FROST EFFECT ON NUTRIMENTAL ANDQUALITY FACTORS IN BEANS

Abstract

Early frost is a phenomenon that affects a large area of bean crop (Phaseolus vulgaris L.) in the rainfed area of the country. In spite of the damage that the grain suffers it is generally used for human consumption. Because of that, the present study was carried out at the Protein Quality Laboratory of CIFAP-MEXICO in order to examine the effects of early frost on the nutritional, physical and physicochemical traits of beans. The varieties: Pinto Nacional Morelos, Ojo de Cabra-73, and Ojo de Cabra Regional were grown at Bustillos, Cd. Cuauhtémoc, Chih. during the spring-summer season, 1989. To study the chemical composition and technological characteristics of its kernel two samples of each variety, one normal development and the other affected by early frost were evaluated. lt was observed that frost stimulates changes in the grain composition such as increases in protein content, tryptophan, glutelin fraction and crude fiber. The major constituent of bean protein was the albumin + globulin fraction. On the other hand, negative changes from the consumer's stand point ocurred in the physical and physicochemical characteristics of affected materials. For example grain weight decreased between 20 and 35 % while grain size also decreased. Water volume absorbed by grains per unit of time during soaking was increased approximately four times. Coat percentage also increased from 25 % for Pinto Nacional Morelos to 92 % for Ojo de Cabra-73.