Water-soluble Polyuronides Research Articles

Cell wall composition and enzyme-related activities in eggplant as affected by hot water, 1-MCP and calcium chloride treatments.

The effects of postharvest applications of hot water (HWT) (45, 50, and 55 °C), 1-MCP (1, 5, and 10 μL/L), and CaCl2 (1, 2, and 3%) on polygalacturonase (PG), pectin methylesterase (PME), α-galactosidase (α-Gal), β-galactosidase (β-Gal) and β-1,4-glucanase (β-1,4-Glu) activities, and the fruit firmness and cell wall composition of eggplant fruit were investigated. The results showed that the decrease in the eggplants firmness was delayed by HWT, 1-MCP, and CaCl2 treatments during storage compared with the control. However, HWTs were less effective than the 1-MCP and CaCl2 treatments. The results show that 1-MCP and CaCl2 treatments inhibited the depolymerization of water (WSP), CDTA (CSP), and sodium carbonate (SSP) soluble polyuronides. The results suggest that 1-MCP (5 and 10 μL/L) and CaCl2 (1, 2, and 3%) could prevent eggplant softening by inhibiting hydrolase enzymes and reducing the disintegration of the polysaccharides. In addition, 1-MCP and CaCl2 were more effective than hot water treatment in extending postharvest storage life. There is a significantly high correlation between firmness, polyuronide content and cell wall enzyme activity.

The influence of pre- and postharvest 1-MCP application and oxygen regimes on textural properties, cell wall metabolism, and physiological disorders of late-harvest ‘Bartlett’ pears

Late-harvest (LH) pears are prone to postharvest disorders and eating-quality deterioration in storage and retailing. The purpose of this work was to evaluate the effects of pre- and post-harvest 1-methylcyclopropene (1-MCP, Harvista (H) and SmartFresh (SF)) on LH ‘Bartlett’ pears under the various O2 regimes. Spraying 320 μL L−1 H delayed fruit maturation and suppressed ethylene production rate (EPR) when pears were harvested at 70.51 N (LH, whereas commercial harvest (CH) at 75.04 N). However, the H-treated LH fruit had 100 % decay after 5 months of regular-air (RA) storage. The 0.15 μL L−1 SF and SF + 160 μL L−1 H extended melting texture life of LH fruit to 5 months with high levels of water-soluble polyuronides (WSP) and CDTA-soluble polyuronides (CSP) and activities of pectin methylesterase (PME), pectate lyase (PL), and α-arabinofuranosidase (α-ARF). Raising H application concentration from 160 to 320 μL L−1 in H + SF treatments resulted in blockage of ripening capacity. Decreasing O2 concentration from 2 to 1 % did not impact LH pears’ ripening, but effectively curtailed the development of melting texture in H-treated LH fruit by suppressing EPR, degradation of pectin polyuronides, and activities of PL and β-galactosidase (β-GAL). Furthermore, applying SF in H-treated LH pears stored in 1 or 2 % O2 resulted in the loss of ripening capacity. Results indicated that 160 μL L−1 H + SF and H at 160−320 μL L−1 extended the melting period and controlled physiological disorders in LH ‘Bartlett’ pears for 5 and 7 months of storage in RA and 2 % O2, respectively.

Textural property and cell wall metabolism of ‘Golden Bosc’ and ‘d’Anjou’ pears as influenced by oxygen regimes after long-term controlled atmosphere storage

