Postharvest Softening Research Articles

Development and evaluation of a precision heat treatment device for delaying postharvest softening of muskmelon

Development and evaluation of a precision heat treatment device for delaying postharvest softening of muskmelon

Transcriptome analysis reveals regulatory mechanism of postharvest softening in kiwiberry

BackgroundKiwiberry is an emerging edible fruit with market potential owing to its advantages of small size, thin and hairless skin, and sweet taste. However, kiwiberry is highly susceptible to softening after harvest, which poses a challenge for storage and transport. To reveal the underlying cause of kiwiberry softening, it is essential to investigate the characteristics of postharvest fruit and the molecular mechanisms that affect changes in fruit firmness.ResultsMorphological observations and analysis of physical parameters showed that the skin of kiwiberry did not change markedly from the 1st to the 7th day after harvest, while the colour of the inner pericarp gradually turned yellow. By the 9th day of room temperature storage, the kiwiberries began to rot. The hardness decreased rapidly from the 1st to the 5th day postharvest, reaching the low level on the 5th day. The starch and pectin contents of kiwiberry showed a downward trend with increasing storage time. Transcriptome sequencing and weighted gene co-expression network analysis identified 29 key genes associated with the changes in the hardness of kiwiberry after harvest. Gene Ontology enrichment analysis indicated that these 29 genes are mainly involved in pectin metabolism, starch synthesis, starch decomposition, and starch metabolism. In addition, three transcription factors, AGL31, HAT14, and ALC, were identified to be strongly positively correlated with the 29 genes that affect the hardness changes of kiwiberry after harvest, and 28 of the 29 key genes were predicted to be regulated by HAT14.ConclusionsThese results reveal the changes in morphological characteristics and physiological indicators during the postharvest ripening and softening of kiwiberry stored under room temperature conditions. Transcriptome analysis identified 29 key genes and three transcription factors that affect the firmness changes of postharvest kiwiberry. The results of this study thus provide insight into the transcriptional regulatory mechanism of kiwiberry softening during storage to improve the postharvest quality.

Impacts of Fruit Frosting Coverage on Postharvest Softening of Prunes under Vibration Stress

The surface of prune fruit has a thick layer of frosting, which is easily damaged and lost during prunes harvest or postharvest handling, and there is no clear information on the effect of prune surface frost on postharvest storage quality. To investigate the effect of fruit frosting on the softening of prune fruits during storage under vibration stress, prunes were divided into three grades according to fruit frosting in this study and were vibrated for 8 h at a frequency of 5 Hz at 4 °C; then, samples were selected once every 8 d. The results showed that the heavy fruit frosting (HFF) group maintained higher hardness (21.47%), L* (20.85%), and total soluble solids (12.79%) levels at the end of storage and inhibited cell wall-modifying enzyme activities (polygalacturonase, pectin methylesterase, glycosidase, β-glucosidase, and cellulase) compared to frosting-less fruit (FF) group. This group also showed improved expression of key cell wall-modification genes (ADPG2, PME31, CESA1, BGAL3, XTH33, BGLU41) as well as chelate-soluble pectin (72.11%), Na2CO3-soluble pectin (42.83%), and cellulose (36.89%) solubilization and maintained lower water-soluble pectin (34.23%). Microscopic observations showed that the fruit frosting could delay the dissolution of pectin components and protect the cell wall structure. In summary, fruit frosting can effectively inhibit fruit softening and maintain fruit quality.

Cell wall disassembly events accompanying softening in the core and external zones of the strawberry fruit receptacle

Softening is one of the most important changes determining the quality and postharvest life of strawberry. Though some studies have characterized the cell wall modifications accompanying firmness loss during storage, the reports on polysaccharide disassembly are widely variable and in some cases contradictory. To further understand strawberry postharvest softening, conducted a comprehensive cell wall analysis including polymer solubilization, depolymerization and composition of the Core and External zones of fruit´s receptacle during storage. Core tissues were firmer and stiffer and softened more than the External receptacle zone. Wall dismantling was remarkably different depending on the region evaluated. Core tissues showed greater losses and size downshift of hemicelluloses as well as more extensive depolymerization of pectin. Instead, softening in the External region occurred with limited depolymerization and with massive loss of arabinose and xylose. Xyloglucans showed active turnover in the Core, whereas xylans were the most degraded hemicelluloses in the External region. Results show that each discrete region of the strawberry fruit receptacle has a unique sequence of biochemical wall dismantling events leading to postharvest softening.

