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Increasingly globally prevalent obesity and related metabolic disorders have underscored the demand for safe and natural therapeutic approaches, given the limitations of weight loss drugs and surgeries. This study compared the phytochemical composition and antioxidant activity of five different varieties of citrus physiological premature fruit drop (CPFD). Untargeted metabolomics was employed to identify variations in metabolites among different CPFDs, and their antilipidemic effects in vitro were assessed. The results showed that Citrus aurantium L. ' Daidai ' physiological premature fruit drop (DDPD) and Citrus aurantium ' Changshan-huyou ' physiological premature fruit drop (HYPD) exhibited higher levels of phytochemicals and stronger antioxidant activity. There were 97 differential metabolites identified in DDPD and HYPD, including phenylpropanoids, flavonoids, alkaloids, organic acids, terpenes, and lipids. Additionally, DDPD and HYPD demonstrated potential antilipidemic effects against oleic acid (OA)-induced steatosis in HepG2 hepatocytes and 3T3-L1 adipocytes. In conclusion, our findings reveal the outstanding antioxidant activity and antilipidemic effects of CPFD, indicating its potential use as a natural antioxidant and health supplement and promoting the high-value utilization of this resource.

To investigate the influence of heat treatment (HT) on Satsuma mandarin fruit's postharvest quality and cuticle composition, we immersed the fruit for 3 min in hot water at 52°C and subsequently stored them at room temperature (25°C) for 28 days, and fruit quality parameters, such as good fruit rate, weight loss rate, firmness, total soluble solids, total titratable acidity, and ascorbic acid content, were monitored. Additionally, changes in the peel's cuticle composition were analyzed, and wax crystal morphologies on the fruit surface were examined using scanning electron microscopy (SEM). The findings revealed that appropriate HT effectively preserved fruit quality. The main compositions of wax and cutin on the fruit's surface remained consistent between the HT and the CK during storage. The total content of wax and cutin initially increased, peaking on the 14th day of storage, and then decreased, falling below the levels observed on day 0. Notably, the total amount of cutin in the HT group exceeded that of the control group. Specifically, ω-hydroxy fatty acids with mid-chain oxo groups and mid-oh-ω-hydroxy fatty acids constituted approximately 90% of the total cutin content. Moreover, the HT group exhibited higher (p < 0.05) total wax content in relation to the control. Fatty acids and alkanes were the predominant components, accounting for approximately 87.5% of the total wax. SEM analysis demonstrated that HT caused wax crystals to melt and redistribute, effectively filling wax gaps. It suggests that HT holds promising potential as a green, safe, and eco-friendly commercial treatment for preserving the postharvest quality of Satsuma mandarin. PRACTICAL APPLICATION: In this study, Satsuma citrus (Citrus unshiu) underwent heat treatment (HT) and was subsequently preserved at room temperature (25°C) for 28 days. The findings revealed that HT significantly improved fruit quality compared to the control group. These findings provide valuable insights into the advancement of eco-friendly and pollution-free citrus preservation methods, offering essential strategies and process parameters for their practical application., (© 2023 Institute of Food Technologists.)

Listeria monocytogenes, which could cause severe disease of listeriosis, is one of the most concerned foodborne pathogens worldwide. Citrus medica L. var. sarcodactylis Swingle (Fingered Citron) is one of the citrus species cultivated in south China. Here, we investigated the efficacy of Fingered Citron essential oil (FCEO) against L. monocytogenes and explored the response of L. monocytogenes in the presence of FCEO using genome-wide transcriptome analysis. FCEO exhibited strong anti-listeria activity and obvious alterations of cell morphology were observed by scanning electron microscopy and transmission electron microscopy. Moreover, GO analysis demonstrated many potential cell responses, including metabolic process, cellular process, single-organism process, cell part, membrane, catalytic activity, binding, and transporter activity. KEGG analysis suggests that L. monocytogenes respond and adapt by (1) increasing motility through the enhancement of flagella rotation; (2) promoting cell tumbles and re-orientating to escape from FCEO; (3) enhancing the uptake of carbohydrates from environment to gain more energy; (4) changing the uptake of several metallic cations, including iron, zinc, cobalt, and nickel. Our research contributes to the understanding of the adaptive responses of L. monocytogenes exposed to FCEO and provides novel insights for finding new targets of anti-listeria therapy., (Copyright © 2021. Published by Elsevier Ltd.)

