Temporal sequence of cell wall disassembly events in developing fruits. 1. Analysis of raspberry (Rubus idaeus)

Raspberry fruits were harvested at five developmental stages, from green to red ripe, and the changes in cell wall composition, pectin and hemicellulose solubilization, and depolymerization were analyzed. Fruit softening at intermediate stages of ripening was associated with increased pectin solubilization, which occurred without depolymerization. Arabinose was found to be the most abundant noncellulosic neutral sugar in the cell wall and showed dramatic solubilization late in ripening. No changes in pectin molecular size were observed even at the 100% red stage. Subsequently, as fruit became fully ripe a dramatic depolymerization occurred. In contrast, the hemicellulosic fractions showed no significant changes in content or polymer size during ripening. The paper discusses the sequence of events leading to cell wall disassembly in raspberry fruit.     

Compositional changes in 'Bartlett' pear ( Pyrus communis L.) cell wall polysaccharides as affected by sunlight conditions

Preharvest conditions can have a great impact on fruit quality attributes and postharvest responses. Firmness is an important quality attribute in pear, and excessive softening increases susceptibility to bruising and decay, thus limiting fruit postharvest life. Textural characteristics of fruits are determined at least in part by cell wall structure and disassembly. Few studies have analyzed the influence of fruit preharvest environment in softening, cell wall composition, and degradation. In the current work 'Bartlett' pears grown either facing the sun (S) or in the shade (H) were harvested and stored for 13 days at 20 °C. An evaluation of fruit soluble solids, acidity, color, starch degradation, firmness, cell wall yield, pectin and matrix glycan solubilization, depolymerization, and monosaccharide composition was carried out. Sun-exposed pears showed more advanced color development and similar levels of starch degradation, sugars, and acids than shaded fruit. Sunlight-grown pears were at harvest firmer than shade-grown pears. Both fruit groups softened during storage at 20 °C, but even after ripening, sun-exposed pears remained firmer. Sunlight exposure did not have a great impact on pectin molecular weight. Instead, at harvest a higher proportion of water-solubilized uronic acids and alkali-solubilized neutral sugars and a larger mean molecular size of tightly bound glycans was found in sun-exposed pears. During ripening cell wall catabolism took place in both sun- and shade-grown pears, but pectin solubilization was clearly delayed in sun-exposed fruit. This was associated with decreased removal of RG I-arabinan side chains rather than with reduced depolymerization.     

Simultaneous transgenic suppression of LePG and LeExp1 influences fruit texture and juice viscosity in a fresh market tomato variety

Tomatoes are grown for fresh consumption or for processing of the fruit. Some ripening-associated processes of the fruit can either contribute to or degrade attributes associated with both fresh and processing quality. For example, cell wall disassembly is associated with loss of fresh fruit firmness as well as with loss of processed tomato product viscosity. Several enzymes contribute to cell wall polysaccharide disassembly. Polygalacturonase (PG, poly[1,4-alpha-d-galactouronide] glucanohydrolase, EC 3.2.1.15) is among the most abundant polysaccharide hydrolases in ripening tomato fruit and is the major contributor to pectin depolymerization. Expansin (LeExp1) is also abundant in ripening fruit and is proposed to contribute to cell wall disassembly by nonhydrolytic activity, possibly by increasing substrate accessibility to other enzymes. Suppression of either LePG or LeExp1 expression alone results in altered softening and/or shelf life characteristics. To test whether simultaneous suppression of both LePG and LeExp1 expression influences fruit texture in additive or synergistic ways, transgenic Lycopersicon esculentum var. Ailsa Craig lines with reduced expression of either LePG or LeExp1 were crossed. Fruits from the third generation of progeny, homozygous for both transgenic constructs, were analyzed for firmness and other quality traits during ripening on or off the vine. In field-grown transgenic tomato fruit, suppression of LeExp1 or LePG alone did not significantly increase fruit firmness. However, fruits suppressed for both LePG and LeExp1 expression were significantly firmer throughout ripening and were less susceptible to deterioration during long-term storage. Juice prepared from the transgenic tomato fruit with reduced LePG and LeExp1 expression was more viscous than juice prepared from control fruit.     

