Cold-stored Fruit Research Articles

Differential regulation of the phenylpropanoid pathway highly contributes to the susceptibility of chilling-induced necrotic peel disorders in cold-stored hardy kiwifruit

Fruit of hardy kiwifruit cultivars respond differently to chilling stress during cold storage. Therefore, this study aimed to evaluate the differential responses of fruit quality attributes, physiological disorders, and untargeted and targeted metabolites of two contrasting hardy kiwifruit cultivars, ‘Greenheart’ and ‘Daebo’ during cold storage. During cold storage, the ‘Daebo’ cultivar exhibited more severe symptoms of chilling injury, such as peel browning and peel pitting, compared to the ‘Greenheart’ cultivar. Untargeted and targeted metabolic analyses indicated that syringic acid, total phenolic compounds, total flavonoids, catechin, rutin, ferulic acid, quinic acid, citramalic acid, and isoquercitrin levels were higher in ‘Greenheart’ compared to ‘Daebo’ during cold storage. However, citric, isocitric, and threonic acids, gamma-aminobutyric acid, cysteine, β-alanine, titratable acidity, epicatechin, and proline were high in the ‘Daebo’ cultivar. Peel browning and pitting were positively correlated with soluble carbohydrates, organic acids, and amino acids but negatively correlated with individual phenolic compounds in ‘Daebo’ cultivar. The tricarboxylic acid cycle, glyoxylate and dicarboxylate metabolism, arginine and proline metabolism, biosynthesis of unsaturated fatty acids, arginine biosynthesis, and alanine, aspartate, and glutamate metabolism were upregulated in the ‘Daebo’ cultivar, whereas the phenylpropanoid pathway was upregulated in the ‘Greenheart’ cultivar. Our study showed that differentially upregulated pathways could lead to the contrasting development of necrotic peel disorders in these two hardy kiwifruit cultivars during cold storage. Our results suggest that the distinctive responses of metabolic analyses to chilling stress can contribute to susceptibility in chilling-induced necrotic peel disorders in cold-stored fruit of the ‘Daebo’ hardy kiwifruit cultivar.

L-Glutamate treatment alleviates chilling injury of prune (Prunus domestica L.) fruit by regulating ROS homeostasis, GABA shunt, and energy metabolism

The impacts of L-glutamate (L-Glu) treatment on chilling injury (CI), Ca2+ signaling, mitochondrial ultrastructure, and metabolisms of reactive oxygen species (ROS), γ-aminobutyric acid (GABA), energy of prune fruit under chilling stress were studied. The results found that the optimal concentration of L-Glu to suppress CI occurrence and maintain quality in prune fruit was 0.1 g L−1, which also enhanced the PdGLRs expression, cytoplasmic Ca2+ concentration, the contents of CaM, and CML under cold stress. Moreover, L-Glu treatment could reduce ROS accumulation and increase GABA content, and energy level, contributing to maintaining the integrity of the mitochondrial structure in cold-stored prune fruit. More importantly, PdGLRs expression and CaM/CML content positively correlated with antioxidant enzyme activities, GABA shunt, and energy status in prune fruit. These results indicated that the enhanced cold resistance of L-Glu-treated prunes might be attributed to the activated Ca2+ signaling, thus improving the antioxidant capacity, GABA, and energy levels.

Blue lighting combined with cold storage temperature can suppress gray mold in strawberry fruit

Cold storage is an optimal way of preventing quality deterioration in fruit crops, and this is exemplified by strawberries. However, Botrytis cinerea, the causal agent of gray mold, is cold-adaptive and can cause losses to cold-stored fruit. This study evaluated the regulatory effects of the spectral quality of light on the fungal growth in vitro, and the development of gray mold on postharvest strawberries at both ambient (21 ℃) and cold (4 ℃) temperatures. None of the light qualities tested (white, blue, green, or red) significantly affected colony growth of B. cinerea compared with the dark conditions in which they were tested at 21 ℃. In fungal cultures kept at 4 ℃, blue light significantly retarded colony expansion compared to other light conditions and darkness. Moreover, blue light and cold conditions can synergistically result in an increased number of septa, hyphal abnormality and intracellular vacuoles. An enhanced accumulation of reactive oxygen species (ROS) was also observed in fungal hypha exposed to blue light under cold conditions. Infection assay on strawberries demonstrated that blue light caused insignificant and significant suppressive effects at 21 ℃ and 4 ℃, respectively. In addition, blue-light caused significant weight loss in strawberries compared with all other treatments. Consequently, blue-light illumination under cold conditions may result in oxidative stress to the B. cinerea cells, thus preventing this cold-adaptive pathogen from causing unexpected deterioration in the stored fruit.