Assessing the Effect of Cold Plasma on the Softening of Postharvest Blueberries through Reactive Oxygen Species Metabolism Using Transcriptomic Analysis.

The postharvest softening and corresponding quality deterioration of blueberry fruits are crucial factors that hinder long-distance sales and long-term storage. Cold plasma (CP) is an effective technology to solve this, but the specific mechanism of delaying fruit softening remains to be revealed. Here, this study found that CP significantly improved blueberry hardness. Physiological analysis showed that CP regulated the dynamic balance of reactive oxygen species (ROS) to maintain hardness by increasing antioxidant content and antioxidant enzyme activity, resulting in a 12.1% decrease in the H2O2 content. Transcriptome analysis revealed that CP inhibited the expression of cell wall degradation-related genes such as the pectin hydrolase gene and cellulase gene, but up-regulated the genes of the ROS-scavenging system. In addition, the resistance genes in the MAPK signaling pathway were also activated by CP in response to fruit ripening and softening and exhibited positive response characteristics. These results indicate that CP can effectively regulate the physiological characteristics of blueberries at a genetic level and delay the softening process, which is of great significance to the storage of blueberries.

Transcriptomic analysis reveals ozone treatment delays kiwifruit postharvest softening by modulating cell wall metabolism.

Kiwifruit ripening and senescence after harvesting are closely related to its economic value. Transcriptome analysis and biochemical parameters were used to investigate the differences in gene expression levels and the potential regulation of cell wall metabolism in kiwifruit treated with ozone, thereby regulating fruit softening and prolonging postharvest life. Compared to the control group, the activities of the cell wall modification enzyme were lower under ozone treatment, the content of polysaccharide in the cell wall of primary pectin and cellulose was higher, and the content of soluble pectin was lower. Meanwhile, ozone treatment delayed the degradation of the cell wall mesosphere during storage. A total of 20 pectinesterase (PE)-related genes were identified by sequencing analysis. The data analysis and quantitative polymerase chain reaction results confirmed that cell wall modifying enzyme genes played an important role in softening and senescence after harvesting, which may reduce or induce the expression of certain genes affecting cell wall metabolism. Ozone treatment not only regulates active genes such as xyloglucan endo glycosyltransferase/hydrolase, cellulose synthase, polygalacturonase, and PE to maintain the quality of fruit after harvest but also acts synergically with cell wall modifying enzymes to inhibit the degradation of cell wall, resulting in changes in the ultrastructure of cell wall, thereby reducing the hardness of kiwifruit. In addition, according to the results of cis-acting elements, cell wall degradation is also related to downstream hormone signaling, especially PE-related genes. These results provide a theoretical basis for studying the mechanism of firmness and cell wall metabolism difference of kiwifruit and also lay a good foundation for further research.

Genome-wide identification of MAPK family in papaya (Carica papaya) and their involvement in fruit postharvest ripening