The Dicer protein is one of the most important components of RNAi machinery because it regulates the production of small RNAs (sRNAs) in eukaryotes. Here, Dicer1-like gene (Pit-DCL1) and Dicer2-like gene (Pit-DCL2) RNAi transformants were generated via pSilent-1 in Penicillium italicum (Pit), which is the causal agent of citrus blue mold. Neither transformant showed a change in mycelial growth or sporulation ability, but the pathogenicity of the Pit-DCL2 RNAi transformant to citrus fruits was severely impaired, compared to that of the Pit-DCL1 RNAi transformant and the wild type. We further developed a citrus wound-mediated RNAi approach with a double-stranded fragment of Pit-DCL2 generated in vitro, which achieved an efficiency in reducing Pi-Dcl2 expression and virulence that was similar to that of protoplast-mediated RNAi in P. italicum, suggesting that this approach is promising in the exogenous application of dsRNA to control pathogens on the surface of citrus fruits. In addition, sRNA sequencing revealed a total of 69.88 million potential sRNAs and 12 novel microRNA-like small RNAs (milRNAs), four of which have been predicated on target innate immunity or biotic stress-related genes in Valencia orange. These data suggest that both the Pit-DCL1 and Pit-DCL2 RNAi transformants severely disrupted the biogenesis of the potential milRNAs, which was further confirmed for some milRNAs by qRT-PCR or Northern blot analysis. These data suggest the sRNAs in P. italicum that may be involved in a molecular virulence mechanism termed cross-kingdom RNAi (ck-RNAi) by trafficking sRNA from P. italicum to citrus fruits.

To elucidate the role of fruit cuticle in fungal infection, changes in cuticle composition and morphology of 'Satsuma' mandarin during ambient (at 25 °C) storage and their role in Penicillium digitatum infection were investigated. Results showed that the epicuticular wax yield increased from 1.11 μg cm -2 to 4.21 μg cm -2 during storage for 20 days and then decreased to 1.35 μg cm -2 as storage time prolonged to 40 days. Intracuticular wax content of fruits stored for 20 days showed a peak value that was 1.7-fold higher than that of fruits stored for 40 days. The contents of cutin monomers of fruits showed a decreased trend during storage, while their proportions in the cutin stayed stable. Acids were identified as the most abundant components in epicuticular wax independently of the storage time, followed by alkanes and terpenoids. Terpenoids were found as the predominant components in intracuticular wax during the whole storage, followed by alkanes and acids. The flattened platelets crystals of fruits at harvest changed into small granule-like wax ones after 10 days of storage then gradually distributed across the surface of the fruits as stored for 40 days. Results of in vitro tests showed that mycelial growth of Penicillium digitatum could be promoted by epicuticular wax and conidial germination could be inhibited by cutin at different storage stages. These results shed new light on the chemical basis for cuticle involvement in fungal infection.

This study aimed to compare the flavonoid accumulation between ozone-treated and untreated Satsuma mandarin ( Citrus unshiu Marc.) fruits. The fruits exposed to gaseous ozone were found to have higher antioxidant activities and content of flavonoid during the storage period by ultra-high performance liquid chromatography (UPLC). To reveal the molecular regulation of flavonoid accumulation by ozone, chalcone synthase ( CHS ), chalcone isomerase ( CHI ), β-1,3-glucanase ( GLU ), chitinase ( CHT ), phenylalanine ammonia-lyase ( PAL ), and peroxidase ( POD ) were identified and their expression was examined by quantitative real-time polymerase chain reaction (q-PCR). These results support the promising application of ozone treatment as a safe food preservation technique for controlling postharvest disease and extending shelf-life of harvested Satsuma mandarin., Competing Interests: The authors declare no conflict of interest.

