In the previous paper, the authors reported on the precipitate which was considered as one of the causes of thiamine loss, when high concentration of tannin and thiamine were mixed. The mechanism of thiamine loss in the case of low concentration of tannin solution, which was so tiny that no precipitate was formed even when mixed with thiamine, was further examined. A marked decrease of thiamine was observed when the thiamine and tannin mixture was brought to pH 7 at 60.The products formed in this reaction was analysed with paper chromatography and others. A small amount of thiamine disulfide (TDS) was found. The longer the reaction time continued, the more the thiamine decreased.But the amount of TDS formed was not always incresed in proportion to the thiamine loss.Besides TDS, thiochrome, vitachrome, thiothiamine and thiazole compound were detected by various methods.Thiamine-decomposite formed by tannin was not recovered by the addition of acid. From an evidence of little change of TDS by tannin, it was proved that TDS would hardly be decomposed by tannin.Finally, at this reaction, TDS seemed to be formed only a little and the majority of thiamine is probably destroyed to physiologically inactive compounds.
A simple, rapid, accurate method for the determination of total cholesterol in foods has been devised. The method involves saponification of the food with alcoholic KOH, extraction of the free cholesterol with petroleum ether and measurement of the cholesterol by means of the Liebermann-Burchard color reaction. The following experiments have been carried out for the investigation of the proposed method. 1.In the recovery test with cholesteryl-palmitate, the reproducibility was 99.3%. 2. In the addition test with fish samples, 100±3% of cholesterol was recovered. 3. The proposed method was compared with Schoenheimer-Sperry method for fish samples, and slightly higher values were obtained by the former. 4. The influences of fat soluble vitamins on the method were studied, and the result showed that there was no influence by fat soluble vitamins on Liebermann -Burchard reaction in the ordinary or common foods.
The contents of crude fat, free and total cholesterol and phosphatide in food materials were determined. The average content of total cholesterol in 31 kinds of fishes was 91.6±18.0mg% and that of phosphatides was 476.4±150.8mg%. In general, high phosphatide contents were obtained in fishes which had high level of cholesterol. The cholesterol and phosphatide levels of cuttle-fishes, ocutopuses, lobsters, spawns and milts were higher than those of fishes. Those of cuttle-fishes, spawns and milts were quadruple as much as the mean level of fishes.
The growth of albino rats was retarded when fed on skim-milk only, and could not improve with addition of soybean oil. Supplement of whole powdered milk gave no effect. Supplement of rice flour with powdered skim-milk, however, promoted their growth remarkably, and an unsuccessful attempt was made to attribute reason for this fact to some property of polished rice flour except starch.
Observation was made on the growth of albino rats fed on the flour products saled for baby's food A, B and C. The products A and B were manufactured from polished rice. When fed on A only gave an inferior effect on the growth, but addition of lysine to A, and fed on B only, gave about the same effect of polished rice flour. From these results, A is considered to have lost lysine through heating treatment in the course of manufacture. Rats administered with only C, products from starch, lost weight and suffered from lypoproteinemia.
It was demonstrated that thiamine was decomposed by the extract of green tea and the active fraction was separated by the aid of paper chromatography with some solvent extractions. The results obtained from the experiments at pH 7 and 60°C indicated that the fraction contained the thermostable thiamine-decomposing factor which is different from tannin and flavonoids which have been hitherto regarded as the agents of this phenomenon. Some parts of thiamine was oxidized to disulfide form.