BackgroundPapaya (Carica papaya) is an economically important fruit cultivated in the tropical and subtropical regions of China. However, the rapid softening rate after postharvest leads to a short shelf-life and considerable economic losses. Accordingly, understanding the mechanisms underlying fruit postharvest softening will be a reasonable way to maintain fruit quality and extend its shelf-life.ResultsMitogen-activated protein kinases (MAPKs) are conserved and play essential roles in response to biotic and abiotic stresses. However, the MAPK family remain poorly studied in papaya. Here, a total of nine putative CpMAPK members were identified within papaya genome, and a comprehensive genome-wide characterization of the CpMAPKs was performed, including evolutionary relationships, conserved domains, gene structures, chromosomal locations, cis-regulatory elements and expression profiles in response to phytohormone and antioxidant organic compound treatments during fruit postharvest ripening. Our findings showed that nearly all CpMAPKs harbored the conserved P-loop, C-loop and activation loop domains. Phylogenetic analysis showed that CpMAPK members could be categorized into four groups (A-D), with the members within the same groups displaying high similarity in protein domains and intron–exon organizations. Moreover, a number of cis-acting elements related to hormone signaling, circadian rhythm, or low-temperature stresses were identified in the promoters of CpMAPKs. Notably, gene expression profiles demonstrated that CpMAPKs exhibited various responses to 2-chloroethylphosphonic acid (ethephon), 1-methylcyclopropene (1-MCP) and the combined ascorbic acid (AsA) and chitosan (CTS) treatments during papaya postharvest ripening. Among them, both CpMAPK9 and CpMAPK20 displayed significant induction in papaya flesh by ethephon treatment, and were pronounced inhibition after AsA and CTS treatments at 16 d compared to those of natural ripening control, suggesting that they potentially involve in fruit postharvest ripening through ethylene signaling pathway or modulating cell wall metabolism.ConclusionThis study will provide some valuable insights into future functional characterization of CpMAPKs, and hold great potential for further understanding the molecular mechanisms underlying papaya fruit postharvest ripening.

Pulse electric field pretreatment delays the texture deterioration of sweet persimmon (Diospyros kaki L.) during postharvest storage

The food industry is highly concerned with food processing and waste reduction sustainability. Therefore, it is essential to develop new technologies to minimize waste and extend the shelf life of products. In this study, pulsed electric field (PEF) treatments were used at 25, 50, and 100 kV/m to investigate the potential for reducing the postharvest softening of persimmons. The results showed that after storing for 28 days, the firmness loss under 50 kV/m was maintained at 58.40 ± 0.36%, whereas that in the untreated group was 87.6 ± 0.14 %. The mobility of bound water was higher in the 50 kV/m group than in the 25 kV/m and untreated groups. PEF treatment also effectively reduced electrolyte leakage. This research also showed that PEF treatment could help reduce respiration by 12.5–31.22 CO2 mL/h/kg—an effective delay of 50 kV/m for soft rot and texture deterioration. In summary, applying PEF technology was found capable of extending the shelf life of persimmons under refrigeration by up to 14 days compared with the untreated group.

Alternative splicing of the PECTINESTERASE gene encoding a cell wall-degrading enzyme affects postharvest softening in grape

The firmness of table grape berries is a crucial quality parameter. Despite extensive research on postharvest fruit softening, its precise molecular mechanisms remain elusive. To enhance our comprehension of the underlying molecular factors, we initially identified differentially expressed genes (DEGs) by comparing the transcriptomes of folic acid (FA)-treated and water-treated (CK) berries at different time points. We then analyzed the sequences to detect alternatively spliced (AS) genes associated with postharvest softening. A total of 2,559 DEGs were identified and categorized into four subclusters based on their expression patterns, with subcluster-4 genes exhibiting higher expression in the CK group compared with the FA treatment group. There were 1,045 AS-associated genes specific to FA-treated berries and 1,042 in the CK-treated berries, respectively. Gene Ontology (GO) annotation indicated that the AS-associated genes in CK-treated berries were predominantly enriched in cell wall metabolic processes, particularly cell wall degradation processes. Through a comparison between treatment-associated AS genes and subcluster-4 DEGs, we identified eight genes, including Pectinesterase 2 (VvPE2, Vitvi15g00704), which encodes a cell wall-degrading enzyme and was predicted to undergo an A3SS event. The reverse transcription polymerase chain reaction further confirmed the presence of a truncated transcript variant of VvPE2 in the FA-treated berries. Our study provides a comprehensive analysis of AS events in postharvest grape berries using transcriptome sequencing and underscores the pivotal role of VvPE2 during the postharvest storage of grape berries.

The apple transcription factor MdZF-HD11 regulates fruit softening by promoting Mdβ-GAL18 expression.

