Degradation Of Cell Wall Polysaccharides Research Articles

The role of water distribution, cell wall polysaccharides, and microstructure on radish (Raphanus sativus L.) textural properties during dry-salting process

Radish (Raphanus sativus L.) undergoes texture changes in their phy-chemical properties during the long-term dry-salting process. In our study, we found that during the 60-day salting period, the hardness and crispness of radish decreased significantly. In further investigation, we observed that the collaborative action of pectin methylesterase (PME) and polygalacturonase (PG) significantly decreased the total pectin, alkali-soluble pectin (ASP), and chelator-soluble pectin (CSP) content, while increasing the water-soluble pectin (WSP) content. Furthermore, the elevated activities of cellulase and hemicellulase directly led to the notable fragmentation of cellulose and hemicellulose. The above reactions jointly induced the depolymerization and degradation of cell wall polysaccharides, resulting in an enlargement of intercellular spaces and shrinkage of the cell wall, which ultimately led to a reduction in the hardness and crispness of the salted radish. This study provided key insights and guidance for better maintaining textural properties during the dry-salting process of radish.

Degradation of Cell Wall Polysaccharides during Traditional and Tank Fermentation of Chinese Liupao Tea.

The increase of polysaccharides in the dark tea pile process is thought to be connected to the cell wall polysaccharides' breakdown. However, the relationship between tea polysaccharides (TPSs) and tea cell wall polysaccharides has not been further explored. In this study, the structural changes in the cell wall polysaccharides [e.g., cellulose, hemicellulose (HC), and pectin] in Liupao tea were characterized before and after traditional fermentation and tank fermentation. Additionally, the degradation mechanism of tea cell wall polysaccharides during fermentation was assessed. The results showed that cellulose crystallinity decreased by 11.9-49.6% after fermentation. The molar ratio of monosaccharides, such as arabinose, rhamnose, and glucose in HC, was significantly reduced, and the molecular weight decreased. The esterification degree and linearity of water-soluble pectin (WSP) were reduced. TPS content increases during pile fermentation, which may be due to HC degradation and the increase in WSP caused by cell wall structure damage. Microorganisms were shown to be closely associated with the degradation of cell wall polysaccharides during fermentation according to correlation analyses. Traditional fermentation had a greater effect on the cellulose structure, while tank fermentation had a more noticeable impact on HC and WSP.

Metagenomic insights into the dynamic degradation of brown algal polysaccharides by kelp-associated microbiota.

Marine bacteria play important roles in the degradation and cycling of algal polysaccharides. However, the dynamics of epiphytic bacterial communities and their roles in algal polysaccharide degradation during kelp decay are still unclear. Here, we performed metagenomic analyses to investigate the identities and predicted metabolic abilities of epiphytic bacterial communities during the early and late decay stages of the kelp Saccharina japonica. During kelp decay, the dominant epiphytic bacterial communities shifted from Gammaproteobacteria to Verrucomicrobia and Bacteroidetes. In the early decay stage of S. japonica, epiphytic bacteria primarily targeted kelp-derived labile alginate for degradation, among which the gammaproteobacterial Vibrionaceae (particularly Vibrio) and Psychromonadaceae (particularly Psychromonas), abundant in alginate lyases belonging to the polysaccharide lyase (PL) families PL6, PL7, and PL17, were key alginate degraders. More complex fucoidan was preferred to be degraded in the late decay stage of S. japonica by epiphytic bacteria, predominantly from Verrucomicrobia (particularly Lentimonas), Pirellulaceae of Planctomycetes (particularly Rhodopirellula), Pontiellaceae of Kiritimatiellota, and Flavobacteriaceae of Bacteroidetes, which depended on using glycoside hydrolases (GHs) from the GH29, GH95, and GH141 families and sulfatases from the S1_15, S1_16, S1_17, and S1_25 families to depolymerize fucoidan. The pathways for algal polysaccharide degradation in dominant epiphytic bacterial groups were reconstructed based on analyses of metagenome-assembled genomes. This study sheds light on the roles of different epiphytic bacteria in the degradation of brown algal polysaccharides.IMPORTANCEKelps are important primary producers in coastal marine ecosystems. Polysaccharides, as major components of brown algal biomass, constitute a large fraction of organic carbon in the ocean. However, knowledge of the identities and pathways of epiphytic bacteria involved in the degradation process of brown algal polysaccharides during kelp decay is still elusive. Here, based on metagenomic analyses, the succession of epiphytic bacterial communities and their metabolic potential were investigated during the early and late decay stages of Saccharina japonica. Our study revealed a transition in algal polysaccharide-degrading bacteria during kelp decay, shifting from alginate-degrading Gammaproteobacteria to fucoidan-degrading Verrucomicrobia, Planctomycetes, Kiritimatiellota, and Bacteroidetes. A model for the dynamic degradation of algal cell wall polysaccharides, a complex organic carbon, by epiphytic microbiota during kelp decay was proposed. This study deepens our understanding of the role of epiphytic bacteria in marine algal carbon cycling as well as pathogen control in algal culture.

