The influence of predrying treatment and of suspension solution conditions on the rehydration of apple cell wall materials

The aim of this work was to investigate the influence of structure variations, predrying treatment and the suspension solution conditions on the hydration properties of cell wall materials from apples. For this purpose, materials with high methoxylated (HM) as well as with low methoxylated (LM) pectin components were treated in the wet state (predrying treatment) and as dried preparations (rehydration) with water (W, reference) or with potassium acetate (K) and malic acid (A) solutions, respectively. It was found that the results were determined by interactions of the examined influencing factors to a great extent. The best hydration properties of all the samples investigated were achieved by a combined demethoxylation and a charging with potassium ions during predrying treatment. In this way, mean values for the maximum W-retention capacities from 73–82 g W/g dried sample were obtained. In contrast, all other LM samples were characterised by reduced hydration properties, independent of the conditions applied (W-retention capacities 30–46 g/g). In the case of HM materials, predrying treatment with K or A decreased the hydration properties compared with the reference material (treatment with W, W-retention capacities 53–57 g/g). In comparison with the rehydration of HM preparations with W, the use of A solution affected the hydration properties negatively, but the application of K solution enhanced the velocity of rehydration. The results of the hydration properties and of the rheological properties of the rehydrated samples were interpreted regarding the preformation of the structure/state during predrying treatment as well as the changes occurring during drying and rehydration.     

Aspects of material science in food processing: changes in plant cell walls of fruits and vegetables

 Foods can be regarded as complex, dispersed systems which are normally metastable. Food processing causes state transitions (second-order transitions) when raw materials, food components or food systems are subjected to external stresses. The state transitions occurring during processing are detectable as changes in structure and properties of the investigated systems. The processing of fruits and vegetables is often connected with changes in cell walls. Cell wall materials in dispersed fruit and vegetable systems can be regarded as a model substrate of the dispersed phase. During processing, cell walls undergo modifications in terms of their physical state, macrostructure, microstructure, and composition, as well as structure-dependent changes in their functional and material properties. The interactions and connections (dependencies) between state transitions, and various changes in structure and properties, are very complex and multivariate and are not well understood as yet. For the evaluation of changing material properties during processing, examination of hydration, rheological (external mechanical stress) and thermal (external thermal stress) characteristics is important. The changes occurring during the processing of fruits and vegetables are determined by external factors (especially various mechanical and thermal stresses) and by internal factors. External stress in many cases causes solubilisation of the cell wall, loss of firmness and favours cell separation. Thermal processing increases pectin degradation by β-elimination. Internal factors such as pH and modified ionic strength, e.g. by applying soak solutions, can have an important influence on the changes in the cell wall during processing. So, calcium ions on the one hand can favour cell wall degradation by β-elimination and, on the other hand, after low temperature blanching and de-esterification of the pectin by activated pectin methyl esterase, can contribute to stabilisation of the texture by formation of a calcium-pectin complex. Knowledge about cell wall degradation mechanisms can be markedly improved by studies using model substrates such as pectin, or cell wall materials like the alcohol-insoluble residue and materials with cellular structure. This knowledge has been used to improve the technology used to process fruits and vegetables and to produce products with better properties. Moreover, testing and applying cell wall materials as ingredients for the production of textured foods and potential health-related foods is suggested. Received: 21 July 1998     

Dietary fiber from coconut residue: effects of different treatments and particle size on the hydration properties

The present work is aimed at the production of dietary fiber from underutilized coconut residue left after the extraction of milk, by subjecting it to physical treatments such as water washing, hot water washing, boiling water washing and pressure cooking, as well as solvent extraction. The fat content was reduced from 62% to 45% and 41% by treatment with boiling water and pressure-cooking, respectively. Water-holding, water retention and swelling capacities increased with decreasing fat content. A marked increase was observed in hydration properties when the fat content decreased from 10 to 2%. The hydration properties were maximum for 550 m particle size coconut fiber. For the higher particle size (1,127 m), the oil was trapped inside the fiber matrix, resulting in decreased hydration properties, whereas for the lower particle size (390 m) the rupture of the fiber matrix was responsible for low hydration properties. An attempt was made to compare the hydration properties of coconut dietary fiber with other commercially available dietary fibers.     