The eco-friendly polyelectrolyte bilayer films were prepared by layer-by-layer (LBL) casting method using chitosan (CS) and four types of edible citrus pectin as film substrates. The results showed that the polyelectrolyte bilayer films exhibited excellent comprehensive properties. Furthermore, the interaction between CS and pectin was closely related to the degree of methyl-esterification (DM), molecular weight (Mw), and zeta potential of pectin. The low DM, Mw, and high zeta potential of the low methyl-esterified pectin (LM) resulted in a denser internal structure of the bilayer film, stronger UV shielding performance, and stronger gas barrier ability. The high DM and Mw of the high methyl-esterified pectin (HM) endow the bilayer film with stronger mechanical properties, thermal stability, and antifogging property. The microstructural and spectroscopic analysis showed that there are hydrogen bonds and electrostatic interactions between the layers. Overall, the developed CS-pectin polyelectrolyte bilayer films provided potential applications for food bioactive packaging. [ABSTRACT FROM AUTHOR]

The nondestructive characterization of citrus varieties (Egyptian sweet orange, Lane Late navel orange, Australian orange, and Blood orange) was developed based on near-infrared diffuse reflectance spectroscopy (NIRDRS) together with principal component analysis (PCA) and Fisher linear discriminant analysis (FLDA). An experiment for the penetration of NIRDRS into the peel was designed and the effects of different spectral acquisition points were investigated. Pretreatments were used to eliminate the spectral interferences. As an unsupervised pattern recognition method, PCA was used to establish the characterization models. Furthermore, supervised pattern recognition based on PCA and FLDA was employed to enhance the accuracy. The results of the penetration experiments show that near-infrared light enters the citrus peel and is able to characterize the internal composition. Even with the optimized spectral pretreatment, accurate characterization of citrus varieties was not achieved by PCA. However, the accurate characterization of citrus varieties was provided by PCA-FLDA. The accuracies of four spectral acquisition points are 95%, while the characterization accuracies of six spectral acquisition points are 100% combined with optimized spectral pretreatment. Therefore, NIRDRS with PCA-FLDA is suitable for the rapid and nondestructive characterization of citrus varieties. [ABSTRACT FROM AUTHOR]

The lack of a direct connection between solid edible or medical natural products and bioactive compound profiling is a bottleneck in natural product research and quality control. Here, a novel integrated system, online extraction (OLE)–2,2′-diphenyl-1-picrylhydrazyl (DPPH)–HPLC−DAD−QTOF-MS, was fabricated to extract, screen, and identify antioxidants from the whole fruit of Citrus aurantium L. var. amara (CAVA, Rutaceae) simply, rapidly, and efficiently. The system consumes less sample (1.0 mg of CAVA powder) and requires a shorter analytical time (45 min for sample extraction, antioxidants screening, separation, and identification). Eight antioxidant flavonoids were screened and identified, and six available flavanones were sensitively, precisely, and accurately quantified. Two major flavanone glycosides, naringin (50.37 ± 0.43 mg/g) and neohesperidin (38.20 ± 0.27 mg/g), exhibit potent DPPH scavenging activities with IC50 values of 111.9 ± 10.06 and 178.55 ± 11.28 μg/mL. A minor flavanone aglycone, hesperitin (0.73 ± 0.06 mg/g), presents stronger DPPH scavenging activity (IC50, 39.07 ± 2.51 μg/mL). Furthermore, density functional theory calculations demonstrated their electron transport ability and chemical reactivity, which confirmed the screened results. The results indicate that the developed OLE–DPPH–HPLC−DAD−QTOF-MS system provides new perspectives for analysis of antioxidants from complex natural products, which also contribute to the quality evaluation of CAVA. [ABSTRACT FROM AUTHOR]

