Insoluble Pectin Research Articles

Ethylene-Induced Postharvest Changes in Five Chinese Bayberry Cultivars Affecting the Fruit Ripening and Shelf Life

Ethylene is an essential indicator of fruit ripening and climacteric or non-climacteric nature. This study investigated the postharvest behavior of five Chinese bayberry cultivars ‘Biqi’, ‘Dongkui’, ‘Fenhong’, ‘Xiazhihong’, and ‘Shuijing’. The fruits were harvested mature and stored at room temperature (25 °C) and under cold storage conditions (4 °C) to investigate the dynamics of ethylene production, firmness, anthocyanin content, and cell wall polysaccharide composition, as well as basic fruit physicochemical characteristics. The results show that Chinese bayberry is a climacteric fruit with ethylene production peaking shortly after harvest, especially at room temperature. Fruit color intensified over time due to anthocyanin accumulation, particularly in the flesh core. Darker cultivars produced more ethylene, which correlated with higher anthocyanin levels. At room temperature, ‘Biqi’ (black) had the highest ethylene production (4.03 µL·kg−1·h−1) and anthocyanin content (0.91 mg/g FW), while ‘Shuijing’, the white cultivar, had the lowest ethylene levels (1.9 µL·kg−1·h−1) and anthocyanin content (0.03 mg/g FW). Firmness significantly decreased at room temperature due to the degradation of hemicellulose and insoluble pectin, whereas cold storage mitigates this effect. After 3 days at room temperature, the average of firmness decreased by 23.7% in the five cultivars, compared to 12.7% under cold storage. Total soluble solids increase during storage, enhancing sweetness, especially at room temperature, with ‘Biqi’ increasing from 9.2 to 10.9% at 4 °C. Titratable acidity slightly decreased over time: the value for ‘Biqi’ decreased from 1.2% to 0.95% at room temperature and 1.1% at 4 °C. Citric, malic, and tartaric acid generally declined at room temperature but stabilized under cold storage. Sucrose, fructose, and glucose increased or remained stable, with significant varietal differences. Our results indicate that storing Chinese bayberry at 4 °C effectively preserves its quality and extends postharvest life. These findings underscore ethylene’s key role in regulating ripening, postharvest quality, and shelf life by influencing fruit color, firmness, and overall consumer appeal.

Theanine enhances resistance to Botrytis cinerea in postharvest strawberry fruit via modulating cell-wall and phenylpropanoid metabolisms

Theanine (N-ethyl-γ-glutamine), as a unique non-protein amino acid, plays vital roles in abiotic stress resistance, while its roles in biotic stress resistance are still unclear. Gray mold caused by Botrytis cinerea is a major disease in strawberries. Effects of theanine on the development of gray mold, cell-wall and phenylpropanoid metabolisms in strawberries were investigated in this study. Results showed that 5 mmol L−1 theanine treatment reduced disease incidence and severity of gray mold in strawberries with antifungal activity in vitro. Meanwhile, theanine treatment enhanced the accumulation of phenolic compounds and lignin, especially ellagic acid, cyanidin, and quercetin, which was associated with increased phenylpropanoid pathway related enzyme activities. Moreover, theanine induced callose deposition and suppressed cell- wall disassembling enzymes, accompanied by higher levels of water insoluble pectin, hemicellulose and cellulose. Therefore, theanine treatment could alleviate decay of B. cinerea-inoculated strawberries by regulating phenylpropanoid and cell-wall metabolisms, maintaining higher levels of phenolic compounds and cell-wall components, thereby contributing to disease resistance and cell-wall structure integrity.