Effect of ageing-induced changes in rice physicochemical properties on digestion behaviour following storage

The changes in rice grains structure and digestion behaviours were investigated following storage at 4 °C and 37 °C, respectively. Pasting study indicated that rice samples stored at 37 °C demonstrated a consistent increase in the time to peak viscosity of the Rapid ViscoAnalysis parameters, implying a quick ageing progress. Compared to the rice stored at 4 °C, aged rice (stored at 37 °C) showed a coarser morphology after cooking by SEM, suggesting a limited starch gelatinization. Consistently, ageing process led to a decrease in the leaching of starch molecules in cooking residual water, which further confirmed that starch granules in aged rice grain caused less hydration and swelling. The analysis of the amount of cell wall remnants showed that rice stored at 37 °C caused a significant increase in the amount of cell wall remnants along the storage at 37 °C, which might suggest that the cell wall structure of the rice grains became more lignified because of the ageing. Furthermore, the ageing process significantly reduced rice digestion kinetics both in rate and extent. Thus, it is assumed that ageing process leads to the cell walls becoming more strengthened and lignified, which makes the rice grain more organized in its structure, and subsequently reduces starch granules disruption and molecules leaching during the cooking. Therefore, this study suggests that the changes in digestion behaviours of rice are highly associated with the changes in rice physical and chemical properties occurred during storage and the ageing process might be another option for manipulating rice digestion properties.     

Role of pectic polysaccharides in structural integrity of apple cell wall material

Texture modulating properties of aqueous dispersions of apple cell wall material differed from those of tomato or kiwifruit, particularly under high shear. It was previously hypothesized that this may be due to the fact that the apple cell wall showed less in vivo solubilization of pectic polysaccharides during ripening compared to tomato or kiwifruit. However, in vitro solubilization of the pectic polysaccharide content of apple CWM by endo-polygalacturonase and/or extraction with 0.05 M sodium carbonate, did not affect the loss in wall integrity shown by tomato or kiwifruit CWMs under shear. In addition, the pectin-depleted residue after Na₂CO₃ extraction possessed better water retaining and viscosity generating properties than the original cell wall material. Following treatment of apple CWM with cellulase, the viscosity of suspensions decreased, emphasising the role that the cellulose–hemicellulose network plays in the water-retaining capacity of the cell wall. Residue from CWM after cellulase treatment consisted of ∼85% pectic polysaccharides. Surprisingly, the integrity of these “cellulose-free” walls was maintained after shear. It is concluded that differences in structural properties of the CWMs of apple compared to kiwifruit or tomato are not simply related to pectin solubilization but to a fundamental difference in the architecture of the apple cell wall.     

Effects of air-drying temperature on the cell walls of kiwifruit processed at different stages of ripening

The effects of air-drying temperature on the cell wall components of three sets of fresh kiwifruits at different degrees of ripening, unripe, half-ripe and ripe samples, have been evaluated. The modifications affecting the physico-chemical properties of cell wall polysaccharides were largely dependent, not only on the air-drying temperature used (from 30 °C to 90 °C), but also on the initial stage of ripening of the processed kiwifruits. Thus, whereas in comparison with the fresh fruits, dehydrated unripe and half-ripe kiwifruits maintained their overall cell wall composition better, processed ripe kiwifruits seemed to be more sensitive to cell wall degradation/solubilisation. In fact, important losses of cell wall material (CWM), mainly pectins and, also, hemicelluloses, were detected in the riper kiwifruits when these samples were dehydrated at high temperature (up to 30% CWM losses when drying was carried out at 90 °C). Heating also promoted considerable modifications of the degree of methyl-esterification (DME) of pectins. In general, an increase in the DME corresponded to an increase in the degree of ripening of the processed samples, suggesting that methylated pectins exhibited a higher resistance to the degradation/solubilisation caused by heating. All these changes in composition were clearly reflected in the solubility and functional properties (FP) of processed CWMs. Hydration properties, swelling and water retention, and, in particular, the capacity to absorb lipids, were modified after processing. In general, CWMs from processed half-ripe kiwifruits exhibited the highest FP values. Overall, the study clearly reflects the importance of taking into consideration the stage of ripening of fruits in order to determine the final quality of CWMs, and therefore, the properties of the dietary fibre (DF) which could be obtained from processed kiwifruit samples.     

