Fruit Softening Research Articles

PrupeFUL4 regulates ripening and softening of peach fruits through ethylene biosynthesis

PrupeFUL4 regulates ripening and softening of peach fruits through ethylene biosynthesis

Fusion of data-driven model and mechanistic model for kiwifruit flesh firmness prediction

Kiwifruit are often harvested unripe and stored to ripen in cool storage for extended periods of time. Flesh firmness (FF) is one of the most important postharvest quality attributes for kiwifruit which determines the storability of individual and/or batches of fruit. Pre- and postharvest factors can influence the softening rate of fruit in cool storage, and this results in a wide range of FF retention capabilities creating challenges for prediction of shelf-life performance. Two general streams of modelling methodologies have previously been investigated: 1) mechanistic modelling which attempts to describe the biochemical pathways occurring during fruit softening and environmental interactions which also influence softening rate; and 2) data-driven black-box modelling which utilises sensor data as an input to extrapolate potential firmness outcomes. Both approaches have limitations on their own, and as such adaptation at the industry level is restricted. This work demonstrates the feasibility of a novel model fusion approach which integrates the two types of models by incorporating at-harvest non-destructive sensor data as functional covariates into a mechanistic model. A closed-form solution to a kinetic model was first derived which provides a flexible parametric form for incorporation of covariates utilising non-destructive sensor data and temporal effects. The closed-form model was then integrated with functional regression to enable prediction of post-storage FF values of individual fruit using at-harvest near infrared spectral data obtained from the same fruit. The resulting fused model showed superior performance in forecasting post-storage quality indices of kiwifruit compared with conventional benchmarks including partial least squares and support vector machines regression. However, improvement in prediction accuracy for FF is not yet adequate to justify industrial applicability. Nonetheless, the significance of this work is the demonstration of a physics-guided data-driven modelling approach which is both highly interpretable and flexible in incorporation of other types of measurable covariates such as grading-line sensor data, preharvest growth factors, and harvest conditions. A more generic fused model will need to be developed for future studies in order to allow flexibility in changes in environmental conditions during storage.

ROS scavenger Hypotaurine delays postharvest softening of ‘Kyoho’ grape by regulating pectin and cell metabolism pathway

The rapid softening of postharvest fruit has a serious detrimental effect on quality and market value. In this study, postharvest grape berries treated with hypotaurine (HT) or H2O2 were employed to explore the dynamic physical and transcriptional changes after the treatment. The berry firmness and the content of propectin were higher in the berries with HT treatment compared to the control (CK) and H2O2 treatment. A total of 1774 differentially expressed genes (DEGs) were identified from comparisons of CK_vs_HT (1,020) and CK_vs_H2O2 (1,072). Weighted gene coexpression network analysis (WGCNA) showed that genes assigned to ‘MEgreen’ were predicted to be highly correlated to fruit firmness and propectin content. Based on transcriptome and quantitative real-time polymerase chain reaction (RT-qPCR), expression levels of VvMYB-like, VvNAC22, VvPEI and VvCESA-like were upregulated whereas VvMADS-box and VvPG were downregulated in HT-treated berries compared to H2O2 treatment. Dual luciferase reporter assay confirmed that VvMYB-like and VvNAC22 upregulate the expression of VvPEI and VvCESA respectively by binding to the corresponding sites of their promoters. Meanwhile, HT treatment triggered the differential expression of Accelerated Cell Death 6 (VvACD6), VvXyloglucan galactosyltransferase (VvXyG galactosyltransferase) and Cell wall/Vacuolar Inhibitor of Fructosidase 1-like (VvC/VIF1-like). Finally, a possible regulatory model that HT delays berry softening by regulating pectin and cell metabolism pathway through VvMYB-like and VvNAC22 was proposed. This study laid a foundation for understanding the molecular mechanisms of delaying berry softening which HT mediated.

Roles of abscisic acid in regulating ripening and quality of strawberry, a model non-climacteric fruit.

