Changes on amino acids content in soybean, garbanzo bean and groundnut during pre-treatments and tempe making

Abstract

Fermentation of legumes is a well-recognised preserving method that not only diversifies the sensory attributes of the legume-based foods but also enhances its nutritional value. This study aimed to evaluate the changes in amino acids content of soybean, garbanzo bean and groundnut upon pre-treatments (soaking and steaming) and fermentation times (18, 24 and 30 h). The amino acids analysis was performed with a HPLC system using AccQTag method. The results obtained showed that raw soybean contain the highest amount of essential and non-essential amino acids followed by raw garbanzo bean and groundnut. After the soaking process, the amount of amino acids obtained was significantly increased in all three legumes. However, the steaming process was found to cause significant decrease in the amino acids content. After the steaming process, the legumes were inoculated with Rhizopus oligosporus and incubated at 30oC and 65% RH. At 18 h of fermentation time, the amount of total amino acids were found to increase by 26% in fermented groundnut and 16% in both soybean and garbanzo bean compared to after steaming. Further fermentation time of 24 h shows further enhancement in the amino acids content in all three legumes. Groundnut shows the highest increased of 71% in total amino acids content followed by 63% increased in garbanzo bean and 53% increase in soybean. However, prolong fermentation time of 30 h shows a decrease in total amino acids content in all three legumes which indicates the slow process of mould degradation have occurred. Therefore, fermented legumes must be consumed at the appropriate time of fermentation in order to get the benefit from the highest accumulation of amino acids content.