Tissue-specific and developmental modifications of grape cell walls influence the adsorption of proanthocyanidins

Cell wall material from Vitis vinifera L. cv. Cabernet Sauvignon grape skin and flesh was isolated at different stages of grape maturity to determine whether developmental changes in cell wall composition in different tissue types influence the binding of proanthocyanidins (PAs). Trends in cell wall adsorption of, and selectivity for, PAs were determined using two skin PAs that differed in their average molecular masses. Flesh cell walls consistently bound a higher amount of PA than those from skin. Key structural differences that reduced PA adsorption in skin cell walls by comparison with flesh cell walls were endogenously higher concentrations of insoluble PA, Klason lignin, and lower cell wall-bound protein. These differences may confer reduced flexibility and porosity of skin cell walls relative to flesh cell walls. Analysis of skin and flesh cell wall properties revealed that the onset of ripening was associated with a loss of type I arabinogalactan and galacturonic acid, which indicated a degradation of pectin within the cell wall. Flesh cell walls consistently bound PAs of larger molecular mass, and changes in PA adsorption properties after the onset of ripening were minor. For skin cell walls, adsorption of PA was lowest immediately following solubilization of galacturonic acid, and high molecular mass PAs were poorly bound. As ripening progressed, PAs of higher molecular mass were selectively adsorbed by skin cell walls, which indicates that ongoing cell wall remodeling during ripening may confer an increased porosity within the skin cell wall matrix, resulting in a greater adsorption of PA within a permeable structure.     

Determination and isolation of a thioesterase from passion fruit (Passiflora edulis Sims) that hydrolyzes volatile thioesters

Volatile organosulfur compounds (VOSCs) are high impact aroma chemicals characteristic of tropical fruits which are active as both free thiols and the respective thioesters. Using a simple and sensitive colorimetric enzyme assay, a thioesterase activity toward VOSCs has been identified in ripening purple passion fruit ( Passiflora edulis Sims). The assay was based on determining the release of free thiols from 2-methyl-3-furanthiol acetate using Ellman's reagent. The major thioesterase in the fruit was found to be a wall-bound protein in the mesocarp. The extracted enzyme activity was purified 150-fold and shown to be associated with a 43 kDa monomeric serine hydrolase which was selectively labeled with a fluorophosphonate suicide probe. MS-MS sequencing identified the thioesterase as a class 13 glycoside hydrolase, most similar to pectin acetylesterase, an enzyme involved in cell wall modifications in the peel of a number of fruit. Our results suggest that cell wall hydrolases in tropical fruit may have additional useful roles in biotransforming VOSCs.     

Olive fruit cell wall: degradation of cellulosic and hemicellulosic polysaccharides during ripening

Cellulose and hemicelluloses obtained from the cell walls of partially depectinated olives have been studied at three stages of ripening (green, cherry, and black). Hemicelluloses were fractionated into two groups, the amounts of which diminished during ripening: those soluble in 4% KOH diminished between the cherry and black stages, whereas those soluble in 24% KOH did so between the green and cherry stages. Arabinoxylans, xyloglucans, and homo- and/or rhamnogalacturonans to a lesser extent were present in these fractions. After ion exchange and size exclusion chromatographies, decreases in the molecular weights of hemicelluloses, mainly in the neutral fractions, were observed. The amount of cellulose also decreased, but at the second stage of the ripening process. Approximately 2 mg/fruit of glucose was lost from cellulose, and the amount of uronic acids increased (0.23 mg/fruit).     

Impact of UV-C irradiation on the cell wall-degrading enzymes during ripening of tomato (Lycopersicon esculentum L.) fruit

The effect of a hormic dose of UV-C (254 nm) on changes in fruit firmness and cell wall-degrading enzyme (CWDE) activity was determined using tomato fruit. Throughout the storage period, a decrease in firmness was jointly observed with an increase of the CWDE (polygalacturonase, pectin methyl esterase, cellulase, xylanase, beta-D-galactosidase, and protease) activity for all treatments, suggesting the involvement of these enzymes in the ripening process. However, the enhancement in the activity of the CWDE was significantly less in fruit subjected to the hormic dose of UV-C. This reduction may explain why irradiated fruit were firmer than control and consequently may explain how UV-C could delay the ripening and senescence process. We suggest that the CWDE are one of the targets of the UV-C, and by this action, irradiation contributed to a delay of the cell wall degradation and consequently retarded softening of the tomato fruit tissues.     