Controlled atmosphere (CA) allows long-term storage of European pears (Pyrus communis L.) without chemical treatment to deliver a natural melting (buttery and juicy) texture for consumers. However, the relationship between textural properties and cell wall metabolism as influenced by O2 regimes has not been comprehensively determined. In this study, ‘Golden Bosc’ and ‘d’Anjou’ pears were stored in 21 (air), 2, 1, or 0.5% O2 with < 0.5% CO2 for up to 8 and 10 months at −1.1 °C plus 7 d of ripening at 20 °C, respectively. Melting texture development in both cultivars showed high correlations with the level of water-soluble polyuronides (WSP) and activity of β-galactosidase (β-GAL). Also, activities of pectin methylesterase (PME) and α-arabinofuranosidase (α-ARF) were associated with softening in ‘Golden Bosc’ pears. Concentrations of CDTA-soluble polyuronides (CSP) and WSP + CSP + sodium carbonate-soluble polyuronides (SSP), as well as ethylene production showed positive correlations to melting texture in ‘d’Anjou’ pears. Reducing O2 concentrations from 21% to 2-–1% and 1–0.5% in ‘Golden Bosc’ and ‘d’Anjou’ pears allowed pears to develop a desirable eating texture during ripening for up to 8 and 10 months, respectively, with a commercially acceptable levels of postharvest disorders. Use of 1–0.5% O2 resulted in a melting texture in ‘Golden Bosc’ pears, but fruit developed more core browning when ripe. These results indicate that O2 regimes regulate textural qualities by influencing WSP level and β-GAL activity.

Compositional changes in cell wall polyuronides and enzyme activities associated with melting/mealy textural property during ripening following long-term storage of ‘Comice’ and ‘d’Anjou’ pears

Irregular ripening is a major deterrent for the purchase of European pears. Cell wall polyuronides and related- modifying enzymes were investigated in two European winter pears, ‘Comice’ and ‘d’Anjou’, during ripening at 20°C following 5 and 8 months of storage at −1.1°C. Both pear cultivars developed a melting (buttery-juicy) texture and higher water-soluble polyuronides (WSP) in flesh tissue after 5 months, but the pears’ texture quality decreased and a mealy (coarse-dry) texture presented in ‘Comice’ pear after long-term storage. Activities of pectin methylesterase (PME) and α-arabinofuranosidase (α-ARF) in ‘Comice’ pears was positively correlated with texture development, whereas in ‘d’Anjou’ pears polygalacturonase (PG), PME, cellulase (CEL), and β-galactosidase (β-GAL) were more highly correlated with texture. 1-MCP reduced pear ripening by inhibiting ethylene production and the activities of cell wall-modifying enzymes, maintaining higher antioxidants, and alleviating membrane lipid peroxidation. These results indicated melting texture developed in European pears as a result of the synthesis of WSP and increase of PME activity during pear fruit softening.

Effect of ethylene and temperature conditioning on sensory attributes and chemical composition of 'Comice' pears.

'Comice' is among the pear varieties most difficult to ripen after harvest. Ethylene, cold temperature, and intermediate (10 °C) temperature conditioning have been successfully used to stimulate the ability of 'Comice' pears to ripen. However, the sensory quality of pears stimulated to ripen by different conditioning treatments has not been evaluated. In this study, a descriptive sensory analysis of 'Comice' pears conditioned to soften to 27, 18, and 9 N firmness with ethylene exposure for 3 or 1 days, storage at 0 °C for 25 or 15 days, or storage at 10 °C for 10 days was performed. Sensory attributes were then related to changes in chemical composition, including volatile components, water-soluble polyuronides, soluble solids content (SSC), and titratable acidity (TA). The sensory profile of fruit conditioned with ethylene was predominant in fibrous texture and low in fruity and pear aroma. Fruit conditioned at 0 °C was described as crunchy at 27 and 18 N firmness and became juicy at 9 N firmness. Fruit conditioned at 0 °C produced the highest quantity of alcohols and fewer esters than fruit conditioned at 10 °C, and they had higher fruity and pear aroma than fruit conditioned with ethylene, but lower than fruit conditioned at 10 °C. Fruit held at 10 °C were predominant in fruity and pear aroma and had the highest concentration of esters. Water-soluble polyuronides were strongly, positively correlated (r > 0.9) with sensory attributes generally associated with ripeness, including juiciness, butteriness, and sweetness and negatively correlated (r > -0.9) with sensory attributes generally associated with the unripe stage, such as firmness and crunchiness. However, water-soluble polyuronides were not significantly different among conditioning treatments. Sensory sweetness was not significantly correlated with SSC, but TA and SSC/TA were significantly correlated with sensory tartness. However, there were no significant differences among the conditioning treatments in sweet or sour taste perception when the fruit fully softened. The results indicate that the various methods of conditioning 'Comice' pear fruits for ripening had different effects on their sensory and chemical properties that may influence their sensory quality.

