresh potato slices to 5 d from less than 1 d of control. Not a big difference in polyphenol oxidase (PPO) activity and tyrosine contents were caused by pre-cutting CDCA treatment compared with control. However, pre-cutting CDCA treatment caused a notable reduction in the contents of malondialdehyde (MDA), superoxide anion (O 2 -), H 2 O 2 , and lipoxygenase (LOX) activity, and elevated the activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). Meanwhile, CDCA suppressed phenylalanine ammonia-lyase (PAL) activity and reduced the contents of both individual and total phenolic compounds. These results suggest that CDCA, an endogenous compound in potato tuber, can improve the anti-browning ability of fresh-cut potatoes mainly by inducing the enhancement of antioxidant capacity. • Five compounds with anti-browning effects were screened using non-targeted metabolomics. • Chenodeoxycholic acid (CDCA) was an endogenous anti-browning agent in potatoes. • The anti-browning effect of pre-cutting CDCA treatment was better than that of post-cutting. • Pre-cutting CDCA treatment induced the enhancement of antioxidant capacity. • Pre-cutting CDCA treatment improved the anti-browning ability of fresh-cut potatoes. [ABSTRACT FROM AUTHOR]

It is crucial for early detection of mechanical damage to improve the quality of commodity fruit. For the problem of low identification accuracy of damage detection models due to the small degree of damage and unclear damage features in the initial damage of fruit and vegetables, this research analyzed the evolution process of spectral information in the initial damage of (0–3 h) of ' Red Delicious ' apples. Three sensitive bands of 650–734 nm, 850–970 nm, and 1255–1314 nm, were extracted, and the average spectral reflectance and spectral curve shape features tanθ of the sensitive bands were analyzed. The conclusion is as follows: (1) In the 650–734 nm band, spectral reflectance decreasing and then stabilizing, reflecting enzymatic browning development. More severe damage led to lower reflectance. Over time, tanθ decreased, with more severe damage showing faster reduction, reflecting changes in chlorophyll content in the peel. (2) In the 850–970 nm band, reflectance showed a decreasing-then-increasing trend, reflecting moisture content changes in the damaged area. More severe damage resulted in lower reflectance. Over time, tanθ initially rose, then decreased and stabilized. More severe damage led to greater tanθ. (3) In the 1255–1314 nm band, reflectance initially increased, then decreased and stabilized, reflecting temperature changes in the damaged area. More severe damage led to higher reflectance. Over time, tanθ first increased, then decreased, with more severe damage showing smaller tanθ. The study on the evolutionary pattern of the spectral features after the impact of ' Red Delicious ' apples provides theoretical basis for more reliable detection of the initial minor damage of apples in the future. • Sensitive bands extracted for early detection of minor damage in apple. • Spectral analysis showed damage patterns indicating severity and progression. • Spectral changes in bands correlated with damage indicators in affected areas. [ABSTRACT FROM AUTHOR]

Enzymatic browning causes a decline in consumer's acceptance of fresh-cut products. Previous study showed reactive oxygen species (ROS) is associated with enzymatic browning, and prohibitin (PHB) is involved in ROS formation. However, whether PHB influences the enzymatic browning is still unknown. In this paper, changes of StPHB3 transcript levels after cutting were investigated, then stphb3 mutants were constructed through CRISPR/Cas9 and the browning difference between stphb3 mutants and wild type was compared, finally the mechanism of PHB influencing the browning was explored. The results showed that the transcript levels of StPHB3 were enhanced in potato (cultivar Desiree) tubers after fresh cutting. Mutation of StPHB3 caused lower browning, less production of soluble quinones, decreased malondialdehyde (MDA) content, increased 1,1-Diphenyl-2-picrylhydrazyl (DPPH) inhibition, and increased total phenol contents. Additionally, polyphenol oxidase (PPO) activity and StPOT32 gene transcript level were also reduced after disturbing StPHB3 gene expression. StPHB3 was found to be located within the chloroplast same as the predominant location and activation site of PPO protein. Yeast two-hybrid (Y2H) and Co-Immunoprecipitation (Co-IP) assays showed StPHB3 interacted with PPO. And mature PPO contents were decreased in stphb3. These results suggest that suppression of StPHB3 can alleviate the browning of fresh-cut potatoes by enhancing the antioxidant activity and inhibiting PPO activation. [ABSTRACT FROM AUTHOR]

Oxalic acid (OA) is a unique organic acid that commonly occurs in plants with distinct functions in modulating metabolic processes. To date, the role of OA has primarily been studied in the deactivation of copper-containing preservatives, detoxification of aluminium toxicity and remediation of organic pollutants. During the last two decades, OA has been considered as an antioxidant compound with focus on its potential to enhance crop yield, improve fruit quality, boost nutritional profile, and delay postharvest senescence in fruit and vegetables. It has been established that pre- and postharvest OA application delays ripening and senescence by down-regulating physiological processes such as water loss, ethylene production and respiration. OA treatment controlled adverse storage effects including chilling injury, enzymatic browning, as well as flesh softening by lowering oxidative stress. OA application has also been found to reduce decay in fresh fruit and vegetables by inducing systemic resistance against pathogens, decontamination from surficial microbial load and pesticide residues. Additionally, OA treatments have shown to effectively improve enzymatic and non-enzymatic antioxidants and maintain attributes for eating quality. Effectively, OA application has been deemed to be a potentially food-safe natural and suitable alternative to synthetic chemicals for up-regulating bioactive compounds in harvested fruit and vegetables and extending storability within the postharvest supply chain. This extensive review covers aspects of OA including its: history, chemistry, biosynthesis in plants, quantification in fruit and vegetables, crosstalk with ripening physiology, past attempts and recent advancements in storage life extension, safety as well as quality management of fruit and vegetables. [Display omitted] • Oxalic acid (OA) is an organic acid containing potential antioxidant capacity. • Pre-harvest OA spray improves yield and bioactive compounds in horticultural produce. • Pre- and postharvest OA treatment reduces microbial spoilage during storage. • Pre- and postharvest OA treatment delays ripening and senescence during storage. • OA application alleviates storage disorders including chilling injury and browning. [ABSTRACT FROM AUTHOR]