Detection of cell membrane disruption using electrical impedance spectroscopy and acceleration of cell wall modification in carrot processed under low temperature blanching

In this study, we evaluated relationships between cell membrane damage and cell wall modification in carrots by low temperature blanching. Electrical impedance analysis was carried out to elucidate the tissue condition during low temperature blanching. The obtained parameters suggested that cell membrane disruption and electrolyte outflow was promoted by low temperature blanching at 60 °C than that at 50 °C. Low temperature blanching at 60 °C for 40 min showed greater softening inhibition than that at 50 °C. Meanwhile, the activity of pectin methylesterase at 60 °C was lower than that at 50 °C. Regarding cell wall condition, increased insoluble pectin and decreased water-soluble pectin were confirmed at 60 °C rather than that at 50 °C. To conclude, cell membrane disruption is assumed to trigger cell wall modification by exposing the cell wall and middle lamella to intracellular ions.

Overexpression of Solanum lycopersicum DDB1 interacting protein 4 (SlDDI4) extends tomato shelf life by methylation-mediated suppression of softening-related genes expression

Prolonging the fruit storage period is strategically important due to the limitation of postharvest life determined by excessive softening. Efforts have been made to alleviate the issue of fruit softening in transgenic fruit by suppressing genes that encode cell wall-degrading proteins. However, individual genes related to the degradation of cell walls have limited ability, resulting in minimal success. SET domain-containing protein (SET protein) is widely expressed in most plant organs and crucial in plant growth and development. A tomato SET protein was previously identified as SlDDI4 (Solanum lycopersicum DDB1 interacting protein 4) with a H3K9 methyltransferase activity involving cell proliferation and organ size regulation. In this study, we demonstrated that SlDDI4 overexpression (SlDDI4-OE) promotes fruit firmness in addition to increased fruit size. Further experimental investigations revealed that the increased expression of SlDDI4 inhibited cellulase and pectinase activities, consequently increasing the proportion of cellulose and insoluble pectin. RNA-seq profiling indicated the genes involved in cell wall metabolism in SlDDI4-OE fruit were significantly down-regulated. DNA methylation and McrBC-PCR analysis at the SlCEL2, SlPG2, and SlEXP12 loci revealed that their down-regulation was associated with the elevated methylation level in the individual promoter regions. Furthermore, up-regulation of SlDDI4 generated fruit with increased lycopene content and prolonging shelf-life by approximately 20 d without adverse impacts on the flavor indicators. Thus, our results suggest that manipulation of SlDDI4 expression enables broad favorable effects on postharvest life as well as fruit size and quality through chromatin remodeling.

Hydrogen sulfide alleviates the chilling-induced lignification in loquat fruit by regulating shikimate, phenylpropanoid and cell wall metabolisms

Lignification is a typical symptom of chilling injury (CI) in loquat fruit under chilling stress. This study investigated the impact of hydrogen sulfide (H2S) on endogenous H2S, shikimate, phenylpropanoid, and cell wall metabolisms of loquat fruit during refrigeration. The findings suggested that H2S treatment hindered the rise in the CI index and firmness while delaying the reduction in extractable juice, soluble sugar, and titratable acid content of loquat fruit. Besides, H2S treatment promoted the endogenous H2S content, which was correlated with the increase in activities of related H2S synthase enzymes. Furthermore, H2S suppressed enzymes involved in shikimate and phenylpropanoid metabolisms, thereby decreasing phenylalanine and lignin accumulation. Simultaneously, H2S treatment retarded the increases in insoluble pectin, hemicellulose, and cellulose by orchestrating cell wall-modifying enzymes. This work indicates that H2S treatment may alleviate chilling-induced lignification by inhibiting lignin accumulation and enhancing the depolymerization and solubilization of cell wall polysaccharides.