Cold shock treatment alleviates pitting in sweet cherry fruit by enhancing antioxidant enzymes activity and regulating membrane lipid metabolism.

In order to comprehend the regulatory mechanisms that result in the alleviation of sweet cherry pitting disorder through cold shock (0 °C ice-water mixture for 10 min), an investigation was conducted into the impacts of cold shock treatment (CST) on membrane lipid metabolism, antioxidant enzyme activity, as well as pitting of cold-stored sweet cherry fruit. CST significantly inhibited the increase in pitting incidence, pitting index, and decay incidence. The CST treatment provided greater titratable acidity, firmness as well as total content of soluble solids. The use of CST prevented the build-up of superoxide anions, hydrogen peroxide, malondialdehyde, and reduced permeability of cell membranes. When in contrast to control group, the CST also raised the expression levels along with activity of the antioxidant enzymes ascorbate peroxidase (APX), glutathione reductase (GR), superoxide dismutase (SOD), and catalase (CAT). Furthermore, CST reduced the amount of fruit cell membrane peroxidation, suppressed the activity of phospholipase and lipoxygenase, postponed the rise in saturated fatty acids (SFAs) and decrease in unsaturated fatty acids (USFAs), ultimately keeping a high ratio of USFAs to SFAs. CST can alleviating pitting disorder in sweet cherry fruit via preventing peroxidation of membrane lipid and elevating the antioxidant enzymes activity. © 2024 Society of Chemical Industry.

Ectopic overexpression of ShCBF1 and SlCBF1 in tomato suggests an alternative view of fruit responses to chilling stress postharvest.

Postharvest chilling injury (PCI) is a physiological disorder that often impairs tomato fruit ripening; this reduces fruit quality and shelf-life, and even accelerates spoilage at low temperatures. The CBF gene family confers cold tolerance in Arabidopsis thaliana, and constitutive overexpression of CBF in tomato increases vegetative chilling tolerance, in part by retarding growth, but, whether CBF increases PCI tolerance in fruit is unknown. We hypothesized that CBF1 overexpression (OE) would be induced in the cold and increase resistance to PCI. We induced high levels of CBF1 in fruit undergoing postharvest chilling by cloning it from S. lycopersicum and S. habrochaites, using the stress-inducible RD29A promoter. Harvested fruit were cold-stored (2.5°C) for up to three weeks, then rewarmed at 20°C for three days. Transgene upregulation was triggered during cold storage from 8.6- to 28.6-fold in SlCBF1-OE, and between 3.1- to 8.3-fold in ShCBF1-OE fruit, but developmental abnormalities in the absence of cold induction were visible. Remarkably, transgenic fruit displayed worsening of PCI symptoms, i.e., failure to ripen after rewarming, comparatively higher susceptibility to decay relative to wild-type (WT) fruit, lower total soluble solids, and the accumulation of volatile compounds responsible for off-odors. These symptoms correlated with CBF1 overexpression levels. Transcriptomic analysis revealed that the ripening and biotic and abiotic stress responses were altered in the cold-stored transgenic fruit. Seedlings grown from 'chilled' and 'non-chilled' WT fruit, in addition to 'non-chilled' transgenic fruit were also exposed to 0°C to test their photosynthetic response to chilling injury. Chilled WT seedlings adjusted their photosynthetic rates to reduce oxidative damage; 'non-chilled' WT seedlings did not. Photosynthetic parameters between transgenic seedlings were similar at 0°C, but SlCBF1-OE showed more severe photoinhibition than ShCBF1-OE, mirroring phenotypic observations. These results suggest that 1) CBF1 overexpression accelerated fruit deterioration in response to cold storage, and 2) Chilling acclimation in fructus can increase chilling tolerance in seedling progeny of WT tomato.

Involvement of energy and cell wall metabolisms in chilling tolerance improved by hydrogen sulfide in cold-stored tomato fruits.