Cell wall modification in 1-methylcyclopropene-treated post-climacteric fresh-cut and intact papaya fruit

Papaya is a climacteric fruit in which ripening is greatly regulated by ethylene often associated with stress responses such as wounding. The changes in cell wall compositions in papaya fruit at an advanced stage of ripening under stress conditions including chilling temperature of 5°C and wounding employed as fresh-cut and how these changes were affected by an ethylene action inhibitor of 1-methylcyclopropopene (1-MCP) were examined in the study. The recovery of ethanol-insoluble solids, total soluble sugars, water-soluble polyuronides, neutral hemicelluloses, and neutral sugars of rhamnose, arabinose, mannose and glucose were not affected by 1-MCP or fresh-cut processing. The fresh-cut processing, however, caused a higher loss of total polyuronides and the neutral sugar galactose while increasing the recovery of chelator-soluble polyuronides. Few significant differences due to 1-MCP application were recorded in the recoveries of alkali-soluble polyuronides, hemicellulosic polyuronides extracted with 4% KOH, and the neutral sugar xylose. Modifications of cell wall polyuronides and hemicelluloses in ripe fresh-cut papaya fruit exhibited mostly similar patterns to those in intact ripe papaya fruit under the chilling temperature of 5°C while minimally affected by 1-MCP.

Effect of Fertilizer Application Level on Pectin Composition of Hakuho Peach (Prunus persica Batsch) During Maturation

Effects of fertilizer application levels on fruit texture and flesh pectin compositions of a melting peach were investigated. Hakuho trees (Prunus persica Batsch) were supplied with normal (M), high (H; M × 2), and superhigh (SH; M × 4) levels of complete liquid fertilizer twice a week. Flesh firmness of the H and SH treatment fruit was lower than that of M treatment fruit at the hard-mature and firm-mature stages, although no difference was detected at the full ripe stage. Sensory scores for flesh texture at the full ripe stage were highest in the N treatment fruit and lowest in the SH treatment fruit. The content of water-soluble polyuronides (WSP) in flesh was highest in SH fruit and lowest in M fruit at the hard-mature stage, although the difference became smaller at the full ripe stage. Molecular mass analysis using a gel filtration column revealed that water-soluble polysaccharides in alcohol-insoluble solids (AIS) of the H and SH fruits had a peak of high molecular mass, ≈200 kDa, at the hard-mature stage, and the molecular mass decreased gradually to ≈23 kDa at the full ripe stage. In the M fruit, however, the molecular mass was rather constant during the ripening period, 112 kDa even at the full ripe stage. The analysis of acidic fractions (pectin) in the polysaccharides using an ion exchange column, as well as juice gellation test by adding Ca and Tris buffer, also indicated that high levels of fertilizer application impairs an early degradation of flesh polyuronides resulting in the accumulation of low-molecular-weight WSP. This may ultimately cause the inferior flesh texture of overfertilized peach fruit.

Effect of storage period on the molecular-mass distribution profile of pectic and hemicellulosic polysaccharides in pears

