Insoluble Pectin Research Articles

A comparative study of the pericarp of litchi cultivars susceptible and resistant to fruit cracking

SummaryTime-course changes of fruit cracking percentage, mechanical properties of pericarp and contents of cell wall components in litchi pericarp were studied by comparing two litchi cultivars differing in cracking susceptibility. Mechanical strength of the pericarp of crack-resistant cv. Huaizhi was greater than that of cracking-susceptible cv. Nuomici. The resistance of `Huaizhi' was also reflected in higher threshold cracking turgor as well as in higher pericarp tensile strength and extensibility. Correspondingly higher contents of calcium and structural components viz. cellulose, hemicellulose and insoluble pectin were found in the pericarp cell walls of `Huaizhi', which might have materially contributed to its higher pericarp strength and thus cracking resistance as compared with `Nuomici'.

TEXTURA DE FEIJÃO-VAGEM (Phaseolus vulgaris L) PROCESSADO OU NÃO: EFEITO DA APLICAÇÃO DE CONCENTRAÇÕES CRESCENTES DE CÁLCIO VIA ABSORÇÃO RADICULAR

Esta investigação teve como objetivo estudar o efeito do cultivo de feijão-vagem com doses crescentes de cálcio na textura das vagens antes e após processo de enlatamento. O experimento foi desenvolvido com a cultivar UEL 1, utilizando-se areia grossa como substrato. Os tratamentos constaram das seguintes concentrações de cálcio em solução nutritiva: 0, 75, 150 e 300 ppm. Foram determinados os teores de cálcio das vagens in natura, substâncias pécticas e textura das vagens in natura e processada. As concentrações de cálcio nas vagens aumentaram em paralelo à elevação dos níveis de cálcio adicionados à solução nutritiva. Os teores de pectina solúvel nas vagens in natura não diferiram entre os tratamentos. Houve um acréscimo da quantidade de pectina insolúvel em função do aumento das doses de cálcio. Após o processamento térmico ocorreu uma solubilização das pectinas. A maior concentração de pectina solúvel nas vagens enlatadas foi observada nas vagens cultivadas sem adição de cálcio na solução nutritiva. As medidas de textura demonstraram uma tendência de aumento de firmeza das vagens concomitante à elevação nos teores de cálcio antes e após o processo de enlatamento.

Effect of pectin Substance on Texture Profiles of Potatoes with Different Specific Gravity

The cause for differences in the specific gravity of potatoes was examined. Thereupon potatoes with different specific gravity, properties of pectin was compared which was the cell binding material. As a result, the total pectin volume of the high specific gravity sample was 1.4 times of 1200 mg/100g in comparison with the low specific gravity sample. Insoluble pectin fraction of the low specific gravity sample showed high composition in comparison with its high specific gravity sample. Endothermic peaks were detected at 61°C and 85°C with both samples as a result of the thermal analysis of insoluble pectin fraction. However, the endothermic capacity of the low specific gravity sample was about 1.4 times in comarison with the high specific gravity sample. Ca and Mg content in AIS of the low specific gravity sample were about 6 times with Ca, about 1.6 times with Mg in comparison with the high specific gravity sample. The Potatoes were softened with EDTA and hardened with Ca, Mg. Water solubilization rate of the pectic substance of potatoes increased with EDTA and decreased with Ca, Mg.

Pectin Coated Hollow Fiber Polypropylene Membranes

The aim of this study was to prepare a composite membrane for the selective, extracorporeal removal of human LDL-cholesterol. Pectin coated on a porous polypropylene membrane (PP) was used as an active LDL adsorber. Three types of membrane preparations were performed: coating of native PP, coating after chemical etching and gamma-irradiated coated PP. Pectin coated fibers (PCF) were examined under scanning electron microscope (SEM) and tested for hydraulic permeability. As a result of the coating of native and etched PP membrane, pectin layers of various thicknesses (2-16 microm) and porosity were obtained. Irradiation by gamma rays gave no insoluble pectin layers.

Haze and cloud in apple juices

Turbidity in apple juice is desirable or undesirable, depending on whether the product fits within consumer expectations. Desirable opalescence is due to soluble pectin and insoluble pectin stabilized particles that show considerable stability. Blanching treatments enhance this stability by reducing particle size and character‐solubilizing pectin, and possibly by the destruction of natural enzymes that may destabilize the cloud over time. Undesirable haze and sediments may arise in apple juice by several mechanisms, including starch (dextrin) retrogradation, protein phenol aggregation, phenol oxidation, crystallization of carbohydrate macromolecules extracted from cell walls, or difficulties during manufacture. The mechanisms of formation of each of these forms of haze are discussed and examples given from the literature. Where available, haze‐sediment morphology by light and/or electron microscopy is documented and the possible role of recently developed “macerase” enzymes in haze/sediment formation discussed.