A clean label O/W pickering emulsion stabilized by pectin-containing lignocellulosic nanofibrils isolated from apple pomace

With the increasing demand for clean-label food, LCNF is considered a promising candidate to replace artificial surfactants in O/W emulsion. However, the isolation of LCNF usually requires the use of costly and toxic oxidants or grafting reagents to introduce charged groups for higher fibrillation degree and better emulsifying properties. In this study, a new pectin-containing apple nanofibril (A-NF) with native dissociated carboxyl groups (-COO-) was successfully produced from apple pomace by alkaline demethylation followed by high-pressure homogenization. These “native” charged A-NFs are 10–30 nm in diameter and ∼1 μm in length, and can be well dispersed in water for several months due to the release of up to 1.30 mmol/g nanofibrils of -COO- from the insoluble pectin (ISP) fraction by alkaline demethylation. Among A-NFs, A–NF–24h showed the best emulsifying properties (70.85 m2/g of EAI and 94.71% of ESI) and highest emulsion stability (∼1.00 μm of the oil droplet size during 14-day storage). Emulsion microstructure showed that LCNF not only irreversibly adsorbed at the oil-water interface, providing electrostatic stability, but also offered depletion stability by fabricating an entangled network with the unabsorbed portion. Moreover, molecular dynamics simulations further explained that the A-NF system displayed lower absorption energy of −1659.43 kJ/mol and diffusion cofactor of oil molecules of 16.67 μm2/s than that of CNF system at the interface, thus enhancing the emulsion stability. Altogether, these native A-NFs exhibit good colloidal stability, comparable emulsifying properties and emulsion stability, and have promising applications in clean-label O/W emulsions.

Juice yield and pectin indicators in apple and carrot pomace

Background: Pectin exhibits different properties based on its degree of esterification, forming gels and serving as a structure-forming agent in food products, or forming complexes with heavy metal ions, finding applications in the development of therapeutic products for the elimination of heavy metal ions from the human body. Context and purpose of this study: The purpose of this study is to investigate the influence of enzymatic treatment on the yield and quality of apple and carrot juices, as well as the quality parameters of pectin in pomace. Our objectives were to select an enzymatic preparation for processing apple and carrot pomace and to study changes in the properties of pectins present in the pomace depending on the dosage of the enzyme preparation.Results: The results of our experiments revealed that for apple pomace processing, it is more beneficial to use the enzyme preparation Vegazym M with a dosage of 0.09% of the pomace mass, while for carrot pomace processing, the enzyme preparation Fructozym MA with a dosage of 0.07% of the pomace mass proved to be the most suitable. These enzyme preparations in the specified amounts ensure maximum juice yield. It has been established that changing the dose of enzymes changes the complexing properties of pectin, which allows its use in food products with therapeutic and prophylactic properties.Conclusions: The enzyme preparations allow for specific modifications, such as pectin modification in this case, enabling the versatile use of pectin as either a structure-forming agent or for the development of therapeutic and preventive food products.Keywords:Apple and carrot juices, enzyme preparations, apple and carrot pomace, pectin, soluble and insoluble pectin, degree of esterification and pectin complexation, functional products.

Melatonin treatment inhibits mango fruit (Cv. ‘Guiqi’) softening by maintaining cell wall and reactive oxygen metabolisms during cold storage

Mango fruit (Mangifera indica L, cv. ‘Guiqi’) was treated with melatonin (1 mM) to explore the changing mechanisms in fruit softening and to examine the effects of melatonin on the interaction between the cell wall and reactive oxygen metabolisms subjected to cold storage. The results depicted that compared to control, melatonin treatment (1) improved storage life by maintaining the higher ascorbic acid (AsA) and reduced glutathione (GSH) contents, as well as maintained higher insoluble pectin, hemicellulose, and cellulose contents, and lower soluble pectin content of ‘Guiqi’ mango fruit. (2) Delayed fruit softening by maintaining higher firmness and suppressing the activities of polygalacturonase (PG), pectin methyl esterase (PME), cellulase (Cx), and β-glucosidase (β-glu); and cell wall degrading genes (MiPG14, MiPME, MiCel, and Miβ-glu). (3) Enhanced storage quality by inhibiting decay incidence, respiration rate, and weight loss rate; increased activity of glutathione reductase (GR) and inhibits reactive oxygen species (ROS) metabolites at cold storage. These results indicate that exogenous melatonin could delay mango fruit softening by maintaining cell wall metabolism, inhibiting ROS metabolites (O2.- and H2O2) accumulation via enhancement of non-enzymatic (AsA and GSH contents) and enzymatic (GR activity) antioxidants, and thus maintaining quality and improved storage life.