We investigated the effects of the storage period on the molecular distribution profile of pectic and hemicellulosic polysaccharides in ‘Maruguerite Marillat’ and ‘La France’ pears. After storage of fruit of both cultivars for 1 month (short-term storage) at 1 °C, or 4 months (long-term storage) for ‘Marguerite Marillat’ and 5 months (long-term storage) for ‘La France’, the fruit were transferred to 20 °C for ripening. Based on the firmness of the flesh, five fruit at different stages of softening (from hard to soft) from each storage condition were selected for analysis. The fruit softened after transfer to 20 °C after storage at 1 °C, independently of the cultivar or storage period. However, after long-term storage, the fruit did not achieve the buttery and juicy texture known as the melting texture, whereas after short-term storage, fruit of both cultivars reached these textures. When the fruit developed the melting texture, both the uronic acid and total sugar components of the water-soluble polyuronides (WSP) showed striking molecular-mass downshifts, concomitant with increases in the levels of smaller polymers. In over-ripe fruit, the molecular-mass downshifts were extensive. In fruit that had been subjected to long-term storage, the uronic acid component of the WSP also showed a tendency toward molecular-mass downshifts as the fruit softened. However, no relationship was observed between fruit softening and changes in the molecular-mass distribution of the total sugar component. In ‘Marguerite Marillat’ and ‘La France’ fruit after short-term storage, the molecular-mass distribution of the total sugar and xyloglucan components of the hemicellulosic polysaccharides did not change significantly until the fruit developed the melting texture. After that point, the peak shifted greatly toward the low-molecular-mass region. In fruit after long-term storage, the total sugar and xyloglucan components also showed molecular-mass downshifts. However, the extent of the downshifts was still larger in fruit after short-term storage than in those after long-term storage. These results suggest that reduced depolymerization of pectic and hemicellulosic polysaccharides is related to an inferior fruit texture after prolonged storage.

Suppression of Avocado (Persea americana Mill.) Fruit Softening and Changes in Cell Wall Matrix Polysaccharides and Enzyme Activities: Differential Responses to 1-MCP and Delayed Ethylene Application

Pre-ripe `Booth 7' avocado (Persea americana Mill.) fruit, a cross of West Indian and Guatemalan strains, were treated with 0.9 μL·L-1 1-methylcyclopropene (1-MCP) for 12 hours at 20 °C. After storage for 18 days in air at 13 °C, at which time whole fruit firmness values averaged about 83 N, half of the 1-MCP-treated fruit were treated with 100 μL·L-1 ethylene for 12 hours and then transferred to 20 °C. 1-MCP delayed softening, and fruit treated with 1-MCP retained more green color than air-treated fruit when full ripe (firmness 10 to 15 N). 1-MCP affected the activities of pectinmethylesterase (EC 3.2.1.11), α-(EC 3.2.1.22) and β-galactosidases (EC 3.2.1.23), and endo-β-1,4-glucanase (EC 3.2.1.4). The appearance of polygalacturonase (EC 3.2.1.15) activity was completely suppressed in 1-MCP-treated fruit for up to 24 days, at which time the firmness of 1-MCP-treated fruit had declined nearly 80% compared with initial values. The effect of exogenous ethylene applied to partially ripened 1-MCP-treated fruit differed for different ripening parameters. Ethylene applied to mid-ripe avocado exerted no effect on the on-going rate or final extent of softening of 1-MCP-treated fruit, even though polygalacturonase and endo-1,4-β-glucanase activities increased in response to ethylene. β-galactosidase decreased in 1-MCP-treated fruit in response to ethylene treatment. 1-MCP delayed the increase in solubility and depolymerization of water- and CDTA (1,2-cyclohexylenedinitrilotetraacetic acid)-soluble polyuronides, likely due to reduced polygalacturonase activity. At the full-ripe stage, the levels of arabinose, galactose, glucose, mannose, rhamnose, and xylose associated with the CDTA-soluble polyuronide fraction were similar among all treatments. In contrast, the galactose levels of water-soluble polyuronides declined 40% and 17% in control and 1-MCP treated fruit, respectively. Hemicellulose neutral sugar composition was unaffected by 1-MCP or ethylene treatment. The data indicate that the capacity of avocado fruit to recover from 1-MCP-mediated suppression of ripening can be only partially amended through short-term ethylene application and differs significantly for different ripening parameters.