This study employs a near‐infrared diffuse reflectance spectroscopy (NIRDRS) system to accurate nondestructive determine citrus soluble solids content (SSC). The penetration experiment results showed that the interference of thick peel is large and NIRDRS light has the ability to penetrate the peel to a certain extent. Partial least squares with different characteristic variable selection methods were used to establish the quantitative model of SSC. The results demonstrated that characteristic variable selection methods can select targeted characteristic variables and improve the accuracy with few variables. Monte Carlo‐uninformative variable elimination method was selected as the optimal prediction performance. In the best prediction model, the correlation coefficient and root mean square error of prediction of the prediction set are 0.854 and 0.7%Brix, respectively, while the variable number decreases to 440 from 1557. Furthermore, the models using the average spectra of four points on the equator are the most appropriate. Novelty impact statement: The penetrating ability of near‐infrared diffuse reflectance spectroscopy (NIRDRS) light to thick peel and the prediction of internal quality of citrus is still unsatisfactory with traditional partial least squares (PLS) algorithm due to the interference of thick peel. In this study, a nondestructive method for the analysis of soluble solids content (SSC) in citrus was established by NIRDRS with characteristic variable selection algorithms. The results demonstrated that NIRDRS light has the ability to penetrate the peel to a certain extent, while characteristic variable selection methods can select targeted characteristic variables and improve the accuracy of quantitative analysis models with fewer variables. [ABSTRACT FROM AUTHOR]

Aspergillus aculeatus ZC-1005 (ZC-1005 was used as the abbreviation of this strain) is a hemicellulase-producing strain isolated from rotten citrus rind buried in the soil. Our previous study has shown its biochemical properties including high xylanase activity, mannanase activity, and degradation reaction with citrus mesocarp. In this study, we focused more on the enzyme safety evaluation and the genome sequencing via PacBio and Illumina platforms. High biological safety of the crude enzymes of ZC-1005 has been proven by the acute oral toxicity test, sub-chronic toxicity test, micronucleus test, and sperm malformation test. The genome of ZC-1005 had a GC content of 52.53%, with a size of 35,458,484 bp, and encoded 10,147 genes. Strain ZC-1005 harbored 269 glycosyl hydrolase (GH) genes of 64 families. The fungus produces cellulose-acting (GH3, GH5, GH12, and GH1) and hemicellulose-acting enzymes (GH16, GH31, GH2, and GH92). In genome annotation, we paid more attention to the genes encoding xylanase, such as gene 01512, gene 05833, gene 05469, gene 07781, gene 08432, gene 09042, gene 08008, and gene 09694. The collaboration between complete genome information and the degradation test confirmed that ZC-1005 could degrade cellulose and xylan. Our results showed that the citrus enzymatic decapsulation technology was efficacious and safe for canned citrus product processing, which may also solve the industrial waste problem. Therefore, ZC-1005 and the crude enzyme secreted from the strain were very promising to be used in the citrus processing industry. [ABSTRACT FROM AUTHOR]

A simple and nondestructive method for the analysis of soluble solid content in citrus was established using portable visible to near‐infrared spectroscopy (Vis/NIRS) in reflectance mode in combination with appropriate chemometric methods. The spectra were obtained directly by the portable Vis/NIRS without destroying samples. Outlier detection was performed by using leave‐one‐out cross‐validation (LOOCV) with the 3σ criterion, and the calibration models were established by partial least squares (PLS) algorithm. Besides, different data pretreatment methods were used to eliminate noise and background interference before calibration, to determine the one that will lead to better model accuracy. However, the correlation coefficients are all <0.62 and the results of all pretreatments are still unsatisfactory. Variable selection methods were discussed for improving the accuracy, and variable adaptive boosting partial least squares (VABPLS) method was used to get higher robustness models. The results show that standard normal variate (SNV) transformation is the best pretreatment method, while VABPLS can significantly simplify the calculation and improve the result even without pretreatment. The correlation coefficient of the best prediction models is 0.82, while the value is 0.48 for the raw data. The high performance shows the feasibility of portable Vis/NIRS technology combination with appropriate chemometric methods for the determination of citrus soluble solid content. [ABSTRACT FROM AUTHOR]

Aspergillus japonicas PJ01 (A. japonicas PJ01) is a strain isolated from the rotten branches. In previ-ous studies, it was shown that it can produce complex enzymes to degrade polysaccharide com-ponents. In this study, we evaluated the safety of its crude enzyme solution. Acute oral toxicity, subchronic toxicity, micronucleus and sperm malformation tests all validated the high biologi-cal safety for the crude enzymes. Secondly, we carried out the citrus segment degradation ex-periment of crude enzyme solution. Compared with the control group, the crude enzyme solu-tion of A. japonicas PJ01 can completely degrade the segments in 50 min, which provides the basis for enzymatic peeling during juice processing. The whole genome sequencing showed that the genome of A. japonicus PJ01 has a GC content of 51.37% with a size of 36204647 bp, and encoded 10070 genes. GO, COG, KEGG and CAZy databases were used in gene annotation analyses. Pathway enrichment showed many genes related to carbohydrate metabolism, rich in genes re-lated to pectinase, xylanase and carboxylcellulase. Therefore, the complex enzyme produced by A. japonicus PJ01 can be used in gizzard juice processing to achieve efficient enzymatic decapsu-lation. [ABSTRACT FROM AUTHOR]