Cultivar-dependent cell wall modification of strawberry fruit under NaCl salinity stress

Strawberry cultivars differ in their sensitivity to NaCl; fruits of cv. Elsanta suffer from softening, whereas those of cv. Korona retain their firmness. The mean fruit fresh weight is reduced in cv. Elsanta up to 46% and in cv. Korona up to 26%. Cell walls of fruits grown under 0, 40, or 80 mmol/L NaCl were extracted and analyzed. In fruits of cv. Korona, the content of the alcohol-insoluble residue remained comparatively stable as salt levels increased but was reduced in cv. Elsanta. The water-soluble pectin fraction was not affected in cv. Korona, but the content of low methoxy pectinates increased significantly, indicative of the generation of calcium and magnesium bridges that stabilize pectin polysaccharides of cell walls. In cv. Elsanta, the content of water-soluble pectin rose, indicating pectin solubilization. For both cultivars, the significant negative correlation of fruit Cl(-) contents with the contents of NaOH-soluble pectinates, when expressed per fruit fresh mass, indicated that covalently bound pectic substances were degraded. Especially the response of cv. Elsanta is in line with the general observation that severe osmotic stress results in slower cell expansion and weaker cell walls.     

Olive fruit cell wall: degradation of pectic polysaccharides during ripening

Olive fruits at three stages of ripening (green, cherry, and black) have been studied. After cell wall isolation, the compositions of the cell wall and that of the phosphate-soluble polysaccharides were determined. In cell walls, decreases in arabinose, xylose, glucose, and uronic acid levels were observed, together with a slight increase in mannose on ripening. At the beginning of ripening, fragments of pectic polymers were the major constituents of the phosphate-soluble fraction, with the hemicellulosic ones increasing toward the end of the process. The molecular weight of the fragments solubilized was approximately 6 kDa. After cell wall fractionation, the pectic polysaccharides soluble in imidazole and sodium carbonate were also studied. In both fractions, between the green and cherry stages of ripening, a significant loss of homogalacturonans took place. Between the cherry and black stages of ripening, rhamnogalacturonan side chains were also released in addition to homogalacturonans. In any of the pectic fractions, changes in apparent molecular weight were quantified.     

Effect of cooking on banana and plantain texture

The effect of temperature and duration of cooking on plantain and banana fruit texture and cytpoplasmic and cell wall components was investigated. The firmness of both banana and plantain pulp tissues decreased rapidly during the first 10 min of cooking in water above 70 degrees C, although plantain was much firmer than banana. Cooking resulted in pectin solubilzation and middle lamella dissolution leading to cell wall separation (as observed by SEM). Dessert banana showed more advanced and extensive breakdown than plantain. Although dessert banana had a higher total pectin content than plantain, the former had smaller-sized carboxyethylenediaminetetraacetic acid (CDTA) soluble pectic polymers which are associated with plant tissues that have a propensity to soften. Plantain had higher levels of starch and amylose than banana but this was associated with a firmer fruit texture rather than a softening due to cell swelling during starch gelatinization. Different cooking treatments showed that cooking in 0.5% of CaCl(2) solution and temperatures below 70 degrees C had significant effects on maintenance of pulp firmness.     

糖液与钙盐组合渗透脱水处理对冻融蓝莓品质的影响

为探究钙盐作为冷冻保护剂与高浓度糖液浸渍组合在常温下进行渗透脱水处理对冷冻蓝莓融化后质地品质的影响。对比以丙酸钙、乳酸钙、氯化钙为代表的3种钙盐冷冻保护剂及质量浓度为0.5、1.5、3.0、5.0 g/mL丙酸钙处理对冻融蓝莓品质的影响。通过观测蓝莓冻融后外观,测定硬度值、弹性、咀嚼性、胶着性、内聚性和回复性品质指标及可溶性果胶、共价结合型果胶和离子结合型果胶的含量。结果表明：添加钙盐结合糖液渗透脱水处理组均可减少蓝莓冻融后皱缩和质地瘫软现象,丙酸钙结合糖液渗透脱水处理组的汁液流失率比对照组降低约25.42%,显著低于（P＜0.05）其他处理组,丙酸钙处理组为较优的钙盐添加种类。对丙酸钙添加浓度进行优化筛选,发现当丙酸钙添加浓度为1.5 g/mL时可显著降低（ P ＜0.05）蓝莓果实的汁液流失和细胞膜透性,冻融后硬度为1.54 N、弹性0.75 mm,可溶性果胶、共价结合型果胶和离子结合型果胶含量分别达到1.03、0.83 和0.68 mg/g,减少蓝莓果实的质地瘫软现象并保持最佳冻融品质。丙酸钙浓度为1.5 g/mL结合渗透脱水技术使冻融蓝莓具有更好的品质,有利于食用和加工。研究结果不仅为解决蓝莓加工行业出现的由于长期冷冻所造成果实质地瘫软问题提供数据基础,还为研发提升果蔬原料冷冻贮藏品质的助冻剂及改性技术提供一定的理论依据。     