Methyl de-esterification as a major factor regulating the extent of pectin depolymerization during fruit ripening: a comparison of the action of avocado ( Persea americana) and tomato ( Lycopersicon esculentum) polygalacturonases

Pectinmethylesterase (PME, EC 3.2.1.11) and polygalacturonase (PG, EC 3.2.1.15) are known to operate in tandem to degrade methylesterified polyuronides. In this study, PGs purified from tomato and avocado fruit were compared in terms of their capacity to hydrolyze water-soluble polyuronides from avocado before and following enzymic or chemical de-esterification. When assayed using polygalacturonic acid or polyuronides from avocado fruit, the activity of PG from tomato fruit was 3-4 times higher than that from avocado fruit. High molecular mass, low methylesterified (33%) water-soluble polyuronides (WSP) from pre-ripe avocado fruit (day 0) were partially depolymerized upon incubation with purified avocado and tomato PGs. In contrast, middle molecular mass, highly methylesterified (74%) WSP from day 2 fruit were largely resistant to the action of both PGs. PME or weak alkali treatment of highly methylesterified WSP decreased the methylesterification values to 11 and 4.5%, respectively. Treatment of de-esterified WSP with either avocado or tomato PGs caused extensive molecular mass downshifts, paralleling those observed during avocado fruit ripening. Although PME and PG are found in many fruits, the pattern of depolymerization of native polyuronides indicates that the degree of cooperativity between these enzymes in vivo differs dramatically among fruits. The contribution of PME to patterns of polyuronide depolymerization observed during ripening compared with physically compromised fruit tissues is discussed.

Activities of several membrane and cell-wall hydrolases, ethylene biosynthetic enzymes, and cell wall polyuronide degradation during low-temperature storage of intact and fresh-cut papaya (Carica papaya) fruit

Abstract Fresh-cut fruit tissue deteriorates more rapidly than its intact counterpart. A study was conducted to determine changes in firmness, cell-wall polyuronides, and the activities of cell-wall and membrane hydrolases and ethylene biosynthetic enzymes in intact and fresh-cut papaya fruit during storage at 5 °C. Processing of papaya fruit was performed under sanitized conditions at 5 °C, and fruit pieces were stored for 8 days at 5 °C. Levels of total and CDTA-soluble polyuronides in intact fruit did not change during storage, but water-soluble polyuronides increased significantly by day 8 (15%). In contrast, total polyuronide content of fresh-cut papaya decreased (9.5%), whereas levels of CDTA- and water-soluble polyuronides increased 45 and 30%, respectively. Firmness and mol mass of polyuronides decreased more rapidly in fresh-cut fruit than in intact fruit. The activities of polygalacturonase (EC 3.2.1.15), alpha- (EC 3.2.1.22) and beta-galactosidases (EC 3.2.1.23), lipoxygenase (EC 1.13.11.12), phospholipase D (EC 3.1.4.4), and ACC synthase (EC 4.4.1.14) and ACC oxidase increased within 24 h in fresh-cut fruit, and remained significantly higher compared with levels in intact fruit throughout the storage period. Pectin methyl esterase (EC 3.2.1.11), and phospholipase C (EC 3.1.4.3) activities showed no consistent differences between fresh-cut and intact fruit. The data suggest that a wound-induced increase in enzymes targeting cell walls and membranes contributes to the rapid deterioration of fresh-cut fruit. The significantly less pronounced changes observed for intact fruit stored under identical conditions indicate that the enhanced deterioration of fresh-cut fruit does not reflect low-temperature injury.

Extensive solubilization and depolymerization of cell wall polysaccharides during avocado (Perseaamericana) ripening involves concerted action of polygalacturonase and pectinmethylesterase

During the ripening of avocado (Persea americana Mill.) fruit, water-soluble polyuronides increased dramatically, concomitant with marked downshifts in molecular mass. Treatment of cell walls from pre-ripe fruit with purified avocado polygalacturonase (PG, EC 3.2.1.15) promoted the release and molecular mass downshift of polyuronides. The polyuronides released by PG were similar in size distribution to water-soluble polyuronides from fruit at intermediate stages of ripening. Polyuronides released from pre-ripe fruit by PG, although of relatively high molecular mass, were not further degraded upon additional incubation with fresh enzyme. Similarly, water-soluble polyuronides prepared from fruit at intermediate stages of ripening were largely resistant to the action of purified PG in vitro. When polyuronides derived from fruit at intermediate stages of ripening were treated with weak alkali or pectinmethylesterase (PME, EC 3.1.1.11), extensive molecular mass downshifts occurred in response to incubation with PG. These results suggest that PG plays the central role in polyuronide degradation in ripening avocado fruit cell walls and that partial de-esterification is necessary for the increase in the susceptibility of polyuronides to PG. Differences in the patterns of polyuronide depolymerization in avocado fruit compared with the more thoroughly characterized tomato fruit are discussed.