Abscisic acid (ABA) is a dominant regulator of ripening and quality in non-climacteric fruits. Strawberry is regarded as a model non-climacteric fruit due to its extensive genetic studies and proven suitability for transgenic approaches to understanding gene function. Strawberry research has contributed to studies on color, flavor development, and fruit softening, and in recent years ABA has been established as a core regulator of strawberry fruit ripening, whereas ethylene plays this role in climacteric fruits. Despite this major difference, several components of the interacting genetic regulatory network in strawberry, such as MADS-box and NAC transcription factors, are similar to those that operate in climacteric fruit. In this review, we summarize recent advances in understanding the role of ABA biosynthesis and signaling and the regulatory network of transcription factors and other phytohormones in strawberry fruit ripening. In addition to providing an update on its ripening, we discuss how strawberry research has helped generate a broader and more comprehensive understanding of the mechanism of non-climacteric fruit ripening and focus attention on the use of strawberry as a model platform for ripening studies.

Multi-omics data integration provides insights into the post-harvest biology of a long shelf-life tomato landrace.

In this study we investigated the transcriptome and epigenome dynamics of the tomato fruit during post-harvest in a landrace belonging to a group of tomatoes (Solanum lycopersicum L.) collectively known as "Piennolo del Vesuvio", all characterized by a long shelf-life. Expression of protein-coding genes and microRNAs as well as DNA methylation patterns and histone modifications were analysed in distinct post-harvest phases. Multi-omics data integration contributed to the elucidation of the molecular mechanisms underlying processes leading to long shelf-life. We unveiled global changes in transcriptome and epigenome. DNA methylation increased and the repressive histone mark H3K27me3 was lost as the fruit progressed from red ripe to 150days post-harvest. Thousands of genes were differentially expressed, about half of which were potentially epi-regulated as they were engaged in at least one epi-mark change in addition to being microRNA targets in ~5% of cases. Down-regulation of the ripening regulator MADS-RIN and of genes involved in ethylene response and cell wall degradation was consistent with the delayed fruit softening. Large-scale epigenome reprogramming that occurred in the fruit during post-harvest likely contributed to delayed fruit senescence.

Identification in silico and expression analysis of a β-1-4-endoglucanase and β-galactosidase genes related to ripening in guava fruit

BackgroundGuava fruit softening is a crucial process during ripening and this process involves a number of enzymes that modifies the cell wall. Two of the enzymes that regulate this process are (a) the β-1, 4-endoglucanase 17 (BEG) which hydrolyze β-1, 4 bonds from cellulose and hemicellulose, and (b) β-galactosidase (BGA) that hydrolyzes pectin chains. Bioinformatics and expression analysis information on these genes is limited in guava fruit. ResultsA fragment of a β-1, 4-endoglucanase 17 (PgE17), and another of a β-galactosidase (PgGa1) were identified. These sequences have a similarity of more than 85% with those reported in the NCBI database. In the guava genome, one homologous sequence was found for PgE17 in Chr 4 and two homologous to PgGa1: one in Chr 3 and the other one in Chr 6. Putative protein PgE17 contains part of the glyco_hydro_9 domain. Putative protein PgGa1 has a part of the glyco_hydro_35 domain. Phylogenetic analysis of PgE17 and PgGa1 revealed that both are highly conserved inside the Myrtaceae family. In silico expression analysis showed that both PgE17 and PgGa1 work in a coordinated way with other cell wall modifier enzymes. Expression of these genes was found in all the guava samples analyzed. However, the highest expression was found in the fruit in the breaking and ripe states. ConclusionsA β-1, 4-endoglucanase 17, and β-galactosidase 1 sequences were identified. PgE17 and PgGa1 are expressed in all the plant tissues, and fruit ripening states. Although, the highest expression was on breaker and ripe states.

Transcriptome analysis of peach fruit under 1-MCP treatment provides insights into regulation network in melting peach softening

Abstract Peach (Prunus persica L.) displays distinguish texture phenotype during postharvest, which could be classified into three types, including melting flesh (MF), non-melting flesh, and stony-hard. MF peach would soften rapidly with an outbreak of ethylene production, which causes huge wastage during fruit transportation and storage. 1-Methylcyclopropene (1-MCP) was used to alleviate fruit softening. In this study, we performed RNA-sequencing on two MF peach cultivars (‘YuLu’ and ‘Yanhong’) after 1-MCP treatment to identify the candidate genes participating in peach fruit softening. A total of 167 genes were identified by weighted gene coexpression network analysis and correlation analysis that could respond to 1-MCP treatment and might be related to softening. Among them, 5 auxin-related genes including 2 indole-3-acetic acid, 1 auxin response transcription factor and 2 small auxin-up RNAs, and 4 cell wall modifying genes (PpPG1, PpPG2, PpPG24 and PpPMEI) were characterized as key genes participating in MF peach softening. Furthermore, 2 transcription factors, which belong to HD-ZIP and MYB, were predicted as candidates regulating softening process by constructing a transcriptional network of these 4 cell wall modifying genes combined with expression pattern analysis, of which HD-ZIP could trans-activate the promoter of PpPG1.