Overexpression of the FERONIA receptor kinase MdMRLK2 enhances apple cold tolerance.

Cold is one of the main abiotic stresses in temperate fruit crops, affecting the yield and fruit quality of apple in China and European countries. The plant receptor-like kinase FERONIA is widely reported to be involved in abiotic stresses. However, its function in apple cold resistance remains unknown. Modification of cell wall components and accumulation of soluble sugars and amino acids are important strategies by which plants cope with cold. In this study, expression of the apple FERONIA receptor-like kinase gene MdMRLK2 was rapidly induced by cold. Apple plants overexpressing MdMRLK2 (35S:MdMRLK2) showed enhanced cold resistance relative to the wild type. Under cold conditions, 35S:MdMRLK2 apple plants had higher amounts of water insoluble pectin, lignin, cellulose, and hemicellulose, which may have resulted from reduced activities of polygalacturonase, pectinate lyase, pectinesterase, and cellulase. More soluble sugars and free amino acids and less photosystem damage were also observed in 35S:MdMRLK2 apple plants. Intriguingly, MdMRLK2 interacted with the transcription factor MdMYBPA1 and promoted its binding to MdANS and MdUFGT promoters, leading to more anthocyanin biosynthesis, particularly under cold conditions. These findings complemented the function of apple FERONIA MdMRLK2 responding to cold resistance.

Changes in Pectic Substances and Cell Wall Degrading Enzymes During Muskmelon Fruit Ripening

Changes in pectic substances and the activities of the cell walldegrading enzymes, pectin esterase (PE) and polygalacturonase (PG) wereevaluated during muskmelon fruits ripening. Respiration rateprogressively increased in a climacteric pattern. Fruit flesh firmnesssteadily declined and rind yellow colour increased during ripening. Totaland insoluble pectins progressively decreased, while the soluble pectinsincreased with fruit ripening. Positive correlation coefficients wereobtained between total and insoluble pectins, and fruit flesh firmness.Total protein and PE activity increased up to the climacteric peak ofrespiration and decreased afterwards. PG activity progressively increasedduring fruit ripening, with high correlation between the increase inenzyme activity and fruit softening in the three muskmelon cultivars. Thismay indicate that the two enzymes polygalacturonase (PG) and pectinesterase (PE) are the main enzymes responsible for fruit softening duringmuskmelon fruit ripening.

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.

Rootstock effects on bitter pit incidence in 'Honeycrisp' apples are associated with changes in fruit's cell wall chemical properties.

Bitter pit (BP) is a physiological disorder of apples that often appears during or after cold storage. Despite being defined as a calcium deficiency disorder, BP is a complex process that is not only affected by the total Ca2+ content in the fruit but also by the proper cellular Ca2+ homeostasis and partitioning. Early investigations have also suggested that rootstocks could affect BP development and severity. In the present study, rootstock effects on BP development were assessed on ‘Honeycrisp’ trees that were grafted on 14 different rootstocks (B.10, G.11, G.202, G.214, G.30, G.41, G.935, G.969, M.26 EMLA, M.9, V.1, V.5, V.6, and V.7). We evaluated BP incidence at harvest, and three months after cold storage for four, and three growing seasons, respectively. BP incidence was significantly reduced in ‘Honeycrisp’ trees on B.10 compared to other rootstocks, whereas trees on V.6 showed the highest percentage of BP at harvest and after cold storage. ‘Honeycrisp’ apples were collected from three different rootstocks (B.10, G.41, and V.6) two months after cold storage and evaluated for mineral nutrient composition, Ca2+ homeostasis, and cell wall properties, e.g., pectin content, pectin de-esterification rate and pectin methylesterase (PME) activity. Water-soluble and insoluble pectin content was markedly higher in fruits from B.10 than in G.41 and V.6. We also observed increased PME enzyme activity and a greater degree of water-insoluble pectin de-esterification in ‘Honeycrisp’ apples from V.6 compared to those from B.10. A significantly higher Ca2+ was found in the fruits from B.10 than G.41 and V.6. Higher Ca2+ and lower Mg2+ levels were also observed in the cell wall and water-insoluble pectin fractions of the fruits from B.10 compared to G.41 and V.6. However, the ratio of cell wall-bound Ca2+ to total Ca2+ was lower in B.10 compared to G.41 and V.6. Together, our results indicate that the tolerance of B.10 to BP could be attributed to a reduced PME activity and lower pectin de-esterification level, which in turn reduced the amount of Ca2+ cross-linked with pectin, and probably increased the apoplastic free calcium concentrations that is essential for maintaining cell membrane integrity and reducing BP development.

