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€Œ€This research aimed to characterize the tolerance to flooding and alterations in pectic andhemicellulose fractions from mesocotyl of maize tolerant to flooding when submitted to hypoxia.In order to characterize tolerance seeds from maize cultivars Saracura BRS-4154 and BR€107 tolerantand sensitive to low oxygen levels, respectively, were set to germinate. Plantlet survival was evaluatedduring five days after having been submitted to hypoxia. After fractionation with ammonium oxalate0.5% (w/v) and KOH 2M and 4M, Saracura BRS-4154 cell wall was obtained from mesocotyl seg-ments with different damage intensities caused by oxygen deficiency exposure. The cell wall fractionswere analyzed by gel filtration and gas chromatography, and also by Infrared Spectrum with FourrierTransformation (FTIR). The hypoxia period lasting three days or longer caused cell lysis and in ad-vanced stages plant death. The gelic profile from pectic, hemicellulose 2M and 4M fractions fromsamples with translucid and constriction zone showed the appearance of low molecular weight com-pounds, similar to glucose. The main neutral sugars in pectic and hemicellulose fractions were arabi-nose, xilose and mannose. The FTIR spectrum showed a gradual decrease in pectic substances frommesocotyl with normal to translucid and constriction appearance respectively.Index terms: pectic substances, hemicellulose.Tolerância ao alagamento e alteracies de parede celular em mesocotilo de milho durante hipoxiaResumo€Œ€Objetivou-se caracterizar a tolerância ao alagamento e alteracies nas fracies pOcticas ehemicelulosicas de mesocotilos de milho submetidos a hipoxia. Sementes de milho cultivar SaracuraBRS-4154 e BR€107, tolerante e sensivel a hipoxia, respectivamente, foram submetidas a germinacaoe a sobrevivŒncia das plântulas em condicies de hipoxia, foi avaliada durante cinco dias. O€material deparede celular, obtido de segmentos de mesocotilos da cultivar Saracura BRS-4154 com diferentesintensidades de danos causados por hipoxia, foi submetido a fracionamento com oxalato de amonio0,5% e KOH 2M e€4M. As€fracies de parede celular obtidas foram analisadas por cromatografia emgel, cromatografia gasosa e espectro de infravermelho com transformacao dos dados pela sOrie deFourrier (FTIR). Periodos de hipoxia superiores a trŒs dias causaram a lise celular (aparŒncia translœcida),e, em estAEdios mais avancados, a morte das plantas. O€perfil gOlico das fracies pOcticas, hemicelulose2M e 4M das amostras de mesocotilos translœcidos e com constricao apresentaram compostos de bai-xos pesos moleculares semelhantes a glicose. Os€principais acœcares neutros nas fracies pOcticas ehemicelulosicas foram arabinose, xilose e manose. O€espectro de FTIR mostrou um decrOscimo gradu-al nas substâncias pOcticas do mesocotilo com aparŒncia normal, para translœcido e constricao respec-tivamente.Termos para indexacao: substâncias pOcticas, hemicelulose.

