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Enzymatic browning is a major quality defect of packaged “ready-to-eat” fresh-cut lettuce salads. While there have been many research and breeding efforts to counter this problem, progress is hindered by the lack of a technology to identify and quantify browning rapidly, objectively, and reliably. Here, we report a deep learning model for lettuce browning score prediction. To the best of our knowledge, it is the first-of-its-kind on deep learning for lettuce browning prediction using a Siamese Quadratic Swin (SQ-Swin) transformer with several highlights. First, our model includes quadratic features in the transformer model which is more powerful to incorporate real world representations than the linear transformer. Second, a multi-scale training strategy is employed to augment the data and explore more of the inherent self-similarity of the lettuce images. Third, the proposed model uses a siamese architecture which learns the inter-relations among the limited training samples. Fourth, the model is pretrained on the ImageNet and then trained with the reptile meta-learning algorithm to learn higher-order gradients than a regular one. Experiment results on the fresh-cut lettuce datasets show that the proposed SQ-Swin outperforms the traditional methods and other deep learning-based backbones.

Flammulina velutipes was treated with 10, 50, and 250 μL L−1 isoamyl isothiocyanate (IAITC), and effects on quality preservation were assessed. IAITC displayed positive effects during the storage of F. velutipes: (i) maintained tissue integrity, reduced weight loss rates; (ii) reduced browning degree by inhibiting the activities of browning-related enzymes; (iii) enhanced activities of two antioxidant enzymes (superoxide dismutase and catalase) and increased ascorbic acid content; (iv) ameliorated microbial spoilage by inhibiting bacterial growth, especially Serratia, a major bacterial community on the surface of F. velutipes; (v) enhanced chitin content and thereby maintained structural integrity; and (vi) maintained levels of Asp, Glu, linoleic acid, and polyunsaturated fatty acids. In conclusion, IAITC reduced catalase activity and total phenolic content in F. velutipes during storage. The most suitable concentration of IAITC in the preservation of F. velutipes was 50 µL L−1. [ABSTRACT FROM AUTHOR]

This research scrutinised the opportunity of upcycling waste from the food industry by extracting dietary fibre from purple aubergine. One of the challenges addressed was enzymatic browning, which negatively influenced the quality of the fibre extracted from fresh aubergine. Various pre-treatment procedures were assessed, including using citric acid, sulphite immersion, peeling and thermal processing, to determine their effects on extraction yield, colour, and the functionality of the resultant dietary fibre. Findings indicated that a pre-treatment method involving aubergine peeling, sulphite solution immersion, and subsequent steaming before extraction produced optimal results, enhancing both whiteness index and water-holding capacity. Experiments were conducted with traditional enzymes supplemented with cellulase, xylanase, and lipase for enzymatic extraction. The addition of lipase notably elevated the extraction yield and water-holding capacity, albeit with an undesired darkening effect on the dietary fibre. In contrast, the application of xylanase emerged as the most effective treatment, delivering the highest overall quality for the derived dietary fibre. [ABSTRACT FROM AUTHOR]

Litchi (Litchi chinensis Sonn.) fruit deterioration occurs rapidly after harvest and is characterized by pericarp browning, pulp softening, and decay. In this study, we found that calcium chloride (CaCl2) treatment (5 g L−1 CaCl2 solution vacuum infiltration for 5 min) affected the cell wall component contents and cell wall-degrading enzyme activities of litchi fruit during storage at room temperature. CaCl2 treatment significantly increased the contents of Ca2+ and cellulose, while it decreased the water-soluble pectin content, and the activities of polygalacturonase, β-galactosidase, and cellulase in the litchi pericarp. Meanwhile, the treatment resulted in significantly increased contents of Ca2+, water-soluble pectin, ionic-soluble pectin, covalent-soluble pectin and hemicellulose, and upregulated activities of pectinesterase and β-galactosidase, while significantly decreasing the activities of polygalacturonase and cellulase in litchi pulp. The above results indicate that CaCl2 treatment strengthened the cell wall structure of litchi fruit. More importantly, the enzymatic browning of the pericarp, softening of the pulp, and disease incidence were delayed. The treatment had a more pronounced effect on the pericarp than on the pulp. We consider CaCl2 treatment to be a safe and effective treatment for maintaining the postharvest quality of litchi fruit. [ABSTRACT FROM AUTHOR]

The enzymatic browning of apples by polyphenol oxidase is a major drawback in the food industry. The change in the color, taste, and texture discourage the client from buying these fruits in the market. The description of this enzyme's characteristics can be helpful in preventing the adverse consequences of the reaction. A study was carried out using polyphenol oxidase extracted from "Red delicious" apples cultivated in Laklouk, a small mountainous village located 69 km northeast of Beirut, Lebanon. The enzyme extraction was performed using phosphate buffer (0.1 M, pH 6.5), ascorbic acid, 3% polyvinylpolypyrrolidone, and 0.5% TritonX-100. The enzymatic reaction catalyzed by polyphenol oxidase was held using pyrocatechol (20 mM) as substrate. The optimum temperature and the optimum pH at which the enzyme shows maximal activity were determined. The stability of the enzyme after incubation at different temperatures was studied, and the major kinetic and thermodynamic parameters were calculated. The enzyme exhibits optimal activity at pH 5.5 and at 303 K. Higher or lower temperatures majorly reduce the enzyme activity. Apple polyphenol oxidase heat inactivation showed a first-order decay approach. The means of thermodynamic parameters suggest that polyphenol oxidase catalyzed reaction is endergonic with insignificant dispersion in the reaction medium. The results also provided information on the stability and structural resistance of the enzyme. This study determines for the first time some characteristics of polyphenol oxidase extracted from Lebanese apples. The knowledge of the enzyme activity can generate helpful instructions. This data taken into consideration while harvesting, handling, and processing apples, will help in reducing undesirable wastage of fruits and permitting economical savings. [ABSTRACT FROM AUTHOR]

Chinese cymbidiums are important flowering ornamental plants. Traditional propagation via seed or division cannot satisfy growers' demand for commercialization of new cultivars, and in vitro propagation has a low micropropagation efficiency due to the browning of rhizomes. In this study, rhizomes of Cymbidium '14-16-13' and '14-16-5' were cultured on half-strength Murashige and Skoog (MS) medium supplemented with 6-benzyl aminopurine (BAP), NAA (a-napthaleneacetic acid), or BAP with NAA under either the dark or light. The degree of browning was read, and rhizome proliferation or sprouting (sprout numbers) was evaluated. Results showed that there was significant difference in browning grade of rhizomes between '14-16-13' and '14-16-5' regardless of dark and light culture. Dark culture induced rhizome proliferation but failed to induce sprouts. Light culture slightly elevated the degree of browning but induced sprouting. Among the growth regulators evaluated, BAP was more effective for sprout induction. As rhizome browning appeared to be inevitable in micropropagation of the cymbidiums, a compromise between browning and sprout production could be a realistic approach. Our study showed that rhizomes cultured on half-strength MS medium supplemented with 1.5 mg·L21 BAP were able to produce more than 16 sprouts per vessel even though browning occurred in the rhizomes. Thus, culturing rhizomes in this medium could be a practical solution for in vitro propagation of Chinese cymbidiums. [ABSTRACT FROM AUTHOR]