Fruit ripening and the associated softening are major determinants of fruit quality and post-harvest shelf life. Although the mechanisms underlying fruit softening have been intensively studied, there are limited reports on the regulation of fruit softening in apples (Malus domestica). Here, we identified a zinc finger homeodomain transcription factor MdZF-HD11that trans-activates the promoter of Mdβ-GAL18, which encodes a pectin-degradation enzyme associated with cell wall metabolism. Both MdZF-HD11 and Mdβ-GAL18 genes were up-regulated by exogenous ethylene treatment and repressed by 1-methylcyclopropene treatment. Further experiments revealed that MdZF-HD11 binds directly to the Mdβ-GAL18 promoter and up-regulates its transcription. Moreover, using transgenic apple fruit calli, we found that overexpression of Mdβ-GAL18 or MdZF-HD11 significantly enhanced β-galactosidase activity, and overexpression of MdZF-HD11 induced the expression of Mdβ-GAL18. We also discovered that transient overexpression of Mdβ-GAL18 or MdZF-HD11 in 'Golden Delicious' apple significantly increased the release of ethylene, reduced fruit firmness, promoted the transformation of skin color from green to yellow, and accelerated ripening and softening of the fruit. Finally, the overexpression of MdZF-HD11 in tomato also promoted fruit softening. Collectively, these results indicate that ethylene-induced MdZF-HD11 interacts with Mdβ-GAL18 to promote the post-harvest softening of apple.

Alleviatory effects of salicylic acid on postharvest softening and cell wall degradation of 'Jinshayou' pummelo (Citrus maxima Merr.): A comparative physiological and transcriptomic analysis.

The regulatory mechanisms underlying the salicylic acid (SA)-mediated inhibition of senescence in pummelo fruit, the largest known citrus variety, remain unclear. Herein, postharvest 0.3% SA treatment was demonstrated to delay postharvest 'Jinshayou' pummelo senescence, as evidenced by the inhibitions in firmness loss, electrolyte leakage increase, and color change. Using comparative transcriptomic data, a total of 4367, 3769, and 1659 DEGs were identified between CK0 and CK60, CK0 and SA60, and CK60 and SA60, respectively. Further GO analysis revealed that DEGs were mainly implicated in the processes of cell wall modification and phenylpropanoid pathway during fruit senescence. More importantly, postharvest exogenous 0.3% SA treatment was observed to inhibit CWDEs activities and their encoding gene expression, retain higher protopectin, cellulose, and hemicelluloses contents, as well as reduce WSP content, thus maintaining cell wall structure. These findings collectively indicated that postharvest SA treatment was a green and useful preservative for alleviating fruit senescence and prolonging the storage life of harvested 'Jiashayou' pummelo fruit.

Effect of Cold Plasma Treatment on the Softening of Winter Jujubes (Ziziphus jujuba Mill. cv. Dongzao)

Cold plasma (CP) is a green and efficient preservation technology, but its effect on preventing the postharvest softening of fruits and vegetables is still unclear, and the effects of different CP intensities on the postharvest softening of winter jujubes (Ziziphus jujuba Mill. cv. Dongzao) have been little studied. In this study, we investigated the effects of different CP intensities (0 kV, 40 kV, and 80 kV) on the postharvest storage quality of winter jujubes and the activities of key enzymes related to softening during storage. The results showed that compared with the control group, the contents of firmness, total soluble solids (TSS), titratable acidity (TA), and vitamin C (VC) in the CP treatment group were higher and the respiratory intensity and weight loss rate were lower. In addition, CP treatment can also inhibit the degradation of protopectin and cellulose and the accumulation of soluble pectin. Moreover, CP treatment inhibited the activities of polygalacturonase (PG), pectin methyl esterase (PME), 3α-L-arabinoside (α-L-Af), 4β-galactosidase (β-gal), cellulase (Cx), and β-glucosidase (β-Glu). This shows that CP treatment has a positive effect on the preservation of winter jujubes, and the preservation effect of the 80 kV treatment was better than that of the 40 kV treatment. This provides a certain basis for cold plasma treatment in the preservation of winter jujubes.