Effect of dips in a 1-methylcyclopropene-generating solution on 'Harrow Sun' plums stored under different temperature regimes

The effect of postharvest dips in a 1-methylcyclopropene-generating solution of the formulation AFxRD-038 (Rohm & Haas) on plum fruit (Prunus salicina Lindell cv. 'Harrow Sun') quality and ripening during storage was determined. Fruit weight loss, tissue firmness, soluble solids content (SSC), titratable acidity (TA), ethylene production, respiration, and the activities of the cell wall modifying enzymes polygalacturonase (PG), 1,4-beta-D-glucanase/glucosidase (EGase), beta-galactosidase (beta-gal), and pectin methylesterase (PME) were measured. Fruit reddening, anthocyanin content, and phenylalanine ammonia-lyase (PAL) activity were also analyzed. The 1-MCP-treated fruit showed reduced ethylene production and respiration rate and delayed softening, which was associated with the reduction in the activity of PG, EGase, and beta-gal. The immersion in 1-MCP-generating solutions also decreased weight and acidity loss without modifying the fruit SSC. The immersion treatment was particularly effective in the fruit stored at 5 degrees C, keeping higher overall quality, maintaining lower levels of anthocyanins and PAL activity, and preventing flesh reddening. The present data show that beneficial effects in delaying plum fruit ripening and controlling chilling injury can be obtained by dipping the fruits in a solution of this novel 1-MCP-generating formulation.     

钙处理对葡萄柚果实细胞壁物质代谢及其相关基因表达的影响

【目的】研究采前、 采后钙处理对葡萄柚果实细胞壁组分、 细胞壁降解酶活性变化及其相关基因表达的影响,可为了解钙与果实细胞壁物质代谢之间的关系,揭示钙对果实软化的作用机理,为调控葡萄柚果实膳食纤维含量,提高果实质地品质提供理论依据。【方法】试验于2011年2月至11月在云南省玉溪市葡萄柚果园进行,供试品种为‘里约红’葡萄柚,该品种于2005年嫁接于当地砧木,株行距为3 m×3 m。试验由采前和采后钙处理两部分组成。采前钙处理在幼果初期、 幼果末期、 膨大初期、 膨大末期、 转色期,叶面喷施2% CaCl2; 采后钙处理在果实成熟采后浸于2% CaCl2溶液5 min, 室温贮藏。之后每15天取样一次,每次取10个果实,测定葡萄柚果肉细胞壁组分、 细胞壁降解酶活性及其基因表达量。【结果】随葡萄柚果实后熟软化,紧密结合型果胶(共价结合型果胶)解聚为松散结合型果胶(水溶性果胶、 离子结合型果胶),紧密结合型半纤维素(24% KOH可溶性半纤维素)解聚使其含量下降,而松散结合型半纤维素含量增加(4%KOH可溶性半纤维素)。果实PG、 PME、 Cx、 α-L-Af和β-Gal酶活性及其基因表达量均随果实软化呈不同程度增加。PME活性在果实采收后表现出较高含量,而PG活性在果实贮藏前期急剧增加,其酶基因的表达量与酶活性变化趋势基本一致。Cx、 α-L-Af和β-Gal活性在贮藏中、 后期上升较快,相关酶基因的表达量亦明显增加。钙处理显著地降低果实细胞壁降解酶活性和基因表达水平,其中采后钙处理对α-L-Af和β-Gal活性和基因表达在贮藏中、 后期的调控作用较显著,酶活性和基因表达均维持在较低水平。【结论】外源钙处理降低细胞壁降解酶活性及其基因表达,抑制了细胞壁物质的解聚,采后钙处理对细胞壁物质代谢的调控效果优于采前钙处理。外源钙处理抑制了细胞壁降解酶基因表达水平,降低了细胞壁降解酶活性,减缓了果胶、 半纤维素的解聚,从而达到调控果实膳食纤维含量、 维持果实质地品质、 延长果实货架期寿命的目的。     

Proteomic analysis of up-accumulated proteins associated with fruit quality during autumn olive (Elaeagnus umbellata) fruit ripening

