Postharvest Application of 24-Epibrassinolide Reduces Chilling Injury Symptoms and Enhances Bioactive Compounds Content and Antioxidant Activity of Blood Orange Fruit

Mechanisms of Litchi Response to Postharvest Energy Deficiency via Energy and Sugar Metabolisms

In the post-harvest phase, fruit is inexorably subjected to extrinsic stressors that expedite energy expenditure and truncate the storage lifespan. The present study endeavors to elucidate the response strategies of litchi to the alterations of energy state caused by 2,4-Dinitrophenol (DNP) treatment through energy metabolism and sugar metabolism. It was observed that the DNP treatment reduced the energy state of the fruit, exacerbated membrane damage and triggered rapid browning in the pericarp after 24 h of storage. Furthermore, the expression of genes germane to energy metabolism (LcAtpB, LcAOX1, LcUCP1, LcAAC1, and, LcSnRK2) reached their peak within the initial 24 h of storage, accompanied by an elevation in the respiratory rate, which effectively suppressed the rise in browning index of litchi pericarp. The study also posits that, to cope with the decrease of energy levels and membrane damage, litchi may augment the concentrations of fructose, glucose, inositol, galactose, and sorbose, thus safeguarding the canonical metabolic functions of the fruit. Collectively, these findings suggest that litchi can modulate energy and sugar metabolism to cope with fruit senescence under conditions of energy deficiency. This study significantly advances the understanding of the physiological responses exhibited by litchi fruit to post-harvest external stressors.

Anthocyanin in blood oranges: a review on postharvest approaches for its enhancement and preservation

Anthocyanin concentration is considered an important fruit quality index of blood oranges and has gained popularity among consumers due to its antioxidant capacity, therapeutic properties, and prevention of some human diseases. Anthocyanin biosynthesis occurs in the cytoplasmic face of the endoplasmic reticulum by multi-enzymes complexes through the flavonoid pathway. Polyphenoloxidase (PPO) and β-glucosidase (anthocyanase) are the enzymes responsible for anthocyanin degradation. Blood oranges are cold-dependent for anthocyanin biosynthesis and accumulation, and thus, the low temperature of storage can enhance anthocyanin concentration and improve internal fruit quality. In addition, anthocyanin accumulation can be accelerated by postharvest technologies, either physical treatments or chemical elicitors. However, low temperatures can induce chilling injury (CI) incidence in blood oranges. Postharvest chemical elicitors treatments can enhance anthocyanin accumulation and prevent CI. This review provides the most updated information about postharvest tools modulating the anthocyanin content, and the role of enhancing and preserving pigmentation to produce blood orange with the highest quality standards.

Efficacy of 24-epibrassinolide-chitosan composite coating on the quality of 'Williams' bananas during ripening

BACKGROUND

Banana fruit undergo rapid metabolic changes following the induction of ripening. They result in excessive softening, chlorophyll degradation, browning, and senescence during postharvest life. As part of a continuous effort to extend fruit shelf life and maintain the best possible quality, this study examined the effect of a 24-epibrassinolide (EBR) and chitosan (CT) composite coating on 'Williams' bananas ripening in ambient conditions. Fruit were soaked in 20 μM EBR, 10 g L-1 CT (w/v), and 20 μM EBR + 10 g L-1 CT solutions for 15 min and were kept at 23 ± 1 °C and 85-90% (RH) for 9 days.

RESULTS

The combined treatment (20 μM EBR + 10 g L-1 CT) clearly delayed fruit ripening; bananas treated with this showed less peel yellowing, weight loss, and total soluble solids, and greater firmness, titratable acidity, membrane stability index, and ascorbic acid content than the untreated control. After the treatment, the fruit also presented higher radical scavenging capacity, and higher total phenol and flavonoid content. The activity of polyphenoloxidase and hydrolytic enzymes was lower, and that of peroxidase was higher in both the peel and pulp of all the treated fruit than in the control.

CONCLUSION

The combined treatment (20 μM EBR + 10 g L-1 CT) is suggested as an effective composite edible coat to retain the quality of 'Williams' bananas during ripening. © 2023 Society of Chemical Industry.