Sulfur dioxide is the most used additive today for preventing browning in grape musts and wines. However, since wine consumers are increasingly interested in healthier wines, the wine industry is keen to reduce its use. Some promising alternatives to sulfur dioxide have been proposed in recent years, including glutathione, both pure and in the form of inactivated yeasts, and Metschnikowia pulcherrima used as a bioprotective agent. Some information exists about the protective effect against oxidation of glutathione but there is very few about the use of bioprotection for that purpose. Supplementation with glutathione, regardless of the commercial form, reduced oxygen consumption and browning intensity when laccase was not present in the grape juice. Metschnikowia pulcherrima also reduced browning intensity in the absence of laccase but increased the total oxygen consumption. However, in the presence of laccase, glutathione and Metschnikowia pulcherrima were not effective enough to adequately prevent the grape juice from browning. Glutathione, both pure and in the form of inactivated yeasts, and Metschnikowia pulcherrima are interesting tools for protecting grape must against browning, and thus reducing the use of sulfur dioxide. [ABSTRACT FROM AUTHOR]

Indian gooseberry (Phyllanthus emblica) is a seasonal and highly nutritious fruit with shorter shelf-life and astringent taste limiting its utilization. The enzymatic browning and flavor loss are major concerns which makes pre-processing a crucial step for further processing. In this context, dry microwave blanching (MWB) was explored as an alternative to hot-water (HW) blanching to reduce its nutrition losses particularly ascorbic acid (AA) and makes it easier for removal of seed kernel. This study focused on the effect of MW power level (200–500 W) and blanching time (50–100 s) on AA content, color attributes (L*, a*, b*), and enzymatic inhibition in Indian gooseberry. The optimized MWB conditions were 294 W MW power with 70 s blanching time providing satisfactory enzymatic inhibition (75.47%), and retention of AA (417.70 mg/100 g pulp) and color attributes (L*: 58.42, a*: 4.57, b*: 26.23). As compared to HWB (80 °C, 5 min), MWB showed least AA degradation, higher total phenolic content and softening percent with less total color difference owing to its shorter processing time and dry blanching. Quantitative descriptive analysis (QDA) demonstrated that raw and MW blanched Indian gooseberries are the most accepted, followed by HW blanched samples. MWB showed better nutrient retention than HWB with easier seed removal showed the application of MW radiation for blanching of other fruits. [ABSTRACT FROM AUTHOR]

This research evaluated the effect of guided inquiry approach-based laboratory activity within the scope of lifelong learning, in which daily life context is used, on developing pre-service science teachers' learning processes. The study groups for the research consisted of six pre-service science teachers who were seniors in the science education department at a university in the west of Turkey. The holistic single-case design was used as the research method in this study. One of the topics related to enzymes we encounter in many areas of daily life is the concept of enzymatic browning. In this study, starting from a daily life context, an activity that includes the chemical change emphasis underlying the enzymatic browning event and the factors affecting the work of enzymes is discussed. In this context, the guided inquiry learning approach, in which the hypothetico-deductive reasoning cycle is used in laboratory practices in teacher education, is based on the activity. At the end of the activity, experiment reports, science journals, and concept maps were evaluated. As a result of the evaluation, it was seen that the students not only designed scientific research and tested their hypotheses consistently and accurately but also obtained subject gains related to enzymes and chemical change. Since it is understood that the activity supports lifelong learning in terms of both the skills developed and the ideas reflected by the pre-service teachers, using similar practices in teacher education can be recommended. [ABSTRACT FROM AUTHOR]

Copyright of Acta Agriculturae Slovenica is the property of Biotechnical Faculty of the University of Ljubljana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective of this study was to evaluate the effect of antioxidant treatments on the conservation of cut eggplants (Solanum melongena L.), which was carried out in two stages. Initially, the effect of citric acid (CA), ascorbic acid (AA) and cysteine (Cys) solution at 0.5 and 1% on sensory attributes (general appearance and browning), and color parameters during storage were evaluated. Immersion in 1% AA was considered the best antioxidant since it maintained visual quality for 6 days. Subsequently, hot water dipping (HWD) treatments followed by the 1% AA solution were evaluated and optimized through the Response Surface Methodology (RSM). Sensory attributes, color parameters, respiration rate (RR), phenolic compounds (PhC), antioxidant capacity, as well as the activity of polyphenol oxidase (PPO) and peroxidase (POD) were assessed during cold storage. The results showed that HWD at 50 °C, 60 s and 1% AA was the optimal combination to control enzymatic browning and extend its fresh quality for up to 8 days. Furthermore, that combination of treatments reduced the PPO and POD activities and increased the PhC compared to the control (untreated), not finding significant differences between them in antioxidant capacity and RR. Therefore, the application of this combination would be the most appropriate to preserve the quality of the fresh-cut eggplants for 8 days of storage at 4 °C. [ABSTRACT FROM AUTHOR]

The color changes brought on by the enzymatic interactions of phenolic compounds with released endogenous polyphenol oxidase and the penetration of oxygen into the tissue has a significant impact on the commercialization of fresh-cut fruit, such as apples. This process causes a loss of quality in fresh-cut apples, resulting in browning of the fruit surface. By acting as a semipermeable barrier to gases and water vapor and thus lowering respiration, enzymatic browning, and water loss, edible coatings can provide a chance to increase the shelf life of fresh-cut produce. In this study, the effect of edible coatings composed of carboxymethylcellulose (CMC, 1%), sodium alginate (SA, 1%), citric acid (CA, 1%), and oxalic acid (OA, 0.5%) on fresh-cut 'Annurca Rossa del Sud' apple was studied. Four formulations of edible coatings, A. SA+CMC, B. SA+CMC+CA, C. SA+CMC+OA, and D. SA+CMC+CA+OA, were tested. Fresh-cut apples were dipped into different solutions and then stored at 4 °C, and physicochemical and biochemical analyses were performed at 0, 4, 8, and 12 days of storage. Results demonstrated that all four combinations improved the shelf-life of fresh-cut apple by slowing down the qualitative postharvest decay, total soluble solid, and titratable acidity. The browning index was highest in the control samples (82%), followed by CMC+SA (53%), CMC+SA+CA (32%), CMC+SA+OA (22%), and finally CMC+SA+CA+OA (7%) after 12 days of cold storage. Furthermore, coating application increased the bioactive compound content and antioxidant enzyme activities. Furthermore, the synergistic activity of SA+CMC+CA+OA reduces enzymatic browning, prolonging the postharvest life of minimally processed 'Annurca Rossa del Sud' apples. [ABSTRACT FROM AUTHOR]