Esta pesquisa avaliou as modificações dos componentes estruturais de parede celular do melão tipo Galia (Cucumis melo L. var. reticulatus) durante o armazenamento refrigerado (7°C±1, UR: 88% ±3). O material de parede celular e suas frações foram determinados por gravimetria. Determinou-se o conteúdo de açúcares neutros na fração hemicelulósica e no resíduo celulósico, o teor de ácidos urônicos e o grau de esterificação na fração de substâncias pécticas, e o teor de cálcio total e ligado. A fração de substâncias pécticas foi submetida à cromatografia de filtração em gel e os açúcares neutros da fração hemicelulósica foram analisados por cromatografia a gás. O conteúdo de material de parede celular mostrou pouca variação durante o armazenamento. As variações mais expressivas foram registradas nas frações isoladas da parede celular (fração de substâncias pécticas, fração hemicelulósica e fração celulósica), sendo que para as duas primeiras verificou-se redução durante o armazenamento e para a última observou-se elevação. O conteúdo de açúcares neutros não celulósicos mostrou tendência de redução apenas durante as duas semanas iniciais de armazenamento. Praticamente, não houve alteração no grau de esterificação e nos conteúdos de cálcio total e cálcio ligado. A principal característica foi a manutenção dos níveis de xilose e glicose na parede celular, o que indicou constância do polímero xiloglucana.This research evaluated changes in the cell wall components in ‘Galia’ melons (Cucumis melo L. var. reticulatus) during refrigerated storage (7°C±1, RH: 88% ±3). Cell wall material and their fractions were determined by gravimetry method. Neutral sugars in hemicellulosic fraction and cellulosic residue, uronic acids content and degree of esterification in pectic fraction, , total calcium and bound calcium were analyzed. The pectic fraction was analyzed by gel chromatography and neutral sugars in hemicellulosic fraction were analyzed by gas chromatography. Cell wall material content showed minimum variation during storage. The major variations occurred in cell wall fractions (pectic, hemicellulose and cellulose fractions), decreasing in the former two during storage and increasing in the latter. Non cellulosic neutral sugars content showed reduction tendency only in two former storage weeks. Practically, the degree of esterification (degree of methylation) in pectic substances and bound calcium did not change. Gelic chromatography revealed dispolymerization trend in pectic substances. There were no variation in the xylose and glucose contents. This was the major characteristic related with softening process during storage.

O presente estudo caracterizou quantitativa e qualitativamente as mudanças nos componentes de parede celular do melão tipo Galia, híbrido Nun 1380, associadas ao processo de maturação. Os frutos foram avaliados em cinco estádios de maturação (I-V). O material de parede celular e suas frações foram determinados por gravimetria. Determinou-se o conteúdo de açúcares neutros na fração hemicelulósica e no resíduo celulósico, o teor de ácidos urônicos e o grau de esterificação na fração de substâncias pécticas, e o teor de cálcio total e ligado. A fração de substâncias pécticas foi submetida à cromatografia de filtração em gel e os açúcares neutros da fração hemicelulósica foram analisados por cromatografia a gás. O conteúdo do material de parede celular (MPC) mostrou pouca variação durante a maturação. O conteúdo de ácidos urônicos da fração péctica e o conteúdo de açúcares neutros na fração hemicelulósica (ramnose, arabinose e glicose) apresentaram tendência de redução com o avanço da maturação do fruto. Praticamente não houve variação para o grau de esterificação (% de esterificação) da fração de substâncias pécticas e para o teor de cálcio ligado. Houve redução no teor de celulose durante a maturação. A cromatografia em gel não revelou tendência de despolimerização das substâncias pécticas.This research characterized changes in the cell wall components in ‘Galia’, hybrid Nun 1380 melons during maturation. Fruits were evaluated at five maturation stages (I-V). Cell wall material and their fractions were determined by gravimetry method. Neutral sugars in hemicellulosic fraction and cellulosic residue, uronics acids content in pectic fraction, degree of esterification, total calcium and bound calcium were analyzed. The pectic fraction was analyzed by gel chromatography and neutral-sugars in hemicellulosic fraction were analyzed by gas chromatography. Minimum variation during maturation was observed in the cell wall material. Neutral sugars (rhamnose, arabinose and glucose) and uronics acids contents decreased following maturation. No variation in the degree of esterification in pectic substances and bound calcium was observed. Gel chromatography did not reveal dispolymerization in pectic substances.

To enable structural characteristics of individual cell wall polysaccharides from rapeseed (Brassica napus) meal (RSM) to be studied, polysaccharide fractions were sequentially extracted. Fractions were analysed for their carbohydrate (linkage) composition and polysaccharide structures were also studied by enzymatic fingerprinting. The RSM fractions analysed contained pectic polysaccharides: homogalacturonan in which 60% of the galacturonic acid residues are methyl-esterified, arabinan branched at the O-2 position and arabinogalactan mainly type II. This differs from characteristics previously reported for Brassica campestris meal, another rapeseed cultivar. Also, in the alkali extracts hemicelluloses were analysed as xyloglucan both of the XXGG- and XXXG-type decorated with galactosyl, fucosyl and arabinosyl residues, and as xylan with O-methyl-uronic acid attached. The final residue after extraction still contained xyloglucan and remaining (pectic) polysaccharides next to cellulose, showing that the cell wall matrix of RSM is very strongly interconnected.