Fruit ripening is a complex phenomenon that makes berries attractive and also determines their nutritional value. Autumn olive ( Elaeagnus umbellata Thunb.) fruit is a rich source of many human health-related nutrients. The changes in pericarp color are initiated at early developmental stages, coinciding with the fast increase in fruit size. Fruit quality traits with special emphasis on soluble sugars, organic acids, lycopene, and total protein contents were assayed during the fruit ripening. In the fully ripe fruit, glucose and fructose were the principal sugars, malic acid was the most abundant organic acid, and lycopene concentration was extremely high. A proteomic analysis was used to identify up-accumulated proteins induced by the ripening. Among 63 up-accumulated protein spots, 43 were successfully identified by MALDI-TOF/TOF-MS. All 43 proteins were novel for autumn olive, and 8 were first reported in the fruit. Twenty-one proteins of known function were involved in sugar metabolism, citric acid cycle, isoprenoid metabolism, fatty acid synthesis, and protein hydrolysis. The possible roles of these 21 accumulated proteins in autumn olive fruit quality are discussed.     

Pectic methyl and nonmethyl esters in potato cell walls.

Because pectins are released from potatoes and other plants under conditions that cleave ester linkages, it has been suggested that there are other galaturonoyl ester cross-links between pectin chains in addition to the known non-cross-linking methyl esters. A microscale titration method and a copper binding method were developed for the measurement of total polymer carboxyl (essentially pectic) ester content in potato cell walls. Relative to the uronic acid content of the cell walls, the degree of total esterification was 57-58%. Comparison with levels of methanol released on ester hydrolysis allowed nonmethyl uronoyl esters to be estimated to be 14-15% relative to total uronic acid. The possibility of nonmethyl-esterified linkages being formed in potato cell walls by a side-reaction catalyzed by pectin methyl esterase (PME) was investigated, but no increase in nonmethyl-esterified pectin was observed under conditions where pectin was being effectively de-esterified by endogenous PME activity.     

Metabolism of phenolic compounds during loquat fruit development.

Phenolic compounds in loquat fruit were identified as 5-caffeoylquinic acid (chlorogenic acid), neochlorogenic acid, hydroxybenzoic acid, 5-p-feruloylquinic acid, protocatechuic acid, 4-caffeoylquinic acid, epicatechin, o-coumaric acid, ferulic acid, and p-coumaric acid. Neochlorogenic acid was found to be dominant in the early stages of loquat fruit development. Both the concentrations and types of phenolic compounds were high in young fruit but then decreased steadily during growth. However, the concentration of chlorogenic acid increased during ripening and became predominant in ripe fruit. The large rise in chlorogenic acid concentration appears to be a characteristic of loquat fruit ripening. In all of the cultivars tested, the types of phenolic compounds were similar but the total phenolic content varied from 81.8 to 173.8 mg/100 g of fresh pulp. In the biosynthetic pathway of chlorogenic acid, the enzyme activities of phenylalanine ammonia-lyase (PAL), 4-coumarate:CoA ligase (CL), and hydroxycinnamoyl CoA:quinate hydroxycinnamoyl transferase (CQT) were high at the early stage of growth, diminished to low levels approximately 3 weeks prior to harvest, but then rose to a peak at 1 week before harvest. The changes of these enzyme activities seemed to be associated with variations in chlorogenic acid concentration during development, maturation, and ripening of loquat fruit.     

猕猴桃果实贮藏期间细胞壁多糖物质降解特性及组织结构差异分析

为了深入了解猕猴桃果实采后细胞壁多糖物质降解及组织结构变化与果实贮藏性的关系,本研究以红阳和华特猕猴桃果实为试材,对25和4℃贮藏期间的细胞壁多糖物质含量及果胶降解酶活性进行测定,并比较两品种果实在25℃贮藏期间的细胞显微结构和钙组分含量差异。结果表明,在25和4℃贮藏条件下,随着贮藏时间的延长,红阳和华特猕猴桃果实中半纤维素（HCL）、纤维素（CL）和共价结合型果胶（CSP）含量不断降低,水溶性果胶（WSP）含量不断上升,离子结合型果胶（ISP）含量相对稳定。红阳猕猴桃各细胞壁多糖组分含量变化速度较快。两品种猕猴桃果实硬度均与WSP含量呈显著负相关,与CSP含量呈显著正相关。果胶降解酶活性检测结果显示,25℃贮藏前期,红阳猕猴桃中果胶酸裂解酶（PL）和β-半乳糖苷酶（β-Gal）活性显著高于华特;贮藏中后期,红阳中果胶甲酯酶（PME）活性显著高于华特。4℃贮藏期间,红阳中PME活性仍显著高于华特;4℃贮藏前期,红阳中β-Gal活性与华特无显著差异,而PL活性低于华特。相关性分析表明,25℃贮藏期间,与红阳和华特果实软化显著相关的果胶降解酶分别是PME和PL;4℃贮藏期间,与华特果实软...     