Enhancive effect of instant controlled pressure drop (DIC) pre-treatment on pectin extractability from peach pomace

This study aimed to investigate if instant controlled pressure drop (DIC) processing can enhance pectin extractability from plant material. Peach pomace was treated by 0-, 1-, or 3-cycle of DIC processing at 90 or 105 °C. Pectin fractions including water soluble pectin and insoluble pectin were isolated from dried peach pomace and characterized by degree of methoxylation, neutral sugar composition, and molecular weight distribution. The results demonstrated that the thermomechanical effect of DIC processing induced a strong solubilization of in situ pectic polysaccharides of peach pomace, especially for water insoluble pectin fractions. This solubilization effect resulted in a more than 10% increasing ratio of extractable pectin yield from peach pomace over the maximum yield without the thermomechanical effect of DIC processing. Meanwhile, DIC processing conducted at 90 °C with 1-cycle affected pectin structure and property insignificantly. • DIC process induced solubilization of in situ pectic polysaccharides of peach pomace. • DIC treatment increased the pectin extractive yield of peach pomace by more than 10%. • 1-cycle DIC treatment at 90 °C affected slightly on pectin structure and properties.

Preharvest Spraying of CaCl2 Alleviates the Scape Bending of Gerbera ‘Harmony’ Flowers by Strengthening the Pectin Crosslinks through Ca2+ Bonds

Scape bending is the primary cause shortening the vase life of cut gerbera flowers (Gerbera jamesonii ‘Harmony’). A previous study showed that this bending is closely related to the scape hardness, which is attributed to cell wall rigidity maintained by calcium ion bonds. In this experiment, the developing gerbera scape was sprayed with 0.5 and 1% calcium chloride to determine whether exogenous calcium directly influences scape hardness and whether it is related to pectin crosslinks. The calcium spray hardened the scape by 12% and efficiently reduced bending, thereby prolonging the vase life of the cut gerbera flowers. A 9% increase in calcium ions (Ca2+) was detected in the CaCl2-treated flowers compared to the control flowers. Additionally, the pectin content increased by up to 14% in the CaCl2-treated flowers as compared to that in the control. Pectins are the main polysaccharides of cell walls that impact plant tissue integrity and rigidity, with calcium ions acting as bonds for pectin crosslinking. Calcium treatment efficiently increased the content of total pectin in the cell walls and slowed the conversion of insoluble pectin (IP) to water-soluble pectin (WSP) during vase life. The results suggest that exogenously applied calcium increases the Ca2+ in cellular tissue and affects the pectin levels, which may aid in increasing the scape hardness by strengthening the calcium–pectin combination in cell walls.