Hydrogen sulfide improved cold resistance of tomato fruits by regulating energy metabolism and delaying cell wall degradation, thereby alleviating the damage of cold storage on fruits. Postharvest cold storage in tomato fruits extended shelf life but caused the appearance of chilling injury (CI), appeared by softness and spots on the surface of the fruits. These changes were linked closely with energy and cell wall metabolisms. Hydrogen sulfide (H2S), as the gaseous fresh-keeping regulator, was used in the present study to investigate the effects of H2S on energy and cell wall metabolisms in tomato fruits during cold storage. Fruits after harvest were fumigated with different concentrations (0, 0.5, 1, 1.5mM) of sodium hydrosulfide (NaHS) solution as H2S honor for 24h and stored at 4°C for 25days. The results showed that 1 and 1.5mM NaHS solution fumigation promoted the accumulation of endogenous H2S, followed by the increase in L-cysteine desulfurase (LCD) and D-cysteine desulfurase (DCD) activities in fruits during cold storage. It was also found that 1 and 1.5mM NaHS treatments improved H+-ATPase, Ca2+-ATPase, cytochrome C oxidase (CCO), and succinic dehydrogenase (SDH) activities. Moreover, the contents of cellulose and hemicellulose were increased by 1 and 1.5mM NaHS, following down-regulated activities of cellulase (CL), pectin lyase (PL), α-mannosidase (α-man) and β-Galactosidase (β-Gal) and down-regulated expression of PL1, PL8, MAN4 and MAN7 genes. Thus, H2S alleviates CI led by cold storage in tomato fruits via regulating energy and cell wall metabolisms.

Preserving functional properties and inhibiting postharvest peel browning in guava during cold storage via 24-epibrassinolide application

Postharvest peel browning is one of the primary issues accountable for the subdued consumer acceptability and market value of guava fruit. However, postharvest treatment with brassinosteroid can reduce the peel browning to some extent through various modes of action. In current study, the influence of exogenous 24-epibrassinolide (EBL) application on antioxidant system and chilling injury (CI) characteristics of guavas during cold storage at 10 ± 1 ℃ were assessed. The mature green fruit exposed to various concentrations (15, 30, 45, 60 and 75 µg kg−1) of EBL displayed a notably lower fruit weight loss, respiration rate, electrolyte leakage and CI index, while higher consumer acceptability. Further, treatment with EBL has recorded lower amassing of hydrogen peroxide and malondialdehyde by suppressing lipoxygenase activity. Postharvest EBL application also heightened the content of total phenolics, ascorbic acid, total flavonoids and total antioxidant capacity. The enhanced activities of ascorbate peroxidase, catalase, superoxide dismutase and peroxidase due to EBL application impede the burst of reactive oxygen species. Moreover, correlation and regression analysis of tested biochemical parameters including enzymatic and non-enzymatic antioxidants exhibited a strong association and contributed 98.24–99.88 % variability in fruit weight loss, respiration rate, electrolyte leakage, CI index and consumer acceptability. Among different concentrations tested, 60 µg kg−1 EBL-treated guavas exhibited the desirable qualities and least CI index. From the study, it is concluded that the novelty of EBL can be gainfully harnessed in a postharvest handling system to induce cold tolerance and widen the storage life of cold-stored guava fruit.

Characterisation of the MLP genes in peach postharvest cold storage and the regulatory role of PpMLP10 in the chilling stress response

The major latex proteins/ripening-related proteins are a subfamily of the Bet v 1 protein superfamily and are commonly involved in plant development and responses to various stresses. However, the functions of MLPs in the postharvest cold storage of fruits remain uninvestigated. Herein, we identified 30 MLP genes in the peach (Prunus persica) genome that were clustered into three subgroups. Chromosomal location analysis revealed that the PpMLP genes were unevenly distributed on five of the eight peach chromosomes. Synteny analysis of the MLP genes between peach and seven other plant species (five dicotyledons and two monocotyledons) explored their evolutionary characteristics. Furthermore, the PpMLP promoters contained cis-elements for multiple hormones and stress responses. Gene expression analysis revealed that PpMLPs participated in chilling stress responses. Ectopic expression of PpMLP10 in Arabidopsis improved chilling stress tolerance by decreasing membrane damage and maintaining membrane stability. Additional research confirmed that PpWRKY2 participates in PpMLP10-mediated chilling stress by binding to its promoter. Collectively, these results suggest the role of PpMLP10 in enhancing chilling stress tolerance, which is significant for decreasing chilling injury during the postharvest cold storage of peaches.