Rapeseed meal (RSM) was subjected to different physical or chemical pretreatments to decrease residual, hard to degrade carbohydrates and to improve fermentability of RSM polysaccharides. Next, these pretreated samples were in vitro digested and fermented, with or without the addition of commercial pectinolytic enzymes. Remaining carbohydrates were quantified, and two physical characteristics were analyzed: (1) water-binding capacity (WBC) of the insoluble residue and (2) viscosity of the soluble fraction. Mild acid pretreatment in combination with commercial pectinolytic enzyme mixtures showed best digestion of RSM carbohydrates; only 32% of the total carbohydrate content remained. For most pretreatments, addition of commercial pectinolytic enzymes had the strongest effect on lowering the WBC of the in vitro incubated RSM. In the cases that less carbohydrate remained after in vitro digestion, the WBC of the residue decreased, and less gas seems to be produced during fermentation.

Summary The composition of apple juices produced by diffusional extraction under different processing regimes was investigated. It was demonstrated that the viscosity characteristics of a juice are dependent on the amount and nature of its pectic substances. With the exception of the addition of a pectin-degrading enzyme, the juice viscosity was most strongly dependent on the degree of esterification of the juice pectin and was also affected by the presence of calcium ions. the degree of esterification of the pectin, and hence the juice viscosity, could be manipulated by changing the process temperature or by changing the residence time in the extractor.

International audience; Passion fruit fiber pectin gels represent a new alternative pectin source with potential for food and non-food applications on a commercial scale. Pectic polysaccharides were extracted from passion fruit (Passiflora edulis) fiber using citric acid as a clean catalyst and autoclaved for 20 to 60 min at $121^{circ}C$. The best condition of pectin yield with the highest molecular weight was obtained with 1.0% of citric acid (250 mg/g dry passion fruit fiber pectin) for 20 min of autoclaving. Spectroscopic analyses by Fourier transform infrared, enzymatic degradation reactions, and ion-exchange chromatography assays showed that passion fruit pectin extracted for 20 min was homogeneous high methoxylated pectin (70%). Gel permeation analysis confirmed that the pectin extract obtained by autoclaving by 20 min showed higher molecular weights than those autoclaved for 40 and 60 min. Passion fruit pectin extracted for 20 min was enzymatically modified with fungal pectinmethylesterase to create restructured gels. Short autoclave treatment (20 min) with citric acid as extractant resulted in a significant increase of gel strength, improving pectin extraction in terms of functionality. The treatment of solubilized material (pectic polysaccharides) in the presence of insoluble material (cellulose and hemicellulose) with pectinmethylesterase and calcium led to the creation of a stiffer passion fruit fiber pectin gel, while syneresis was not observed.

Croatia in the Neretva valley produces remarkable quantities of mandarins and usually it is not possible to consume whole yield like fresh fruit so some of them are processed into jams. Mandarin like other citrus fruit is rich on polyphenolic compounds which are liable to quantitative and qualitative changes during processing. Therefore, the aim of this research work was to investigate polyphenolic content (total phenols, flavonoids and nonflavonoids by spectrophotometric method) and antioxidant capacity (FRAP method) as well as physicochemical parameters (dry matter, pH, total acidity, sugars and colorimetrically pectic substances) in fresh mandarins’ pulp and peel and in related jams. Two mandarin species Citrus unshiu (cultivar Saigon) and Citrus clementine (cultivar Corsica SRA 63) (grown in Neretva valley) and jams produced according to several recipes with fruit level variations were investigated. Pulp and peel of both investigated mandarin cultivars had very similar values of physicochemical parameters, whereas cv. Citrus clementine had a little bit higher all values except content of pectin substances. Similar values of physicochemical parameters were established in pulp and peel of both investigated mandarin cultivars unless in cv. Citrus Clementine where all values, except content of pectic substances were slightly higher. Also, higher amount of investigated polyphenolics was determined in Citrus clementine (fresh pulp, peel and jams) and flavonoids were most abounded group (55-85%) of polyphenolics in all jams what is contrary with pulp and peel where amount of nonflavonoids was higher (approximately 60% in total phenols) than flavonoids. Furthermore, the amount of polyphenolics and antioxidant capacity decreased during processing into jams and the losses considerably depend on fruit level, so higher amount of polyphenolics as well as antioxidant capacity were determined in jams with higher fruit level.