Effects of postharvest ripening on physicochemical properties, microstructure, cell wall polysaccharides contents (pectin, hemicellulose, cellulose) and nanostructure of kiwifruit (Actinidia deliciosa)

Kiwifruit undergoes rapid softening and quality changes after harvest, which has an important impact on consumer appeal, shelf life and market value. Effects of postharvest ripeness on physicochemical properties, microstructure, cell wall fraction (pectin, hemicellulose and cellulose) contents and nanostructure, and pectin molecular weight were investigated. As the postharvest time increased from 0 to 6 days, the contents of total soluble solid and water-soluble pectin increased by 77.4% and 113.0%, respectively; while the content of starch, water insoluble pectin, and hemicellulose decreased by 89.9%, 46.5%, and 33.5%, respectively. Disappearance of starch granules and the increase of intercellular space were observed using SEM. AFM analysis showed that both hemicellulose and pectin depolymerized gradually during storage. Measurements of the molecular weight confirmed the occurrence of depolymerization and degradation of pectin, while the cellulose content, nanostructure, and diameter of individual microfibrils did not change significantly. The findings in current work revealed the quality evolution and related mechanism of kiwifruit during storage.

Kinetics of Pectin Reactions in Apple Pomace During Hydrothermal Treatment

The kinetics of pectin reactions in apple pomace were modelled preparatory to developing a time-temperature operating map for quantity and quality of solubilized pectin and other reactions in apple pomace. This graph can be used for selecting suitable time-temperature conditions for hydrothermal treatments to ensure a safe product with expected quality. Kinetics were measured for the major reactions in apple pomace heated at 90–140 °C for 0–210 min, in particular for the solubilization and depolymerization reactions of pectin. Maximum levels of soluble pectin (~ 605 μmol galacturonic acid/g dry pomace) were observed when heating pomace (diluted 1:2) at 130 and 140 °C for 15 and 7 min, respectively. Acid hydrolysis and β-elimination reactions showed temperature-dependent behaviour, with activation energies of 81 and 65 kJ/mol, respectively. Heating at temperatures ≥ 110 °C resulted in degradation of soluble pectin into ethanol-soluble galacturonic acid. Depolymerization reactions of pectin occurred at non-esterified sites within the pectin polymers, as suggested by the high degree of esterification of the remaining insoluble pectin.

Structure and composition of blueberry fiber pectin and xyloglucan that bind anthocyanins during fruit puree processing

Blueberry is a well-known source of antioxidants and prebiotic dietary fiber yet the fate of these health-beneficial ingredients during fruit processing it is not understood. Detailed composition and structure of blueberry pomace (PF) remaining after commercial blueberry fruit puree processing, as well as the water soluble and water insoluble fractions, were determined. The PF was comprised of dietary fiber (60.8%) that was largely insoluble (46.2% vs. 14.6% soluble dietary fiber) pectin, xyloglucan, arabinoxylan and mannan polysaccharides, fructose (11.22%) and glucose (10.37%) free sugars, protein (9%), fat (5%), and anthocyanins (6444.5 μg/g). The most abundant anthocyanins detected in PF were malvidin 3-arabinoside and peonidin 3-glucoside and the pectin was determined to be methyl-esterified and acetylated rhamnogalacturonan I with a 4,5-unsaturated function at the non-reducing end based on oligosaccharide structural analysis. Blueberry PF xyloglucan oligosaccharide side chain structures included xylose, arabinose and galactose consistent with arabino-xyloglucan structure. Microwave-assisted extraction of blueberry PF (pH 2 for 10 min at 80 °C) was performed to more clearly elucidate pectin structure, and revealed a pectin polymer with high molar mass (1072 kDa) and viscosity that was dependent upon the molar mass. A random coil shape was confirmed for both the blueberry PF and microwave extracted blueberry pectin, which agreed with previous reports that flexible blueberry pectin contributes to strong anthocyanin binding. In summary, the blueberry pomace anthocyanin content was slightly higher than that reported for fresh whole blueberry fruit, which suggests that most blueberry anthocyanins adhered to the pomace fiber, and most likely the insoluble pectin, during and after processing.

