Effect of bio-chemical changes due to conventional ageing or chemical soaking on the texture changes of common beans during cooking.

[Display omitted] • Texture of seven bean varieties after storage / chemical soaking was explored. • Texture changes are positively correlated with IP 6 changes in beans after storage. • Chemical soaking can be used to estimate sensitivity of beans to HTC development. • Soaking in acetate buffer is a suitable tool to estimate IP 6 hydrolysis during storage. To establish the HTC defect development, the cooking kinetics of seeds of ten bean accessions (belonging to seven common bean market classes), fresh and conventionally aged (35 °C, 83% RH, 3 months) were compared to those obtained after soaking in specific salt solutions (in 0.1 M sodium acetate buffer at pH 4.4, 41 °C for 12 h, or 0.01 M CaCl 2 at pH 6.2, 25 °C for 16 h and subsequently cooking in CaCl 2 solution, or deionised water). The extent of phytate (inositol hexaphosphate, IP 6) hydrolysis was evaluated to better understand the role of endogenous Ca2+ in the changes of the bean cooking kinetics. A significant decrease in the IP 6 content was observed after conventional ageing and after soaking in a sodium acetate solution suggesting phytate hydrolysis (release of endogenous Ca2+). These changes were accompanied by an increase in the cooking time of the beans. Smaller changes in cooking times after soaking in a sodium acetate solution (compared to conventionally aged beans) was attributed to a lower ionisation level of the COOH groups in pectin (pH 4.4, being close to pKa value of pectin) limiting pectin Ca2+ cross-linking. In beans soaked in a CaCl 2 solution, the uptake of exogenous cations increased the cooking times (with no IP 6 hydrolysis). The change in cooking time of conventionally aged beans was strongly correlated with the extent of IP 6 hydrolysis, although two groups of beans with low or high IP 6 hydrolysis were distinguished. Comparable trends were observed when soaking in CaCl 2 solution (r = 0.67, p = 0.14 or r = 0.97, p = 0.03 for two groups of beans with softer or harder texture during cooking). Therefore a test based on the Ca2+ sensitivity of the cooking times, implemented through a Ca2+ soaking experiment followed by cooking can be used as an accelerated test to predict susceptibility to HTC defect development during conventional ageing. On the other hand, a sodium acetate soaking experiment can be used to predict IP 6 hydrolysis of conventionally aged bean accessions and changes of cooking times for these bean accessions (with exception of yellow bean-KATB1). [ABSTRACT FROM AUTHOR]