A High-Quality Genome Sequence of the Penicillium oxalicum 5-18 Strain Isolated from a Poplar Plantation Provides Insights into Its Lignocellulose Degradation.

Studies on the degradation of plant cell wall polysaccharides by fungal extracellular enzymes have attracted recent attention from researchers. Xylan, abundant in hemicellulose, that play great role in connection between cellulose and lignin, has seen interest in its hydrolytic enzymatic complex. In this study, dozens of fungus species spanning genera were isolated from rotting leaves based on their ability to decompose xylan. Among these isolates, a strain with strong xylanase-producing ability was selected for further investigation by genome sequencing. Based on phylogenetic analysis of ITS (rDNA internal transcribed spacer) and LSU (Large subunit 28S rDNA) regions, the isolate was identified as Penicillium oxalicum. Morphological analysis also supported this finding. Xylanase activity of this isolated P. oxalicum 5-18 strain was recorded to be 30.83 U/mL using the 3,5-dinitro-salicylic acid (DNS) method. Further genome sequencing reveals that sequenced reads were assembled into a 30.78 Mb genome containing 10,074 predicted protein-encoding genes. In total, 439 carbohydrate-active enzymes (CAZymes) encoding genes were predicted, many of which were associated with cellulose, hemicellulose, pectin, chitin and starch degradation. Further analysis and comparison showed that the isolate P. oxalicum 5-18 contains a diverse set of CAZyme genes involved in degradation of plant cell wall components, particularly cellulose and hemicellulose. These findings provide us with valuable genetic information about the plant biomass-degrading enzyme system of P. oxalicum, facilitating a further exploration of the repertoire of industrially relevant lignocellulolytic enzymes of P. oxalicum 5-18.

Effect of vibration and broken cold chain on the evolution of cell wall polysaccharides during fruit cucumber (Cucumis sativus L.) shriveling under simulated transportation

The fruits and vegetables often result in shriveling, which can significantly affect the quality in terms of texture, appearance, and saleable weight during transportation and storage. In this study, fruit cucumbers (Cucumis sativus L.) were subjected to vibration followed by storing them under isothermal and non-isothermal conditions (simulated broken cold chain) for 15 days. Water movement, cell wall polysaccharides and degrading enzymes, cell wall structure of cucumbers were determined. The findings revealed that water initially migrated from the inner pericarp of cucumber. Vibration and broken cold chain damaged the fruit cell wall and cell wall polysaccharides, and increased degrading enzymes, which promoted the water movement from the tissues to the exterior, causing severe shriveling of cucumber. Firmness loss accompanied with cucumber shrivel appeared by as early as 6 days of storage after vibration (5.5 Hz), with decrease of 19.88–29.93 %. However, this phenomenon was not observed in the control cucumber until 12 days after storage with firmness of 8.22 N. Therefore, this study shows that simulated transport vibration and broken cold chain could cause intracellular damage in cucumber tissues, which expedites the process of water loss, degradation of cell wall polysaccharides and shriveling process. The study also reveals that precise temperature control and avoiding vibration of transportation in cold chain logistics of cucumbers are important in maintaining the product quality during storage and transport.