The design of functional delivery systems is crucial for achieving sustained flavor release in food products. In this study, we compared the stabilizing effects of β-cyclodextrin (CD)-based Pickering emulsions loaded with lemon essential oil (LEO) mediated by cellulose nanocrystals (CNC) and bacterial cellulose (BC). We also explored the potential mechanisms underlying the sustained flavor release in terms of emulsion properties, droplet micromorphology, and interfacial properties. CNC and BC mediation improved the overall stability of emulsions, primarily reflected by increased droplet dispersion and a slight reduction in droplet size (from 10.83 μm to 6.20 and 6.99 μm, respectively). High concentrations (0.12% and 0.24%) of BC mediation led to a sharp increase in emulsion viscosity (from 56.60 to 1872.57 and 6194.29 mPa s, respectively), and the strong network formed by BC in the continuous phase prevented droplet migration. In contrast, the distribution of CNC at the oil-water interface allowed droplets to possess a double-layer interfacial structure, effectively enhancing interfacial tension and interfacial dilatation modulus, and creating a greater barrier to LEO diffusion. These findings provide a scientific basis for the structural design of delivery systems to achieve regulated release of flavor factors. [Display omitted] • Cellulose was utilized to stabilize β-cyclodextrin-based essential oil emulsions. • Bacterial cellulose can enhance emulsion stability by increasing its viscosity. • Cellulose nanocrystals improve emulsion stability via adsorption at the interface. • Emulsion viscosity and interfacial layer restrained the flavor release of the emulsions. • Interfacial barrier was more effective in delaying the diffusion of essential oil. [ABSTRACT FROM AUTHOR]

In this paper, the penetration ability of near infrared (NIR) diffuse reflectance light to peel was studied with grating NIR spectrometer. 15 kinds of fruit, including 3 kinds of thin-peel non-citrus fruit, 9 kinds of medium-peel citrus and 3 kinds of thick-peel citrus were investigated. A new strategy to evaluate the NIR penetration ability was developed with a designed penetration experiment and chemometric methods. The penetration abilities of different integration time, peel thickness and wavelength bands were compared. The results show that NIR light can easily penetrate the peel of thin-peel fruit, while it is not easy to penetrate the peel of citrus due to the thick peel. Both the thickness and composition of the peel have relationship with the penetration ability. Increase of integration time can improve the penetration ability to some extent. However, as the integration time lengthens, noise interference and spectral distortion may appear in long wave near infrared (LWNIR) region. The optimal integration time is 65 ms for citrus. Besides, the penetration ability of short wave near infrared (SWNIR) light is better than that of LWNIR light, and the absorption peaks of peel are mainly located in LWNIR region, indicating that SWNIR is more suitable for fruit internal quality detection. [Display omitted] • A new method to evaluate the NIR penetration ability of peel was developed. • Penetrability of integration time, peel thickness and wavelength was compared. • It is not easy for NIR light to penetrate peel of citrus due to the thick peel. • Increase of integration time can improve NIR penetration ability to some extent. • Penetration ability of SWNIR light is better than those of LWNIR light. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes (L. monocytogenes) is an important foodborne pathogen which may cause listeriosis and poses potential risks to human health. The aim of this study was to estimate the efficacy of essential oil from Citrus Changshan - huyou Y.B. Chang (Huyou) on both planktonic cells and biofilm against L. monocytogenes , and further to elucidate the potential mechanism of this action. Results showed that Citrus Changshan - huyou Y.B. Chang essential oil (Huyou EO) exhibited significantly in vitro antimicrobial ability against L. monocytogenes , both of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations confirmed the physical damage, considerable morphological alteration and the leakage of intracellular constituents. Meanwhile, XTT and crystal violet (CV) assay indicated that Huyou EO was able to destroy preformed biofilm through decreasing the biomass and cellular activity. SEM, confocal scanning laser microscopy (CLSM) and COMSTAT analysis revealed the extensive disruption and architectural changes of biofilm. Moreover, the potential antimicrobial mechanisms were demonstrated by RNA sequencing. Enriched GO analysis identified 8 terms related to cellular components (CC), 50 terms for biological processes (BP) and 21 terms for molecular functions (MF). 35 pathways were significantly enriched in KEGG analysis. The transcriptome analysis offered novel antimicrobial molecular mechanisms of Huyou EO. • Huyou EO exhibited significant antimicrobial ability against planktonic L. M cells • Huyou EO could significantly destroy the preformed biofilm of L.M • SEM and TEM results showed the morphological changes of L.M • The potential antimicrobial mechanisms were demonstrated by RNA sequencing • Huyou EO have great potential to be used as a preservative in food industry [ABSTRACT FROM AUTHOR]