Pectic substances are structural heteropolysaccharides that occur in the middle lamellae and primary cell walls of higher plants. They are composed of partially methyl-esterified galacturonic acid residues linked by alpha-1, 4-glycosidic bonds. Pectinolytic enzymes are complex enzymes that degrade pectic polymers and there are several classes of enzymes, which include pectin esterases, pectin and pectate lyases and polygalacturonases. Plants, filamentous fungi, bacteria and yeasts are able to produce pectinases. In the industrial world, pectinases are used in fruit juice clarification, in the production of wine, in the extraction of olive oil, fiber degumming and fermentation of tea, coffee and cocoa.

Pectic substances are structural heteropolysaccharides that occur in the middle lamellae and primary cell walls of higher plants. They are composed of partially methyl-esterified galacturonic acid residues linked by alpha-1, 4-glycosidic bonds. Pectinolytic enzymes are complex enzymes that degrade pectic polymers and there are several classes of enzymes, which include pectin esterases, pectin and pectate lyases and polygalacturonases. Plants, filamentous fungi, bacteria and yeasts are able to produce pectinases. In the industrial world, pectinases are used in fruit juice clarification, in the production of wine, in the extraction of olive oil, fiber degumming and fermentation of tea, coffee and cocoa.

Action of xylogalacturonan hydrolase (XGH) towards xylogalacturonan (XGA) present in the alkali saponified “modified hairy regions” from potato and apple pectin was studied. Analysis of enzymatic degradation products from XGA in these complex pectins demonstrated that the degradable xylogalacturonans from both sources have a similar xylose side chain distribution. The disaccharide β- d -Xyl-(1,3)-GalA was the predominant product from these substrates. The number of enzymatic degradation products from xylogalacturonan present in apple and potato pectin was much lower than the number of products from a xylogalacturonan derived from Gum Tragacanth. This suggests a relatively uniform distribution of xylose in the degradable part of XGA from apple and potato pectin. In addition, dimeric side chains of xylose were observed in digests of XGA from both pectins, which apparently did not hinder the action of XGH. From this it is assumed that Xyl–Xyl as well as Xyl substituted GalA residues are accepted in subsite −1 of xylogalacturonan hydrolase.

Peaches were harvested in three stages of ripeness (treshold-mature-I, firm-ripe-II and ripe-II).Firm ripe (II) peaches were stored for 9 days at 4 and 22 oC.The amount of water-soluble, oxalate-soluble and alkali-soluble pectin were extracted and quantitatively determined as galacturonic acid, neutral sugars were determined as glucose. Jams were made with all peach samples as well as gels from extracted fractions. Gel strength of jams and gels was measured. Dry matter, sugar composition (amount of sucrose and reducing sugars) and pH value were determined and very little change was found during the ripening period and storage, too. Alkali-soluble fraction was more abounding than water-soluble fraction. The oxalate-soluble pectic fraction was found to be a minor fraction in all peach samples. The amount of total pectin and the amount of alkali-soluble pectin fraction dropped markedly after te 1st stage ripening, after the 2nd day of storage at 22 oC and slightly after the 6th day of storage at 4 oC. The level of alkali-soluble pectin in total pectin was inversely proportional to the level of water-soluble pectic fraction, and the level of oxalate soluble pectic fraction in total pectin content was fairly constant during the ripening and storage. Gel strength of jams and gels correleted vary well with changes of the amount of alkali soluble pectic fraction. The extracted alkali-soluble pectic fraction was capable of forming an acidic gel. Extracted oxalate-soluble pectic fraction forms a gel in the presence of calcium and solid matter more than 77%. It seems that the amount of alkali-soluble pectic fraction in peaches in responsible in producing peach jams according to gel strength.