Konjac glucomannan/low-acyl gellan gum edible coating containing thymol microcapsule regulates cell wall polysaccharides disassembly and delays postharvest softening of blueberries

Softening is one of the crucial factors causing the deterioration of postharvest fruit quality. In this study, the effects of konjac glucomannan/low-acyl gellan gum/microcapsule of thymol (TKL) coating on the storage characteristics, the ultrastructure of cell wall and transcription expression of pectin-related metabolism of blueberries fruits during low-temperature storage were investigated. TKL coating suppressed the expression of pectin-related enzymes disassembly (VaPE2, VaPE3, VaPG3, VaPL2 and Vaβ-Gal2), reduced the activity of cell wall polysaccharide degrading enzymes (PG, PE, PL, β-Gal, α-Man, α-Af, Xth, β-Xyl, Cx, β-Glu), maintained the normal morphological structure and stability of cell wall, and prolonged the shelf life of blueberries fruits. Overall, TKL is a promising coating that can effectively maintain the firmness, inhibit the postharvest softening and prolong the shelf life of the blueberries during storage period.

Low temperatures inhibit the pectin degradation of ‘Docteur Jules Guyot’ pear (Pyrus communis L.)

The most remarkable characteristic of European pears is extremely perishable and difficult to store after postharvest softening. Low-temperature storage is one of the most commonly used methods to prolong the shelf life of European pears. However, the regulatory mechanism of the low-temperature delay of the softening of European pears is still unclear. In this study, the fruit firmness, pectin polysaccharide content, pectin-degrading enzyme activity, and pectin degradation gene expression of ‘Docteur Jules Guyot’ pears under low temperature (LT) and room temperature (RT) were analyzed. It was found that water-soluble pectin (WSP) was significantly negatively correlated with fruit flesh firmness, and the activities of several pectin-degrading enzymes were inhibited under LT storage conditions. In addition, it was also found that the gene expression patterns of PcPME2, PcPME3, PcPG1, PcPG2, PcPL, PcGAL1, PcGAL2, PcGAL4, and PcARF1 were inhibited by LT. The C-repeat binding factors PcCBF1 and PcCBF2 were also inhibited by long-term LT storage. Correlation analysis showed that the expression of PcCBFs was positively correlated with pectin-degradation enzyme genes, and we found that the promoters of many pectin-degradation enzyme genes contain the CRT/DRE motif, which CBF can directly bind. Therefore, it is speculated that long-term low-temperature conditions inhibit pectin degradation through PcCBFs.

Elevated oxygen atmosphere maintains antioxidant capacity and inhibits cell wall metabolism in postharvest jujube

Fruit of jujube (Ziziphus jujube Mill. cv. Dongzao), known as a high-quality fresh edible variety, is popular among consumers on account of its bright color, crispy texture and abundant nutrients. However, the softening of jujube fruit after harvest seriously shortens its shelf life. To examine possible treatments to reduce softening rate, we evaluated the effect on fruit quality attributes of an elevated atmospheric O2 concentration during cold storage, ultimately unraveling its biological effect on jujube cell wall metabolism and antioxidant level. Our results demonstrated that an elevated O2 atmosphere during cold storage induced both the activity of antioxidant enzymes and relative expression levels of related genes, promoting the scavenging of hydrogen peroxide and superoxide anion. By the end of storage, the activities of superoxide dismutase, peroxidase, and catalase in elevated O2-treated jujubes were 1.9, 1.3, and 1.1 times, respectively, those in the control group. In addition, elevated O2 concentration inhibited the activities of polygalacturonase, pectin methyl esterase, cellulase and the relative abundance of related transcripts, thus delaying the degradation of cellulose and hemicelluloses and reducing the conversion of insoluble pectin to water-soluble pectin and ionic-soluble pectin. These changes presumably contribute to the maintenance of the cell wall components and cell microstructure. In conclusion, an elevated atmospheric O2 concentration of 60 % during cold storage promoted antioxidant capacity and inhibited cell wall metabolism in postharvest jujube fruit, reducing postharvest softening.