An accurate and nondestructive detection method of hidden mold infection in citrus was established based on portable near infrared diffuse reflectance spectroscopy and chemometric methods. [Display omitted] • Nondestructive detection of hidden mold infection in citrus was achieved. • NIRDRS light was demonstrated to penetrate the citrus peel. • Models were validated by the validation and external validation sets. • Identification models of LWNIR were much better than those of SWNIR. • Identification accuracy of LWNIR-DT-PLS-DA model was 100%. An accurate and nondestructive detection method of hidden mold infection in citrus was established based on portable near infrared diffuse reflectance spectroscopy (NIRDRS) and chemometric methods. Penetrability of NIRDRS light on the peel of Chunjian hybrid citrus was studied. The results show that NIRDRS light can penetrate the peel to a certain extent, while the penetrability of short-wave near infrared (SWNIR) was better than that of long-wave near infrared (LWNIR). The identification models of hidden mold infection were established with five pattern recognition methods combined with different wavelength bands. The results show that the identification models of LWNIR were much better than those of SWNIR. 100% identification accuracies of LWNIR were obtained with soft independent pattern classification (SIMCA), support vector machine (SVM), partial least squares discriminant analysis (PLS-DA) and the optimized pretreatment methods. In addition, the developed models were further validated by the external validation set collected one month later. [ABSTRACT FROM AUTHOR]

Abstract In this work, the chemical composition, antimicrobial and antioxidant activities of fourteen species of citrus essential oils (EOs) from the main cultivated varieties in China were evaluated and compared. A total of more than 200 components were identified, which are mainly composed of terpenes, alcohols, aldehydes, esters, ketones and acids. Antimicrobial ability of fourteen EOs and seven major components were tested against six bacteria and two yeasts. The susceptibility of Gram-positive bacteria tested was observed to be greater than Gram-negative bacteria, and the yeasts tested were relatively more susceptive than bacteria. Three groups (Strong, Medium and Weak) were divided according to the antimicrobial ability. The EOs of Citrus Changshan huyou B. Chang and Citrus. medica var. sarcodactylis Swin exhibited the strongest antimicrobial activity against all tested strains. Linalool showed the strongest antimicrobial activity against all microorganisms except Pseudomonas aeruginosa. Three characters and tendencies were found out to correlate chemical composition with antimicrobial activity of different citrus essential oils. The EOs of Citrus aurantium L and Citurs medica var. sarcodactylis Swing showed strong ABTS radical scavenging, and the EOs of Citurs medica var. sarcodactylis Swing and Citrus Changshan huyou B. Chang exhibited strong free radical scavenging activity. Highlights • Chemical composition analysis of 14 citrus EOs of main citrus varieties in China. • Comparison of antimicrobial and antioxidant activity of 14 citrus EOs. • EO of Citrus Changshan huyou B. Chang showed the strongest antimicrobial activity. • EO of Citurs medica var. sarcodactylis Swing showed the best antioxidant activities. • Correlation between chemical composition, antimicrobial and antioxidant activity. [ABSTRACT FROM AUTHOR]