Fruit by-products are considered as a potent natural source for value-added compounds such as starch, pectin as well as bioactive compounds. These are also rich source for carbohydrate, minerals, vitamins, fibers, phenolic compounds, flavonoid compounds, anthocyanin, hydrolysable and condense tannins. The starch and pectin are natural-based polysaccharide produce also after fruit processing; has unique properties to develop biodegradable packaging and can expand the possible range of uses in food industries. Recently, the consumer and industry demand for the biodegradable and edible packaging has been increased. Edible packaging is considered alternatives of the synthetic polymer and help to enhance the shelf life of the food products while retaining their nutritional, biological and sensory quality. It helps in minimizing lipid oxidation; reducing weight loss, retarded respiration and enzymatic browning of the food products, that is, fruits & vegetables and others. The present review explores about the edible packaging, physiochemical properties and edible film forming ability of fruit wastes of apple, banana peel, citrus, grapes, jack fruit, mango, pomegranate, pineapple, and tamarind. Therefore, the by-products of the fruit processing can be utilized to develop edible coating and film to enhance the shelf life of food products at commercial scale. [ABSTRACT FROM AUTHOR]

Polyphenol oxidase (PPO) easily causes fruits and vegetables to lose their color and nutritional value. As a non-thermal process, high-pressure processing (HPP) showed different inactivation effects on endogenous enzymes. In this work, soluble PPO (sPPO) and membrane-bound PPO (mPPO) from 'Lijiang snow' peaches were purified, and then the effect of high pressure on the conformation of sPPO and mPPO was investigated and compared at the molecular level. The maximum activation of sPPO and mPPO by 11.2% and 4.8% was observed after HPP at 200 MPa, while their activities both gradually decreased at 400 MPa and 600 MPa; in particular, the residual activities of sPPO and mPPO at 600 MPa for 50 min were 41.42% and 72.95%, respectively. The spectroscopic results indicated that the secondary structure of PPOs was little affected by HPP, but HPP led to obvious changes in their tertiary structure. The simulations showed that the decreasing distance between the copper ion and His residue in the copper-binding region of two PPOs at 200 MPa was favorable to catalytic activity, while the increasing distance between copper ions and His residues and the disordered movement of the loop region above 400 MPa were unfavorable. In addition, the structure of sPPO was relatively looser than that of mPPO, and high pressure showed a more significant effect on the conformation of sPPO than that of mPPO. This study clarified the effect of HPP on PPO's structure and the relationship between its structure and activity and provided a basis for the prevention of enzymatic browning. [ABSTRACT FROM AUTHOR]

Browning of fresh-cut plants is mainly attributed to the enzymatic browning of phenolic compounds induced by polyphenol oxidase (PPO), producing browning products such as anthraquinones, flavanol oxides, and glycosides, which are usually considered to be non-toxic. Could browning bring any benefits on behalf of their bioactivity? Our previous study found that browned lotus root extracts (BLREs) could reduce the cholesterol level in obese mice as fresh lotus root extracts (FLREs) did. This study aimed to compare the mechanisms of FLRE and BLRE on cholesterol metabolism and verify whether the main component's monomer regulates cholesterol metabolism like the extracts do through in vitro experiments. Extracts and monomeric compounds are applied to HepG2 cells induced by free fatty acids (FFA). Extracellular total cholesterol (TC) and triglyceride (TG) levels were also detected. In addition, RT-PCR and Western blot were used to observe cholesterol metabolism-related gene and protein expression. The in vitro results showed that BLRE and FLRE could reduce TC and TG levels in HepG2 cells. In addition, BLRE suppressed the synthesis of cholesterol. Meanwhile, FLRE promoted the synthesis of bile acid (BA) as well as the clearance and efflux of cholesterol. Furthermore, the main monomers of BLRE also decreased cholesterol synthesis, which is the same as BLRE. In addition, the main monomers of FLRE promoted the synthesis of BAs, similar to FLRE. BLRE and FLRE promote cholesterol metabolism by different pathways. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of edible films (EFs) on important parameters of fresh guacamole and to select the best EF for evaluating its stability and protection effect after 28 days of storage (at 4 and 20°C). EFs based on chitosan (2%), glycerol (1%), citric acid (1.5–2.5%), and lemon-onion extract (0–2%) were applied on the surface of fresh guacamole to evaluate its effect in its color and microbiological and antioxidant properties after 48 h of storage (at 4 and 20°C). Results indicated that EFs delay the total color change and increase the antioxidant capacity of guacamole, while the microbial count was less than 100 CFU/g and 10 CFU/g for mesophylls and molds plus yeasts, respectively. According to the lowest total color change (7.93–14.92) and highest antioxidant capacity (1201.22 mg Trolox/100 g), EF1 (2% chitosan, 1% glycerol, 1.5% citric acid, and 2% lemon-onion extract) was selected for its analysis during the storage. After 28 d of storage at 4 and 20°C, a slight change in the physical characteristics of the EF was observed, while microbial load and antioxidant properties remained constant. Moreover, the selected EF maintained its capacity to avoid guacamole browning, being well-accepted by consumers (I like - I like much) who did not detect the application of EF, even after 24 h of its application onto the fresh guacamole. Results presented in this study indicated that developed EF maintained the quality characteristics of guacamole, and its effect did not change after 28 d of storage.

The insecticides use is important for crop improvement and protection, but in excessive amounts, they would induce a dysfunction of metabolic enzymatic systems in plant tissues, leading to undesirable qualitative changes. In this context, we are interested in peroxidase (POD), an important enzyme in plant physiology but whose activity seems to be conditioned by the presence of insecticides in the soil. This work aims to study the impact of locally used insecticides (chlorpyrifos and dimethoate) on the activity of POD in parsley, onion, celery and garlic grown in soils treated or not. POD extraction was performed using Tris-HCl buffer (pH 7.3); its activity was measured using the substrate o-dianisidine in the presence of H2O2. Our result showed that POD activity for insecticide treated parsley, celery and onions increased by 30 % 127 % and 341 % respectively, however did not change significantly for garlic. Thus, the action of these chemicals is not trivial because they may alter non-target pathways, especially when doses are not adjusted accordingly. We found that insecticide stress would increase POD activity in all vegetables except garlic, which showed tolerance to insecticides. Our findings suggest that organic farming conditions could minimize peroxidase activity in parsley, celery and onion. We add that overproduction of POD negatively affects the quality and reduces the shelf life of vegetables, thus would be a very interesting biomarker of insecticide stress.