Cell wall composition and degradability of forage stems following chemical and biological delignification

Chemical and biological delignification methods were used to investigate the relationship between the concentration and composition of lignin and degradation of forage cell walls. Stem material from lucerne (Medicago sativa L), smooth bromegrass (Bromus inermis Leyss) and maize (Zea mays L) stalks was treated with alkaline hydrogen peroxide, potassium permanganate, sodium chlorite, sodium hydroxide, nitrobenzene, and the lignolytic fungus Phanerochaete chrysosporium. Klason lignin and esterified and etherified phenolic acids were delermined. Cell wall neutral sugar and uronic acid composition and the extent of in-vitro degradability were measured. Chemical delignification generally removed lignin. but the fungal treatment resulted in the removal of more polysaccharide than lignin. The concentrations of esterfied and etherified p-coumaric and ferulic acids were generally reduced in treated cell walls; chlorite treatment preferentially removing p-coumaric acid whereas nitrobenzene treatment removed more ferulic acid. Syringyl moieties were completely removed from the core lignin polymer by nitrobenzene treatment of forage stems. Alkaline hydrogen peroxide and nitrobenzene were generally the most effective delignification treatments for improving polysaccharide degradability, with the grass species responding similarly to delignification whereas lucerne was somewhat less responsive. Fungal delignification, under these experimental conditions, did not improve cell wall degradability of these forages. Multiple regression and covariate analyses indicated that the lignin components measured were not powerful predictors of cell wall degradability. Neither the concentration nor the composition of the lignin fractions was consistently correlated with degradation. This lack of effect was attributed to the more generalised disruption of the cell wall matrix structure by delignification treatments.     

The influence of mechanical and enzymatic disintegration of carrots on the structure and properties of cell wall materials

The aim of this study was to investigate the influence of different disintegration procedures on the structure and properties of cell wall materials from carrots. While the cold-water-extracted reference material consisted mainly of tissue particles, wet homogenisation resulted in cell fragments with nearly unchanged composition and a tendency to aggregate during drying. In contrast, enzymatic treatments changed both the particle size and the chemical composition of the prepared materials. Increasing enzymatic degradation (macerated and liquefied materials) led via single cells to cell fragments and to increasing galacturonan loss as well as to a high aggregation tendency. The particle size and the chemical composition of the materials strongly influenced their properties. Thus, different hydration behaviour, rheological properties and physiological effects were found for the homogenised and for the enzyme-treated materials. Additionally, the properties depend essentially on the mechanical stress applied during rehydration. Such mechanical stress can cause the disaggregation of particles, so it can improve markedly the functional properties. In this way, good hydration properties could be achieved for all the materials prepared. The highest binding capacity of bile acids was determined for macerated material. The concentration of short-chain fatty acids, formed during fermentation with human faeces flora, decreased with increasing degradation of the materials. The complex connections between the structure/composition of the materials and their properties are important for food science and nutrition.     

Decrease in Fruit Moisture Content Heralds and Might Launch the Onset of Ripening Processes

Abstract: It is known that fruit ripening is a genetically programmed event but it is not entirely clear what metabolic cue(s) stimulate the onset of ripening, ethylene action notwithstanding. Here, we examined the conjecture that fruit ripening might be evoked by an autonomously induced decrease in tissue water status. We found decline in water content occurring at the onset of ripening in climacteric and nonclimacteric fruit, suggesting that this phenomenon might be universal. This decline in water content persisted throughout the ripening process in some fruit, whereas in others it reversed during the progression of the ripening process. Applied ethylene also induced a decrease in water content in potato (Solanum tuberosum) tubers. In ethylene‐mutant tomato (Solanum lycopersicum) fruit (antisense to1‐aminocyclopropane carboxylate synthase), cold‐induced decline in water content stimulated onset of ripening processes apparently independently of ethylene action, suggesting cause‐and‐effect relationship between decreasing water content and onset of ripening. The decline in tissue water content, occurring naturally or induced by ethylene, was strongly correlated with a decrease in hydration (swelling) efficacy of cell wall preparations suggesting that hydration dynamics of cell walls might account for changes in tissue moisture content. Extent of cell wall swelling was, in turn, related to the degree of oxidative cross‐linking of wall‐bound phenolic acids, suggesting that oxidant‐induced wall restructuring might mediate cell wall and, thus, fruit tissue hydration status. We propose that oxidant‐induced cell wall remodeling and consequent wall dehydration might evoke stress signaling for the onset of ripening processes. Practical Application: This study suggests that decline in fruit water content is an early event in fruit ripening. This information may be used to gauge fruit maturity for appropriate harvest date and for processing. Control of fruit hydration state might be used to regulate the onset of fruit ripening.     

