Insight into pectin-cation-phytate theory of hardening in common bean varieties with different sensitivities to hard-to-cook.

In this study, a detailed quantitative analysis of the mechanisms linked with pectin-cation-phytate hypothesis of hard-to-cook development (HTC) was evaluated to assess the plausibility of this hypothesis. Several common bean varieties with varying sensitivities to HTC were characterized for pectin, cell wall bound calcium and inositol hexaphosphate (InsP6) content before and after ageing. Ageing resulted in a significant decrease in InsP6 content (resulting in calcium release) in all varieties. Despite not significantly changing during ageing, the cell wall bound calcium content significantly increased in most aged bean varieties upon short cooking indicating enhanced internal cation migration during the early phase of cooking in contrast to during ageing and soaking. Among the parameters evaluated in this study, the relative changes in InsP6 content significantly correlated with the change in cooking times as well as changes in cell wall bound calcium content. Results obtained in this study suggest that in some bean varieties, pectin-cation-phytate hypothesis is the predominant mechanism by which hardening occurs during storage while in other varieties, the role of other factors such as phenolic crosslinking as suggested in literature cannot be ruled out.

Thermal treatment of common beans (Phaseolus vulgaris L.): Factors determining cooking time and its consequences for sensory and nutritional quality.

Over the past years, the shift toward plant-based foods has largely increased the global awareness of the nutritional importance of legumes (common beans (Phaseolus vulgaris L.) in particular) and their potential role in sustainable food systems. Nevertheless, the many benefits of bean consumption may not be realized in large parts of the world, since long cooking time (lack of convenience) limits their utilization. This review focuses on the current insights in the cooking behavior (cookability) of common beans and the variables that have a direct and/or indirect impact on cooking time. The review includes the various methods to evaluate textural changes and the effect of cooking on sensory attributes and nutritional quality of beans. In this review, it is revealed that the factors involved in cooking time of beans are diverse and complex and thus necessitate a careful consideration of the choice of (pre)processing conditions to conveniently achieve palatability while ensuring maximum nutrient retention in beans. In order to harness the full potential of beans, there is a need for a multisectoral collaboration between breeders, processors, and nutritionists.

Detailed analysis of seed coat and cotyledon reveals molecular understanding of the hard-to-cook defect of common beans (Phaseolus vulgaris L.).

The hard-to-cook (HTC) defect in legumes is characterized by the inability of cotyledons to soften during the cooking process. Changes in the non-starch polysaccharides of common bean seed coat and cotyledon were studied before and after development of the HTC defect induced by storage at 35°C and 75% humidity for 8months. Distinct differences in the yields of alcohol insoluble residues, degree of methoxylation (DM), sugar composition, and molar mass distribution of non-starch polysaccharides were found between the seeds coat and cotyledons. The non-starch polysaccharide profiles, both for seed coats and cotyledons, significantly differed when comparing HTC and easy-to-cook (ETC) beans. In conclusion, differences in the structure, composition and extractability of non-starch polysaccharides between the ETC and HTC beans confirmed the significant role of pectin polysaccharides in interaction with divalent ions in the HTC development, which consequently affect their cooking behaviors.

Pectin fraction interconversions: Insight into understanding texture evolution of thermally processed carrots.

In situ changes in pectin fractions for thermally processed carrots were related to textural changes. The texture of pretreated and subsequently thermally processed carrot disks was determined. Alcohol insoluble residue (AIR) was extracted from the pretreated and thermally processed tissues. The AIR was characterized in terms of the degree of methylation (DM) and changes in pectin fractions. Distinct differences in texture and DM were observed during thermal processing. Pretreatment conditions that induced a significant decrease in DM showed better textures. Demethoxylation caused interconversion of pectin fractions, water soluble pectin (WSP) changing into water insoluble pectin [chelator (CSP) and alkali (NSP) soluble pectin]. This process was reversed during cooking accompanied by remarkable alterations in molecular weight (MW) distribution patterns. The WSP depicted polydisperse MW distribution patterns, strongly dependent on the pretreatment condition. Confirmatory results of interconversions of pectin fractions (WSP, NSP) were demonstrated by the MW distribution patterns and neutral sugar profiles. All thermal related transformations of pectin structural parameters were decelerated by lowering the DM.

Mode of de-esterification of alkaline and acidic pectin methyl esterases at different pH conditions.

Highly esterified citrus pectin was de-esterified at pH 4.5 and 8.0 by a fungal pectin methyl esterase (PME) that was shown to have an acidic isoelectric pH (pI) and an acidic pH optimum and by a plant PME that was characterized by an alkaline pI and an alkaline pH optimum. Interchain and intrachain de-esterification patterns were studied by digestion of the pectin products with endo-polygalacturonase and subsequent analysis using size exclusion and anion-exchange chromatography. No effect of pH was observed on the de-esterification mode of either of the two enzymes. Acidic, fungal PME converted pectin according to a multiple-chain mechanism, with a limited degree of multiple attack at the intrachain level, both at pH 4.5 and at pH 8.0. A multiple-attack mechanism, with a high degree of multiple attack, was more appropriate to describe the action mode of alkaline, plant PME, both at pH 4.5 and at pH 8.0.