Postharvest quality deterioration is the major reason for food loss and waste, which hinder global food security, environmental sustainability and human health. Spray-induced gene silencing (SIGS) is a technique involving spraying double-stranded RNA (dsRNA) onto the plant surface for targeted RNA interference, providing a new solution for pests and disease control in agriculture products. Here, fresh-cut browning, which is a common and visible quality deterioration in potatoes, was taken as the indicator for the exploratory SIGS technology in postharvest quality deterioration control. The polyphenol oxidase (PPO) encoding genes StPPO and StPPOD , and the phenylalanine ammonia-lyase (PAL) encoding gene StPAL2 , were identified as important transcripts associated with the browning process in freshly-cut potatoes of the Yunshu 505 cultivar. Inhibition of StPPO and StPAL2 using dsRNA-PPO and dsRNA-PALX resulted in a decrease in the expression levels of the two genes, consequently leading to reduced activities of polyphenol oxidase and phenylalanine ammonia-lyase, as well as a decrease in the brown index. Spraying a mixture of these two dsRNAs demonstrated browning control capabilities similar to those of ascorbic acid. The distribution of dsRNA-Cy5 in cells confirmed its uptake and internalization by fresh-cut potatoes. In addition, the application of dsRNA-MYB12 resulted in a reduction of up to 78 % in tuber StMYB12 levels and decreased StPPO and StPAL1 expression. Spraying dsRNAs effectively reduced fresh-cut browning, highlighting the potential application of SIGS in reducing the browning of fresh-cut potatoes. • dsRNA- StPPO decreased polyphenol oxidase activity and the browning index. • dsRNA-Cy5 could be taken up and internalized by fresh-cut potato. • Spraying the dsRNA mixture for controlling browning is equivalent to using ASA. • StMYB12 act as transcriptional activator regulating StPPO and StPAL2 expression. [ABSTRACT FROM AUTHOR]

The short shelf life of button mushroom is a serious problem in its postharvest distribution. One approach is the application of plant extract (mainly polyphenolic compounds) to inhibit tyrosinase activity. The inhibitory activity of pistachio green hull extract (PGHE), sodium metabisulfite (MET), and ascorbic-citric acids (ASC-CIT) on mushroom tyrosinase was investigated at different concentrations (0.05–0.8% w/v) and IC 50 value was determined (0.07%). Prevention of button mushroom postharvest browning was investigated by vacuum impregnation pretreatment with PGHE, MET, and ASC-CIT. Physicochemical, organoleptic, and microbial properties of the treated mushrooms were determined over 10 d of storage (at 4 °C). The results of the browning index (BI) showed that the PGHE-treated mushrooms had lower BI than the other samples. On the 10th d, only the mushrooms treated with PGHE had highest phenolic content (10.4%). The antioxidant activity of PGHE-treated mushrooms was higher than the control (4.5%). The mushrooms treated by PGHE had 13.9% higher firmness than the control. The sensory evaluation results showed that the samples treated with PGHE had the highest sensory scores. Also, the main components of PGH extract determined by RP-HPLC-DAD were phloroglucinol, gallic acid, naringin, vanillic acid, catechin, and protocatechuic acid. The inhibitory activity of two main components, pure phloroglucinol, gallic acid and the mixture of them, on tyrosinase were 43.6, 24.4 and 42.5%, respectively. It could be concluded that these compounds have a synergistic effect. It can be concluded that pistachio green hull extract is a new natural tyrosinase inhibitor that can delay browning reactions in mushrooms. [ABSTRACT FROM AUTHOR]

Photosensitizers are organic compounds which can generate reactive oxygen species in the presence of light. Such photodynamic reactions have been paid attention due to their effectiveness to inactivate microorganisms. The purpose of this study was to analyze progresses already known about the effect of postharvest application of photosensitizers on the quality of fruit and vegetables. First of all, the generalities of this technology are reviewed and a number of photosensitizer compounds potentially useful are described. Later, the main results achieved in those studies evaluating such strategy in postharvest are discussed. Some compounds consistent with food, such as some vitamins and natural additives, are photosensitizers, while others correspond to plant-derived secondary metabolites, potentially compatible with food. Compounds mostly studied have been curcumin and chlorophyllin and, to a lesser extent, riboflavin, pheophorbide a , hypericin, carvacrol and menadione, while other compounds are still to be evaluated. Different combinations of photosensitizers and light have achieved microbial control, rot reduction and extension of postharvest life in strawberry, cherry tomato and grape; and P. digitatum and B. cinerea control in orange and apple, respectively. In some cases, the induction of defense enzymes has been reported. In minimally processed products, treatments with photosensitizers have controlled the microbial development, reduced enzymatic browning and improved texture. The great efforts carried out to date have yielded promissory results. However, our knowledge about the use of this technology in postharvest is far from fully understood. Thus, different questions and lines of investigation for further research are posed. We therefore hope to foster further studies to enlarge our knowledge concerning the use of this emerging technology to reduce losses and preserve the postharvest quality of vegetables and fruit. • Via photodynamic reactions photosensitizing compounds (PSs) + light generate ROS. • Natural and GRAS-PSs are especially interesting for F&V conservation. • PSs and light can control both phytopathogen and human pathogenic microorganisms. • Some PSs reduce F&V decay and modulate plant defense and ROS scavenging enzymes. • PS treatments control browning, softening, and antioxidant losses of some F&V. [ABSTRACT FROM AUTHOR]

Enzymatic browning of fresh-cut potatoes (Solanum tuberosum L.) is an urgent problem to be solved in the potato industry. The transcript level of snakin-2 (StSN2) increased with prolonged fresh-cut potato storage time, and StSN2 overexpression reduced the enzymatic browning of fresh-cut potato compared to wild type (WT). Further studies suggested that overexpression of StSN2 effectively enhanced polyphenol oxidase (PPO), peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) activity, decreased phenolic and soluble quinone contents. The measurement of total free amino acid results showed that the contents of proline, isoleucine, and gamma-aminobutyric acid were increased, and the contents of cystine, methionine, and tyrosine were decreased in StSN2- overexpressing transgenic lines. Quantitative phosphoproteome analysis showed that 1515 proteins were phosphorylated in transgenic fresh-cut potato. Among them, 123 kinases were found to change phosphorylation levels, and a kinase-substrate network of serine/arginine proteins and mitogen-activated protein kinases was predicted. Our results indicated that overexpression of StSN2 inhibited the enzymatic browning of fresh-cut potatoes by enhancing antioxidant enzyme activity and decreasing phenolic and soluble quinone contents while also changing vital kinase and other protein phosphorylation levels. This study demonstrated a new function of StSN2 and provided target genes for enzymatic browning resistance breeding of potatoes. • StSN2 overexpression reduced the enzymatic browning of fresh-cut potato. • Overexpression of StSN2 effectively enhanced antioxidant enzyme activity and decreased phenolic and soluble quinone contents. • The content of total free amino acid was changed in StSN2 overexpression tuber. • 1515 proteins including 123 kinases were changed phosphorylated level in StSN2 overexpression tuber. [ABSTRACT FROM AUTHOR]