Metabolism and transcriptional regulation in chilling injury development of nectarine fruit during postharvest cold storage

Peach fruit is susceptible to chilling injury during postharvest long-term cold storage, but the understanding of metabolic and transcriptional reaction of nectarine cultivar fruit to cold storage remains incomplete. In this study, nectarine fruit was used for a low temperature treatment, which gradually leading to the deterioration of fruit quality. Comparative metabolome and transcriptome analyses were performed to comprehensively understand the metabolic and transcriptional changes occurring during cold storage in nectarine fruit. The result showed that numerous primary and secondary metabolites exhibited increased levels following the low-temperature treatment. And there were 3400 differentially expressed genes continuously regulated by cold storage, which were mostly enriched in metabolic and secondary metabolite biosynthesis pathways. The combined pathways enrichment of differential metabolites and genes were primarily centered on secondary metabolite biosynthesis. Correspondingly, a strong correlation was observed between changes in secondary metabolites and the expression of key enzymes including 4-coumarate CoA ligase (4CL), hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyl transferase (HCT), flavonol synthase (FLS), dihydroflavonol reductase (DFR), and UDP-glycose flavonoid glycosyltransferase (UFGT), which were involved in flavonoids biosynthesis. Additionally, several fruit quality characteristics (carotenoids, cell wall components, antioxidant enzymes) and stress related signaling genes were markedly affected by cold storage. These findings offer new insights into the networks governing metabolic and transcriptional regulation during nectarine fruit cold storage.

Melatonin treatment induces DNA methylation to alleviate chilling induced-browning in cold stored peach fruit

Chilling injury (CI) often occurs in postharvest peach fruit during low-temperature storage, and exogenous melatonin (MT) treatment has been demonstrated to alleviate CI in cold-stored peach fruit. In this study, we further investigated the effect of MT treatment on DNA methylation in relation to the chilling-induced browning in cold stored peaches. The results revealed that MT treatment upregulated PpPAL expression while simultaneously suppressing the transcripts of PpPPO and PpPOD. This dual effect resulted in the increased accumulation of phenolics, effectively reducing the incidence of browning in peaches stored at 4 °C. In addition, MT treatment increased the activities of methylesterase and demethylase, affecting significant changes in the DNA methylation levels of the local genes PpPPO, PpPOD and PpPAL, which suggested that MT treatment could mediate DNA methylation of the browning-related genes such as PpPPO, PpPOD and PpPAL, and consequently increased the phenolic contents and alleviated browning symptoms in cold-stored peaches.

Effect of coating using beeswax and sodium nitroprusside on chlorophyll stability and quality factors of lime during cold storage.

Lime (Citrus floridana) is a quickly perishable fruit, limiting its shelf life because of reduced chlorophyll content and post-harvest quality under different storage conditions. To increase chlorophyll stability as well as other quality factors of limes, they were coated with beeswax in 0.1 wt.% and sodium nitroprusside in three various concentrations (0.1, 0.2, and 0.4 mM) at 25 °C for 3 min and then stored at 8 °C for 60 days. In this research, changes in weight loss, juice content, firmness (F), chlorophyll, chlorophyllase activity, polyphenol oxidase activity, color, total acidity (titratable acidity), ascorbic acid (ASA) and sensory evaluation were studied. During storage at low temperatures, BW surface coating (0.1%) alone, sodium nitroprusside alone, and also in combination with each other and a double layer were effective in maintaining chlorophyll and the qualitative characteristics of limes. In our observations, the best treatment was the treatment where the limes were coated by beeswax enriched by sodium nitroprusside coating. This treatment contained the highest content of lime juice and the highest chlorophyll plus the lowest activity of chlorophyllase and polyphenol oxidase, while the amount of green color was maintained to a large extent. As a result, it is possible to use beeswax enriched by sodium nitroprusside coating method to maintain the quality and chlorophyll of cold-stored lime fruits.

