Production of enzymatically hydrolyzed soybean protein isolate by a novel neutral protease from Enterobacter sp. NRCM1 to be used as a base precursor of thermal process flavours

A novel neutral protease from a newly isolated and identified bacteria Enterobacter sp. NRCM1 was used to produce the enzymatic hydrolyzed soybean protein isolate (E-SPM1). The protease was purified and biochemically characterized. The effect of hydrolysis time on degree of protein hydrolysis and released free amino acids was investigated. The enzymatic hydrolysates (E-SPM124, E-SPM148 and E-SPM172) produced after 24, 48 and 72 h, respectively were used as main precursors of beef-like flavours. The generated volatiles were determined by solid phase microextraction combined with gas chromatography- mass spectrophotometer (SPME- GC-MS). The results revealed that the optimum pH and temperature of protease activity were 7.0 and 50oC, respectively. Sample E-SPM172 showed the highest degree of hydrolysis (43.71%) and content of free amino acids (5.78 g/mL). The headspace volatiles of the model mixture based on E-SPMI72 comprised the highest content of the most important compounds for meat aroma. The results of odour sensory analysis confirmed those of GC-MS for all investigated samples. The highest score of beefy note of sample E-SPMI72was mainly correlated to the significant increase of 2-methyl-3-furanthiol, the most potent aroma compound in beef flavour. The gradual increase of savoury note was consistent with that of the disulfide compounds, which possess savoury aromatic note.