Pericarp browning is known as one of the leading problems during the supply chains of litchi fruit. The effects of pre-storage kojic acid (KA) application on pericarp browning, activities of antioxidative enzymes in the pericarp tissues, and the quality attributes, soluble solid concentrations, titratable acidity and ascorbic acid concentrations of the flesh of ‘Gola’ litchis have been investigated. Fruit were treated with 2, 4 or 6 mmol L −1 KA and stored at 5 ± 1 °C with 90 ± 5% relative humidity for 20 d. Fruit treated with 4 mmol L −1 KA had reduced fruit weight loss and fruit decay; while, 6 mmol L −1 KA delayed pericarp browning by maintaining higher total anthocyanin and phenolic concentrations, and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. Reduced malondialdehyde, and hydrogen peroxide concentrations, and activities of oxidative enzymes such as peroxidase and polyphenol oxidase were also observed in 6 mmol L −1 KA-treated fruit. In contrast, activities of ascorbate peroxidase, catalase and superoxide dismutase enzymes were found to be higher in pericarp tissues of fruit subjected to 6 mmol L −1 KA application. Moreover, soluble solid concentrations, titratable acidity, ascorbic acid concentrations and sensory characteristics were also higher in 6 mmol L −1 KA-treated litchi fruit. In conclusion, pre-storage application of 6 mmol L −1 KA to litchi fruit delayed pericarp browning and maintained activities of antioxidative enzymes. [ABSTRACT FROM AUTHOR]

Enzyme inhibitors were studied as adjuvant treatments in the control of litchi pericarp browning by protection against desiccation during reefer transport. Various organic acids (acetic, malic, citric, and oxalic acid) and inorganic salts (NaCl, CaCl 2 ) were investigated for in vitro inhibitory effects on the peroxidases (POD) and phenol oxidases (including laccase) extracted from litchi pericarp. Promising inhibitors were tested on ‘Hong Huey’ litchi fruit for their capability to prevent pericarp browning during cold storage (21 d, 5 °C, 90% relative humidity) with and without foil wrapping. An enzyme assay had been optimized for measuring the in vitro activities of phenol oxidases toward (−)-epicatechin, being the natural phenolic key substrate in litchi. Phenol oxidase activities were chiefly pH-dependent and completely inactivated at pH ≤ 3.5 by the organic acids used for buffering, whereby chelating agents performed best, especially oxalic acid. POD activity was stable over wider pH and ionic strength ranges, with inhibition being maximal (84%) in 0.25 M oxalic acid buffer (pH 3.5). CaCl 2 (0.25 mol L −1 ) decreased POD activity by 68%, while rising doses increased the initial lag phase up to 2.5 min. In contrast to these in vitro enzyme-inhibiting effects, postharvest fruit treatments with these phenol oxidase and peroxidase inhibitors did not improve color retention during cold fruit storage, but proved ineffective or even favored pericarp browning compared to the control fruit. Pericarp color retention was maximal (96–97%) throughout cold storage of fruit in gas-permeable but moisture-retaining foil bags for at least two weeks, whether the fruit had been dipped into cold water (control) or into citrate (25 mmol L −1 ) solution. Consequently, pericarp color retention only required an intact pericarp at harvest and postharvest protection against desiccation. Preventing water loss through preservation of cell compartmentation thus proved to be crucial and sufficient for the control of enzymatic browning under reefer conditions. [ABSTRACT FROM AUTHOR]

Surface browning, tissue softening, and aroma alteration are the primary quality deterioration in fresh-cut peaches. The visual appearance, textural attributes, antioxidant activity, and volatile compounds of fresh-cut peaches pre-treated with 1 μL L−1 of 1-methylcyclopropene (1-MCP) as whole fruit, and soaked in 0.05% of phytic acid (PA) for 3 min after cutting, alone or combined, were evaluated during cold storage at 0 ºC for 10 d. 1-MCP treatment of whole fruit showed minor effects on the textural attributes but restrained the production of reactive oxygen species of cut peaches. In contrast, PA treatment inhibited cut surface browning of fresh-cut peaches. The combined treatment synergistically promoted the total phenolic contents and antioxidant capacity, and inhibited the polyphenol oxidase (PPO) and peroxidase (POD) activities. The ultrastructure of cell wall and plasma membrane was maintained by the combined treatment, and the malondialdehyde (MDA) accumulation was restrained. E-nose and SPME GC-MS were used to assess the production of volatiles as influenced by 1-MCP and/or PA treatments. Results showed that the volatile aroma was improved by PA alone or in combination with 1-MCP especially on aldehydes, esters, and alcohols. Overall, PA mainly retarded the surface browning and improved the aroma quality of fresh-cut peaches, while 1-MCP combined with PA promoted the visual, textural, and aromatic qualities during the cold storage, suggesting the treatment can be used as a beneficial approach for the storage of fresh-cut peaches. • 1-methylcyclopropene (1-MCP) and phytic acid (PA) minorly affects peach texture. • PA alleviates the surface browning and enhances volatile aroma. • 1-MCP + PA promoted the phenolics and inhibited PPO and POD activities. • 1-MCP + PA retards MDA accumulation and retains cell membrane ultrastructure. [ABSTRACT FROM AUTHOR]

Browning is accepted as a main factor affecting quality of fresh cut products. Physical treatments maintaining quality of fresh-cut products have been recently considered by consumer safer than chemical treatments. This study investigated whether preprocess diode laser irradiation can improve the physicochemical quality of fresh-cut potatoes. Laser irradiation at a 450-nm wavelength for 30 min prevented the browning of potato slices during short-term storage at 25 °C. Compared with no treatment, preprocess laser irradiation preserved the appearance and whiteness and inhibited browning and delayed weight loss in potato slices when refrigerated at 4 °C for 96 h. The increases in the total phenol concentration and phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) activities of fresh-cut potatoes were diminished after laser irradiation. Moreover, the laser irradiation also enhanced antioxidant activities in the samples. The expression of PAL, PPO and POD genes was suppressed by the laser treatment. Therefore, the laser irradiation at 450 nm wavelength for 30 min effectively eliminates discolouration and improves quality of sliced potatoes during cold storage. • Pre-processing of blue light laser (450 nm) for 30 min maintained potato slice quality. • The laser treatment inhibited enzymatic browning. • Antioxidant activity was enhanced by the laser treatment. • The laser treatment suppressed PAL, PPO and POD genes expressions. [ABSTRACT FROM AUTHOR]