Pectin esterase activity and pectin methyl esterification in heated golden delicious apples

Pectin methylesterase activity and the degree of methyl esterification of cell wall pectins were measured in Golden Delicious apples after a 4 day heat treatment at 38° and after subsequent storage at 0° of heated and unheated apples. Enzyme activity increased similarly during storage in both heated and unheated apples, although heated fruit softened much less than unheated. During storage, the degree of esterification decreased in both heated and unheated apples in water- and CDTA-soluble pectin, but not in insoluble pectin. In a comparison of three methods of determining methyl groups, similar values were obtained for degree of bulk esterification of apple cell walls, regardless of treatment. Results presented do not confirm a role for pectin methylesterase or for de-esterification in apple fruit softening.

THE ROLE of PULP INTERPARTICLE INTERACTION IN DETERMINING TOMATO JUICE VISCOSITY

Pulp interparticle interaction plays a major role in determining the viscosity of tomato juice. Indices of second order and of compounded high order interparticle interaction have been evaluated by diluting tomato juice samples with their own serum, and determining the slope of the reduced viscosity curves at the very dilute and at the original concentration regions, respectively. the second order interaction index, reflecting the behavior of a pair of colliding particles, has practically a similar value for samples having the same process history. On the other hand, tomato juice samples differ markedly in their value of the interaction index describing the effect of high order interparticle interaction on the viscosity at the original juice concentration. the higher that value, the higher the viscosity. the value of this index decreases by concentrating the tomato juice and increases by homogenization. It has a maximum value at pH 4–4.5 and most importantly it is greatly dependent on the mechanical abuse history of the juice. Enzymatic depolymerization of the soluble and especially the insoluble pectin markedly reduces the value of the interaction index, indicating that pectin plays a major role in determining the level of that interparticle interaction.

Effect of harvest maturity on pectic substances, internal conductivity, soluble solids and gel breakdown in cold stored ‘Songold’ plums

Abstract ‘Songold’ plums (Prunus salicina Lindl.) were harvested at optimum and post-optimum maturity with a flesh firmness of 64 and 44 N, respectively. After cold storage for 10 days at −0.5 °C, followed by 18 days at 7.2 °C, the plums were ripened for 14 days at 10 °C. The fruit was analysed for soluble solids, internal conductivity, pectic composition and viscosity of water soluble pectin at eight examination stages during storage and ripening. Insoluble pectin levels declined during cold storage and ripening while soluble pectin levels increased to make up the difference. Neither harvest maturity nor storage time had a significant effect on the concentration of calcium pectate, and this pectic fraction did not appear to influence development of gel breakdown (GB). Water soluble pectin and availability of cell fluids, as indicated by viscosity and internal conductivity, respectively, indicated a high gel potential in plums of both maturities, but at different stages during storage and ripening. Significant levels of GB developed only in plums harvested at post-optimum maturity. In this fruit, significantly higher sugar levels and loss of cell membrane integrity early in storage probably enhanced formation of pectin-sugar gels as cell fluids bind with pectins in cell walls.

A rapid method for quantitative determination of pectic substances

A rapid and quantitative method has been developed to determine the amount of soluble and insoluble pectins. The method does not require extraction or purification, even plant homogenates may be used, and it can be applied to pectins of various origin. The determination of pectic substances by previous methods can be performed only on pectins in solution. The present rapid method is based on the titration of deesterified pectins after acid precipitation. The speed and simplicity also makes this quantitative method highly useful for the determination of pectins during food processing.

Molecular Characteristics of Pectic Constituents in Relation to Firmness, Extractable Juice, and Woolliness in Nectarines

`Flavortop' nectarines [Prunus persica (L.) Batsch] were either stored for 4 weeks at -0.5C or not subjected to cold storage before being ripened at 15C. The differences in extractable juice, woolliness, composition, and gelling characteristics of extracted pectins between the two treatments were determined during ripening. As ripening progressed, the extractable juice in both treatments decreased to low values after which it increased with further ripening. Woolliness only occurred in fruit that was cold stored. Nectarines became woolly from the 2nd day and peaked on the 6th day of ripening in fruit cold stored for 4 weeks. As fruit firmness decreased, the soluble pectin concentration increased to the same extent in both treatments at the expense of insoluble pectin. In cold-stored fruit, the viscosity of pectin increased gradually until the 6th day of ripening, while in noncold-stored fruit maximum viscosity was higher and occurred between the 4th and 6th day of ripening. From the 6th day, the viscosity decreased in both treatments to levels lower than the initial viscosity. The extractable juice was lowest when the viscosity of soluble pectins and percentage of woolly fruit were highest. Molecular mass distribution of soluble pectins decreased considerably during ripening at 15C.