Characterization of p‐coumarate accumulation,p‐coumaroyl transferase,and cell wall changes during the development of corn stems

BACKGROUND: Developmental changes occur in corn (Zea mays L.) stems from cell initiation to fully mature cell types. During cell wall maturation the lignin is acylated with p‐coumarates (pCA). This work describes characterization studies of the p‐coumaroylation process in relation to corn stem development. RESULTS: Corn plants from three locations were harvested and tissues were analyzed from all nodes and even‐numbered internodes above soil line. Changes in carbohydrates reflect a shift to lignification at the expense of structural polysaccharide synthesis. Accumulation of pCA paralleled the incorporation of lignin while ferulate (FA) remained relatively constant as a proportion of the cell wall (5–7 g kg^?1 CW). The p‐coumaroyl transferase (pCAT), which is responsible for attaching pCA to lignin monomers, displayed maximum levels of activity in the middle region of the stem (internodes 10–12, 2–3 nmol L^?1 min^?1 mg^?1). The syringyl content as a proportion of the total lignin did not change significantly with cell wall maturation although there was a trend towards increased amounts of syringyl units in the more mature cell walls. CONCLUSIONS: Incorporation of pCA into corn cell walls not only mirrored lignification but the pCAT activity as well. Levels of pCAT activity may be an indicator of rapid lignification specifically for syringyl type lignin. Copyright © 2008 Society of Chemical Industry     

A protein which masks galactose receptor mediated phage susceptibility in Lactococcus lactis subsp. lactis MPL56

A 28.5-kb plasmid, isolated from Lactococcus lactis subsp. lactis MPL56, causes complete inhibition of four lactococcal phages. Cell wall characteristics of wild-type strain MPL56 were compared with its 28.5 kb plasmid-cured, phage-sensitive derivative MPL56-22. After proteolytic enzyme treatments, adsorption of phages occurred at high levels, an example is 94.6–98.5% in MPL56 cells. Analysis of cell wall extracts of MPL56-22 by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) indicated that the only difference between strains was the 55.4 kDa band in protein patterns of MPL56. Adsorption of the four phages was completely inhibited when MPL56-22 cells were subjected to SDS, Triton-X-100, HCl and NaOH treatments. Lectins that were specific for glucose/mannose and N-acetylglucosamine did not prevent adsorption of phages in cell wall extracts of MPL 56-22. However a lectin specific for galactose (MCA; Momordica charantia ) completely inhibited adsorption of these phages in cell wall extracts of MPL56-22. HPLC patterns of cell wall carbohydrates of MPL56-22 and its HCl treated preparations showed that the most prevalent difference was the galactose on untreated MPL56-22 cell wall chromatograms.     

Preparation and characterisation of arabinoxylan and (1,3)(1,4)-β-glucan alternating multilayer edible films simulated those of wheat grain aleurone cell wall

Various observations show a lamellar organisation of wheat aleurone cell walls, that likely acted as barriers to regulate the water diffusion rate in wheat grains. In this study, arabinoxylan (AX) and (1,3)(1,4)-β-glucan (BG) alternating multilayer films which mimic cell wall of aleurone structure were prepared. Twenty layers of alternating multilayer films of AX/BG were prepared with individual thicknesses of 20 µm. The water diffusion and water mobility of the films were determined using dynamic vapour sorption and time-domain nuclear magnetic resonance spectroscopy. The AX/BG alternating multilayer films exhibited unique mechanical and hydration properties, which could be explained by their unique nanostructure and microporosity. The edible films with this structure were found to exhibit high ultimate stress and ultimate strain, and low rates of water diffusion.     