Enzymatic browning is a major factor limiting the shelf life of minimally processed yam slices. The effect of ascorbic acid and calcium chloride (AACCl) dip and UV-C treatment on the browning index (BI), browning related enzymes (i.e. polyphenol oxidase, PPO; peroxidase, POD; phenylalanine ammonia lyase, PAL) and total phenolic content of yam slices during a 10 days storage period at 4 ± 1 °C was investigated. Results showed that untreated yam slices had significantly (p < 0.05) higher BI, PPO and POD activities throughout the storage period. In the case of PAL activity, yam slices treated with only UV-C at 13.68 KJ m −2 exhibited significantly high (p < 0.05) PAL activity throughout the storage period as compared to other treatments. In addition, untreated yam slices had the lowest total phenolic content during the storage period. Yam slices treated with the AACCl dip and a UV-C dosage of 6.84 KJ m −2 were found to be the best as they showed significantly low (p < 0.05) BI, PPO, POD and PAL activities throughout the storage period. In addition, this treatment also maintained a high but insignificant (p> 0.05) total phenolic content throughout the storage period. In summary, AACCl dip plus a UV-C dosage of 6.84 KJ m −2 could be useful in preventing browning of minimally processed yam slices under storage at 4 ± 1 °C. [ABSTRACT FROM AUTHOR]

L -phenylalanine (L -phe) is the initial substrate of phenylpropanoid metabolism. This study aimed to investigate the effect of four preharvest spray with 8 mM L -phe during fruit development and wound healing ability in harvested muskmelons (cv. Manao) and to explore the related mechanisms. The results revealed that preharvest L -phe sprays promoted phenylalanine ammonialyase, cinnamate-4-hydroxylase, 4-coumaric acid coenzyme A ligase and cinnamyl alcohol dehydrogenase activities, and elevated the level of four phenolic acids (p -coumaric, caffeic, cinnamic, ferulic acids), three lignin monomers (sinapyl, coniferyl, cinnamyl alcohols), total phenols, flavonoids and lignin at wounds of harvested fruit. L -phe treatment increased peroxidase activity, H 2 O 2 level, and accelerated the deposition of suberin polyphenolic and lignin at wounds, which led to lower weight loss and disease index of harvested muskmelons during healing. Moreover, the treatment enhanced polyphenol oxidase activity and induced enzymatic browning at wounds. Thus, preharvest L -phe sprays promoted wound healing of harvested muskmelons by eliciting phenylpropannoid metabolism and enzymatic browning at wounds. • Preharvest L -phe sprays activated phenylpropanoid pathway at wounds of muskmelons. • L -phe sprays accelerated the deposition of SPP and lignin at wounds. • L -phe sprays promoted enzymatic browning at wounds by increasing PPO activity. • L -phe sprays reduced weight loss and diseases index of muskmelons during healing. [ABSTRACT FROM AUTHOR]

Enzymatic browning is problematic for the fresh-processed potato (Solanum tuberosum L.) industry. Previously, we identified a serine protease inhibitor gene StSPI128 , which may alleviate potato browning. Therefore, the effects of StSPI128 on potato browning and browning-related factors were investigated by overexpressing the gene in this study. The results showed that overexpression of StSPI128 significantly alleviated potato browning and increased phenolic content. However, not all the decreases in protease activities or accumulations of total free amino acid and tyrosine caused by StSPI128 -overexpression were significant among three transgenic lines. Besides, overexpression of StSPI128 reduced PPO activity in potatoes. Moreover, overexpression of StSPI128 increased the total antioxidant abilities and membrane stability, elevated SOD and CAT activities, and decreased ROS and MDA accumulation. In vitro experiments demonstrated that the variation in browning-substrates and PPO activities did not induce the differences in potato browning. These results indicated that enhanced expression of StSPI128 alleviated potato browning mainly by increasing antioxidant ability, not via altering browning substrates or PPO activities. This work suggested that StSPI128 is a promising potential target for browning control in fresh-processed potatoes. • Enhanced expression of StSPI128 delayed the browning of fresh-cut potatoes. • Overexpressed (OE)- StSPI128 reduced PPO activity and elevated phenolics in potatoes. • OE- StSPI128 enhanced the total antioxidant ability and lowered MDA content. • OE- StSPI128 increased CAT and SOD activities, and reduced ROS accumulation. • OE- StSPI128 inhibited potato browning mainly via increasing total antioxidant ability. [ABSTRACT FROM AUTHOR]

Lettuce is one of the major fresh-cut products in the market. However, browning is the main cause of quality loss in fresh-cut lettuce during storage. Here, the effects of different hormones on the browning control in fresh-cut lettuce were investigated. Results showed that 6-Benzylaminopurine (6-BA) was the optimal hormone to delay the fresh-cut lettuce browning. Metabolome profiling showed that 392 metabolites were detected in fresh-cut lettuce, including 250 primary metabolites and 92 secondary metabolites. Five phenolic-related metabolites, including chrysin O-malonylhexoside, calycosin-7-O-glucoside, chrysoeriol 7-O-rutinoside, glycitin, and scopoletin, increased with browning but reduced by 6-BA treatment. Transcriptome profiling revealed that phenolic-related metabolites pathways, especially the scopoletin, were enriched by differentially expressed genes, supporting that 6-BA reduced the fresh-cut lettuce browning through transcriptional regulation of phenolic-related metabolites biosynthesis, and scopoletin could serve as a marker compound for browning prediction. These results suggest that 6-BA is a promising anti-browning agent for fresh-cut lettuce. • Effects of various hormones on the browning of fresh-cut lettuce were investigated. • 6-Benzylaminopurine (6-BA) was optimal for reducing the fresh-cut lettuce browning. • Metabolomic and transcriptomic profilings analysis of 6-BA treated fresh-cut lettuce. • Strong accumulation of scopoletin correlated with fresh-cut lettuce browning. • Differentially expressed genes in the scopoletin biosynthesis were identified. [ABSTRACT FROM AUTHOR]

To elucidate the browning inhibition mechanism of nanocomposite packaging (nano-PM) Agaricus bisporus during cold storage, we analyzed the biophysical and biochemical indices, including substrates, key enzymes, and relative gene expression associated with browning. The results showed that nano-PM could maintain a higher total phenol content and lower flavonoid content of mushrooms throughout the storage period than the commercial polyethylene packaging treatment (control). The activity of phenylalanine ammonia lyase (PAL) and its relative gene expression were inhibited by nano-PM, whereas cinnamic acid-4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL) activities were promoted. Nano-PM promoted the synthesis of γ- L -glutaminyl-4-hydroxybenzene (GHB), tyrosine, and catechol, but inhibited the synthesis of soluble quinone, γ- L -glutaminyl-3,4-dihydroxybenzene (GDHB), and 3,4-dihydroxyphenylalanine (DOPA), which were mainly attributed to polyphenol oxidase (PPO), tyrosinase (TYR), and laccase (LAC) activities as well as gene relative expression at low levels. Nano-PM increased the enzyme activities of the phenylpropanoid pathway by activating their relative gene expression, promoting the accumulation of phenolic substances to enhance the resistance of mushrooms to harsh environments. Additionally, nano-PM inhibited TYR activity to delay the conversion of GHB to GDHB and tyrosine to DOPA, which ultimately reduced melanin formation and delayed mushroom browning, leading to a longer shelf life. • Nano-PM regulated the phenylpropanoid and melanin pathways in A. bisporus. • Nano-PM maintained total phenolic content and kept GHB, tyrosine at high levels. • The gene expression and activities of PAL, PPO and TYR were inhibited. • Nano-PM maintained low levels of DOPA and GDHB. [ABSTRACT FROM AUTHOR]