Tyrosinase inhibitors are capable of preventing unfavorable enzymatic browning of fruits and vegetables. In this study, the capacity of Acacia confusa stem bark proanthocyanidins (ASBPs) to inhibit tyrosinase activity was evaluated. ASBPs were shown to be a high-potential inhibitor of tyrosinase with IC50 values of 92.49 ± 4.70 and 61.74 ± 8.93 μg/mL when using L-tyrosine and L-DOPA as the substrate, respectively. The structural elucidation performed with UV-vis, FT-IR spectroscopy, ESI-MS and thiolysis coupled to HPLC-ESI-MS suggested that ASBPs had structural heterogeneity in monomer units and interflavan linkages and consisted mainly of procyanidins dominant with B-type linkages. To gain insights into the inhibitory mechanisms of ASBPs against tyrosinase, different spectroscopic and molecular docking methods were further conducted. Results validated that ASBPs possessed the ability to chelate copper ions and could prevent the oxidation process of substrates by tyrosinase. The hydrogen bond formed with Lys-376 residue played a key role in the binding force of ASBPs with tyrosinase that induced a certain alteration in the microenvironment and secondary structure of tyrosinase, resulting in the enzymatic activity being ultimately restricted. It was also observed that ASBPs treatment effectively inhibited the activities of PPO and POD to retard the surface browning of fresh-cut asparagus lettuce and thus extended their shelf-life. The results provided preliminary evidence supporting the exploitation of ASBPs into potential antibrowning agents for the fresh-cut food industry. [ABSTRACT FROM AUTHOR]

Petal browning is a significant issue that causes cut narcissus flowers to lose their economic value, quality, and vase life. GABA has been shown to have a number of roles in plant growth and development. The effects of exogenous GABA treatment compared to control (distilled water) and sucrose (2%) on the browning process and vase life quality of cut narcissus flowers kept at 20 ± 2 °C with a relative humidity of 60–70% were examined in this study. GABA significantly improved the quality of narcissus by delaying petal browning during storage, according to research. The 1 mM GABA treatment resulted in the lowest overall color alterations (ΔE) and the greatest brightness (L*). The activities of peroxidase and polyphenol oxidase were found to be substantially inhibited when GABA was used. GABA also enhanced the relative water content of narcissus petals during storage by reducing alterations in the cellular membrane stability index. Exogenous GABA may therefore be a viable strategy for inhibiting enzymatic browning and extending the vase life of flowers. [ABSTRACT FROM AUTHOR]

Polyphenol oxidase (PPO) is present in most higher plants, but also in animals and fungi. PPO in plants had been summarized several years ago. However, recent advances in studies of PPO in plants are lacking. This review concludes new researches on PPO distribution, structure, molecular weights, optimal temperature, pH, and substrates. And, the transformation of PPO from latent to active state was also discussed. This state shift is a vital reason for elevating PPO activity, but the activation mechanism in plants has not been elucidated. PPO has an important role in plant stress resistance and physiological metabolism. However, the enzymatic browning reaction induced by PPO is a major problem in the production, processing, and storage of fruits and vegetables. Meanwhile, we summarized various new methods that had been invented to decrease enzymatic browning by inhibiting PPO activity. In addition, our manuscript included information on several important biological functions and the transcriptional regulation of PPO in plants. Furthermore, we also prospect some future research areas of PPO and hope they will be useful for future research in plants. [ABSTRACT FROM AUTHOR]

Copyright of Storage & Process is the property of Tianjin Academy of Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effects of intense pulsed light (IPL) pretreatment combined with humidity-controlled drying on storage quality of shiitake mushroom were evaluated. The results showed that IPL pretreatment could reduce the respiration rate of fresh and dried shiitake mushroom, by 76.69% and 84.65%, respectively, and improved the retention rate of reducing sugar during storage. The polyphenol oxidase (PPO) activities of the fresh and dried shiitake mushrooms during storage were 1.73 times and 1.39 times that of the IPL-pretreated samples, respectively, and the enzymatic browning reaction was inhibited, thereby increasing the retention rate of total phenols. IPL treatment was found to improve the quality, polysaccharide retention rate, and antioxidant capacity of fresh and dried shiitake mushroom during storage and delayed softening. IPL treatment also reduced the total bacterial count of fresh shiitake mushroom (from 6.43~8.02 to 3.29~4.66 log CFU/g) but had little effect on the total bacterial count of dried shiitake mushroom. IPL treatment improved the storage quality of shiitake mushrooms to a greater degree than did blanching treatment. Therefore, IPL treatment can be used as a stable pretreatment method for the drying and preservation of shiitake mushrooms. [ABSTRACT FROM AUTHOR]

Skin and hair pigmentation, skin cancer, and enzymatic browning of plants and fruits are caused by tyrosinase, a di‐copper oxidase. In the present work, we developed a novel series of substituted benzyl‐1,2,3‐triazole derivatives linked to hydrazinecarbothiamide via methoxyphenyl linker and assessed them for their tyrosinase inhibitory effects in the presence of L‐dopa as substrates. The majority of the synthesized compounds inhibited tyrosinase at sub‐micromolar concentrations. Compounds with 3,4‐dichloro, 4‐fluoro, and 3‐chloro on the benzyl ring, respectively, exhibited exceptionally high potency against tyrosinase with IC50 values of 0.22, 0.22, and 0.24 μM in the presence of L‐dopa as substrates, which is significantly lower than that of kojic acid as the positive control with an IC50 value of 9.64 μM. Result of kinetic assay demonstrated mixed type of inhibition by 9 g. The experimental findings of the potent compounds with the target enzyme, tyrosinase, were corroborated by molecular docking studies. The results of the molecular docking analysis showed the presence of critical pi‐pi interactions between potent compounds and residues Phe264, and His263. [ABSTRACT FROM AUTHOR]

Enzymatic browning is the main quality issue of fresh-cut stem lettuce (Lactuca sativa L. var. angustana Irish). In this research, the effect of diacetyl on the browning and browning-related mechanisms of fresh-cut stem lettuce was explored. The data showed that diacetyl treatment with 10 μL L−1 inhibited the browning of fresh-cut stem lettuce and extended the shelf life by over 8 d at 4 °C compared with the control. Diacetyl treatment repressed gene expression and decreased the activities of PAL (phenylalanine ammonia-lyase), C4H (cinnamate-4-hydroxylase) and 4CL (4-coumarate-CoA ligase), which thus reduced the accumulation of individual and total phenolic compounds. Moreover, diacetyl enhanced the antioxidant ability and reduced ROS accumulation, improving the anti-browning ability and indirectly suppressing the biosynthesis of phenolic compounds. These results indicated that diacetyl treatment repressed the browning of fresh-cut stem lettuce by regulating the phenylpropanoid metabolism pathway and antioxidant ability. This study is the first to report that diacetyl has an effective anti-browning role for fresh-cut stem lettuce. [ABSTRACT FROM AUTHOR]

