Abstract
Volatile carbonyl compounds and their related compounds of “Tofuyo” were separated by steam distillation and analyzed by gas liquid chromatography. The contents of volatile carbonyl compounds and reducing sugar and the protease activity were analyzed as a function of the aging period.
Judging from the yields of 2, 4-dinitrophenylhydrazones (2, 4-DNPH), it would be assumed that maximum production of carbonyl compounds would be at 3 months of aging period and the 2, 4-DNPH contents in “Tofuyo” soaked in “Awamori, ” in 45% ethanol and crude “Tofu” were 0.38-0.54, 0.27-0.43 and 0.04g/kg, respectively.
Direct gas liquid chromatography (GLC) analysis of volatile carbonyl compounds at 1, 3 and 6 months of aging period of “Tofuyo” revealed the presence of 9 (include 2 broad peaks) to 12 peaks, and 11 of them were identified from the retention time of standard compounds. They were formaldehyde, acetoaldehyde, propionaldehyde, iso-butyraldehyde, diacetyl, 2-methylbutyraldehyde, n-valeraldehyde capronaldehyde, 2-heptanone and furfural.
The protease activity in “Tofuyo” was determined and relatively high activities were found at pH 3.0-4.0 and at 5.5-7.0. Reducing sugar contents were attained to the maximum at 1 month of period and then decreased. This decrease would be due to the browning reaction.