This research aimed to screen out safe and effective inhibitors of enzymatic browning from food-derived sulfur-containing compounds. Among eighteen candidate compounds, three were found to reduce the browning of fresh potato mashes. One of these compounds, S-furfuryl thioacetate (S-Ft) at only 0.04 and 0.07 mM inhibited the browning of fresh potato sticks, for over 10 d at 4 °C with an efficacy close to sodium bisulfite at 2.40 mM. S-Ft also reduced the browning of eggplant and asparagus lettuce slices. S-Ft retarded the browning occurrence of potato mashes and tyrosine solutions, but it did not cause the brown pigments colorless. Both the decrease in tyrosine contents and the increase in quinone contents were slowed by S-Ft in potato mashes. Compared with control, S-Ft at 0.04 and 0.07 mM reduced polyphenol oxidase (PPO) activity by 91.22 % and 91.77 %, and addition of copper acetate recovered the PPO activities to 55.62 % and 59.45 % of control, respectively. Kinetics results showed S-Ft inhibited PPO activity in a reversible mixed-type manner. The data of circular dichroism analysis and fluorescence emission spectra indicated S-Ft treatment caused the decrease in α-helix content, the increase in β-sheet content and the change in secondary structure of PPO. Molecular docking results illustrated S-Ft could act with Cu2+ and amino acid residues of PPO. By comparison with other anti-browning inhibitors, S-Ft has the characteristics of low dosage and long shelf-life extension. These results demonstrated that S-Ft could be a novel and promising enzymatic browning inhibitor by chelating Cu2+ and changing the conformation of enzyme to reduce PPO activity. • S-Furfuryl thioacetate (S-Ft) is a promising food-derived browning inhibitor. • S-Ft reduced the conversion of tyrosine into quinones by inhibiting PPO activity. • S-Ft inhibited PPO activity in a reversible mixed-type manner. • The binding of S-Ft to PPO induced the conformational changes of PPO. • S-Ft acted with Cu2+ and amino acid residues of PPO. [ABSTRACT FROM AUTHOR]

Highlights: [•] A SPI–Cys edible coating helped control enzymatic browning of fresh-cut eggplants. [•] An increase of Cys content from 0.5 to 1% extends the shelf life to 8–9 storage days. [•] Conventional MA packaging conditions induced browning of fresh-cut eggplants. [•] High O2 MA packaging and atmospheric conditions helped maintain the visual quality. [Copyright &y& Elsevier]

Highlights: [•] The relationship between PPO activity and browning in pears depends on the phenolic substrate. [•] PPO activity against a water-soluble pear extract did not correlate with tissue color changes. [•] PPO activity is not a good indicator of tissue browning in fresh-cut pear. [•] Direct assessment of color changes is a rapid and accurate method to estimate relevant response to antibrowning treatments. [•] pH of the antibrowning solution significantly affects color changes. [ABSTRACT FROM AUTHOR]

Highlights: [•] TRS was able to nondestructively detect internal browning in intact Braeburn apples. [•] The μ a780 increased with the presence and severity of browning. [•] The μ s′780 showed the highest values in healthy apples. [•] Best classification model was based on μ a780 and μ s′780 and 8 measurement points. [•] Misclassifications were found when browning occurred in the core or in flesh spots. [ABSTRACT FROM AUTHOR]

Highlights: [•] Gaseous chlorine dioxide fumigation can reduce pericarp browning of longan fruit. [•] 10mg/L chlorine dioxide is the most effective dose in reducing pericarp browning. [•] Gaseous chlorine dioxide fumigation can maintain longan fruit quality. [ABSTRACT FROM AUTHOR]

Highlights: [•] Antioxidants were tested in persimmon extracts and precipitates (in vitro studies). [•] Effective antioxidants in the in vitro study were tested on cut tissue (in vivo studies). [•] PA, Cys, CD, and HMP were not effective in in vitro studies. [•] CaCl2 slightly decreased browning of cut persimmon and Hexyl damaged the tissue. [•] AA and CA extended the limit of marketability of persimmon slices to 5–7 days. [Copyright &y& Elsevier]

Highlights: [•] Controlled atmosphere extends storage life of sugarcane stalks. [•] Low oxygen atmospheres reduced respiratory rate, POD activity, and reducing sugar content. [•] These results can be used to guide the choice of plastic films for storing sugarcane stalks in a controlled atmosphere. [Copyright &y& Elsevier]

Highlights: [•] Nitric oxide and nitrous oxide could inhibit the activity of browning enzymes in the pericarp of longkong fruit. [•] Sodium nitroprusside (SNP, NO donor) was effective in preventing browning in longkong fruit. [•] The gaseous form (nitrous oxide) was more effective than a solution (nitric oxide). [Copyright &y& Elsevier]

Abstract: This study evaluated the effects of sodium chlorite (SC) alone and its sequential treatment with edible coatings on browning inhibition and quality maintenance of fresh-cut d’Anjou pears. Edible coatings were prepared from chitosan (CH) and its water-soluble derivative carboxymethyl chitosan (CMCH), separately. Pear wedges were immersed in SC solution, followed by coating with CH or CMCH solutions. The samples were packed in unsealed bags and stored at 4°C for subsequent color, firmness, and weight loss measurement. The effects of the SC and coating treatments on polyphenol oxidase (PPO) inhibition and microbial inactivation were also evaluated. Results indicated that SC exhibited significant (P <0.05) inhibition of browning and PPO activity. The SC treatment was also strongly effective in inactivating Escherichia coli O157:H7 on pear slices. Coating SC-treated pear slices with CH adversely affected the quality of pear slices by accelerating the discoloration of cut surfaces and increasing the PPO activity. On the contrary, coating SC-treated samples with CMCH significantly prevented the browning reaction and inhibited PPO activity. In addition, SC and CH/CMCH coatings maintained tissue firmness and did not affect weight loss. Our study may provide a scientific basis for the use of SC+CMCH treatment as an alternative preservation treatment for fresh-cut fruits and vegetables. [Copyright &y& Elsevier]

