Amino Acid Availability and Availability-Corrected Amino Acid Score of Red Kidney Beans (Phaseolus vulgaris L.)

Thermal effect on availability of individual amino acids (AIAA) of red kidney beans was evaluated. Sulfur amino acids (SAA), methionine and cystine (Met + Cys), are the limiting amino acids (AA) and have the lowest availability among the AAs in nine treatments. The availability of SAA (ASAA) ranged from −18.6% in raw beans to 39.8−68.0% in thermally processed beans. Autoclaving at 121 °C for 10−90 min gradually reduced ASAA values. The mean availability for each AA (MAEAA) is the average of the AIAA values for the same AA. MAEAA values ranged from 82.1% (arginine) to 50.4% (Met + Cys). The mean availability in each treatment (MAET) is the average of the AIAA values in the same treatment. The difference between MAET and true digestibility of protein (TDP) was less than 7%. However, the differences between ASAA and TDP (16−37%) and between ASAA and MAET (14−30%) were large. The ASAA-corrected amino acid score (AASASAA) for raw beans was negative (−29.4%) and ranged from 61.8 to 42.1% for thermally processed beans. From a comparison among the protein quality indexes, AASASAA is the preferred method to evaluate protein quality of beans. Keywords: Amino acid availability; availability-corrected amino acid score; red kidney beans