Opuntia ficus indica mucilage coatings regulate cell wall softening enzymes and delay the ripening of banana fruit stored at retail conditions

Rapid ripening and softening due to cell wall polysaccharide degradation and disassembly pose major challenges in extending fruit storability. This study aimed to examine the efficacy of Opuntia ficus indica mucilage (OFIM) edible coating in minimizing softening in bananas under retail conditions. Mucilage was extracted from freshly harvested prickly pear cladodes and dried into a powder. Phenolic compounds in OFIM powder were quantified using liquid chromatography-mass spectrometry (LC-MS). OFIM concentrations (1, 2 and 3 % (w/v)) were prepared, and their physicochemical properties were examined. The prepared coatings were applied to harvested banana fruit by dipping and stored at room temperature for 12 days. During the experiment, several parameters were measured, including fruit weight loss, total soluble solids (TSS), titratable acidity (TA), peel color, pulp firmness, ethylene production, respiration rate, ion leakage, malondialdehyde (MDA) content, total chlorophyll and carotenoids, chlorophyll-degrading enzymes, protopectin content and water-soluble pectin (WSP) and softening-related enzymes in the peel. Results showed that mucilage treatments effectively delayed cell wall and chlorophyll degradation, as well as carotenoid accumulation, thus inhibiting ripening-associated processes compared to control fruit. OFIM-treated fruit exhibited significantly higher firmness, chlorophyll content, and TA, lower TSS content, ethylene production, respiration rate, MDA concentration, ion leakage and protopectin content than uncoated fruit. This suggests that OFIM edible coating has the potential to maintain quality and extend the shelf life of bananas by suppressing softening enzymes during storage.

Reduced degradation of the cell wall polysaccharides maintains higher tissue integrity of papaya (Carica papaya L.) during chilling storage

Papaya (Carica papaya L.) fruit are vulnerable to chilling injury (CI), and the symptoms of CI develop more intensively when the fruit are stored at 6 ℃ rather than 1 ℃. This is considered to be abnormal CI behavior of papaya fruit, a phenomenon that is unclear but thought to be related to cell wall metabolism. Thus, this study examined the relationship between the development of CI and alterations of the cell wall metabolism in papaya fruit stored at 1 ºC and 6 ℃. The 1 ℃-storage maintained the integrity of the papaya exocarp and alleviated the development of CI and the loss of free moisture. Ultrastructural observations demonstrated that the middle lamellae were denser in papaya fruit stored at 1 ℃ than those in 6 ℃-storage, which alleviated the disintegration of cell wall at 1 ℃-storage. Compared with 6 ℃-storage, 1 ℃-storage inhibited the degradation of Na2CO3-soluble pectin, CDTA-soluble pectin, and cellulose. The 1 ℃-storage also delayed the solubilization of water-soluble pectin and the transformation of 24% KOH-soluble fraction to the 4% KOH-soluble fraction. Lower activities of cell wall-modifying enzymes, including pectin methylesterase, polygalacturonase, pectate lyase, β-galactosidase, xyloglucan endotransglycosylase, and cellulase, were observed in papaya fruit stored at 1 ℃. These results suggest that alleviating the degradation of cell wall polysaccharides maintains higher tissue integrity in papaya fruit during chilling storage.

Enzyme synergy for plant cell wall polysaccharide degradation.

Valorizing plant cell wall, marine and algal polysaccharides is of utmost importance for the development of the circular bioeconomy. This is because polysaccharides are by far the most abundant organic molecules found in nature with complex chemical structures that require a large set of enzymes for their degradation. Microorganisms produce polysaccharide-specific enzymes that act in synergy when performing hydrolysis. Although discovered since decades enzyme synergy is still poorly understood at the molecular level and thus it is difficult to harness and optimize. In the last few years, more attention has been given to improve and characterize enzyme synergy for polysaccharide valorization. In this review, we summarize literature to provide an overview of the different type of synergy involving carbohydrate modifying enzymes and the recent advances in the field exemplified by plant cell-wall degradation.

Integrated transcriptomics-proteomics analysis reveals the regulatory network of ethanol vapor on softening of postharvest blueberry

Fruit firmness is an important trait of postharvest blueberry, and ethanol vapor treatment has been shown to can retard blueberry softening by inhibiting the degradation of cell wall polysaccharides in our previous work. However, fruit softening is a complex process regulated by many factors. Here, the regulation mechanism of ethanol mediated delaying blueberry softening at the levels of mRNA and protein were explored with integrated transcriptomics-proteomics analysis. Results revealed that, 9158 differentially expressed genes (DEGs) and 1223 differentially expressed proteins (DEPs) were identified in the ethanol vapor-treated blueberry (E20) compared with the control (C20) at the 20th day of cold storage, 351 correlation molecules (DEG/DEP) were obtained through correlation analysis. Ethanol treatment reduced the overall metabolism level of blueberry, downregulated the gene expression of polygalacturonase, glucan-1,3-β-glucosidase and endoglucanase in carbohydrate metabolism pathway, and slowed down the degradation of cell wall polysaccharides such as pectin and cellulose; downregulated the gene expression of ACC oxidase, the key enzyme for ethylene synthesis, reduced the production of ethylene, reducing the ripening and softening effect of ethylene on the fruit, and then delayed the softening process of blueberry fruit. Collectively, ethanol vapor is a promising technology for retarding the softening of fruit and vegetables.