Ultrasound Treatment Improves Fruit Quality of Postharvest Blood Oranges (Citrus sinensis L. Osbeck): Anthocyanin Enrichment and Its Biosynthesis

This study was to investigate the effects of different nonthermal treatments on quality attributes, anthocyanin profiles, and gene expressions related to anthocyanin biosynthesis during low-temperature storage, including pulsed light (PL), magnetic energy (ME), and ultrasound (US). Among these treatments, 1 min US treatment was the most effective method for improving fruit quality and increasing total anthocyanin contents (by 29.89 ± 3.32%) as well as individual anthocyanins during low-temperature storage of 28 days. This treatment resulted in high color intensity, intact cellular architectures, and positive sensory evaluation. In contrast, PL and ME treatments displayed negative effects on quality improvement, leading to the destruction of cell architectures and inhibiting anthocyanin levels. Furthermore, qPCR analysis revealed that the structural genes (C4H, CHS1, CHS2, CHI, F3H, ANS, and GST) related to anthocyanin biosynthesis and transport were the target genes and upregulated in response to the cavitation effect of US treatment.

Role of melatonin in enhancing arbuscular mycorrhizal symbiosis and mitigating cold stress in perennial ryegrass (Lolium perenne L.)

Melatonin is a biomolecule that affects plant development and is involved in protecting plants from environmental stress. However, the mechanisms of melatonin's impact on arbuscular mycorrhizal (AM) symbiosis and cold tolerance in plants are still unclear. In this research, AM fungi inoculation and exogenous melatonin (MT) were applied to perennial ryegrass (Lolium perenne L.) seedlings alone or in combination to investigate their effect on cold tolerance. The study was conducted in two parts. The initial trial examined two variables, AM inoculation, and cold stress, to investigate the involvement of the AM fungus Rhizophagus irregularis in endogenous melatonin accumulation and the transcriptional levels of its synthesis genes in the root system of perennial ryegrass under cold stress. The subsequent trial was designed as a three-factor analysis, encompassing AM inoculation, cold stress, and melatonin application, to explore the effects of exogenous melatonin application on plant growth, AM symbiosis, antioxidant activity, and protective molecules in perennial ryegrass subjected to cold stress. The results of the study showed that compared to non-mycorrhizal (NM) plants, cold stress promoted an increase in the accumulation of melatonin in the AM-colonized counterparts. Acetylserotonin methyltransferase (ASMT) catalyzed the final enzymatic reaction in melatonin production. Melatonin accumulation was associated with the level of expression of the genes, LpASMT1 and LpASMT3. Treatment with melatonin can improve the colonization of AM fungi in plants. Simultaneous utilization of AM inoculation and melatonin treatment enhanced the growth, antioxidant activity, and phenylalanine ammonia-lyase (PAL) activity, while simultaneously reducing polyphenol oxidase (PPO) activity and altering osmotic regulation in the roots. These effects are expected to aid in the mitigation of cold stress in Lolium perenne. Overall, melatonin treatment would help Lolium perenne to improve growth by promoting AM symbiosis, improving the accumulation of protective molecules, and triggering in antioxidant activity under cold stress.

Changes in Polyphenolic Compounds of Hutai No. 8 Grapes during Low-Temperature Storage and Their Shelf-Life Prediction by Identifying Biomarkers

The aim of this experiment was to assess the effect of different storage temperatures on the texture quality, phenolic profile, and antioxidant capacity of a grape. Fresh grapes were stored at 4 and 25 °C for nine days and sampled on alternate days. The hardness, total phenolics, total flavanones, total flavanols, total anthocyanin content, antioxidant activity, differential metabolite screening, and key gene expression were evaluated. In addition, four phenolic compounds were screened out as differential metabolites in response to storage temperature by OPLS-DA analysis. The results showed that the fruit firmness was better maintained in low-temperature storage and the storage life was longer than that at 25 °C. During the whole storage process, the contents of phenolics, flavanones, flavanols, and anthocyanins all showed an increasing trend first and then decreased regardless of what temperature. Since the antioxidant capacity of a grape was positively correlated with the contents of total phenols and total flavonoids, the same trend was also shown. However, the grape's phenolic compound content and antioxidant activity were higher at 25 °C than at 4 °C. Furthermore, through qualitative and quantitative analysis of 16 monomeric phenols, this study selected catechin, 1-O-vanilloyl-β-d-glucose, p-coumaric acid 4-glucoside, and resveratrol-3-O-glucoside as the main differentially expressed metabolites at the two temperatures. In conclusion, for a short shelf life or immediate consumption, keeping grapes at room temperature is more beneficial to obtain high antioxidants. However, if the goal is to prolong the storage period of the fruit, keeping the fruit at 4 °C is recommended.