Hydrogen sulfide retards fruit softening and prevents flesh browning in cold-stored peaches by regulating cell wall-modifying enzymes, phenolic, and proline metabolism

Utilizing transcriptome analysis, higher expression of genes encoding hydrogen sulfide (H2S) synthetase in fruit stored at 0 ℃, where the expression pattern of differentially expressed genes (DEGs) correlated with softening and phenolic synthesis demonstrated more alterations than fruit storage at 5 ℃ and 15 ℃. Further research into how exogenous H2S affected the unappealing swift softening and internal browning (IB) of fruit was investigated. H2S orchestrated the cell wall-modifying enzymes, inhibiting polygalacturonase, cellulase, β-glucosidase, and pectin methyl esterase, and incompletely suppressing α/β-galactosidase and α-mannosidase during later storage. In H2S-treated fruit, total phenolic content was higher and IB symptoms were alleviated. In addition to enhancing phenylpropanoid metabolism, correlation analysis supported the hypothesis that H2S promoted phenolics in fruit by possibly facilitating proline accumulation. Cys192 and Cys217 of PpMYB75, which are involved in the biosynthesis of anthocyanin, were potential targets for persulfidation, and application of H2S reduced anthocyanin content in peach fruit. Together, our results demonstrate that H2S could ameliorate the chilling injury of cold-stored peach fruit and provide a perspective for controlling phenolic synthesis.

The promoters of two CpMYB106-like paralog genes respond to abiotic stresses and phytohormones and drive differential expression in contrasting cultivars of Cucurbita pepo

Zucchini fruit (Cucurbita pepo L.) is susceptible to chilling injury (CI) during its postharvest life, with this response being cultivar-dependent. A previous transcriptomic analysis comparing cold-tolerant fruit from the cultivar ‘Natura’ with cold-sensitive fruit from the cultivar ‘Sinatra’, revealed the transcription factor (TF) CpMYB106-like as a relevant candidate gene for the acquisition of postharvest low-temperature tolerance. C. pepo has two CpMYB106-like paralogs, which are differentially present in the ‘Natura’ (CpMYB106-likeA) and ‘Sinatra’ (CpMYB106-likeB) cultivars due to gene and promoter deletions. The aim of this study was to investigate the transcriptional regulation of the CpMYB106-like paralogs to unravel their role in the postharvest life of zucchini fruit. For this, gene expression was analyzed and promoter sequences and their activities were studied through reporter β-glucuronidase (GUS) gene analysis in heterologous systems. An expression analysis showed that CpMYB106-like mRNA levels were induced only in the cold-stored fruit of ‘Natura’. The analysis of the promoter sequences showed numerous cis-regulatory elements (CREs), many of which have a differential distribution or frequency between the two paralogs. Promoter basal activity was determined by transient transformation of Nicotiana benthamiana leaves, which showed a higher expression driven by the promoter from the cold-tolerant cultivar ‘Natura’, which could be explained by the presence of three additional copies of the enhancer element EECCRCAH1 in proMYB106A. The tissue-specific expression pattern, and the response to abiotic stresses and phytohormones controlled by CpMYB106-like promoters was analyzed in transgenic Arabidopsis thaliana plants. GUS activity was mainly detected in the vascular system, leaves, and inflorescences, especially in siliques. With respect to abiotic stresses, low temperature decreased GUS expression in Arabidopsis, but increased it in plants carrying the ‘Natura’ promoter after a 24-h acclimation period at 22 °C. Salt treatment induced GUS activity driven by both promoters in Arabidopsis seedlings, but it was higher with the ‘Natura’ promoter. Furthermore, methyl jasmonate (MeJA) also induced a sharp increase of GUS controlled by proMYB106A. These results suggest that the regulation of CpMYB106-like TFs in zucchini is promoter-driven, and reveal the involvement of these genes in the acquisition of cold tolerance in fruit during postharvest stress conditions.

