Studies on Flavor and Taste Components in Shochu Making from Sweet Potato using a Saccharifying Enzyme

Abstract

The shochu made from cooked sweet potato using a saccharifying enzyme was a new type one, but its taste lacked smoothness. To improve the taste, fermentation tests were done by the same method as in the previous paper except for the use of shochu yeast, SZ.
The fermentation was terminated after 48 hr at 27°C with the enzyme concentration of 30 Ufg total sugar, but the shochu made from the mash fermented for 72 hr lacked smoothness, either.
Main flavor components produced were n-propyl, i-butyl, and i-amyl alcohols, and their formation could be explained by the over flow theory in the amino acid biosynthetic pathway, which was proved by fermentation tests using an auxotroph of Saccharomyces cerevisiae, HM 2 (Ile^-, Val^-).
However, the concentration of isoamyl acetate was low, being 3.2 mg//. The concentration of isoamyl alcohol was almost the same as compared with that produced by Kyokai 7 and 701, but the activity of alcohol acetyltransferase (A ATase) was only one forth that of the latters.
Ethyl stearate, ethyl oleate and ethyl linoleate in shochu made from the fermented mash were also much less than those in shochu made by the conventional method with rice koji. Then, fermentation of cooked sweet potatoes by adding either cooked or raw rice was done under the same conditions, resulting in an increase of isoamyl acetate and ethyl esters of higher fatty acids in shochu, which made the taste smoother. The shochu made by this method is a new type one with good flavor and satisfactory smoothness.