Glycine betaine inhibits postharvest softening and quality decline of winter jujube fruit by regulating energy and antioxidant metabolism

Winter jujube fruit easily softens after harvest. To investigate the effects of glycine betaine (N,N,N-trimethylglycine; GB) treatment on the quality of postharvest jujubes, fresh winter jujubes (Zizyphus jujuba Mill. cv. Dongzao) were immersed in 20 mmol·L−1 GB for 20 min. The results showed that GB application can effectively maintain cell wall component content by restraining gene expression and enzyme activities, including PG, CX, PME and β-Glu. Meanwhile, the activities of antioxidant enzymes (APX, CAT, SOD, POD) and the contents of nonenzymatic antioxidants (MDA, H2O2, ASA, GSH) were enhanced in treated jujubes, thereby reducing the content of ROS. In addition, energy metabolism enzyme activities (H+-ATPase, Ca2+-ATPase, SDH and CCO) and gene expression were also significantly increased, thus maintaining higher energy levels (ATP, ADP, AMP and EC). In summary, GB enhances ATP biosynthesis by increasing energy metabolism. It offers essential energy for the antioxidant metabolism, thus retarding the softening of postharvest jujubes.

Transcriptomic and physiological analysis reveals the possible mechanism of ultrasound inhibiting strawberry (Fragaria × ananassa Duch.) postharvest softening.

Ultrasound effectively inhibited strawberry softening but the mechanism was not clear. In this study, physical data including firmness, soluble pectin (SP) contents, pectin esterase (PE), polygalacturonase (PG) activity and transcriptome sequencing data were analyzed to explore the mechanism of strawberry response to ultrasonic treatment. After 24 days storage, the firmness reduction rate and soluble contents (SP) increased rate of the strawberry treated with ultrasound (25 kHz, 0.15 W/cm2) for 3 min decreased 41.70 and 63.12% compared with the control, respectively. While the PG and PE enzyme activities of ultrasound-treated strawberries were significantly lower than control after storage for 18 days. A total of 1,905 diferentially expressed genes (DEGs) were identified between ultrasound-treated and control, with 714 genes upregulated and 1,254 genes downregulated, including 56 genes in reactive oxygen species (ROS), auxin (AUX), ethylene (ETH) and jasmonic acid (JA) signaling pathways. At 0 h, 15 genes including LOX, JMT, ARP, SKP, SAUR, IAA, ARF, and LAX were significantly upregulated compared with the control group, which means reactive oxygen specie, auxin, ethylene and jasmonic acid-mediated signaling pathway respond to ultrasound immediately. ERF109, ERF110, and ACS1_2_6 downregulated before 2 days storage indicated ethylene signaling pathway was inhibited, while after 2 days, 9 genes including ERF027, ERF109, and ERF110 were significantly upregulated indicating that the response of the ethylene signaling pathway was lagging. Therefore, in strawberry ultrasound enhanced ROS scavenging and activated JA biosynthesis, which acts as a signal for delaying the activation of ET signaling pathway, thus suppressing the activity of pectin-degrading enzymes PE and PG, and ultimately inhibiting postharvest softening.

The calcium-mediated homogalacturonan pectin complexation in cell walls contributes the firmness increase in loquat fruit during postharvest storage

IntroductionPostharvest textural changes in fruit are mainly divided into softening and lignification. Loquat fruit could have severe lignification with increased firmness during postharvest storage. Pectin is mainly associated with the postharvest softening of fruit, but some studies also found that pectin could be involved in strengthening the mechanical properties of the plant. ObjectivesThis study focused on characterizing the dynamics of pectin and its complexation in the cell wall of lignified loquat fruit during postharvest storage, and how these changes could influence fruit firmness. MethodsThe homogalacturonan (HG) pectin in the cell wall of loquat fruit was identified using monoclonal antibodies. An oligogalacturonide (OG) probe was used to label the egg-box structure formed by Ca2+ cross-linking with low-methylesterified HG. An exogenous injection was used to verify the role of egg-box structures in the firmness increase in loquat fruit. ResultsThe JIM5 antibody revealed that low-methylesterified HG accumulated in the tricellular junctions and middle lamella of loquat fruit that had severe lignification symptoms. The pectin methylesterase (PME) activity increased during the early stages of storage at 0 °C, and the calcium-pectate content and flesh firmness constantly increased during storage. The OG probe demonstrated the accumulation of egg-box structures at the cellular level. The exogenous injection of PME and Ca2+ into the loquat flesh led to an increase in firmness with more low-methylesterified HG and egg-box structure signals. ConclusionPME-mediated demethylesterification generated large amounts of low-methylesterified HG in the cell wall. This low-methylesterified HG further cross-linked with Ca2+ to form egg-box structures. The pectin-involved complexations then contributed to the increased firmness in loquat fruit. Overall, besides being involved in fruit softening, pectin could also be involved in strengthening the mechanical properties of postharvest fruit. This study provides new ideas for obtaining a better texture of postharvest loquat fruits based on pectin regulation.