Melatonin mobilizes the metabolism of sugars, ascorbic acid and amino acids to cope with chilling injury in postharvest pear fruit

Chilling injury manifesting as internal browning is an irreversible physiological disorder in cold-stored ‘Yali’ pear fruit, which seriously restricts postharvest handling and commercialization of pear fruit. This study investigated the impact of melatonin (MN) treatment on chilling injury and the metabolism of sugars, ascorbic acid (AsA), proline, and γ-aminobutyric acid (GABA) during chilling injury development in ‘Yali’ pears. The findings revealed that MN-treated pear fruit exhibited considerably improved tolerance to chilling stress compared with untreated control fruit. MN application augmented proline accumulation, likely owing to increased activities and transcriptional concentrations of Δ1-pyrroline-5-carboxylate synthase and ornithine-δ-aminotransferase as well as diminished activity and transcriptional level of proline dehydrogenase. MN immersion increased enzyme activities and gene expression related to the GABA shunt pathway, leading to increased GABA concentrations in cold-stored pear fruit. Furthermore, MN treatment elevated AsA concentrations in the fruit, exerting protective effects against cell membrane damage and mitigating oxidative stress damage caused by chilling. Compared with the control group, MN-treated fruit exhibited reduced neutral invertase enzyme activity and gene expression. Additionally, MN treatment increased both sucrose-phosphate synthase and sucrose synthase activities and gene expression in pear fruit. These observations indicated that the enhanced chilling tolerance of ‘Yali’ pear fruit following MN treatment may be associated with the regulation of proline, GABA, AsA, and soluble sugars metabolism.

Exogenous application of salicylic acid regulates antioxidant enzyme activities and quality attributes of Umran ber (Ziziphus mauritiana) fruits under cold storage

The present study was carried out to observe the influence of pre-harvest application of salicylic acid (1, 2 and 3 mM) on shelf life and quality attributes of ber fruits cv. Umran (Ziziphus mauritiana Lamk.) under cold storage conditions (7.5±10C and 90–95% RH). The cold-stored fruits were assessed for various physico-chemical attributes and enzymatic activities at 7 days interval up to 28 days of storage. Above study revealed that fruits treated with salicylic acid @3 mM resulted in reduced physiological loss in fruit weight, spoilage and increased firmness, soluble solids content, antioxidant activity and carotenoids. Furthermore, it suppressed activities of cell wall degrading enzymes like PG, PPO, PME and increased the activity of superoxide dismutase peroxidase and catalase enzymes. It was concluded that pre-harvest spray of salicylic acid @3 mM was more effective in regulating enzymatic activities, thereby improving quality attributes and shelf life of ber fruits up to 21 days at cold storage.

The metabolism of membrane lipid participates in the occurrence of chilling injury in cold-stored banana fruit

Banana fruit is highly vulnerable to chilling injury (CI) during cold storage, which results in quality deterioration and commodity reduction. The purpose of this study was to investigate the membrane lipid metabolism mechanism underlying low temperature-induced CI in banana fruit. Chilling temperature significantly induced CI symptoms in banana fruit, compared to control temperature (22 °C). Using physiological experiments and transcriptomic analyses, we found that chilling temperature (7 °C) increased CI index, malondialdehyde content, and cell membrane permeability. Additionally, chilling temperature upregulated the genes encoding membrane lipid-degrading enzymes, such as lipoxygenase (LOX), phospholipase D (PLD), phospholipase C (PLC), phospholipase A (PLA), and lipase, but downregulated the genes encoding fatty acid desaturase (FAD). Moreover, chilling temperature raised the activities of LOX, PLD, PLC, PLA, and lipase, inhibited FAD activity, lowered contents of unsaturated fatty acids (USFAs) (γ-linolenic acid and linoleic acid), phosphatidylcholine, and phosphatidylinositol, but retained higher contents of saturated fatty acids (SFAs) (stearic acid and palmitic acid), free fatty acids, phosphatidic acid, lysophosphatidic acid, diacylglycerol, a lower USFAs index, and a lower ratio of USFAs to SFAs. Together, these results revealed that chilling temperature-induced chilling injury of bananas were caused by membrane integrity damage and were associated with the enzymatic and genetic manipulation of membrane lipid metabolism. These activities promoted the degradation of membrane phospholipids and USFAs in fresh bananas during cold storage.

Use of spermidine to preserve organic acids, polyphenols, and quality of cold stored plum fruits

One of the primary goals of fruit production and storage is to ensure pre-and post-harvest food quality. Polyamines have recently been used to improve food quality after harvest. We used spermidine concentrations of 0.5, 1, and 1.5 mM in plum fruits for 20 and 40 days of cold storage. Each dose provided significantly higher preservation of sensory properties, organic acids, and phenolic compounds than the control, with a gradual improvement by doses. Malic acid was the predominant organic acid and was gradually preserved by spermidine doses, including 25% more malic acid for the 1.5 mM spermidine treatment. Similarly, chlorogenic acid, the most abundant phenolic compound studied, was also 25% higher when the spermidine dose rose to 1.5 mM. The 1.5 mM spermidine notably inhibited weight loss and respiration rate. Organic acids and phenolic compounds were particularly protected by the 1 and 1.5 mM doses, and multivariate approaches suggested that spermidine has a comprehensive stability effect on secondary metabolites. This study proposes spermidine as a comprehensive metabolic preserver that protects polyphenols and organic acids, thus preserving the taste and healthiness of cold-stored plum fruits.