Abstract: Membrane lipid degradation catalyzed by phospholipase D (PLD) results in postharvest browning and senescence of litchi fruit. The effects of n-butanol, a specific PLD inhibitor, on enzymatic browning and oxidative stress during storage of litchi fruit at room temperature were evaluated. n-Butanol-treated fruit had a lower browning index and disease index than untreated fruit. n-Butanol treatment also decreased PLD activity. As a result, the decompartmentalization of litchi polyphenoloxidase and substrates was reduced. The conversion of substrates (−)-epicatechin and procyanidin A2 into quinones was slowed down and enzymatic browning of litchi pericarp tissues was lower after 6d storage. Additionally, n-butanol-treated fruit possessed significantly lower malondialdehyde contents than untreated fruit after 4d storage. Analysis of antioxidative enzyme activities showed that n-butanol treatment inhibited oxidative stress mainly by maintaining high catalase activity in litchi pericarp tissues. Consequently, senescence of litchi fruit during storage was moderated. [Copyright &y& Elsevier]

Abstract: The main objective of this study was to develop a vision system that is able to classify fresh-cut apple slices according to the development of enzymatic browning. The experiment was carried out on ‘Granny Smith’ apple slices stored at 7.5°C for 9 days (n =120). Twenty-four samples were analyzed per day: at zero time and after storage for 1, 3, 7 and 9 days, which corresponds to treatments t 0, t 1, t 3, t 7 and t 9 respectively. Multispectral images were acquired from the samples by employing a 3-CCD camera centered at the infrared (IR, 800nm), red (R, 680nm) and blue (B, 450nm) wavelengths. Apple slices were evaluated visually according to a visual color scale of 1–5 (where 1 corresponds to fresh samples without any browning and 5 to samples with severe discoloration), to obtain a sensory evaluation index (I SE ) for each sample. Finally, for each sample and for each treatment, visible (VIS) relative reflectance spectra (360–740nm) were obtained. In order to identify the most related wavelengths to enzymatic browning evolution, unsupervised pattern recognition analysis of VIS reflectance spectra was performed by principal components analysis (PCA) on the autoscaled data. Maximum loading values corresponding to the B and R areas were observed. Therefore, a classification procedure was applied to the relative histograms of the following monochromatic images (virtual images), which were computed pixel by pixel: (R−B)/(R+B), R−B and B/R. In all cases, a non-supervised classification procedure was able to generate three image-based browning reference classes (BRC): Cluster A (corresponding to the t 0 samples), Cluster B (t 1 and t 3 samples) and Cluster C (t 7 and t 9 samples). An internal and an external validation (n =120) were carried out, and the best classifications were obtained with the (R−B)/(R+B) and B/R image histograms (internal validation: 99.2% of samples correctly classified for both virtual images; external validation: 84% with (R−B)/(R+B) and 81% with B/R). The camera classification was evaluated according to the colorimetric measurements, which were usually utilized to evaluate enzymatic browning development (CIE L*a*b* color parameters and browning index, BI) and according to I SE . For both validation phases a*, b*, BI and I SE increased while L* values decreased with image-based class number, thereby reflecting their browning state. [Copyright &y& Elsevier]

Abstract: Quality, microbiological and enzymatic characteristics of fresh-cut lettuce (Lactuca sativa var. longifolia, ‘Duende’), grown in floating system with three electrical conductivities of nutrient solutions (2.8, 3.8 and 4.8mScm−1), were investigated in order to evaluate the effect of salinity on product shelf-life during cold storage (9d at 4°C). Pre-harvest salinity of 3.8 and 4.8mScm−1 improved the properties of fresh-cut lettuce, since CO2 production was reduced with a subsequent control of the decay process. Fresh-cut processing caused an activation of polyphenol oxidase and peroxidase; in all cases the product obtained by salinity treatments was less subject to oxidase activity and browning phenomena during storage. Increased salinity reduced the number of mesophilic bacteria and of moulds and yeasts, assessed by plate counts on different culture media; in contrast, Enterobacteriaceae levels were unaffected by pre-harvest treatments. The research demonstrated that an increase in nutrient solution electrical conductivity, through the use of floating system, affects fresh-cut lettuce characteristics, improving shelf-life of the product. [ABSTRACT FROM AUTHOR]

Abstract: ‘Rocha’ pear (Pyrus communis L.) was used as a model system to assess the effect of pH of dipping solutions on quality retention of fresh-cut fruit and its interaction with calcium additives. Pear slices were dipped for 60s in a buffer solution at pH 3.0, 5.0 or 7.0 and stored at 4.5°C for 13 days. In other experiments, pear slices were dipped for 60s in buffer solutions containing 250mM of calcium ascorbate, lactate, chloride, and propionate, at pH 3.0 or 7.0, and stored at 4.5°C for 6 days. Browning and softening were more intense in slices dipped in a solution at pH 3.0 than at pH 5.0 or 7.0, but microbial growth was lower in slices treated at pH 3.0. The effect of calcium additives depended on the anion and significant interactions between the effects of calcium salt and pH were observed. Calcium ascorbate was very effective in preserving color and reducing microbial growth irrespective of pH, but enhanced pectin solubilization and tissue softening at pH 3.0. Slices treated with 250mM calcium propionate or calcium lactate were softer and had higher electrolyte efflux when treated at pH 3.0 than at pH 7.0. Calcium lactate enhanced browning and reduced microbial growth at pH 3.0 but did not affect color or microbial counts at pH 7.0. All calcium treatments enhanced electrolyte leakage. pH of the dipping solution can affect, per se, the quality of fresh-cut fruit. The choice of calcium additives to prevent undesirable changes on visual and sensory quality of cut produce should involve pH ranges that provide the expected benefits. [ABSTRACT FROM AUTHOR]

Abstract: Effects of aqueous chlorine dioxide (ClO2) treatment on enzymatic browning and shelf-life of fresh-cut asparagus lettuce (Lactuca sativa L. var. angustana) were investigated. Fresh-cut asparagus lettuce was treated at different concentrations (10, 40, and 100mgL−1) for different times (5, 10, and 20min). Following treatments, lettuce slices were stored at 4°C for 14 d. The activities of polyphenol oxidase (PPO) and peroxidase (POD) in the lettuce were reduced by ClO2, and degradation of color was also delayed. Thus ClO2 concentration and treatment time were two significant factors affecting ClO2 treatment on enzymatic browning of fresh-cut asparagus lettuce. From the microbiological and sensory quality perspectives, the treatment with 100mgL−1 ClO2 for 20min could prolong the shelf-life to 14 d compared to 4 d for the control. These results indicated that ClO2 treatment was a promising approach to inhibit enzymatic browning and prolong shelf-life of fresh-cut asparagus lettuce. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated the impact of pulsed light treatments on microbial quality, enzymatic browning, texture and antioxidant properties of fresh-cut mushrooms. The reduction of the native microflora of sliced mushrooms ranged from 0.6 to 2.2log after 15 days of refrigerated storage by flashing at 4.8, 12 and 28Jcm−2. Pulsed light treatments allowed extension of the microbiological shelf life of fresh-cut mushrooms by 2–3 days in comparison to untreated samples, while providing a high quality product. The use of high pulsed light fluencies (12 and 28Jcm−2) dramatically affected the texture of sliced mushrooms due to thermal damage induced by the treatments. Enzymatic browning was also promoted by an increase in polyphenol oxidase activity when the highest dose of pulsed light was applied. At 28Jcm−2, phenolic compounds, vitamin C and antioxidant capacity were significantly reduced. Our results suggest that the application of pulsed light at doses of 4.8Jcm−2 could extend the shelf life of fresh-cut mushrooms without dramatically affecting texture and antioxidant properties. [Copyright &y& Elsevier]