Effects of tea polyphenols (TP) on the physical properties, barrier properties and functionality of potato starch-based film were determined, while the interaction mechanism between TP and starch in film and the application of this film in fruit packaging were further evaluated. TP exhibited different effects on the physical properties of potato starch-based film, including thickness (0.083 to 0.087 mm), moisture content (9.27% to 9.68%), color (ΔE value: 5.41 to 10.55), light transmittance (51% to 62%), tensile properties and thermal properties, and improved its barrier properties, including water vapor permeability (9.68 to 11.84 × 10−11 g m−1 s−1 Pa−1),oxygen permeability (1.25 to 2.78 × 10−16 g m−1 s−1 Pa−1) and antioxidant activity. According to the determination of wide-angle X-ray diffraction, Fourier transform infrared and scanning electron microscope, TP could interact with starch chains via hydrogen bonds to form non-crystal complexes, thus affecting the cross-linking among starch chains and further changing the microstructure of film. Furthermore, film incorporated with TP could improve the storage quality (including weight and texture) of blueberries, and inhibit the enzymatic browning of fresh-cut bananas during storage. All present results suggested that tea polyphenols had potential to enhance the properties and function of potato starch-based film, and the film exhibited the application prospect in fruit packaging and preservation. [ABSTRACT FROM AUTHOR]

Enzymatic browning could negatively affect the sensory and nutritional properties of eggplants post-harvest. Polyphenols, polyphenol oxidase (PPO), and reactive oxygen species (ROS) are three material conditions involved in enzymatic browning. This paper seeks to evaluate the effect of fertilization techniques and grafting on the activity of PPO and colorimetric parameters in cultivated eggplants. Fertilization alone significantly increased the PPO activity in all eggplant fleshes (p ≤ 0.05), whereas the grafting technique combined with fertilization decreased the PPO activity in most of the samples significantly (p ≤ 0.05). Moreover, there was a significant positive correlation between the PPO activity and the a* values of the eggplants. The a* values in grafted eggplants were significantly different from each other (p ≤ 0.05), showing that grafting the fertilized eggplants could be effective in controlling the enzymatic browning. The eggplant slices exposed to air for 60 min at room temperature showed a significant increase (p ≤ 0.05) in PPO activity, browning index (BI), total color difference (ΔE), and a*, b*, and c* values. Thus, it is necessary to minimize the exposure time of the slices to air at room temperature, even if combining fertilization techniques with grafting could delay the enzymatic browning in fresh-cut eggplants. [ABSTRACT FROM AUTHOR]

Potato sprouts, an underutilized by-product of potato processing, could be exploited for the recovery of caffeoyl-quinic acids (CQAs), a family of polyphenols with well-recognized biological activities. In this work, the predominant compound of this class, 5-CQA, was extracted by Ultrasound-Assisted Extraction (UAE) under conditions optimized by an Experimental Design. The investigated variables solid/solvent ratio (1:10–1:50 g/mL), water content in ethanol (30–100% v/v) and UAE time (5–20 min) highlighted a critical influence of the last two factors on the extraction efficiency: extracts richer in 5-CQA were obtained with lower water content (30%) and time (5 min). The addition of ascorbic acid (1.7 mM) as anti-browning agent to the extraction solvent improved the extraction efficiency of 5-CQA compared to acetic and citric acids (3158.71 μg/mL, 1766.71 μg/mL, 1468.20 μg/mL, respectively). A parallel trend for the three acids and an increase in 5-CQA recovery was obtained with the use of freeze-dried sprouts (4980.05 μg/mL, 4795.62, 4211.25 μg/mL, respectively). Total antioxidant capacity (TAC) in vitro demonstrated UAE being a more valuable technique than conventional maceration. Furthermore, three-times-higher values of TPC (7.89 mg GAE/g) and TAC (FRAP: 24.01 mg TE/g; DPPH: 26.20 mg TE/g; ABTS 26.72 mg TE/g) were measured for the optimized extract compared to the initial one. An HPLC-DAD method was applied to monitor 5-CQA recovery, while an LC-HRMS/MS investigation allowed us to perform analyte identity confirmation along with detection of the glycoalkaloids α-solanine and α-chaconine. This evidence underlines the necessity to develop purification strategies in order to maximize the potential of potato sprout waste as a source of 5-CQA. [ABSTRACT FROM AUTHOR]

Chinese yam is a kind of food with high nutritional value. Browning is one of the main problems affecting the quality of Chinese yam during processing and storage. It is of great significance to effectively control the browning of Chinese yam, maintain its color and nutritional characteristics, and improve its shelf life in order to guarantee the quality of Chinese yam and improve the acceptance of consumers. On the basis of previous studies, the mechanism of enzymatic browning and non-enzymatic browning of Chinese yam are described in this paper. The mechanism of enzymatic browning of Chinese yam is explained by three elements of enzymatic browning including phenolic substrate, enzyme and oxygen, and the mechanism of Maillard reaction and non-enzymatic browning of caramelization in processing and storage of Chinese yam are introduced. In this paper, the control effects of different browning control techniques on Chinese yam are summarized, the existing problems are analyzed, and the future prospects are prospected, in order to provide reference for the research and application development of control techniques on Chinese yam browning.

Enzymatic browning caused by polyphenol oxidases, tyrosinase and laccase, continues to be one of the main problems in winemaking. Therefore, wineries are very interested in studying the mechanisms of browning and procedures for decreasing the use sulphur dioxide. This research proposes a model to study tyrosinase activity from grape must using different substrates: one monophenol (p -hydroxybenzoic acid), two diphenols (caftaric acid and (−)-epicatechin) and one triphenol (gallic acid). The kinetic constants of tyrosinase, Vmax and K M , indicate that caftaric acid is the best substrate for tyrosinase, followed in decreasing order by (−)-epicatechin, gallic acid and p -hydroxybenzoic acid. This last acid does not appear to be susceptible to browning by the action of grape must tyrosinase. The influence of pH, temperature and ethanol on grape must tyrosinase were also determined and the results indicate that tyrosinase Vmax increases when pH and temperature are higher and that the presence of ethanol reduces it. • A method to study the grape must tyrosinase activity is proposed. • This method has been proved with caftaric, gallic and p-hydroxycinnamic acids and (−)-epicatechin. • The kinetic constants, Vmax and KM, of grape tyrosinase have been determined for different substrates. • Caftaric acid is the best substrate for grape tyrosinase of all those studied • The influence of pH, temperature and ethanol on the kinetic constants have been studied [ABSTRACT FROM AUTHOR]