Effect of acetaldehyde and anaerobiosis as postharvest treatments on the quality of peaches and nectarines

Abstract Three varieties of peaches and one variety of nectarines were treated for 24 h with acetaldehyde vapour, 86% CO 2 , or 97% N 2 immediately after harvest. The fruits were then held for 7 days at 20°C, or stored at 0°C, 90% RH before being kept at 20°C. Treated fruit softened more slowly than control fruit. Insoluble pectin content remained higher, and polygalacturonase activity increased more slowly in treated fruit. Immediately after treatment, ethanol content was much higher in treated fruit but decreased during the period at 20°C and was similar to control fruit after 7 days. Ethanol content of control fruit increased during ripening. Ethylene production was inhibited by both CO 2 and N 2 treatment, with the latter being more effective. Taste tests after 5 days at 20°C revealed a preference for the treated over the control fruit. N 2 -treated fruit was generally rated higher than CO 2 -treated fruit.

Calcium and Heat Treatments to Improve Storability of `Anna' Apples

Apples (Malus domestica Borkh. cv. Anna) were treated at harvest by a dip in 3% CaCI2 solution, heated for 4 days at 38C, or the two treatments combined, before being placed in OC storage. After removal of the apples from storage and holding them for 1 week at 20C, the combined treatment maintained fruit quality best. The fruit remained firmer than with either treatment separately, and peel yellowing and decreased titratable acidity caused by the heat treatment were less pronounced. Heat treatment alone maintained fruit firmness, while CaCI2 alone had no effect on fruit quality, although it raised the fruit calcium level more than the combined treatment in most experiments. Altering the temperature (0, 20, or 38C) of the CaCl2 dip did not change its efficacy. There was less soluble and more insoluble pectin in cell wall extracts of apples from the combined treatment than from other treatments. In addition, proportionally less Ca was present in the water-soluble pectin fraction of the combined treatment compared to other treatments, indicating different binding properties in the cell wall.

Studies on apple protopectin V: Structural studies on enzymatically extracted pectins

Apple insoluble pectins were extracted by pectolytic enzymes alone and combined with side-chain degrading enzymes or endo-glucanase. The highest yield of pectic material was obtained with the combination pectinlyase plus endo-glucanase, showing the existence of a connection between rhamnogalacturonan and xyloglucan. The extracts were fractionated on Sephacryl S 500 and DEAE Sepharose CL-6B. Methylation analysis of high-molecular-weight material coming from the ‘hairy’ regions showed the presence of highly branched arabinans and arabinogalactans of type I and II side-chains, and of terminal xylose residues linked to the rhamnogalacturonan backbone.

Quality and Cell Wall Components of `Anna' and `Granny Smith' Apples Treated with Heat, Calcium, and Ethylene

`Anna' and `Granny Smith' apples (Malus domestics Borkh.) that were held at 38C for 4 days before storage at 0C not only were firmer than controls upon removal from storage, but also softened more slowly during shelf life at 17C. Skin yellowing and loss of acidity attendant upon the heat treatment were not prevented by dipping fruit in 2% CaCl2 before heating. Both heat-treated and control fruit softened at the same rate upon exposure to ethylene at 100 μl·liter-1 upon removal from storage. The insoluble pectin content of cortical tissues was higher in heat-treated fruit than in controls after 10 days at 17C, while soluble pectin levels were lower. Arabinose and xylose levels were lower in cell walls from heat-treated cortical tissue, but the treatment had no effect on loss of galactose residues during shelf life.

Studies on apple protopectin: I. Extraction of insoluble pectin by chemical means

The pectic material from Golden Delicious apples, strongly bound in the cell walls of parenchymatous tissues (not extractible with Cyclohexane-Diamino-Tetracetic Acid (CyDTA)) was extracted by: (i) successively, hot buffer, hot acid and cold sodium hydroxide, (ii) sodium carbonate (4°C then 20°C) and (iii) chlorite. The pectin extracts were analysed for uronide, neutral sugars and protein contents, and degrees of methylation and acetylation. They were also subjected to gel-filtration and ion-exchange chromatography. Subfractions obtained by ion-exchange were also analysed. Approximately 55% of the pectic material was not extracted by the CyDTA. Hot buffer, hot acid and chlorite extracted small amounts of relatively highly methoxylated and acetylated pectins. The most efficient extractants were the cold carbonate and the cold sodium hydroxide. They extracted saponified pectins that exhibited similar behaviour on gel-filtration and ion-exchange chromatography, showing two subfractions, of which one was rich in neutral sugars and had a high molecular weight. There was no evidence of phenolic interlinkages.

