청국장 메주 발효과정중의 질소화합물의 소장에 관한 연구(Ⅰ) : 대두단백질의 소장에 관하여 Changes of Soybean Protein during Chung - Kook - Jang Meju Fermentation = Studies on the N - compounds during Chung - Kook - Jang Meju Fermentation(1)

다국어 초록 (Multilingual Abstract)

Three lots of Chung-Kook-Jang were prepared by the use of 2 strains of Bacillus subtilis and Bacillus natto. For four samples taken from each lot in 12 hrs interval changes of nitrogenous compounds, insoluble protein, water soluble protein, peptides, free amino acids, amino and ammonia nitrogens during Chung-Kook-Jang fermentation, were studied together with the changes of moisture, pH, proteolytic enzyme activity. In addition the average peptide length of the peptides of a Bacillus subtilis lot was determined by the method of molecular sieving using ion exchange resin. The results were as follows:
1. The contents of moisture and total-nitrogen changed little in all samples throughout the fermentation as it would be expected.
2. In all three experimental lots the pH became higher gradually from the initial value of 6.65 to the final 7.5∼7.85 during the fermentation. Proteolytic enzyme activities, in accordance with this pH change, steadily increased up to 48∼60 hrs. of fermentation and then slightly decreased, probably affected by the high pH. The most strong proteolytic activity was observed in the experimental Chung-Kook-Jang fermentation lot using the Bacillus subtilis K-27 isolated by the author.
3. The contents of insoluble protein nitrogen in soybeans increased markedly (5%) by the cooking, after steeping 12 hrs in water. During the Chung-Kook-Jang fermentation, however, it decreased from 1/2 to 1/10 of that of the cooked soybeans.
4. The contents of water soluble protein nitrogen (5%) whereas, greatly decreased to the value of 1.0% by the cooking; but little changed further during the fermentation.
5. The total contents (0.25%) of peptides, amino, and ammonia-nitrogens, PAA-N., increased almost double by the cooking and steadily became higher as the fermentation proceeded, reaching finally up to 4∼7% in 72 hrs fermentation.
6. The amounts of free amino acids of soybean generally decreased during the processing of cooking, even some of them like glutamic acid were destroyed completely. However in the subsequent Chung-Kook-Jang fermentation for 72 hrs., they showed from several to a few hundreds folds increases depending upon the kinds of amino acids.
Valine which was contained in HCl-hydrolyzed steeped or cooked soybeans in amounts 220∼267㎎% was not detected at all as the free amino acid in all fermented samples.
7. Average peptide length (APL) of all fractions, eluted and fractionated by using the Dowex-50 ion exchange resin column, and fraction collector showed the highest value for the cooked soybean and then decreased as the fermentation proceeded. The APL value of effluent showed the highest in 12 hrs fermented sample. The value decreased thereafter by fermentation.