Changes in the amount and composition of pectic substances during storage of Red Haven peaches were observed, as well as influence of these changes on the gel strenght of peach jams and gels made from stored peaches. Peaches were stored for 1, 2, 3, 4, 6 i 9 days at 4 oC. Amount of pectic substances were expressed as content of total pectin. The proportion of water-soluble (WSPF), oxalate-soluble (OSPF) and alkali-soluble (ASPF) pectic fractions were determined to etablish the composition of pectic substances. Those fractions were extracted and quantitatively determined as galacturonic acid (GalA) by colorimetric Internationale Fruchtsaft-Union method. Furthermore, the composition of the extracted pectic fractions was determined to etablish the proportion of GalA and neutral sugars (NS) by using phenol-sulphate method and Scott's method. Gel strenght of peach jams and gels was measured by Sulc pectinometer. During the storage there were some changes of total pectin amount and ASPF, and the highest values were determined between the third and the sixth day of storage. There were no significant changes in amount of WSPF and OSPF during the storage. ASPF was a major fraction and OSPF was a minor pectic fraction found in Red Haven peaches. The highest concentrations of GalA were determined in ASPF and the lowest concentrations were determined in WSPF. Furthermore, the highest concentrations of NS were determined in WSPF and the lowest concentrations were determined in OSPF. Duration of peaches storaging had not significant negative influence on gel strenght of jams and gels. It was established that there was a correlation between ASPF amount with gel strenght of peach jams and gels made from stored peaches.

This research aimed to characterize the tolerance to flooding and alterations in pectic and hemicellulose fractions from mesocotyl of maize tolerant to flooding when submitted to hypoxia. In order to characterize tolerance seeds from maize cultivars Saracura BRS-4154 and BR 107 tolerant and sensitive to low oxygen levels, respectively, were set to germinate. Plantlet survival was evaluated during five days after having been submitted to hypoxia. After fractionation with ammonium oxalate 0.5% (w/v) and KOH 2M and 4M, Saracura BRS-4154 cell wall was obtained from mesocotyl segments with different damage intensities caused by oxygen deficiency exposure. The cell wall fractions were analyzed by gel filtration and gas chromatography, and also by Infrared Spectrum with Fourrier Transformation (FTIR). The hypoxia period lasting three days or longer caused cell lysis and in advanced stages plant death. The gelic profile from pectic, hemicellulose 2M and 4M fractions from samples with translucid and constriction zone showed the appearance of low molecular weight compounds, similar to glucose. The main neutral sugars in pectic and hemicellulose fractions were arabinose, xilose and mannose. The FTIR spectrum showed a gradual decrease in pectic substances from mesocotyl with normal to translucid and constriction appearance respectively RESUMO - Objetivou-se caracterizar a tolerancia ao alagamento e alteracoes nas fracoes pecticas e hemicelulosicas de mesocotilos de milho submetidos a hipoxia. Sementes de milho cultivar Saracura BRS-4154 e BR 107, tolerante e sensivel a hipoxia, respectivamente, foram submetidas a germinacao e a sobrevivencia das plantulas em condicoes de hipoxia, foi avaliada durante cinco dias. O material de parede celular, obtido de segmentos de mesocotilos da cultivar Saracura BRS-4154 com diferentes intensidades de danos causados por hipoxia, foi submetido a fracionamento com oxalato de amonio 0,5% e KOH 2M e 4M. As fracoes de parede celular obtidas foram analisadas por cromatografia em gel, cromatografia gasosa e espectro de infravermelho com transformacao dos dados pela serie de Fourrier (FTIR). Periodos de hipoxia superiores a tres dias causaram a lise celular (aparencia translucida),e, em estadios mais avancados, a morte das plantas. O perfil gelico das fracoes pecticas, hemicelulose 2M e 4M das amostras de mesocotilos translucidos e com constricao apresentaram compostos de baixos pesos moleculares semelhantes a glicose. Os principais acucares neutros nas fracoes pecticas e hemicelulosicas foram arabinose, xilose e manose. O espectro de FTIR mostrou um decrescimo gradual nas substancias pecticas do mesocotilo com aparencia normal, para translucido e constricao respectivamente. Made available in DSpace on 2017-06-09T23:51:39Z (GMT). No. of bitstreams: 1 Floodingtolerance.pdf: 364997 bytes, checksum: d1363ccf173cb60858a44200da90e34d (MD5) Previous issue date: 2001-11-01

