Comparative study of beans from vine and bush type of vegetative growth. Effect of storage on cell wall components as factors in increasing cooking time

RESUMO

Four samples each of black beans representing two types of vegetative growth were collected from farmers' fields in four locationes in Guatemala. Soon after collection, samples were stored at 4 and 38 degrees Celsius at ambient relative humidity and subsamples were withdrawn at 0,45, 90 and 135 days of strage for determination of water absorption, cooking time and analysis of neutral-and acid detergent fiber, cellulose, hemicellulose and lignin. The fiber fraction analysis were done on samples of 0,45 and 90 days of storage. Water absorption for all 4 samples of the bush type was similar at both storage T, however the samples stored at 38 degrees Celsius and at 135 days absorbed more water than when stored at 4 degrees Celsius. The 4 vine types of beans showed different water absorption rates, with two showing patterns similar to those beans of the bush type and two which did absorbed water at a very slow rate. For both types of beans stored at 4 degrees Celsius, cooking time decreased from 0 to 135 days of storage. On the other hand for all bean samples of the two types cooking time increased when stored at 38 degrees Celsius. Analysis of variance showed highly significant effects due to plant type, days of storage, temperature and locality, and for some interactions. Analysis of variance of the fiber fractions showed high significant differences for days of storage for NDF, ADF, cellulose, hemicellulose, and lignin. Plant type gave significant differences for cellulose and hemicellulose. Highly significant differences for hemicellulose were found for the interactions of type x days, type x temperature, locality x type, and type x days x temperature. The rate of synthesis of the 5 fractions were calculated by simple regression analysis. For the bush type of beans some synthesis occurred at 4 degrees Celsius, but it was enhanced when stored at 38 degrees Celsius. For vine type of beans at 4 degrees Celsius relative high rates of synthesis were observed, which were higher at 38 degrees Celsius for NDF, hemicellulose and lignin. Cooking time and fiber fraction contents were subjected to regression analysis. The correlations at 38 degrees Celsius were higher than at 4 degrees Celsius for all fractions for both types of beans, but statistical significance was obtained only for NDF, ADF and cellulose for vince type of beans. These data show therefore that synthesis of cell wall structure fractions, and not only lignin formation, are responsible...