Mitsutoshi Hamano

Purification and Properties of γ-Glutamyltranspeptidase from Bacillus subtilis (natta)

To understand the mechanism by which γ-poly glutamic acid (γ-PGA) in the sticky material of natto was synthesized, we purified the γ-glutamyltranspeptidase (γ-GTP) (EC 2.3.2.2) from the culture broth of Bacillus subtilis (natto) to homogeneity. γ-GTP was composed of two subunits with molecular weight of 45,000 and 22,000. The N-terminal amino acid sequence of light subunit was homologous with that of γ-GTP from Escherichia coli. The optimum pH and temperature of activity were 8.5 and 60°C. The enzyme was inactivated by incubation for 15 min at pH 8.0 and 55°C, but little loss of the activity was detected at 40°C. γ-GTP used glutamine as a γ-glutamyl donor and acceptor for γ-PGA synthesis. Dipeptides were better γ-glutamyl acceptors than free amino acids.

Water Activity and Water Behavior of Soy Sauce, Dehydrated Soy Sauce and the Improvement on Hygroscopicity of Dehydrated Soy Sauce

The state of water in soy sauce (shoyu) containing 65% (w/w) of water, aW 0.803 at 25°C, can be divided into three water regions such as hydration water, eutectic melting, and ice melting, respectively. On the other hand, dehydrated soy sauce, aW 0.203 at 25°C, water content 2.5% (w/w), has many kinds of hygroscopic components such as glucose, lactate, nitrogen compounds, and color components. The improvement of caking and hygroscopicity in dehydrated soy sauce by the addition of saturated fatty acids with 12 to 18 carbon atoms and shoyu oil were achieved. The aroma components in dehydrated soy sauce was improved by adding soy sauce aroma components recovered by the use of the vacuum ethanol distillation method.

Separation of aroma components from soy sauce by continuous supercritical CO 2 extraction

Traditional soy sauce making process have not been able to separate aroma compounds from body component, which are regarded as useful food resources.