Browning significantly affects consumer perception, while texture hardening due to wound healing further reduces the commercial value of fresh-cut potatoes. This study evaluated the effects of 5 g L−1 ascorbic acid (AA), sodium isoascorbate (SI), and calcium ascorbate (CA) on browning and wound healing during ambient storage. The results indicated that AA and SI were more effective than CA and the control in delaying browning and wound healing. By day 3, browning levels in the AA and SI groups were reduced to 65 % and 62 % of the control, respectively, while lignin content decreased by 35 % and 40 %. Additionally, AA and SI treatments reduced reactive oxygen species (ROS) and improved antioxidant capacity, preserving appearance and texture. This study provides insights into the mechanisms of browning and wound healing, suggesting potential strategies for extending the shelf life and improving the quality of fresh-cut potatoes. • AA and SI treatments significantly delayed browning in fresh-cut potatoes. • AA and SI treatments effectively delayed wound healing, reducing lignin accumulation. • AA and SI treatments were linked to improved ROS metabolism and antioxidant capacity. • CA was less effective than AA and SI in controlling browning and wound healing. [ABSTRACT FROM AUTHOR]

Whole white button mushrooms (WWBM) exhibit a limited shelf-life owing to the oxidative enzymatic browning. Inactivation of polyphenol oxidase-PPO and peroxidase-POD in WWBM and its kinetic behavior were studied using pulsed light(PL) treatment (0.13–1.11 J/cm2). The first-order kinetics explained PL-induced enzyme inactivation. Rate constants(k) for PPO and POD were 3.84 and 2.55 cm2/J. FTIR-analysis revealed secondary-structural changes in partially-purified enzyme. PL-treatment retarded browning, retained phenolics and enhanced vitamin D 2. PL-treatment at 1.11 J/cm2 rendered WWBM both microbially and enzymatically stable. The PL-treated WWBM's shelf-life at 4, 20, and 37 °C were 5, 3, and 1 day. At 4 °C, browning increased by 6.1 %; firmness decreased by 55.2 %, while PL-treated mushrooms retained 90.6 % phenolics, 78.9 % antioxidant capacity, and 64.2 % D 2 after 5 days. Higher activation energy value confirmed phenolics were most sensitive during storage. PL-technology supports UN Sustainable Development Goals by reducing chemical use, lowering carbon-footprints, minimizing pollution, and enhancing shelf-life, promoting sustainable global trade. • Pulsed light (PL) treatment at 1.11 J/cm2 led to microbial and enzyme stablity. • First-order kinetics effectively explains PL-induced enzyme inactivation. • PL exposure leads to alteration in secondary structure of partially-purified enzyme. • PL treatment at 1.11 J/cm2 extends mushroom shelf life to 5 days at 4 °C. • PL-treated mushrooms retain 90 % phenolics, 79 % antioxidant, 64 % vitamin D 2 at 4 °C. [ABSTRACT FROM AUTHOR]

Lanzhou lily (Lilium davidii var. willmottiae) are known for its medicinal and culinary attributes and has gained popularity among consumers due to its distinct regional characteristics. However, the bulbs of Lanzhou lily are prone to browning during storage at room temperature, thus adversely affecting their quality and value. X-ray irradiation, a chemical residue-free, and energy-efficient physical technology, emerges as a promising solution for preserving freshly harvested the bulbs of Lanzhou lily. In this study, different doses of X-ray irradiation (0–400 Gy) were applied to the bulbs of freshly harvested Lanzhou lily stored at room temperature, aiming to explore the impact of irradiation on browning development, total phenolic content, and the activity of related antioxidases. The results revealed that X-ray irradiation, especially at the dose of 50 Gy, can effectively maintain the appearance and reduce the browning index (BI) of freshly harvested Lanzhou lily bulbs during storage. The 50 Gy X-ray treatment is found to significantly suppress the activity of polyphenol oxidase (PPO) and peroxidase (POD) in the bulbs of freshly harvested Lanzhou lily, thereby reducing enzymatic browning. Additionally, the X-ray irradiation can elevate the activity of phenylalanine ammonia-lyase (PAL), superoxide dismutase (SOD) and catalase (CAT) while decreasing the accumulation of malondialdehyde (MDA). This led to the preservation of cell membrane integrity, mitigation of lipid peroxidation (LOP), and a delay in browning process. These findings suggested that treating with 50 Gy X-ray irradiation can effectively slow down the color changes of Lanzhou lily bulbs during the storage under the room temperature, which is beneficial to extend the shelf-life of freshly harvested Lanzhou lily bulbs. • X-ray irradiation reduced the browning index of freshly harvested Lanzhou lily bulbs. • The process of membrane peroxidation of lily bulbs after X-ray irradiation was slowed down. • X-ray irradiation increased the activities of SOD and CAT. • X-ray irradiation (50 Gy) can extend the shelf-life of freshly harvested Lanzhou lily bulbs. [ABSTRACT FROM AUTHOR]

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]

Tyrosinase (Polyphenol oxidase), a key enzyme in enzymatic browning, is an attractive target for developing new anti-browning agents in the food industry. In this work, twenty pyrazole-1,2,4-triazole derivatives (3a-3n, 4a-4f) were synthesized and tested in vitro, most of compounds showed potent anti-tyrosinase activity. Of these, 3c (IC 50 = 1.02 ± 0.08 μM) was found to be 14 folds stronger than kojic acid (IC 50 = 14.74 ± 1.23 μM) and behaved as a mixed type inhibitor. Besides, the disappeared peak of dopaquinone in the HPLC assay intuitively validated the inhibitory effect of 3c. Copper ions chelating, fluorescence quenching and molecular docking assays showed that coordination with copper is the key to play a role. Furthermore, 3c exhibited excellent anti-browning ability for the Rosa roxburghii Tratt, the non-enzymatic browning experiment showed that 3c could prevent browning in non-enzymatic ways. It is suggested that these derivatives could serve as the leading compounds to find more efficient anti-browning agents in the future. [Display omitted] • A range of linear pyrazole-1,2,4-triazole derivatives were prepared. • The inhibitory activity of compound 3c is much stronger than that of kojic acid. • Compound 3c could effectively retard the browning of Rosa roxburghii Tratt. • Compound 3c could prevent enzymatic and non-enzymatic browning. [ABSTRACT FROM AUTHOR]

Enzymatic browning is always crucial for maintaining the visual quality of freshly cut vegetables. A high amount of onion peel waste is generated in the food industry globally, and it is rich source of various phytochemicals, possessing different biochemical properties. In this study, onion peel steam distillate has been used as a potential anti-browning agent to inhibit the browning-causing enzymes, i.e. polyphenol oxidase (PPO) and peroxidase (POD), in potato cubes. Studies with different extract-to-material ratio and treatment time were conducted to identify the optimum conditions for the pre-treatment process. Long-chain hydrocarbons tetratetracontane were found in the onion peel steam distillate which was found to inhibit the activity of PPO (84.78 ± 0.11%) and POD (21.30 ± 0.33%) in fresh cut potato cubes. Onion peel steam distillate was found to maintain the CIE colour values (L*, a*, b*) and total phenolic content during storage of potato cubes at 4 ± 1 °C for a period of 8 days. [ABSTRACT FROM AUTHOR]