The reaction conditions were optimized for enzymatic hydrolysis of pectic substances using pectolytic enzymes produced by Aspergillus niger NCIM 548. Response surface methodology was used to optimize the reaction parameters and the central composite design was employed for this purpose. Pectin was used as the substrate for polymethylgalacturonase and pectinlyase, whereas polygalacturonic acid was the substrate for polygalacturonase. The volume ratio of reactants for maximum hydrolysis was determined under the assay conditions. The optimum amount of substrate and enzyme were found to be 0.2 cm 3 and 0.074 cm 3 for polymethylgalacturonase, 0.4 cm 3 and 0.086 cm 3 for polygalacturonase, and 0.63 cm 3 and 0.7 cm 3 for pectinlyase. The pH and temperature optima were found to be 5.3 and 30�C for polymethylgalacturonase, 6.6 and 26�C for polygalacturonase, and 4.8 and 35�C for pectinlyase. Under optimized conditions the enzyme activities were higher when compared to unoptimized conditions. Copyright (C) 1999 Elsevier Science Inc.The reaction conditions were optimized for enzymatic hydrolysis of pectic substances using pectolytic enzymes produced by Aspergillus niger NCIM 548. Response surface methodology was used to optimize the reaction parameters and the central composite design was employed for this purpose. Pectin was used as the substrate for polymethylgalacturonase and pectinlyase, whereas polygalacturonic acid was the substrate for polygalacturonase. The volume ratio of reactants for maximum hydrolysis was determined under the assay conditions. The optimum amount of substrate and enzyme were found to be 0.2 cm 3 and 0.074 cm 3 for polymethylgalacturonase, 0.4 cm 3 and 0.086 cm 3 for polygalacturonase, and 0.63 cm 3 and 0.7 cm 3 for pectinlyase. The pH and temperature optima were found to be 5.3 and 30�C for polymethylgalacturonase, 6.6 and 26�C for polygalacturonase, and 4.8 and 35�C for pectinlyase. Under optimized conditions the enzyme activities were higher when compared to unoptimized conditions.

O presente estudo caracterizou quantitativa e qualitativamente as mudanças nos componentes de parede celular do melão tipo Galia, híbrido Nun 1380, associadas ao processo de maturação. Os frutos foram avaliados em cinco estádios de maturação (I-V). O material de parede celular e suas frações foram determinados por gravimetria. Determinou-se o conteúdo de açúcares neutros na fração hemicelulósica e no resíduo celulósico, o teor de ácidos urônicos e o grau de esterificação na fração de substâncias pécticas, e o teor de cálcio total e ligado. A fração de substâncias pécticas foi submetida à cromatografia de filtração em gel e os açúcares neutros da fração hemicelulósica foram analisados por cromatografia a gás. O conteúdo do material de parede celular (MPC) mostrou pouca variação durante a maturação. O conteúdo de ácidos urônicos da fração péctica e o conteúdo de açúcares neutros na fração hemicelulósica (ramnose, arabinose e glicose) apresentaram tendência de redução com o avanço da maturação do fruto. Praticamente não houve variação para o grau de esterificação (% de esterificação) da fração de substâncias pécticas e para o teor de cálcio ligado. Houve redução no teor de celulose durante a maturação. A cromatografia em gel não revelou tendência de despolimerização das substâncias pécticas. This research characterized changes in the cell wall components in ‘Galia’, hybrid Nun 1380 melons during maturation. Fruits were evaluated at five maturation stages (I-V). Cell wall material and their fractions were determined by gravimetry method. Neutral sugars in hemicellulosic fraction and cellulosic residue, uronics acids content in pectic fraction, degree of esterification, total calcium and bound calcium were analyzed. The pectic fraction was analyzed by gel chromatography and neutral-sugars in hemicellulosic fraction were analyzed by gas chromatography. Minimum variation during maturation was observed in the cell wall material. Neutral sugars (rhamnose, arabinose and glucose) and uronics acids contents decreased following maturation. No variation in the degree of esterification in pectic substances and bound calcium was observed. Gel chromatography did not reveal dispolymerization in pectic substances.