Abstract: Watercore usually spreads in mature ‘Fuji’ apples and may induce flesh browning disorders through unknown mechanisms. We analyzed H2O2 and ascorbic acid (AA) contents and the activities of four enzymes involved in the AA–glutathione (AA–GSH) cycle in watercore and watercore-free tissues in ‘Fuji’ apple fruit during storage. H2O2 levels always were higher in watercore than in watercore-free tissues. AA levels were lower in watercore tissues at harvest and decreased in both tissue types during the storage period. However, AA was completely absent from watercore tissue but not watercore-free tissue three months after harvest. Ascorbate peroxidase (APX) activities were always higher in watercore than in watercore-free tissues, and the activities of dehydroascorbate reductase (DHAR) decreased continuously after harvest in both tissue types. These results suggested that higher production of H2O2 caused by anaerobic conditions in watercore activated APX which acted as a redox signal; the concomitant net consumption of AA was not balanced by the decline of DHAR activity, leading to decreased antioxidant levels. On the other hand, the gradual increases in monodehydroascorbate reductase (MDAR) and glutathione reductase (GR) activity observed during storage accompanied by low AA levels and DHAR activity might indicate a declining efficiency of the AA–GSH cycle. [Copyright &y& Elsevier]

Abstract: Pomegranates are sensitive to low temperatures. When fruit are exposed to temperatures below 5–6°C chilling injury appears as pitting of the skin, browning of the white segments separating the arils and discoloration of the arils, and husk scald, which generally is more severe at temperatures of 6–10°C. The main objective of this work was to assess the effectiveness of individual film packaging, applied as a stand alone treatment or in combination with fludioxonil, on reducing the occurrence of husk scald, weight loss and decay. Fruit were dipped in an aqueous mixture containing 600mgL−1 fludioxonil, wrapped or not wrapped with a polyolephinic heat-shrinkable film and stored at 8°C and 90% RH for 6 or 12 weeks plus one additional week of simulated shelf-life at 20°C and 65–70% RH. Respiration rate decreased both in cold storage and at 20°C. Ethylene production was not detected during cold storage; its rate increased upon transfer to 20°C, but results were inconsistent. Control fruit deteriorated at a very high rate, due to excessive weight loss, skin browning and decay. Film wrapping almost completely inhibited weight loss and husk scald and preserved fruit freshness for the whole storage time. There was no statistical difference in decay incidence between wrapped and control fruit after 6 or 12 weeks of storage and after the first shelf-life, while after the second shelf-life, wrapped fruit had significantly higher decay levels. By contrast, fludioxonil, both alone and in combination with wrapping, effectively controlled mold development, resulting in 50–67% less decay than control fruit after 12 weeks at 8°C plus one week shelf-life. Control fruit showed minor changes in nutritional compounds as well as in total polyphenols, anthocyanins and antioxidant activity, while higher losses were detected in film-wrapped fruit during storage at 20°C. [Copyright &y& Elsevier]

• Ferulic acid (FA) antimicrobial activity was studied in fresh-cut apple and melon. • Immersion was a better application than spray was for antimicrobial purposes. • FA showed no bactericidal effect artificially inoculated pathogens. • After 7-day storage, L. monocytogenes reductions were 2–5 log units (2.5 g L−1 FA). • After 7-day storage S. enterica reductions were 0.5–3 log units in apple and melon. Listeria monocytogenes can grow under conditions at which fresh-cut fruit are stored, whereas Salmonella spp. has been associated with a number of outbreaks related to such products. It is therefore necessary to find products capable of reducing microbial counts while maintaining quality of the product. In this regard, ferulic acid (FA) has shown antimicrobial, antioxidant and many physiological functions in humans. This study aimed to test the efficacy of FA in fresh-cut apple and melon in two ways: (a) to prevent pathogenic growth and (b) to maintain fruit quality during storage, maintaining color and preventing enzymatic browning. For this purpose, L. monocytogenes (3 strains) and S. enterica (4 strains) were inoculated in both fruits. FA at concentrations ranging from 2.5–15 g L−1 were tested against individual strains and the results showed that FA did not have any bactericidal effect after application. FA effect was observed at the end of the storage (7 d, 10 °C) with higher effect against L. monocytogenes (averaging 4.2 ± 0.7 log CFU g−1) than against S. enterica (averaging 1.9 ± 1.3 log CFU g−1). The reductions were significantly different from the samples without FA, but significant differences were not found among the 3 tested concentrations. Comparison between immersion and spray applications of FA revealed that immersion was the best method. When the effect of the selected FA dose on quality was evaluated, we found that FA did not prevent the increase of browning index in apples. However, melon treated samples did not overcome significant color changes during storage at 4 °C. FA did not inhibit the growth of total aerobic mesophylls and yeasts and molds, but maintained overall quality of the fruits, including pH, total soluble solids and titratable acidity. Overall, FA could be used in fresh-cut apple and melon to prevent growth of L. monocytogenes without affecting physicochemical quality, delivering a product with increased antioxidant activity and providing a new source of FA (0.25 ± 0.04 g kg-1 of apple, and 1.22 ± 0.07 g kg−1 of melon, dry weight basis). [ABSTRACT FROM AUTHOR]

• 1-MCP reduced browning and delayed quality deterioration of lotus root slices. • 1-MCP treatment inhibited the phenolic metabolism of fresh-cut lotus root slices. • 1-MCP treatment induced the antioxidant system of fresh-cut lotus root slices. • 1-MCP were involved in the regulation of ethylene biosynthesis and signal transduction. The quality of fresh-cut lotus root slices is greatly affected by enzymatic browning. In this study, we investigated the effects of 1-methylcyclopropene treatment on browning and quality deterioration of lotus root slices. When fresh-cut lotus root slices were immersed in 0.1 mg L−1 1-MCP for 1 h and stored at 10 ℃ for twelve days, microbial growth, respiration, total phenolic content, phenylalanine ammonia lyase activity, polyphenol oxidase activity, and soluble quinone levels in fresh-cut lotus root slices were suppressed. Furthermore, 1-MCP treatment improved the antioxidant capacities, peroxidase activities, superoxide dismutase activities, catalase activities, and DPPH free radical scavenging rates in fresh-cut lotus root slices. In addition, 1-MCP treatment inhibited the production of reactive oxide species, which delayed quality deterioration of fresh-cut lotus root slices. Based on transcriptomics and real-time quantitative PCR results, gene expression levels of NnmetK2 , NnACO , NnETR2 , NnEIN3 , and NnERF1 were up-regulated while expression levels of NnEBF1 were down-regulated. These findings indicate that 1-MCP inhibits ethylene biosynthesis and signal transduction, which suppresses a series of ethylene-induced physiological and biochemical reactions. Based on our findings, we propose a new strategy for inhibiting enzymatic browning in fresh-cut lotus root slices. [ABSTRACT FROM AUTHOR]

