A FAST LABORATORY PROCEDURE TO ASSESS THE HARD-TO-COOK TENDENCY OF COMMON BEAN VARIETIES

Common beans (Phuseolus vulgaris L.) develop the hard-to-cook (HTC) de fect during storage at high temperatures and relative humidities. The objective of this work was to develop a fast laboratory procedure to a ssess the tendency of common bean seeds to become HTC. Four samples of common beans (cv Flor de Mayo, Mayocoba, MAM-13 and MX 2340-5) were g rown under irrigation (Etzatlan and Cocula conditions) and rain-fed (E tzatlan) conditions. Two hardening procedures were used: (1) Storage h ardening- Samples were stored at 33-35-degrees-C, 76% relative humidit y for 120 days, sampling every 20 days; (2) Chemical hardening. Materi als were soaked in 0.1 M acetate buffer, pH = 4.0, at 37-degrees-C for 1-7 h. For both hardening procedures, changes in cooking time and har dness were mathematically estimated with a relative percentage deviati on of 4.8-6.0% and 1.8-5.8%, respectively. Chemical hardening might be useful for screening new bean varieties: its advantage over the stora ge method is its rapidity.