酵母胞壁多糖的乳化性及酯化修饰

酵母胞壁多糖形成的乳化液细腻、稳定，在碱性条件下尤佳，但乳化力不够高。为了提高其乳化能力，采用乙酸酐对其进行酯化，酯化反应的最适条件为：胞壁多糖浓度为２０％、乙酸酐用量为１０ｍｌ／１００ｇ胞壁多糖、ｐＨ值为３、反应温度３０℃、反应时间３ｈ。按此工艺酯化后，胞壁多糖乳化力提高１．５倍。     

Effect of Cell Wall Properties on Porosity and Shrinkage of Dried Apple

Water removal during drying depends on the pathway of water migration from food materials. Moreover, the water removal rate also depends on the characteristics of the cell wall of plant tissue. In this study, the influence of cell wall properties on porosity and shrinkage of dried product was investigated. Cell wall stiffness depends on a complex combination of plant cell microstructure, composition of food materials and the water-holding capacity of the cell. In this work, a preliminary investigation of the cell wall properties of apple was conducted in order to predict changes of porosity and shrinkage during drying. Cell wall characteristics of two types of apple (Granny Smith and Red Delicious) were investigated under convective drying to correlate with porosity and shrinkage. A scanning electron microscope (SEM), 2kN Intron, pycnometer and ImageJ software were used in order to measure and analyse cell characteristics, water holding capacity of cell walls, porosity and shrinkage. The cell firmness of the Red Delicious apple was found to be higher than for Granny Smith apples. A remarkable relationship was observed between cell wall characteristics when compare with heat and mass transfer characteristics. It was also found that the evolution of porosity and shrinkage are noticeably influenced by the nature of the cell wall during convective drying. This study has revealed a better understanding of porosity and the shrinkage of dried food at microscopy (cell) level, and will provide better insights to attain energy-effective drying processes and improved quality of dried foods.     

粉碎粒径对茶叶水不溶多糖功能特性的影响研究

探讨不同粉碎粒径对茶叶水不溶多糖(ITPs)功能特性的影响。方法:制备不同粉碎粒径的茶叶水不溶多糖,通过持水力(包括水合能力和膨胀力)、吸附性能(包括持油性和胆酸钠结合能力)等功能特性的测定,分析粉碎粒径对茶叶水不溶多糖功能特性的影响。结果:粉碎粒径对茶叶水不溶多糖的功能特性可产生较大影响,其结合水力和膨胀力随茶叶水不溶多糖粒径的减小先减小后逐渐增大,其中结合水力在多糖粒径达超微粉时最大,为粗粉的1.20倍,而膨胀力在多糖粒径达细粉级时最大,为粗粉的1.08倍,粒径达超微粉时出现下降趋势。持油性与结合胆酸钠能力均在超微粉时最大,分别是粗粉的1.42倍和1.22倍。结论:本实验为茶叶的开发利用提供了基础研究数据。     

Structural Characterization,Technological Functionality,and Physiological Aspects of Fungal β-D-glucans: A Review

β-D-glucans are a (1→3)-linked glucose polymer with (1→6)-linked side chains and a major component of fungal cell walls. They exhibit structural integrity to the fungal cell wall. In addition, β-glucans are widely used as food adjuvant in food and pharmaceutical industries because of their physico-chemical properties. Several studies have focused on different isolation processes of (1→3) (1→6)-β-glucan that could affect the physico-chemical and functional properties of β-glucan such as chemical composition, solubility, viscosity, hydration properties, and oil binding capacity. Immunological activity is one of the most important properties of β-glucans. Thus, they are effective in inhibiting growth of cancer cells and metastasis and preventing bacterial infection. In humans, β-glucans reduce blood cholesterol, improve glucose absorption by body cells, and so help wound healing. This review described the prebiotic potentiality of fungal β-D-glucans with the objective to detail the methodologies applied for their extraction, their structure and techno-functional properties, and finally their biological effects.     