Cell wall changes in pear fruit softening on and off the tree

Abstract Changes in ethylene production and polyuronides in pear fruit on and off the tree were investigated. In `Marguerite Marillat' fruit, flesh firmness changed little after the optimum time for harvesting (OTH). By contrast, firmness of `La France' fruit decreased gradually after OTH, reaching an average of 30 N for fruit left on the tree for 28 days after OTH. The amount of water-soluble polyuronides increased slightly during ripening on the tree. In both cultivars, the amount 28 days after OTH was less than one-third of that in fruit harvested at OTH and ripened off the tree. Ethylene production did not increase substantially until 28 and 14 days after OTH in `Marguerite Marillat' and `La France' fruit, respectively. Pears off the tree softened to less than 10 N independently of harvest date and cultivar. The amount of water-soluble polyuronides in fruit softened after harvest increased significantly from that at harvest. In both cultivars, the texture of fruit harvested at 14 days and 28 days after OTH and ripened did not become buttery and juicy. Those fruit had less water-soluble polyuronides than fruit which developed a buttery and juicy texture.

Molecular Weight and Degree of Methoxylation in Cell Wall Polyuronide during Softening in Pear and Apple Fruit

The concentrations of water-soluble polyuronides in apples [Malus domestica Borkh.) and pears (Pyrus communis L.) increased, but those of EDTA- and HCl-soluble polyuronides decreased during softening. Total polyuronide content decreased slightly during softening in both fruits. Depolymerization of polyuronides was observed only in the water-soluble fraction in pear fruit during softening, concomitant with an increase in polygalacturonase (PG) activity. No detectable depolymerization was observed in any of the polyuronide fractions during softening of apple fruit nor was any PG activity detected. The polyuronide fractions extracted from pear and apple cell walls contained various amounts of methoxyl groups. Polyuronides with a high degree of methoxylation were preferentially lost from EDTA- and HCl-soluble polyuronides during softening of both fruit. The water-soluble polyuronide had a lower degree of methoxylation than those lost in the EDTA- and HCl-soluble fractions. These results suggest de-esterification of polyuronides with a high degree of methoxylation rather than the depolymerization of polyuronides in the solubilization of polyuronides during ripening of apples and pears.

Changes in Water Soluble Polyuronides in the Pulp Tissue of Ripening ‘Bosc’ Pears following Cold Storage in Air or in 1% Oxygen

Abstract ‘Bosc’ pears (Pyrus communis L.) harvested at an optimum maturity, based on flesh firmness (about 62 N), were stored either in air or 1% O2 (plus &lt;0.03% CO2) at −1°C. Fruit stored in air for 1 to 3 months softened rapidly after 2 days of ripening at 20°C and reached ripeness with flesh firmness of 20 N or lower by the 9th day. Ripening was associated with a reduction in extractable juice (EJ) and an apparent increase in water soluble polyuronides (WSP). Fruit stored in air for 4 to 5 months also softened rapidly after 2 days of ripening, but flesh firmness was still between 26 and 30 N after 9 days; however, EJ and WSP of fruit did not change appreciably during 9 days of ripening. The WSP content in fruit stored in either air or 1 % O2 increased substantially during 6 months of storage at −1°C. Increased WSP content during storage did not affect the quantity of EJ. Fruit stored at 1% O2 showed a reduction in EJ and an increase in WSP during the 9-day ripening period, whereas, in long-term air-stored fruit, EJ did not decline while WSP was degraded. Correlation of EJ and WSP during each ripening period provided an estimation of storage life. Increased WSP after ripening might be responsible for the increase in hygroscopic binding capacity of the ripened pulp tissue.