Involvement of lignin deposition and cell wall degradation in stem senescence of Chinese flowering cabbage during storage

Chinese flowering cabbage is susceptible to leaf yellowing, however, little is known about stem senescence after harvest. Herein, changes in the microstructures, lignin and cell wall polysaccharide contents, and expression of their corresponding genes during the stem senescence of Chinese flowering cabbage were investigated. Anatomical and chemical analyses revealed that an increase in cell wall thickness was accompanied by lignin deposition around the vascular cells in the stem. Concurrently, the collapse of parenchyma cells developed gradually, which was probably related to the degradation of cell wall polysaccharides including pectin, hemicellulose, and cellulose, among others. The outer stem tissues, including epidermal cells to vascular cells, could be directly peeled, and the middle of the stem was found to contain prominent parenchyma cells as pith tissues. Activity of lignin biosynthesis-related enzymes of phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD), and the expression of their corresponding genes BrPAL2/3/6, Br4CL1/4, BrCAD2/4/5/11, and BrPOD31/37 were higher in outer peeled tissues than in pith tissues. The enzyme activity of polygalacturonase and pectin methylesterase, and expression levels of the polysaccharide degradation-related genes BrXET2/3, BrCEL3, and BrMAN1/5 were higher in pith than in outer peeled tissues. These results suggest that lignin deposition around the vascular tissue, and cell wall degradation in pith tissues are involved in the stem senescence of Chinese flowering cabbage after harvest.

Toward gentle chokeberry juice production by ultrasound-assisted enzymatic maceration

Sustainable processes accompanied by high extraction yields and minimized amounts of by-products are a major goal of current fruit juice production. Controlled degradation of cell wall polysaccharides, in particular pectin, may contribute to reduced emergence of side streams. Possible strategies for the optimization are the selection of enzyme preparations based on comprehensive studies of their activities, the adjustment of maceration temperature toward more gentle conditions, and the application of alternative technologies such as ultrasound (US) during maceration. The present study provides insights into the effects of ultrasound-assisted enzymatic maceration (UAEM) on pectin degradation, total anthocyanin content, thermal and storage stability, and juice yield during chokeberry juice production on pilot-plant scale. The two enzyme preparations applied predominantly possessed polygalacturonase or pectin lyase activity. Cell wall polysaccharide degradation was improved by US and resulted in a 3% increase in juice yield by UAEM using an enzyme preparation that shows mostly polygalacturonase activity. Thermostability of anthocyanins was improved in juices produced using pectin lyase and applying US and matched the stability of anthocyanins in juices produced using polygalacturonase. Storage stability of anthocyanins was improved in juice produced using polygalacturonase during UAEM. UAEM also resulted in lower yields of pomace making the production more resource-efficient. Overall, the use of polygalacturonase has promising potential to advance conventional chokeberry juice production by applying US at gentle conditions.

Carbohydrate Depolymerization by Intricate Cellulosomal Systems.

Cellulosomes are multi-enzymatic nanomachines that have been fine-tuned through evolution to efficiently deconstruct plant biomass. Integration of cellulosomal components occurs via highly ordered protein-protein interactions between the various enzyme-borne dockerin modules and the multiple copies of the cohesin modules located on the scaffoldin subunit. Recently, designer cellulosome technology was established to provide insights into the architectural role of catalytic (enzymatic) and structural (scaffoldin) cellulosomal constituents for the efficient degradation of plant cell wall polysaccharides. Owing to advances in genomics and proteomics, highly structured cellulosome complexes have recently been unraveled, and the information gained has inspired the development of designer-cellulosome technology to new levels of complex organization. These higher-order designer cellulosomes have in turn fostered our capacity to enhance the catalytic potential of artificial cellulolytic complexes. In this chapter, methods to produce and employ such intricate cellulosomal complexes are reported.

