| Abstract
| - Five different bean varieties (Phaseolus vulgaris L.) fromKenya, which were obtained either freshlycollected or after having been stored for 5 years in tropicalconditions (30−40 °C, >75% RH), werecompared for their cooking characteristics. Beans under storagewere susceptible to the hard-to-cook (HTC) defect, and the bean cooking time was up to 12 times that ofthe fresh beans, limitingtheir acceptability. A study was undertaken to investigate changesin nutritionally relevantphysicochemical properties of beans during storage. Chemicalanalysis showed that storage resultedin a decrease in pH and an increase in titratable acidity in allvarieties. Total polyphenol, non-tannin polyphenol, tannin, and lignin contents were determined;storage-induced HTC beanscontained lower levels of total polyphenols (especially, non-tanninpolyphenols) than the fresh beansbut higher levels of tannins in all cultivars. Significantincreases in lignin and lignified proteinwere also detected and accompanied by increases in cooking time. Areduction in phytic acid wasalso observed. These results are discussed in relation to themechanisms which may underlie thedevelopment of the HTC defect. Keywords: Beans; hard-to-cook; phenolic compounds; storage
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