• Isoleucine (Ile) could significantly delay the browning of fresh-cut potato. • Ile treatment inhibited PPO activity partially by chelating Cu2+. • Ile treatment suppressed PPO activity by interacting with amino acid residues of PPO. • Ile treatment improved the antioxidant capacity of fresh potato. Fresh-cut potatoes are susceptible to enzymatic browning. In this study, the effect of isoleucine (Ile) on the browning of fresh-cut potatoes was evaluated, and the mechanism by which Ile influenced the browning was revealed. Results showed that exogenous Ile application could reduce the browning of fresh-cut potato chips. At 2–4 °C, control chips had lost saleability on day 1, while 1.0 % Ile treated chips were still acceptable on day 4. Ile alleviated the decrease of tyrosine, prevented the production of brown pigments, and inhibited the browning of potato mashes. The addition of Ile to potato mash decreased polyphenol oxidase (PPO) activity, which was partially recovered after adding copper acetate. Molecular docking showed that Ile could bind with the amino acid residues of PPO. Moreover, Ile treatment increased the activity of catalase (CAT) and peroxidase (POD), improved 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) inhibition rate, and decreased the malondialdehyde (MDA) content. This is the first research to demonstrate that Ile has potential to be used as a natural anti-browning agent and its mechanisms include decreasing PPO activity by chelating Cu2+ and interacting with the PPO amino acid residues, and improving the antioxidant capacity. [ABSTRACT FROM AUTHOR]

• Pre-treatment with proline reduced the browning of fresh-cut potato. • Pre-treatment with proline suppressed the PPO activity and total phenol content. • Pre-treatment with proline caused contents changes of ten amino acids. • Endogenous proline and antioxidant capacity were increased. Fresh-cut potato slices are prone to browning, resulting in a severely reduced commodity value. Hence, a safe and effective method to inhibit the browning of fresh-cut potatoes is urgently needed. In this study, we investigated the effect of pre-treatment with a proline solution on browning, polyphenol oxidase (PPO) activity, total phenol content, antioxidant activity, and free amino acid content of fresh-cut potatoes. The results showed that pre-treatment with 90 mmol L−1 proline for 1 h at 30 °C reduced browning and surface dehydration, improved the overall visual aspect, and extended the shelf-life of potato slices to 4 d at 2−4 °C. The PPO activity and total phenol content in pre-treated potato tubers and slices were lower than control and water treatment. The superoxide dismutase (SOD), catalase (CAT) activities, the percentage inhibition of 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and 2,20-zo-bis-3-ethylben zothiazoline-6-sulfonic acid (ABTS), and the Fe2+ reduction capacity had increased compared with control and water treatment. Compared with control and water treatment, the tyrosine, aspartic acid, glutamic acid, serine, glycine, histidine, and valine content were reduced, whereas proline, histidine, and valine had increased. Mechanistically, pre-treatment with proline inhibited the browning of fresh-cut potatoes by reducing PPO activity, total phenolic content, and the content of several amino acids, while inducing the accumulation of intrinsic proline content and increasing the antioxidant capacity of fresh-cut potatoes. [ABSTRACT FROM AUTHOR]

Consumers demand less use of chemicals on minimally processed fruits and vegetables so more attention has been paid to the search for naturally occurring substances able to act as alternative antimicrobials and antioxidants. The susceptibility of the native microflora of butternut squash and Listeria monocytogenes was analyzed by in vitro assays using (a) film-forming solutions (chitosan, carboxymethyl cellulose and casein), (b) oleoresins (olive, rosemary, onion, capsicum, cranberry, garlic, oreganum and oreganum+carvacrol 5%) and (c) film-forming solutions enriched with oleoresins. Film-forming solutions did not show significant antimicrobial properties. The oleoresins with meaningful antimicrobial activity against both squash native microflora and L. monocytogenes were olive and rosemary. In general, film-solutions containing 1% of different oleoresins showed limited antimicrobial effects against these indicator microorganisms. In vitro antioxidant properties were measured on different crude vegetable extracts. The enzyme source proved to affect peroxidase (POD) and polyphenoloxidase (PPO) susceptibility to the film-forming solutions. Most oleoresins significantly affected POD activity, regardless of the enzyme source. When the film-forming solutions were enriched with oleoresins, the latter lost, or retained their potential to reduce POD and PPO activities. In vivo experiments were focused on the treatments offering potential antibacterial and antioxidant benefits. The use of chitosan coatings enriched with rosemary and olive oleoresins applied to butternut squash did not produce a significant antimicrobial effect, however antioxidant effects were observed during the first day, exerting POD inhibition for up to 5 d of storage. Both oleoresins and chitosan enriched with them exerted significant antioxidant activities over PPO throughout 5 d of storage. The use of chitosan enriched with rosemary and olive did not introduce deleterious effects on the sensorial acceptability of squash. Chitosan enriched with rosemary and olive improved the antioxidant protection of the minimally processed squash offering a great advantage in the prevention of browning reactions which typically result in quality loss in fruits and vegetables. [Copyright &y& Elsevier]

This study has demonstrated the potential of several controlled atmospheres for reducing the respiration rate and browning in minimally processed potatoes (cv. Monalisa) during a 14-day storage period at 4°C. The gas combinations tested were 2.5/0, 2.5/5, 5/0, 5/10, 10/0, 10/10, 80/0, 80/10, 80/20, 90/0, and 90/10 (kPa O2/kPa CO2; N2 balance). Compared to the control atmosphere (synthetic air), minimally processed potatoes stored under the controlled atmosphere composed of 80kPa O2/10–20kPa CO2 afforded the best results in terms of reduced respiration rates (−68% RO2 and −84% RCO2), antibrowning activity (−35% in total surface color change), and mechanical properties (−37% potato hardening) after storage at 4°C for 14 days. Significant decreases in acidity (higher pH values) compared to the fresh product were found at the end of the storage in the minimally processed potatoes stored under low O2/high CO2 and high O2/high–low CO2 conditions. In contrast, dry matter determinations showed no water losses in any of the experimental gas treatment batches. [Copyright &y& Elsevier]