An up-to-date review: differential biosynthesis mechanisms and enrichment methods for health-promoting anthocyanins of citrus fruits during processing and storage

Anthocyanins, naturally found in citrus, play key roles in improving the qualities of citrus fruits and products. Dietary consumption of fruit-derived anthocyanins is concerned increasingly owing to health-promoting properties. However, anthocyanins are vulnerable to many physical and chemical factors during processing and storage, affecting fruit qualities and consumer acceptance. Thus, the aim of this review is to focus on main advances in chemical structures, differential biosynthesis mechanisms, enrichment methods, and bioactivities of anthocyanins in pigmented and unpigmented citrus fruits. In this review, anthocyanin species and concentrations display tissue specificity in citrus, and the chemical structures and contents of main anthocyanins are summarized. For differential biosynthesis mechanisms, the reasons why most citrus fruits lose the ability of anthocyanin biosynthesis compared with pigmented fruits, and the molecular differences of biosynthesis mechanisms in pigmented citrus fruits are both discussed in detail. Furthermore, anthocyanins' enrichment methods (low-temperature stimulus, light irradiation, xenobiotics inductions, and ripeness influence) during processing and storage have been summarized, which achieve quality improvement by promoting structural gene expression, reducing anthocyanin-degrading enzyme activities, or altering DNA methylation status. Meantime, the health benefits of extract from pigmented citrus and their waste are mentioned, which provides a new approach for citrus waste recycling. HIGHLIGHTSChemical structures of individual anthocyanins in citrus are reviewed.Differential anthocyanin biosynthesis in citrus depends on mutations of Ruby genes.Anthocyanins are enriched in response to exogenous stimulus during storage.Health benefits of extract in blood oranges and their waste are summarized.

Exogenous Application of Glycine Betaine Maintains Bioactive Compounds, Antioxidant Activity, and Physicochemical Attributes of Blood Orange Fruit During Prolonged Cold Storage

Exogenous application of glycine betaine (GB) was evaluated on bioactive compounds, antioxidant activity, and physicochemical attributes of blood orange fruit cv. Moro at 3°C for 90 days. Vacuum infiltration (30 kPa) of GB was applied at 15 and 30 mM for 8 min. Parameters were measured after 1, 30, 60, and 90 days of storage plus 2 days at 20°C to simulate the shelf-life period. GB treatments significantly reduced weight and firmness losses in “Moro” blood orange fruit during cold storage. GB treatment maintained a higher concentration of organic acids (citric, malic, succinic, and oxalic acids) and sugars (sucrose, glucose, and fructose), especially for the higher GB doses (30 mM). During storage, GB treatments enhanced total anthocyanin concentration, total phenolic content, and total antioxidant activity. With respect to enzyme activities, the application of exogenous GB showed increases in catalase (CAT), ascorbate peroxidase, superoxide dismutase, phenylalanine ammonia-lyase, while suppressing the polyphenol oxidase activity. Overall, the most effective treatment was 30 mM GB leading to maintaining bioactive compounds, antioxidant activity, and quality in “Moro” blood orange fruit during long-term storage. The positive results would permit the use of GB as a postharvest tool to maintain the quality attributes of blood orange fruit.