[Display omitted] • MG-BLGNPs with different unfolding structures can be induced by heating and SDS. • LN can be loaded into MG-BLGNPs without altering their MG state to form MG-BLG@LN. • Unfolding degree of MG-BLGNPs is associated with enhanced binding and loading of LN. • CMC coatings embedded with MG-BLG@LN show great mechanical and adhesive properties. • MG-BLG@LN/CMC coating effectively mitigate quality deterioration in fresh-cut apples. This investigation employed molten globule state β-lactoglobulin nanoparticles (MG-BLGNPs) for encapsulating linalool (LN) combined with carboxymethyl chitosan (CMC) coating to enhance the shelf-life of fresh-cut apples. The effect of different MG structures on the encapsulation efficiency of BLGNPs and the properties of coating was studied. Structural characterization and molecular simulation showed structural differences between heat-induced MG state (70-BLGNPs, heated at 70 °C for 1 h) and sodium dodecyl sulfate- co -heat-induced MG state (SDS/70-BLGNPs, treated with 0.192 mg/mL SDS for 10 min, then heated at 70 °C for 1 h), with the latter being more unfolded. LN self-assembles into MG-BLGNPs, among the generated particles, SDS/70-BLG@LN exhibits stronger binding effect and higher LN loading capacity. Integration of MG-BLG@LN into CMC enhanced coating's mechanical properties and adhesion to fresh-cut apples. The SDS/70-BLG@LN/CMC coating showed superior preservation on fresh-cut apples during storage, reducing enzymatic browning, membrane lipid oxidation, and microbial growth while maintaining hardness and overall quality. [ABSTRACT FROM AUTHOR]

• Pre-cut L-cysteine activated cysteine and methionine metabolism in apples. • Pre-cut L-cysteine improved ACS, ACO activities and ethylene content. • AVG decreased the effect of pre-cut L-cysteine on browning of fresh-cut apples. • Pre-cut ethylene treatment also inhibited the browning of fresh-cut apples. Enzymatic browning is one of the main problems during storage of fresh-cut apples. Pre-cut treatment with L-cysteine has been shown to effectively inhibit browning on fresh-cut apples, but its mechanism is still unclear. This work investigated the browning-related differentially expressed genes (DEGs) after pre-cut treatment with L-cysteine, and analyzed the relationship between ethylene biosynthesis and L-cysteine through combining with aminoethoxyvinylglycine (AVG) treatment. The results indicated that lots of DEGs related to ethylene biosynthesis on fresh-cut apples were up-regulated, and the ethylene content, 1-aminocyclopropane-1-carboxilic acid (ACC) synthase and ACC oxidase activities were also improved after pre-cut L-cysteine. Further analysis found that AVG alleviated the effects of L-cysteine on the browning index, polyphenol oxidase (PPO) activity, peroxidase (POD) activity, catalase (CAT) activity and glutathione reductase (GR) activity of fresh-cut apples. Also, L-cysteine combined with AVG pretreatment reduced total phenol content and improved phenylalanine ammonia-lyase (PAL) activity compared with individual L-cysteine pretreatment. In addition, ethylene pretreatment also inhibited the browning and PPO activity, and increased POD activity, CAT activity and total phenol content on fresh-cut apples, which was better than that of L-cysteine combined with AVG pretreatment. This indirectly confirmed that pre-cut L-cysteine inhibited the browning of fresh-cut apples partly through regulating ethylene biosynthesis in vivo. The work proposes a novelty viewpoint that enhanced ethylene accumulation before cutting is helpful to inhibit the browning of fresh-cut apples. [Display omitted] [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]

The effects of γ-aminobutyric (GABA) on enzymatic browning, storage quality, membrane and reactive oxygen species (ROS) metabolism in fresh-cut stem lettuce were investigated. The results illustrated that GABA treatment delayed browning degree, polyphenol oxidase (PPO) activity and the expression of LsPPO. Meanwhile, higher chlorophyll and ascorbic acid contents were exhibited in GABA-treated stem lettuce, as well as the slower microbial propagation. Further investigation revealed that exogenous GABA application declined malondialdehyde content, electrolyte leakage and the enzyme activities of membrane metabolism, and the expression levels of related genes were also downregulated. In addition, GABA treatment scavenged ROS and strengthened the enzyme activities of ROS metabolism, as well as the expression levels of corresponding genes. Taken together, these findings implied that the repressed enzymatic browning and microbial propagation in GABA-treated stem lettuce were due to the inhibition of ROS accumulation, enhancement of membrane stability and increased resistance to oxidation. • Exogenous GABA inhibited the enzymatic browning of fresh-cut stem lettuce. • GABA treatment maintained the quality in fresh-cut stem lettuce. • GABA application inhibited the microbial propagation in fresh-cut stem lettuce. • GABA treated-fresh-cut stem lettuce exhibited higher membrane stability. • GABA treatment enhanced the antioxidant capacity in fresh-cut stem lettuce. [ABSTRACT FROM AUTHOR]

Fresh-cut pear fruit is greatly impacted by enzymatic browning, and maintaining quality remains a challenge. This study examined the impact of exogenous α-lipoic acid (α-LA) treatment on enzymatic browning and nutritional quality of fresh-cut pears. Results revealed that 0.5 g/L α-LA treatment effectively maintained color and firmness, and inhibited the increase in microbial number. The α-LA treatment also reduced MDA and H 2 O 2 contents, decreased PPO activity, and enhanced SOD, CAT, and PAL activities. The α-LA treatment notably upregulated phenolic metabolism-related gene expression, including PbPAL , Pb4CL , PbC4H , PbCHI and PbCHS , and then increasing total phenols and flavonoids contents. Furthermore, it also influenced carbohydrate metabolism-related gene expression, including PbSS , PbSPS , PbAI and PbNI , maintaining a high level of sucrose content. These findings indicated that α-LA treatment showed promise in reducing browning and enhancing fresh-cut pears quality, offering a potential postharvest method to prolong the lifespan and maintain nutritional quality. [Display omitted] • Flesh browning, MDA and H 2 O 2 contents were reduced by α-lipoic acid treatment. • α-Lipoic acid inhibited microbial growth and enhanced antioxidant capacity. • α-Lipoic acid maintained total phenols, flavonoids, and ascorbic acid contents. • α-Lipoic acid curbed PPO activity and enhanced PAL, CAT, and SOD activities. • α-Lipoic acid regulated genes expression in carbohydrate and phenolic metabolism. [ABSTRACT FROM AUTHOR]