A novel edible packaging film based on chitosan incorporated with persimmon peel extract for the postharvest preservation of banana

Abstract This study aimed to develop a novel edible packaging film for the postharvest preservation of banana based on chitosan (CS) and persimmon peel extract (PPE). Scanning electron microscopy analysis showed that PPE was evenly distributed in the CS matrix and Fourier transform infrared spectroscopy analysis showed that CS and PPE interacted to form hydrogen bonds, demonstrating good compatibility. Simultaneously, the addition of PPE also significantly improved the physical properties and antioxidant activity of the CS film. Among them, the CS film containing 10% PPE (CS-PPE 10) showed the optimal mechanical properties, water vapor barrier properties and oxygen barrier properties. The CS film containing 15% PPE (CS-PPE 15) exhibited the best thermal stability, UV-Vis barrier properties and antioxidant activity. In the experiment on banana preservation, CS-PPE 10 film obtained optimal performance on decreasing senescence spots, weight loss, fruit softening, and cell wall degradation, inhibiting the activities of polyphenol oxidase and cell wall-degrading enzymes and maintaining the content of total soluble sugar and ascorbic acid during the storage period. Consequently, CS-PPE 10 film was expected to be a novel edible packaging material to maintain banana quality and prolong shelf life.

Effects of melatonin on blueberry fruit quality and cell wall metabolism during low temperature storage

Melatonin is known to influence various physiological processes, including plant ripening; however, the effect of melatonin on postharvest blueberry fruit softening is unknown. Herein, the effects of melatonin at different concentrations (100, 300, and 500 μmol L-1) on the quality parameters, cell wall substances, cell-wall-degrading enzymes, and cell wall ultrastructure of blueberry fruits were investigated during low-temperature storage. Melatonin treatment was found to effectively delay the decline in fruit firmness, slow the loss of soluble solids and titratable acids, and decrease the respiration rate and decay rate of blueberry fruits. The blueberry fruits treated with 300 μmol L-1 melatonin exhibited the best quality. Melatonin treatment promoted anthocyanin accumulation, delayed ascorbic acid degradation, maintained a low relative membrane permeability in pulp, inhibited increases in lipoxygenase (LOX) activity, and reduced membrane lipid peroxidation. Moreover, melatonin controlled the formation of soluble pectin by inhibiting the activities of pectin methylesterase (PME), polygalacturonase (PG), cellulase (Cx), and β-glucosidase (β-Glu) while maintaining high contents of protopectin and cellulose. These results indicate that melatonin can effectively improve blueberry fruit quality and antioxidant capacity as well as and delay fruit softening by inhibiting the degradation of cell wall substances.

Nitric oxide supply reduces ethylene production, softening and weight loss in papaya fruit

Nitric oxide application has been seen as a promising technique to extend the postharvest life of various fresh fruits and vegetables. This is the first work involving the spray application of nitric oxide donor S-nitrosoglutathione (GSNO) on Golden papaya. Considering that results are very distinct depending on the type of the nitric oxide donor, the form of application, the concentration used and the species studied, the application must be adapted to each necessity. The aim of this study was to relate the application of GSNO, spray applied at 10, 100, 1,000 ?M, with the physiological, physical-chemical, and biochemical changes of Golden papaya, in the first 72 h of ripening. Control fruit was sprayed with distilled water. GSNO application did not interfere on color and chlorophyll fluorescence of the peel, on soluble solids, titratable acidity, lipid peroxidation, and in the level of S-nitrosothiols. Control fruit and 10-?M GSNO sprayed showed lower respiration. After 72 h of ripening at 25°C, all fruits showed an increase in ethylene biosynthesis, except for those treated with 10 ?M GSNO. Papaya sprayed with 10-?M GSNO showed the highest pulp firmness and 52% less weight loss when compared to control fruit. GSNO was also responsible for increasing the ascorbic acid in papayas, besides showing an increase in total antioxidant activity production. The results indicated that the application of 10 ?M of GSNO by spray can potentially preserve the quality characteristics of Golden papaya, mainly due to the lower ethylene production, the delay in the firmness loss, and the less weight loss.