Evaluating the Role of Cell Wall Material and Soluble Protein in the Functionality of Cowpea (Vigna unguiculata) Pastes

ABSTRACT: Wet-milling of soaked, decorticated cowpeas generated large amounts of coarse cell wall material (CWM) and soluble protein (SP). CWM with high water-holding and swelling capacities contributed to excellent paste hydration and flow properties; high SP and paste viscosity resulted in superior foaming characteristics. In hydrated cowpea meal, the presence of coarse cellular material adversely affected paste hydration and flow characteristics; low SP and viscosity resulted in poor foaming. Wet-milling of hydrated meal improved viscosity and functionality. Intense dry-milling increased SP but adversely affected paste viscosity and functionality.     

Effect of candying on cell wall polysaccharides of plums (Prunus domestica L.) and influence of cell wall enzymes

“Ameixa d’Elvas” is a candied plum (Prunus domestica L.) produced by a traditional process, using fruits of a specific ‘greengage’ variety, “Rainha Cláudia Verde”. The candying process consists of boiling the intact plums in water for 15 min and then putting them in sugar syrup, which is successively concentrated until 75 °Brix. Although a loss of intercellular adhesion of parenchyma cells after boiling is observed, candied plums are able to recover their cell-to-cell adhesion, giving a final tissue with a consistency similar to that observed for the fresh fruit. In order to explain this observation, cell wall polysaccharides of plums harvested in two orchards, Vila Viçosa (VV) and Cano (CA), from the same geographic region and at the same stage of ripening, were analysed fresh, boiled and candied. Plum cell walls are composed mainly of pectic polysaccharides and cellulose that, during the boiling step, are degraded and solubilised. Highly esterified pectic polysaccharides undergo gelation inside the fruits in the presence of sucrose, leading to the recovery of the fruit’s consistency. During the candying process diffusion of these methylesterified pectic polysaccharides to the sucrose syrup increase the syrup viscosity. The activity of pectin methylesterase, polygalacturonase, and cellulase of fresh fruits explains the observed higher extension of degradation of cell wall polysaccharides of the CA plum tissues after boiling. This higher degradation seems to prevent the complete recovery of the parenchyma cell structure, which was observed for the less degraded polysaccharides of VV plums.     

Cell wall proteins of Kluyveromyces fragilis: Surface and emulsifying properties

Yeast cell wall proteins were extracted from homogenized suspensions with 0.75 mol/l NaOH, yielding after precipitation at isoelectric pH a pale-brown sediment. Lyophilized sample was fractionated on Sephadex G-50 to yield three fractions (Fr 1, Fr 2 and Fr 3). Fr 1, which had the highest yields and protein content, showed the highest molecular weight and best surface properties. Fr 2 and Fr 3 were mainly composed by polysaccharide-protein complexes. Fr 1 was further subfractionated on Sephacryl S-300 to produce three fractions (Fr A, Fr B and Fr C). All subfractions, turned out to be highly foamy during evaporation. The highest yields were obtained for Fr A, which also showed the highest molecular weight. Fractions Fr 1 and their subfractions Fr B and Fr C exhibited good surface activity and high emulsifying activity. Emulsions prepared with these fractions were the most stable against creaming and coalescence. Fr 2 cream phase presented a gel-like behavior as a consequence of polysaccharides acting as thickening agents.     

Characteristics of Cell Wall Structure of Green Beans During Controlled Freezing Point Storage

Controlled freezing-point storage means that the storage temperature is in a non-freezing temperature zone between the freezing point of water and food. It has been demonstrated that controlled freezing-point storage can prolong the storage-life of fresh food. Green beans (Phaseolus vulgaris L.) have been planted extensively in the northeast region of China and harvested seasonally. Degradation of cell wall polysaccharides has greatly affected the texture properties of the green bean cell walls. During controlled freezing-point storage, activities of cellulase, pectin methyl esterase, and polygalacturonase were inhibited effectively. It resulted in a slow degradation of cellulose and pectin, less expansion of the cell wall, and less dissolution of pectin layers. As a result, the web structure of the cell wall was preserved. At controlled freezing temperature, the hardness of green beans decreased slightly. Homogalacturonan of chelate pectin was degraded into galacturonic acid, and the side chains of the soluble alkali pectin were degraded into arabinose and galactose. At the later stage of controlled freezing-point storage, the web structure of the cell wall polysaccharides was destroyed. However, the pectin degradation in the green beans was inhibited significantly during controlled freezing-point storage.