Changes in cell wall components and polysaccharide-degrading enzymes in relation to differences in texture during sweetpotato storage root growth

Sweetpotato has special texture characteristics, which directly affect the eating quality and post-production processing quality of sweetpotato. To investigate the texture change mechanism of sweetpotato during the growth process, this study selected two varieties with significant differences in texture from 35 varieties. The storage roots were sampled at 50, 80, 110, and 140 days after planting. Measure the texture parameters, the cell wall composition content, cell wall-related enzyme activities and the expression of expansin genes of sweetpotato storage roots. The results show that the hardness, adhesiveness and chewiness parameters of ‘Yushu No 10′ were significantly lower than those of ‘Mianfen No 1′, they have significantly different texture properties. In terms of cell wall composition, the soluble pectin content of ‘Yushu No 10′ was more than twice that of ‘Mianfen No 1′, whereas the insoluble pectin content was lower than that of ‘Mianfen No 1′, with the cellulose content of ‘Yushu No 10′ being significantly higher than that of ‘Mianfen No 1′. In terms of cell wall-related enzymes, ‘Yushu No 10′ hardness gumminess and chewiness had a significant correlation with hemicellulose activity, and ‘Mianfen No 1′ had insignificant correlation with four cell wall-related enzymes. Expansin genes were also expressed differently during the various stages of root tubers expansin. The expressions of IbEXP1, IbEXP2 and IbEXPL1 were significantly correlated with the changes in cell wall component content, and were related to the qualitative structure changes. The research conclusion shows that the texture changes during the growth of sweetpotato are related to cell wall composition, cell wall-related enzyme activity changes, and the expression of expansin genes. This study provides theoretical guidance for in-depth study of texture changes of sweetpotato, post-harvest processing and utilization and quality improvement of storage roots.

Effects of 1-MCP and calcium chloride treatments on quality maintenance of full-ripe cherry tomatoes

This study aims to elucidate the effects of separate or combined 1-methylcyclopropene (1-MCP) and calcium chloride (CaCl2) treatment on the post-harvest quality of full-ripe cherry tomatoes (TY high Q cultivar). Full-ripe cherry tomatoes were exposed to 500 ppb 1-MCP (14 h), 2% CaCl2 (2 min), or a combination of both. After treatment, the fruit were evaluated based on the changes in their physicochemical factors, antioxidant activities, lycopene contents, and insoluble pectin contents during storage at 10°C over 17 days. All chemical treatments prevented weight loss and reductions in the insoluble pectin contents over the 17 days period, and also over an additional distribution period of 4 days, when compared to the control fruit. Interestingly, the full-ripe cherry tomatoes treated 1-MCP with CaCl2 exhibited a delay in discoloration until 13 days after treatment compared to the control. In addition, the synergetic effect of 1-MCP and CaCl2 was revealed by following their lycopene levels and antioxidant activities during storage. Furthermore, the insoluble pectin contents of the cherry tomatoes subjected to the combined treatment were higher than those recorded for the separate treatments. These results suggest that treatment with a combination of 1-MCP and CaCl2 can be useful as a post-harvest technique to improve both the post-harvest quality and the beneficial properties of cherry tomatoes even when the fruit is approaching the full-ripe stage.

Exogenous application of melatonin maintains storage quality of jujubes by enhancing anti-oxidative ability and suppressing the activity of cell wall-degrading enzymes

Jujube fruit was treated with melatonin to evaluate the changes of quality parameters, anti-oxidative ability and cell wall-degrading enzymes activities during room temperature storage. The results showed that melatonin treatment significantly inhibited respiratory rate and ethylene release of jujubes. Melatonin treatment also delayed the changes of color and sustained titratable acidity. Moreover, melatonin treatment increased the activities of glutathione reductase, ascorbate peroxidase and monodehydroascorbate reductase, and enhanced ascorbic acid, dehydroascorbic acid and reduced glutathione contents in jujubes. In addition, application of melatonin delayed fruit softening by inhibiting the activities of pectin methylesterase, polygalacturonase, cellulose and β-glucosidase and production of water soluble pectin and maintaining water insoluble pectin content. All these results indicate that application of melatonin after harvest could delay fruit softening, improve anti-oxidative capacity, and thus delay fruit senescence of jujubes.