Structural ripening-related changes of the arabinan-rich pectic polysaccharides from olive pulp cell walls

In this study, the structural features and ripening-related changes that occur in the arabinan-rich pectic polysaccharides highly enmeshed in the cellulosic matrix of the olive pulp fruit were evaluated. These pectic polysaccharides, obtained from two consecutive harvests at green, cherry, and black ripening stages, account for 11-19% of the total pectic polysaccharides found in the olive pulp cell walls and were previously shown to occur as calcium chelating dimers. On the basis of the 13C NMR, (1H, 13C) gHSQC, 2D COSYPR, and (1H,13C) gHMBC carbon and proton resonances of the variously linked arabinosyl residues, we propose a tentative structure. This structure is particularly characterized by T-beta-Araf (1-->5)-linked to (1-->3,5)-Araf residues and by the occurrence of branched and linear blocks in the arabinan backbone. Methylation analysis showed that these pectic polysaccharides of black olives have more arabinan side chains, which were shorter (less (1-->5)-Araf), highly branched (more (1-->3,5)-Araf), and with shorter side chains (fewer (1-->3)-Araf) than those of green and cherry olives. Quantitative 13C NMR data indicated that these modifications involved the disappearance of the characteristic terminally linked beta-Araf residue of the arabinans. This odd feature can be used as a diagnostic tool in the evaluation of the stage of ripening of this fruit, as well as a marker for the presence of olive pulp in matrices containing pectic polysaccharides samples.     

Cell wall polysaccharide chemistry of peach genotypes with contrasted textures and other fruit traits

Cell wall composition, pectin, and hemicellulose fine structure variation were assessed in peach and related genotypes with contrasted texture and fruit shape. Cell walls were prepared from four commercial peaches, eight genotypes from the Jalousia × Fantasia peach cross, and six genotypes from the Earlygold peach × Texas almond cross. Sugar composition was determined chemically while fine structure of homogalacturonan pectin and xyloglucan hemicellulose were assessed by coupling pectin lyase and glucanase degradation, respectively, with MALDI-TOF MS analysis of the degradation products. The results indicate clear compositional and structural differences between the parents and their related genotypes on the basis of pectin versus cellulose/hemicellulose content and on the fine structure of homogalacturonan and xyloglucan. A relation between methyl- and acetyl-esterification of pectin with fruit shape is revealed in the Fantasia × Jalousia peach genotypes.     

Texture of cooked potatoes (Solanum tuberosum). 2. Changes in pectin composition during storage of potatoes

During the storage season changes in the chemical composition of the pectin moiety of the cell walls of raw potatoes were studied. This compositional analysis was performed for the cultivars Nicola and Irene, which represent two extremes with regard to sensory-perceived texture. Both cultivars were divided into three size categories. From each size category a dry matter (DM) distribution was made. From these distributions potatoes at the low and high ends of this distribution were selected for further analysis. In total 12 different samples were analyzed three times during the storage season. The analysis comprised a pectin fractionation study. Pectic fractions were extracted from the cell wall material (CWM) by increasing the harshness of the extraction procedure. This resulted in a calcium-complexed pectic fraction, two pectic fractions weakly bound to the CWM, and a residue fraction, respectively. It was shown that no statistically significant differences (p > or = 0.95), either in yield or in chemical composition, could be observed between the two cultivars studied (Nicola and Irene), between sizes (large, medium, and small), and between potatoes with either high or low DM contents. However, statistically significant effects of storage both on the yield and on the chemical composition of the pectic moiety of the CWM could be observed, irrespective of cultivar, size, and DM content. Despite the substantial changes in the composition of the pectic moiety of the CWM of the raw material, no to minimal changes in the sensory-perceived texture of the cooked potatoes were observed upon storage. This suggests that the observed changes in pectin composition upon storage are overruled by other aspects that contribute more importantly to the sensory-perceived texture of steam-cooked potatoes.