EjCML19 and EjWRKY7 synergistically function in calcium chloride-alleviated chilling injury of loquat fruit

The regulatory function of calcium chloride (CaCl2) in chilling injury (CI) has been proven in loquat fruit. Nevertheless, its physiological and molecular mechanisms are relatively still unclear. In this work, the CaCl2 treatment reduced the CI in loquat fruit, with a lower internal browning index, firmness, and higher extractable juice in comparison with the control. Moreover, CaCl2 application impacted the contents of phenolic acids in cold-stored loquat fruit. Transcriptome analysis identified a total of 5416 differently expressed genes (DEGs), and the key DEGs were enriched in many metabolic pathways, including phenylpropanoid biosynthesis, biosynthesis of secondary metabolites, plant hormone signal transduction, phenylalanine metabolism, membrane lipid degradation, starch and sucrose metabolism. The fold change and the expression intensity of EjCML19 and EjWRKY7 in loquat fruit during cold storage were higher, and EjCML19 could interact with EjWRKY7 in yeast cells. The qRT-PCR analysis found that CaCl2 induced the transcription of EjCML19 and EjWRKY7 but down-regulated browning-related genes EjRBOHC and EjPPO in loquat fruit. The genes (EjRBOHC and EjPPO) contain W-box elements in their promoters, implying that they might be target genes of EjWRKY7. Therefore, EjCML19 and EjWRKY7 were selected and cloned from loquat fruit to explore their regulatory role of EjRBOHC and EjPPO. Further investigation revealed that EjWRKY7 negatively modulated the expression of EjRBOHC and EjPPO by binding to their promoters. EjCML19 enhanced EjWRKY7-mediated transcriptional repression of EjPPO in loquat fruit under cold stress. Taken together, EjCML19 and EjWRKY7 synergistically regulated the transcription of browning-related genes, which functioned a positive role in CaCl2-alleviated chilling injury in loquat fruit under refrigeration.

Carboxymethyl Cellulose from Banana Rachis: A Potential Edible Coating to Extend the Shelf Life of Strawberry Fruit

Cellulose derivatives, as edible coating for fruits and vegetables, have been broadly applied due to their availability, stability, solubility, safety, and low price. Therefore, this study was conducted to (1) extract cellulose from the banana plant rachis, (2) convert it into carboxymethyl (CMC), and (3) use the produced CMC as an edible coating to retard senescence and prolong the storage life of strawberry fruit. Preparation of CMC was accomplished by an etherification process, utilizing sodium hydroxide and monochloroacetic acid (MCA), with ethanol as a supporting medium. Characterization of CMC was done by analyzing the spectra of FTIR, degree of substitution (DS), ash content, CMC yield, water and oil holding capacity, in addition to physical characteristics. A storage study with CMC as an edible coating was conducted to investigate its impact on the shelf life of stored strawberry fruits. High purity food-grade CMC was successfully produced. CMC showed a yield of 156.25% with a DS of 0.78, a water holding capacity of 11.24 g/g, and an oil holding capacity of 1.60 g/g. The resulted CMC was well suited for edible coating preparation and was used effectively to prolong the shelf life of stored strawberry fruits at 22 °C to 6 days and to 16 days for that stored at 4 °C. Weight loss, total soluble solids (TSS), decay percentage, pH, anthocyanin content, ascorbic acid content, firmness, and sensory characteristics of CMC coated strawberry fruit stored at 4 °C were better than those stored at 22 °C. Thus, CMC edible coating prepared from banana rachis could be recommended as a potential postharvest treatment to delay postharvest senescence and maintain the quality of ambient and cold stored fruits.

IOT Based Fruit Cold Storage Monitoring and Controlling System

IOT Based Fruit Cold Storage Monitoring and Controlling System