Synergistic effects of plant hormones on spontaneous late-ripening mutant of ‘Jinghong’ peach detected by transcriptome analysis

Abstract Objectives Peach (Prunus persica L.) is an ancient fruit tree that originated from China. It is the climacteric fruit belonging to genus Prunus in family Rosaceae. Ethylene, which is produced during ripening, accelerates fruit softening, and therefore peaches cannot be stored for a long time. Materials and Methods To study the mechanism of fruit late ripening, transcriptome analysis of the fruit of a late-ripening mutant of ‘Jinghong’ peach was performed to identify genes and pathways involved in fruit late ripening. Results A total of 1805, 1511, and 2309 genes were found to be differentially expressed in W2_vs_M1, W3_vs_M2, and W3_vs_M3, respectively. Functional enrichment analysis of the differentially expressed genes showed they were related to carotenoid biosynthesis, starch and sucrose metabolism plant hormone signal transduction, flavonoid biosynthesis, and photosynthesis. The expression trends of ripening-related genes that encode transcription factors and plant hormone signal transduction-related genes that encode enzymes were similar. Conclusions It will help to elucidate the transcriptional regulatory network of fruit development in the spontaneous late-ripening mutant of ‘Jinghong’ peach and provide a theoretical basis for understanding the molecular regulatory mechanism of fruit ripening.

Manutenção da qualidade de maçã ‘Luiza’ em função de práticas pós-colheita

Abstract This study was carried out to examine the response of ‘Luiza’ apple to different storage atmospheres, durations, and chemical inhibition of ethylene action by 1-MCP. Analysis of fruit quality and physiological disorder incidence were performed every two months during eight months of storage for Exp. 1 and 2, and after eight months for Exp. 3. Both CA storage and 1-MCP treatment reduced fruit ethylene production and respiration and prevented the rapid fruit softening, flesh browning incidence and fungal decay of ‘Luiza’ apple. The combination of 1-MCP treatment before storage in CA provided an additional benefit in firmness retention after simulated marketing conditions at 22oC. Based on the time to reach a firmness of 53 N, the storage life of ‘Luiza’ apple is less than four months in air-storage and more than six months under CA-storage. ‘Luiza’ fruit did not develop symptoms of CO2 injury when stored under high CO2 partial pressures (up to 4.5 kPa). However, we observed increased flesh browning and fungal decay incidence for CA-stored fruit between six and eight months of storage. Therefore, the storage potential of ‘Luiza’ apple fruit may be limited to six months under CA-storage (1.5 kPa O2 and 2.5 kPa CO2).

Could Causal Discovery in Proteogenomics Assist in Understanding Gene-Protein Relations? A Perennial Fruit Tree Case Study Using Sweet Cherry as a Model.

Genome-wide transcriptome analysis is a method that produces important data on plant biology at a systemic level. The lack of understanding of the relationships between proteins and genes in plants necessitates a further thorough analysis at the proteogenomic level. Recently, our group generated a quantitative proteogenomic atlas of 15 sweet cherry (Prunus avium L.) cv. ‘Tragana Edessis’ tissues represented by 29,247 genes and 7584 proteins. The aim of the current study was to perform a targeted analysis at the gene/protein level to assess the structure of their relation, and the biological implications. Weighted correlation network analysis and causal modeling were employed to, respectively, cluster the gene/protein pairs, and reveal their cause–effect relations, aiming to assess the associated biological functions. To the best of our knowledge, this is the first time that causal modeling has been employed within the proteogenomics concept in plants. The analysis revealed the complex nature of causal relations among genes/proteins that are important for traits of interest in perennial fruit trees, particularly regarding the fruit softening and ripening process in sweet cherry. Causal discovery could be used to highlight persistent relations at the gene/protein level, stimulating biological interpretation and facilitating further study of the proteogenomic atlas in plants.