Enzymatic browning and microbial contamination are pervasive issues contributing to the spoilage of fresh-cut fruits and vegetables, presenting a major challenge in food preservation. This study focuses on addressing these challenges by incorporating enriched (E)-cinnamaldehyde extract (CIN) from cinnamon bark (0.5, 1.0 and 2.0 mg/cm2) into cellulose acetate–based active packaging (CA-based AP) to assess both tyrosinase inhibition and antimicrobial properties, alongside a comprehensive evaluation of the physicochemical, barrier and mechanical properties. The research revealed that increasing the concentration of CIN in CA-based AP films increased the tyrosinase inhibition activity (44.75 ± 1.71 to 62.07 ± 1.56%) and antimicrobial inhibition zone (7.89 ± 0.51 to 22.44 ± 0.51 mm) on selected bacterial and fungal strains. Additionally, the incorporation of CIN enhanced UV absorption and water vapour transmission rate but also influenced thickness, moisture content, opacity, colour profile, mechanical strength and surface structure. Despite these changes, the films maintained their semi-crystalline structure and demonstrated efficient release of CIN. The study concludes that a sustainable and bio-renewable CA-based AP film, particularly with an optimal CIN concentration of 1.0 mg/cm2, exhibits balanced properties for the effective preservation of fresh-cut fruits and vegetables. This optimized innovative packaging solution not only combats spoilage mechanisms but also aligns with environmental sustainability goals. [ABSTRACT FROM AUTHOR]

This study aims to prolong the shelf-life and inhibit enzymatic browning of fresh-cut potatoes using mild processing methods, specifically osmotic dehydration and ohmic heating. Osmotic dehydration was refined by varying solution concentrations and immersion times, while ohmic heating was optimized by adjusting electric field strength and heating time using Response Surface Methodology (RSM) and full factorial design. Potatoes treated with osmotic dehydration, ohmic heating, and their combination under optimal conditions were assessed for weight loss, color change, enzymatic activity, microbial load, and sensory attributes. Results showed that osmotic dehydration alone produced the best outcomes in shelf-life, with minimal weight loss (5.2%), slight color change, reduced enzymatic activity (PPO activity reduced by 50%), effective microbial control (microbial load reduction of 3 log CFU/g), while ohmic heating led to superior sensory quality (overall acceptability score of 8.5). Conversely, the combination of osmotic dehydration and ohmic heating did not improve quality attributes and performed suboptimally. This research underscores the efficacy of osmotic dehydration in food preservation while recognizing the significant role of ohmic heating in enhancing sensorial quality, a critical factor for the commercial viability of food products.Graphical Abstract: This study aims to prolong the shelf-life and inhibit enzymatic browning of fresh-cut potatoes using mild processing methods, specifically osmotic dehydration and ohmic heating. Osmotic dehydration was refined by varying solution concentrations and immersion times, while ohmic heating was optimized by adjusting electric field strength and heating time using Response Surface Methodology (RSM) and full factorial design. Potatoes treated with osmotic dehydration, ohmic heating, and their combination under optimal conditions were assessed for weight loss, color change, enzymatic activity, microbial load, and sensory attributes. Results showed that osmotic dehydration alone produced the best outcomes in shelf-life, with minimal weight loss (5.2%), slight color change, reduced enzymatic activity (PPO activity reduced by 50%), effective microbial control (microbial load reduction of 3 log CFU/g), while ohmic heating led to superior sensory quality (overall acceptability score of 8.5). Conversely, the combination of osmotic dehydration and ohmic heating did not improve quality attributes and performed suboptimally. This research underscores the efficacy of osmotic dehydration in food preservation while recognizing the significant role of ohmic heating in enhancing sensorial quality, a critical factor for the commercial viability of food products. [ABSTRACT FROM AUTHOR]

The development of natural inhibitors of polyphenol oxidase (PPO) is crucial in the prevention of enzymatic browning in fresh foods. However, few studies have focused on the effect of subsequent sterilization on their inhibition efficiency. This study investigated the influence and mechanism of high hydrostatic pressure (HHP) on the inhibition of PPO by epigallocatechin gallate (EGCG), cyanidin-3-O-glucoside (C3G), and ferulic acid. Results showed that under the conditions of 550 MPa/30 min, the activity of EGCG-PPO decreased to 55.92%, C3G-PPO decreased to 81.80%, whereas the activity of FA-PPO remained stable. Spectroscopic experiments displayed that HHP intensified the secondary structure transformation and fluorescence quenching of PPO. Molecular dynamics simulations revealed that at 550 MPa, the surface interaction between PPO with EGCG or C3G increased, potentially leading to a reduction in their activity. In contrast, FA-PPO demonstrated conformational stability. This study can provide a reference for the future industrial application of natural inhibitors. • HHP treatment improved the inhibitory efficiency of PPO by EGCG or C3G • The activity of FA-PPO remained stable even at 550 MPa/30 min • TEM observed that HHP promoted the aggregation of PPO in the presence of EGCG • MD simulations showed an increase in interaction between PPO and inhibitors under HHP • FA was embedded inside the PPO to form a complex that exhibited pressure stability [ABSTRACT FROM AUTHOR]

Enzymatic browning is one of the reactions influencing the quality of some fruit juices such as quince juice. Nowadays, there is an increased demand for application of antibrowning agents. This research was aimed at the effects of using each ethanolic and aqueous apple peel extracts (EAPE, AAPE) in two concentrations (0.3 and 3%) as inhibitor agents for polyphenol oxidase activity (PPO) of quince juice and their effects on the browning index (BI), total soluble solids (TSS), pH, total titratable acidity (TA), and total phenolic content (TPC) during storage at 4°C for 15 d. The effectiveness of 3% (w/v) alcoholic apple peel extract efficiently inactivated the activities of PPO compared with another three extracts during whole refrigerated storage time. The lowest inhibition percentage value of BI was found in 0.3% AAPE supplemented quince juices. EAPE and AAPE with concentrations of 3% had significantly larger pH values than that of EAPE and AAPE with concentration 0.3% and untreated quince juices at a final day of cold storage. TA values of juice samples untreated and treated with apple extracts did not show significant changes that ranged between 74-75 mg/100 ml at the beginning of storage and decreased with increased storage time, ranging between 0.68-0.72 mg/100 ml at the end of storage. The addition of apple peel extracts during the storage of quince juice had a positive effect on TSS values of the samples. Significantly larger TPC values (P

In this work, the influence of citric acid & pomelo essential oil nanoemulsion (CA&PEN) assisted with HHP on microbial counts, oxidative enzyme activity and related quality of banana puree were examined. The total aerobic bacteria (TAB) counts of all groups decreased to 1.2 ∼ 2.52 lg CFU/g from 3.97 lg CFU/g, except the CA&PEN group, which was still below the detection level. CA&PEN combined with HHP (500 or 600 MPa, 5 min) succeeded in keeping TAB counts of banana puree below the detection limit for 3 months of cold storage. During 90 days of cold storage, the color, total phenolics, DPPH and ABTS antioxidant capacities were better conserved in acidified groups than non-acidified groups. In conclusion, CA&PEN assisted with HHP can be utilized to promote the inhibition of enzymatic browning and maintain the quality of banana puree, due to its reduced oxidative enzyme activity, low pH, strong antioxidant capacity and excellent color retention.