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.

Four samples each of black beans representing two types of vegetative growth were collected from farmers' fields in four locations in Guatemala. Soon after collection, samples were stored at 4 degrees and 38 degrees C at ambient relative humidity and subsamples were withdrawn at 0, 45, 90 and 135 days of storage for determination of water absorption, cooking time and analysis of neutral- and acid detergent fiber, cellulose,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 C and at 135 days absorbed more water than when stored at 4 degrees C. 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 C, 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 C. 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 C, but it was enhanced when stored at 38 degrees C. For vine type of beans at 4 degrees C relative high rates of synthesis were observed, which were higher at 38 degrees C for NDF, hemicellulose and lignin. Cooking time and fiber fraction contents were subjected to regression analysis. The correlations at 38 degrees C were higher than at 4 degrees C for all fractions for both types of beans, but statistical significance was obtained only for NDF, ADF and cellulose for vine type of beans. These data show therefore that synthesis of cell wall structure fractions, and not only lignin formation, are responsible for the increase in cooking time observed upon storage at high temperature.