Physico‐chemical changes in guava (Psidium guajava L.) during development and maturation

AbstractGuava of the Vietnamese variety is commercially grown in Malaysia. To obtain a better understanding of the fruit, the physical and chemical changes occurring during development and maturation were studied.The weight increase, reduction in hardness, total pectin content, and changes in glucose and ascorbic acid levels showed a sigmoid curve. The maximum weight and glucose increases occurred between weeks 10 and 12. Reduction in hardness, and changes in pectin and ascorbic acid content occurred most between weeks 12 and 14. Reduction in chlorophyll content, and increase in fruit diameter, fructose content and water soluble pectin fraction showed a more linear change. Fructose level was highest among the three sugars (fructose, glucose and sucrose) monitored during maturity. The density of the fruit increased rapidly at the beginning, remained constant between weeks 4 and 12 and then decreased again.The moisture content increased rapidly at first, followed by a more gradual increase and remained constant after week 14. The pH and percentage titratable acidity of the Vietnamese guava fluctuated, being fairly acidic at week 4 (pH 4.5), least acidic at week 10 (pH 5.4) and acidic again on maturity (pH 4.05). The tannin level was high in immature guava but dropped drastically after week 8, and remained at a constant low level after week 10. Soluble pectin increased during development and maturity. Insoluble pectin (NaOH soluble) increased during development but was converted to soluble pectin during maturity (after week 14).

Factors Affecting Drip Loss from Thawing Thornless Blackberries

Abstract Fruits from thornless blackberry (Rubus sp.) cultivars were compared to determine causes of variation in drip losses during thawing after frozen storage. Drip was similar in composition to juice obtained by pressing. Drip losses for different cultivars ranged between 1% and 30% in 1984; increased losses in 1983 were attributed to poor fruit condition (e.g., deterioration during postharvest holding). Drip losses were greater in riper samples but did not depend on fruit size. Drip losses were correlated with low insoluble pectin. Microscopic examination revealed an inverse relationship between the tendency to drip and the epidermal cell layer thickness.

Effects of Water Stress and Degree of Ripeness on Rate of Senescence of Harvested Bell Pepper Fruit

Abstract The physiological changes occurring in green and red bell pepper fruit (Capsicum annuum L. ‘Maor’) before and after harvest were investigated. Red pepper at harvest was less firm and had lower water potential, lower insoluble pectins, and higher water-soluble pectins than green bell pepper. However, the changes occurring in both types of peppers after harvest were similar. Postharvest weight loss was accompanied by a decrease in firmness, decrease in water potential, decrease in insoluble pectin, and an increase in soluble pectin in the cell wall. The production of CO2 showed that there was a slight decrease and a significant but small increase of ethylene after harvest. If weight loss was retarded by holding pepper in a water-saturated atmosphere, then all of these physiological changes were prevented or markedly slowed. It appears that water stress hastens and possibly triggers the onset of senescence in harvested bell pepper fruit.

Mechanism Which Enables the Cell Wall to Retain Homogenous Appearance of Tomato Juice

ABSTRACTIntact or disrupted cell walls from tomato pericarp cannot be suspended in the juice, even at higher densities (up to 1.2 g/ml) or viscosities (up to 70 centistokes) than those of natural juice serum. Hence, the viewpoint of swelled precipitate rather than suspension has to be considered in tomato juice. Degradation of insoluble pectin by a relatively high concentration of exogeneous pectinases led to swelling of the wall and ultrastructural studies revealed partial dispersion of the microfibrilar system in the wall. Cellulase activity led to partial or complete degradation of the microfibrilar system, with a resultant collapse of the precipitate. Expansion of the microfibrilar system and retention of its ability to withstand collapse under gravity stress, make possible the swelled precipitate and homogeneous appearance of insoluble particles along the juice column during shelf life.

Cell wall development in the berries of two grapevines

The cell wall content of the berries of grape cultivars ‘Barbera’ and ‘Freisa’ was examined and analyzed during their growth and ripening from July to October. The build-up of cell wall material was much faster in ‘Barbera’ than in ‘Freisa’, and ended 2 weeks before completion of commercial maturity, while in ‘Freisa’ it progressed at a lower rate, but continued up to picking-time. The two most important groups of cell wall polysaccharides were insoluble pectins and hemicellulose. Their behaviour appeared to be always complementary. Cell number per berry apparently decreased steadily in both cultivars, more rapidly in ‘Freisa’ than in ‘Barbera’. The reason for this is not certain, but appears to be due either to cell fusion or to cell squeezing. The average number of cells per berry in both cultivars was of the same order of magnitude, and in agreement with the findings of other authors.