Insights into the spatio-temporal composition, diversity and function of bacterial communities in seawater from a typical laver farm

Laver is the most widely farmed seaweed with the largest culture area in China. The spatio-temporal variations in composition, diversity, and functional properties of bacteria in seawater as well as the environmental variables of seawater in a large-scale laver farm in China were studied. Both the community richness indices and Shannon index in the laver farming area remained at a relatively stable level during laver cultivation. Fifty-nine prokaryotic phyla were detected in all samples, however, only six of these phyla accounted for 98.84% of all sequences. Proteobacteria, Gammaproteobacteria, Rhodobacterales, Rhodobacteraceae, and Octadecabacter were the most predominant bacterial taxa at different levels of classification. The keystone bacterial taxa were Bacteroidetes, Pseudomonadales, Rhodobacterales, Flavobacteriales, Loktanella, and Pseudoruegeria based on network analysis. Members of representative bacterial biomarker taxa in November may be associated with degradation of algal cell wall polysaccharides. A significant increase in metabolic exchange and transformation nutrients occurred in the seawater during the early and late stage of laver cultivation, indicating that the laver reproductive activities (i.e. the formation/release activities of archeospores and zygotospores) probably drove the variation of metabolic functional diversity of bacterial communities. Based on Mantel test and redundancy analysis, we found the hydrographic parameters (e.g. salinity, temperature, DO, pH) as well as the key carbon (e.g. POC, DOC) and nitrogen parameters (e.g. nitrate, DIN, DON, TDN) were crucial environmental variables to shape the bacterial community composition in the surrounding seawater of laver farm. In a word, our results suggested that the microbial community structure and function significantly changed across the different succession stages during laver cultivation. This work provides new insights on the characteristics of bacterial communities in a large-scale laver farming system and solidifies the importance of laver farming in shaping seawater microbiomes.

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.

DNP and ATP modulate the developments of pulp softening and breakdown in Phomopsis longanae Chi-infected fresh longan through regulating the cell wall polysaccharides metabolism

Compared with P. longanae-infected longan, 2, 4-dinitrophenol (DNP) treatment for P. longanae-infected longan displayed the lower levels of pulp firmness, cell wall materials, ionic-soluble pectin, covalent-soluble pectin, hemicellulose, or cellulose, but the higher amount of water-soluble pectin, the higher activities of cell wall-degrading enzymes (CWDEs) (PG, β-Gal, PME, Cx, and XET), and the higher transcript levels of CWDEs-related genes (DlPG1, DlPG2, Dlβ-Gal1, DlPME1, DlPME2, DlPME3, DlCx1, and DlXET30). On the contrary, ATP treatment for P. longanae-infected longan exhibited opposite effects. The above results imply that DNP accelerated P. longanae-induced pulp softening and breakdown of fresh longan, which was because DNP up-regulated the transcript levels of CWDEs-related genes, enhanced the CWDEs activities, and accelerated the degradation of cell wall polysaccharides (CWP). However, ATP suppressed longan pulp softening and breakdown caused by P. longanae, because ATP down-regulated the transcript levels of CWDEs-related genes, lowered the CWDEs activities, and reduced the CWP degradation.

Red light regulates metabolic pathways of soybean hypocotyl elongation and thickening

Plant stem growth and development are regulated by red light, which is an important environmental signal. Using proteomic and metabolomic approaches, differentially expressed proteins (DEPs) and differentially expressed metabolites (DEMs) in soybean hypocotyls were examined between soybean plants subjected to darkness and red light conditions, elucidating the pathways underlying the regulatory effects of red light on soybean hypocotyl growth. The results revealed that red light inhibits hypocotyl elongation and increases the hypocotyl diameter in soybeans. Red light inhibited hypocotyl elongation mainly by enhancing the firmness of the cell wall. First, red light promoted the expression of enzymes related to the conversion of serine and threonine to glycine, decreased the level of intracellular reactive oxygen species (ROS), and reduced the degradation of cell wall polysaccharides. Furthermore, by enhancing the expression of enzymes involved in the lignin monomer synthetic pathway, red light promoted the biosynthesis of lignin to strengthen the cell wall. Moreover, red light promoted hypocotyl thickening mainly by upregulating the expression of aminocyclopropanecarboxylate oxidase, thereby promoting the accumulation of ethylene precursors. This study provides a theoretical basis for using light to regulate soybean stem growth.