Effect of Chitosan-24-Epibrassinolide Composite Coating on the Quality Attributes of Late-Harvested Pomegranate Fruit under Simulated Commercial Storage Conditions

This study evaluated the efficacy of chitosan (CH) functionalized with 24-epibrassinolide (EBR) coating in terms of preserving the postharvest quality of late-harvested pomegranate (cv. Wonderful) fruit. Late-harvested pomegranate fruit were immersed for 3 min in different surface treatment solutions—CH 1.5% (w/v), CH + 2 µM EBR, CH + 5 µM EBR, CH + 10 µM EBR and CH + 15 µM EBR—and distilled water was used as a control treatment. The fruit were air-dried and subjected to long storage duration at 5 °C with 85 ± 5 RH for 12 weeks. At 4-week sampling intervals, a batch of fruits was placed at 21 ± 2 °C and 65–70% RH for a further 3 d period to simulate retail conditions before measurements were taken. Fruit physiological responses, physico-chemical properties, phytochemical contents, antioxidant capacity and physiological disorders were monitored during storage. The results showed that the CH-EBR composite edible coatings significantly (p < 0.05) delayed degradative processes due to senescence. The CH-EBR treatments delayed colour, texture and total soluble solids (TSS) degradation and reduced weight loss, respiration, electrolyte leakage and spoilage compared to the control and CH treatment. The treatment effect was more noticeable on fruit treated with CH + 10 µM EBR, which exhibited lower weight loss (18.19%), respiration rate (7.72 mL CO₂ kg⁻¹ h⁻¹), electrolyte leakage (27.54%) and decay (12.5%), and maintained higher texture (10.8 N) and TSS (17.67 °Brix) compared to the untreated fruit with respective values of 24.32%, 18.06 mL CO₂ kg⁻¹ h⁻¹, 43.15%, 37.5%, 8.32 N and 17.03 °Brix. This was largely attributed to the significantly higher antioxidant content, including the ascorbic acid content, total phenol content, total anthocyanin content and DPPH (radical scavenging activity), of the coated fruit compared to the control fruit. Therefore, CH + 10 µM EBR treatment is recommended as a postharvest management strategy to improve the quality preservation of late-harvested pomegranate fruit during storage.

Physicochemical Changes, Peel Colour, and Juice Attributes of Blood Orange Cultivars Stored at Different Temperatures

Changes in physicochemical traits, peel colour, and juice attributes of four blood orange cultivars (‘Moro’, ‘Tarocco’, ‘Sanguinello’, and ‘Sanguine’) were evaluated during 180 days at 2 and 5 °C plus 2 days at 20 °C for shelf life. ‘Tarocco’ had the lowest weight and firmness losses at both temperatures during storage. Titratable acidity (TA) at 5 °C was higher than 2 °C, with ‘Sanguinello’ and ‘Tarocco’ showing the highest and lowest TA, respectively. Juice content decreased during storage at both temperatures, although ‘Sanguinello’ had the highest juice content among the tested cultivars. Peel colour parameters including L* (lightness), b*, hue angle (h°), and chroma (C*) decreased during cold storage, while a* and citrus colour index (CCI) increased in all cultivars at both temperatures. The order for CCI was ‘Tarocco’ > ‘Moro’ > ‘Sanguinello’ > ‘Sanguine’. Overall, prolonged storage at 5 °C was considered as optimum temperature for all cultivars, although ‘Sanguinello’ cultivar had a better aptitude for the citrus juice industry.

Fatty acid composition in relation to chilling susceptibility of blood orange cultivars at different storage temperatures

Fatty acid composition in the peel of four blood orange cultivars ('Moro', 'Tarocco', 'Sanguinello', and 'Sanguine') was identified and quantified by gas chromatography-mass spectrometry (GC-MS), in order to find its correlation with chilling susceptibility at harvest time and after 180 days of storage at 2 and 5 °C (2 days at 20 °C for shelf life). Twelve fatty acids were detected including 6 saturated (SFA) and 6 unsaturated (UFA), from which 4 monounsaturated (MUFA) and 2 polyunsaturated (PUFA) fatty acids occurred. The major fatty acids were palmitic, linoleic, and linolenic acids. The chilling injury (CI) index was significantly higher at 2 than 5 °C for all cultivars, with 'Sanguinello' being the more tolerant cultivar. The multivariate statistical analyses showed that 'Sanguinello' had the highest UFA, UFA/SFA ratio, and the lowest SFA, while 'Moro' as a cold sensitive cultivar had the highest SFA, the lowest UFA, and UFA/SFA ratio. Our findings revealed that the higher level of PUFAs (linoleic and linolenic acids) and enhancement of the UFA/SFA ratio are considered the most main adaptive mechanism under low temperatures of storage.