Tragacanth gum coating suppresses the disassembly of cell wall polysaccharides and delays softening of harvested mango (Mangifera indica L.) fruit

Mango is a climacteric fruit and is prone to high perishability. The rapid softening and ripening (due to degradation and disassembly of cell wall polysaccharides) are the major limitations in extending the storability of the harvested mango fruits. Various types of gum-based edible coatings have been reported for the shelf life extension of mango fruits. Tragacanth gum (TCG) also has appropriate coating properties. Its use as an edible coating has been reported on certain fruits. However, the effect of TCG coating in the regulation of harvested mango fruits ripening and softening has not been reported yet. So, the objective of this work was to investigate the effect of TCG (control, 0.5 %, 1 % and 1.5 %) coating on postharvest softening and ripening of harvested mango fruits. TCG coating affected the ripening and softening of mango in a dose-dependent manner. Results exhibited that mango fruits coated with 1.5 % TCG showed substantially lower disease incidence and weight loss. The 1.5 % TCG-coated mangoes showed substantially lower ethylene biosynthesis and respiration rate peaks as well as superoxide anion and hydrogen peroxide contents compared with the control. In the same way, 1.5 % TCG-coated mango fruits had markedly higher total chlorophyll content and lower L*, b* and a* along with substantially lower total carotenoids in peel tissues. Mango fruits coated with 1.5 % TCG exhibited markedly lower water-soluble pectin and higher chelate-soluble pectin, Na2CO3-soluble pectin, protopectin, cellulose and hemicellulose in flesh tissues compared with control. The activity of polygalacturonase (PG), cellulase (CX), pectin methylesterase (PME), β-galactosidase (β-Gal) and β-glucosidase (β-Glu) were significantly lower in flesh of 1.5 % TCG treated fruits along with substantially higher firmness in contrast with control. In addition, 1.5 % TCG coating treatment showed significantly higher activity of antioxidative enzymes and delayed the increase in soluble solids content (SSC) and ripening index (RI) along with considerably higher titratable acidity (TA) compared with the untreated control. So, pre-storage TCG based edible coating (1.5 %) could be applied to delay ripening and softening in mango fruit industry under postharvest ambient conditions.

Effect of Chitosan/Thyme Oil Coating and UV-C on the Softening and Ripening of Postharvest Blueberry Fruits.

This study investigated the possible mechanism of softening and senescence of blueberry after harvest using chitosan/thyme oil coating combined with UV-C (short wave ultraviolet irradiation) treatment. On the 56th day of storage, the CBP, cellulose, and hemicellulose contents in the chitosan/thyme oil coating +UV-C-treated group were 1.41, 1.65, and 1.20 times higher than those in the control group. Compared with the control group, the activities of polygalacturonase (PG), pectin methylesterase (PME), β-glucosidase (β-Gal), and cellulose (Cx) were significantly reduced (p < 0.05) after chitosan/thyme oil coating +UV-C, and their maximum values decreased by 5.41 μg/h g, 5.40 U/g, 12.41 U/g, and 3.85 μg/h g, respectively. Moreover, chitosan/thyme oil coating combined with UV-C treatment inhibited the gene expression of PG, PME, Cx, and β-Gal and then regulated the decrease in PG, PME, Cx, and β-Gal activities, inhibited the degradation of cell wall polysaccharides, and delayed the softening and senescence of postharvest blueberries. The results showed that chitosan/thyme oil coating, UV-C, and chitosan/thyme oil coating + UV-C could significantly inhibit postharvest softening of blueberry; chitosan/thyme oil coating +UV-C had the best effect.