Esta pesquisa avaliou as modificações dos componentes estruturais de parede celular do melão tipo Galia (Cucumis melo L. var. reticulatus) durante o armazenamento refrigerado (7°C±1, UR: 88% ±3). O material de parede celular e suas frações foram determinados por gravimetria. Determinou-se o conteúdo de açúcares neutros na fração hemicelulósica e no resíduo celulósico, o teor de ácidos urônicos e o grau de esterificação na fração de substâncias pécticas, e o teor de cálcio total e ligado. A fração de substâncias pécticas foi submetida à cromatografia de filtração em gel e os açúcares neutros da fração hemicelulósica foram analisados por cromatografia a gás. O conteúdo de material de parede celular mostrou pouca variação durante o armazenamento. As variações mais expressivas foram registradas nas frações isoladas da parede celular (fração de substâncias pécticas, fração hemicelulósica e fração celulósica), sendo que para as duas primeiras verificou-se redução durante o armazenamento e para a última observou-se elevação. O conteúdo de açúcares neutros não celulósicos mostrou tendência de redução apenas durante as duas semanas iniciais de armazenamento. Praticamente, não houve alteração no grau de esterificação e nos conteúdos de cálcio total e cálcio ligado. A principal característica foi a manutenção dos níveis de xilose e glicose na parede celular, o que indicou constância do polímero xiloglucana. This research evaluated changes in the cell wall components in ‘Galia’ melons (Cucumis melo L. var. reticulatus) during refrigerated storage (7°C±1, RH: 88% ±3). Cell wall material and their fractions were determined by gravimetry method. Neutral sugars in hemicellulosic fraction and cellulosic residue, uronic acids content and degree of esterification in pectic fraction, , total calcium and bound calcium were analyzed. The pectic fraction was analyzed by gel chromatography and neutral sugars in hemicellulosic fraction were analyzed by gas chromatography. Cell wall material content showed minimum variation during storage. The major variations occurred in cell wall fractions (pectic, hemicellulose and cellulose fractions), decreasing in the former two during storage and increasing in the latter. Non cellulosic neutral sugars content showed reduction tendency only in two former storage weeks. Practically, the degree of esterification (degree of methylation) in pectic substances and bound calcium did not change. Gelic chromatography revealed dispolymerization trend in pectic substances. There were no variation in the xylose and glucose contents. This was the major characteristic related with softening process during storage.

Pretreatments by immersion in 10 and 100 mM CaCl2 prevent the loss in firmness of sweet frozen cherries. This effect can even be detected in fruits preserved for 6 months in a frozen state. The increase in firmness, through the treatments, is mostly apparent after freezing and is attributed to the formation of calcium bridges in the pectic material, caused by a decrease in the degree of esterification of pectins and an increase in the pectic fraction soluble in EDTA and the Ca2+ cation content in the cell wall. These changes in the pectic materials are of an enzymatic origin, since we observed an increase in the pectinesterase activity of the fruits after treatments with increasing calcium concentrations. © 1995 American Chemical Society., This work has been financed by the Comisión Interministerial de Ciencia y Tecnologia (C.I.C.y.T., Projects ALI9110728 and ALI941943)

The mucilage extracted from the convection-dried cladodes of O. ficus-indica and O. joconostle, two species of economic importance, delivered three fractions after methanol precipitation. Two were composed of high molar mass polysaccharides, and one included water-soluble mono-, di-, and oligosaccharides. The large polysaccharides have a molar mass range of 4.0 × 103 to 8.0 × 105 g·mol−1 and are consistently composed of galactose, arabinose, xylose, and rhamnose; however, the content of galacturonic acid was different between both fractions and species. Their fermentability by selected probiotics was relatively low, 11–27 % compared to glucose, and decreased with increasing levels of galacturonic acid in the molecules. In the third fraction, previously unreported oligosaccharides were found. These include simple- and complex-structured galactooligosaccharides with arabinosyl-, xylosyl- and galacturonosyl acid residues. Their fermentability by prebiotic species can be ascribed more to their structural characteristics and monosaccharide composition than their molecular dimensions.