Abstract
(1) The polarographic method has been applied as the qualitative as well as the quantitative microanalysis on the studies of reducible compounds in the fermentation products, “such as sake” (japanese rice wine), “ushoyu”(soya bean sauce), wine, beer and commercial alcohol.
(2) For the “sake, ” we have found five reducible compounds, which are distinguishable by this method, from the reduction potentials and the saturation curves of polarograms. They are Reduction potential in 0.1 A NH4Cl from N calomel electrode
Compound I -0.22 V
Compound II .-0.40 V
Compound III -0.90 V
Compound I V -1.33 V
Compound V -1.63 V
The reduction potentials of reducible substances possibly present in the sake are measured
Cinnamic aldehyde 0.001% -0.913 V in 0.1 n NH4Cl
Furfural 0.001% -1.302 V in 0.1 a NH4Cl Acetaldehyde 0.001% -1.603 V in 0.1 n NH4Cl
Compound IV and V are found in the distillate (80°-100°C), while compound I and II are observed in the residual solution after distillation; compound III is found in both cases. Thus it is concluded that the compound III corresponds to the aromatic aldehyde, most probably cinnamic aldehyde or benzaldehyde, compound IV to be furfural, compound V to be aliphatic aldehyde, most probably acetaldehyde.
(3) In “shoyu”, compound I, II, III, IV and V are found, in which compound II is much conspicuous than all the other cases.
(4) In wine, five compounds are also found ; but except comp-II, the waves are smaller than in the case of “sake”.
(5) With respect to reducible compounds, beer is much simpler, and comp-111, IV and V only are recognisable, but not comp-I and II.
(6) In the commercial alcohol, reducible substance are also found, although much less in quantity, so it has been suggested, that this method can probably useful as one of the criterion for the purity of alcohol.
(7) Consideration has been given for the quantitative analysis of acet-aldehyde.
(8) Thus the polarographic method has proved to be of much applicable for the studies of the fermentation products, although this method is by no means the decisive identification of the reducible substances.
