Effect of controlled temperature on the amino acid profile and protease activity of fermented bottle gourd seed

Abstract

The effect of controlled temperature on the amino-acid profile and protease activity of bottle gourd seed (BGS) as well as melon seed (MES) was studied. De-hulled seeds were boiled for 6 hours and fermented at 28oC, 35oC and 42oC for 96 hours. The amino-acid profile of raw, boiled and fermented BGS and MES were determined respectively. The protease activity of the seeds was as well determined at various stages of fermentation. The amino-acid profile of the samples showed high content of glutamic acid (152.1 to 158.8 mg/g for BGS and 145.4 to 166.7 mg/g for MES). Generally, the concentration of the respective amino-acids (essential and non-essential amino-acids) present in the seeds decreased with boiling but increased after fermentation. Fermentation was found to significantly (p<0.05) affect the protease activity of the seeds. The magnitude of the effect was dependent on the seed type, fermentation time and temperature. An increase in fermentation temperature from 28 to 42oC led to an increase in the protease activity of the respective seeds (15.8 to 23.8 units/ml for BGS and 21.6 to 23.0 units/ml for MES) which invariably resulted to the increase in the concentration of the amino-acids present in the respective seeds thereby increasing the bioavailability of the proteins present in the seeds. Microorganisms isolated and identified in the fermenting mashes include; Bacillus Subtilis, Bacillus cereals, Micrococcus luteus, Staphylococcus aureus and corynebacterium sp. The results showed that fermented BGS could favourably substitute for fermented MES as a source of cheap and affordable dietary protein.