Integrative transcriptomic and metabolomic alterations unravel the effect of melatonin on mitigating postharvest chilling injury upon plum (cv.Friar) fruit

Plum fruit often suffer severe chilling injury (CI) during storage. Plum (Prunus salicina Lindl. cv. Friar) fruit were treated with melatonin at various concentrations and stored at 0 ℃ for 6 w and additional 3 d of shelf-life at 23 ℃. Observations revealed that the treatment with 1.0 mmol L−1 melatonin mitigated CI of the fruit by reducing flesh-reddening and ‘ethylene burst’. The melatonin treatment also suppressed fruit softening and maintained energy status. Results from UPLC-MS assay showed that several individual phenolic compounds involved in the biosynthesis of flavonoids and anthocyanins, especially, the red pigment of cyanidin-3-O-glucoside, were stimulated by cold stress and its removal, but the stimulation was effectively inhibited by melatonin treatment, and thereby flesh-reddening was alleviated. Results from RNA-sequencing unraveled that cold stress and its removal altered transcriptomic profiling of the plum fruit, but the melatonin treatment hindered the transcription of genes related to the anthocyanin biosynthesis. Correlation analysis indicated that seven MYBs were positively correlated with anthocyanin biosynthesis, which were generally down-regulated in the melatonin-treated plums. The integrative analysis of transcriptomic and metabolic alterations revealed differentially but delicately coordinated inhibition of postharvest physiological metabolisms of ‘Friar’ plums by melatonin in response to cold stress.

The MaC2H2-like zinc finger protein is involved in ripening and ripening disorders caused by chilling stress via the regulation of softening-related genes in ‘Fenjiao’ banana

As one of the largest transcription factor families, C2H2 zinc finger proteins contain a zinc finger motif and a conserved DNA-binding homeodomain. Although C2H2 zinc finger proteins have been found to play an essential role in ethylene biosynthetic and cold stress in banana fruit, their transcriptional regulatory mechanisms involved in the softening of ‘Fenjiao’ banana remain largely elusive. In this study, a new MaC2H2-like gene was identified, which is closely related to fruit softening. MaC2H2-like localizes in the nucleus. MaC2H2-like activated the transcription of four starch (MaBAM4, MaBAM6, MaISA2 and MaPWD1) and five cell wall (MaEXP-A2, MaEXP-A8, MaSUR14, MaSUR14-like and MaXYL32) degradation-related genes, by specifically interacting with their promoters. Protein-protein interaction assays showed that MaC2H2-like cooperates with ethylene-insensitive 3-binding F-box protein (MaEBF1) in vitro and vivo, and their interaction enhanced the binding and activated the promoter activities of MaBAM4, MaPWD1, MaISA2, MaEXP-A2, MaSUR14-like and MaXYL32. The transient overexpression of MaC2H2-like in ‘Fenjiao’ banana fruit promoted fruit ripening and softening by accelerating ethylene production, decreasing fruit firmness and inducing the transcription of starch and cell wall degradation-related genes. Collectively, we uncovered a novel module of MaC2H2-like-MaEBF1 that cooperates in actively impacting starch and cell wall degradation by up-regulating the transcript level of genes related to the degradation of starch and cell walls.

Changes in Homogalacturonan Metabolism in Banana Peel during Fruit Development and Ripening.

Though numerous studies have focused on the cell wall disassembly of bananas during the ripening process, the modification of homogalacturonan (HG) during fruit development remains exclusive. To better understand the role of HGs in controlling banana fruit growth and ripening, RNA-Seq, qPCR, immunofluorescence labeling, and biochemical methods were employed to reveal their dynamic changes in banana peels during these processes. Most HG-modifying genes in banana peels showed a decline in expression during fruit development. Four polygalacturonase and three pectin acetylesterases showing higher expression levels at later developmental stages than earlier ones might be related to fruit expansion. Six out of the 10 top genes in the Core Enrichment Gene Set were HG degradation genes, and all were upregulated after softening, paralleled to the significant increase in HG degradation enzyme activities, decline in peel firmness, and the epitope levels of 2F4, CCRC-M38, JIM7, and LM18 antibodies. Most differentially expressed alpha-1,4-galacturonosyltransferases were upregulated by ethylene treatment, suggesting active HG biosynthesis during the fruit softening process. The epitope level of the CCRC-M38 antibody was positively correlated to the firmness of banana peel during fruit development and ripening. These results have provided new insights into the role of cell wall HGs in fruit development and ripening.