Ripening induced degradation of pectin and cellulose affects the far infrared drying kinetics of mangoes

The quality parameters of mangoes change during ripening, which has a vital impact on processing characteristics. Effects of ripening stage (four stages from the lowest to highest degree—RS-1, RS-2, RS-3, RS-4) on cell wall polysaccharides and far infrared drying kinetics of mangoes were investigated. As ripening progressed, the water-soluble pectin contents increased by 213.5%; while the chelate-, sodium carbonate-soluble pectin and hemicellulose contents decreased by 44.0%, 59.5% and 65.8%, respectively. Moreover, the molecular weight reduction confirmed the degradation of pectin. These further caused the alteration of cell wall structure and changes in water distribution. Meanwhile, the drying time of mangos with different ripeness were in the order: RS-3 > RS-4 > RS-2 > RS-1. It correlated with the degradation of cell wall polysaccharides, the destruction of cell wall and the increases in free water during ripening. The ripeness classification could effectively improve the uniformity and efficiency of fruits drying processing.

Impact of processing on the production of a carotenoid-rich Cucurbita maxima cv. Hokkaido pumpkin juice

Pumpkin juice with high carotenoid content can be attractive natural alternative for artificial food colourants. We evaluated the impact of processing treatments on aqueous carotenoid extraction from pumpkins, aiming to enhance carotenoid transfer into the juice fraction. Crushed whole pumpkins were processed by high pressure homogenization (HPH) for mechanical cell disruption, by enzymatic treatment for cell wall polysaccharide degradation or by a pulsed electric field (PEF) treatment for cell membrane electroporation. Processed purees were separated into juice and pomace and carotenoids were quantified by HPLC-DAD. Whereas only 54–60% of the carotenoids in non-processed puree was transferred into the juice, HPH- and enzyme-assisted processing of purees significantly increased juice yields and total soluble solids, and consequently, carotenoid concentrations in these juices up to 90–98% and 72–90%, respectively. No significant improvement was observed for PEF-treated samples. Results obtained can be industrially useful in producing natural colouring plant concentrates as clean-label ingredients.

Near freezing temperature storage alleviates cell wall polysaccharide degradation and softening of apricot (Prunus armeniaca L.) fruit after simulated transport vibration

The commodity attribute of apricot fruits may greatly decline during transportation and storage. Although the efficacy of near freezing temperature (NFT) storage for maintaining apricot quality has been reported, previous studies did not investigate the effects on cell wall structure, cell ultrastructure, and the composition and activities of cell wall degrading enzymes after simulated transport vibration. The objective of the present study was to evaluate the cell wall metabolism and postharvest quality of ‘Xiaobai’ apricots during storage at 4–6 °C, 1–2 °C, or NFT for 49 d after simulated transport vibration. Quality parameters, cell wall composition, cell wall degrading enzymes, and cell ultrastructure were analyzed. The results indicated that NFT storage considerably delayed the senescence of apricots, including the inhibition of loss of firmness and decrease in total soluble solid content (TSS), titratable acid (TA) content and L*, a*, b*, compared with storage at 4–6 °C and 1–2 °C after simulated transport vibration. NFT storage markedly suppressed the respiration rate and maintained a higher content of ascorbic acid and lower membrane permeability during the storage period compared with storage at 1–2 °C and 4–6 °C. Furthermore, NFT storage could delay apricot fruit softening after simulated transport vibration, as indicated by delayed the degradation of Na2CO3-soluble pectin (NSP) and cellulose content, and slowed down the increase in water-soluble pectin (WSP) and chelate-soluble pectin (CSP) of cell walls, maintained lower pectin methylesterase (PME) and polygalacturonase (PG) activity, and inhibited the increase in cellulase and β-galactosidase (β-Gal) activity compared with storage at 4–6 °C and 1–2 °C. Microscopic observation showed that NFT storage delayed the degradation of pectin fraction and protected the plant cell wall structure. In conclusion, NFT storage changes the cell wall structure and the composition and activities of cell wall degrading enzymes in apricot fruits. These results suggested that NFT storage is an effective method to delay the softening process and preserve the quality of apricots after simulated transport vibration.