Comparative Molecular docking analysis of Target fruit ripening enzyme Tomato Beta galactosidase (TBG-4)

Tomatoes comprise a high level of TBG4 (Tomato Beta galactosidase-4) enzyme activity that plays a key role in fruit softening by significant changes in the galactosyl content in the pericarp cell wall. In the present work, in silico docking studies of beta galactosidase with specific elucidated ligands were carried out. For the better understanding of protein ligand interactions, a set of 16 ligands were used for docking studies. In the present study, two different comparative docking softwares, Autodock4.0 and iGEMDOCK were used to study the protein–ligand interactions and performed to get the best docking scores. PLIP software was used for visualization of protein ligand complex and their interactions. Binding energies of 16 ligands were predicted among which 5 ligands 151, 2FL, B2G, EPE and LAT were analysed and confirmed as best ligands. Among them 151(2S)-3-Methyl-2-((2R,3S)-3- [(Mehtylsulfonyl)amino]-1-[2-(Pyrolidin-1-ylmethyl)- 1,3-Oxazol-4yl} Butanoic acid is the best inhibitor of TBG4 enzyme activity leading to significant enhancement in fruit shelf life.

FvMYB79 Positively Regulates Strawberry Fruit Softening via Transcriptional Activation of FvPME38.

Strawberry is a soft fruit with short postharvest life, due to a rapid loss of firmness. Pectin methylesterase (PME)-mediated cell wall remodeling is important to determine fruit firmness and softening. Previously, we have verified the essential role of FvPME38 in regulation of PME-mediated strawberry fruit softening. However, the regulatory network involved in PME-mediated fruit softening is still largely unknown. Here, we identified an R2R3-type MYB transcription factor FvMYB79, which activates the expression level of FvPME38, thereby accelerating fruit softening. During fruit development, FvMYB79 co-expressed with FvPME38, and this co-expression pattern was opposite to the change of fruit firmness in the fruit of ‘Ruegen’ which significantly decreased during fruit developmental stages and suddenly became very low after the color turning stage. Via transient transformation, FvMYB79 could significantly increase the transcriptional level of FvPME38, leading to a decrease of firmness and acceleration of fruit ripening. In addition, silencing of FvMYB79 showed an insensitivity to ABA-induced fruit ripening, suggesting a possible involvement of FvMYB79 in the ABA-dependent fruit softening process. Our findings suggest FvMYB79 acts as a novel regulator during strawberry ripening via transcriptional activation of FvPME38, which provides a novel mechanism for improvement of strawberry fruit firmness.

Fungus Polygalacturonase-Generated Oligogalacturonide Restrains Fruit Softening in Ripening Tomato.

Fruit softening exacerbates mechanical damage incurred during shipping and handling and the increase in pathogen susceptibility. Here, oligogalacturonides (OGs) produced by fungal polygalacturonase (PG) delayed fruit softening in tomato and maintained fruit firmness at 8.37 ± 0.45 N at 13 d of storage, which was consistent with the fruit firmness level of 5 d in the control groups. From RNA sequencing data in line production of phytohormones, we confirmed ethylene and jasmonic acid signals, the MAPK signaling cascade, and calmodulin involved in the OG-mediated firmness response of whole fruit. SlPG2, SlPL3, and SlPL5 were the major contributing factors for fruit softening, and their expression decreased continuously upon OG application. Suppression of the expression of ethylene response factors using a virus-induced gene-silencing strategy revealed that SlERF6 was negatively involved in OG-restrained fruit softening. Taken together, these results indicated that fungal PG-generated OGs have potential application value in controlling tomato fruit softening.

Inhibitory Effects of CaCl2 and Pectin Methylesterase on Fruit Softening of Raspberry during Cold Storage

Quality of raspberry fruit experiences a rapid decline after harvest due to its vulnerable texture and high moisture content. Application of calcium chloride (CaCl2) combined with pectin methylesterase (PME) is efficient in delaying fruit softening. In this study, the effects of exogenous CaCl2 alone or in combination with PME on the structure of the cell wall, the molecular properties of pectin, and the amount of free water of raspberry during postharvest storage were investigated. The results showed that CaCl2 combined with PME treatment could maintain fruit firmness and inhibit weight loss. The treatment of CaCl2+PME maintained the cell wall structure via sustaining middle lamella integrity and reducing the activities of cell wall-degrading enzymes, such as polygalacturonase, pectin methylesterase, β-galactosidase, α-L-arabinofuranosidase, and β-xylosidase. In addition, CaCl2+PME treatment could effectively increase the content of chelate-soluble pectin (CSP) and develop a cross-linked structure between Ca2+ and CSP. Moreover, CaCl2+PME treatment was of benefit in maintaining free water content. CaCl2 in combination with PME treatment could be a promising method for inhibiting softening and maintaining the quality of postharvest raspberry during cold storage.