• Applied Biological Chemistry
• /
• v.15 no.3
• /
• pp.213-219
• /
• 1972

In order to utilize sweet potatoes for the material of Takju, brewing experiments with raw sweet potatoes, sweet potato chips powder and its koji were conducted; and various tests were carried out on effect of the treatments of acid, alkali, polyphenol oxidase inhibitor, oxidizing and reducing agents upon the prevention against coloring of sweet potato chips by steaming, and on peeling effect of sweet potatoes by the alkali and heat treatments. The results obtained were as follows. 1) In the case of brewing with raw sweet potatose, each plot showed low acid and ethanol content, and its finished Takju had an undersirable color and odor. The plots which were mashed after peeling showed higher ethanol contents than the plots mashed without peeling. 2) In the case of brewing with sweet potato chips powder, each plot contained considerably more amount of ethanol than the plots brewed with raw sweet potatoes, white it contained less amount of acid. The ethanol contents of the plots using wheat bran koji were $10.5{\sim}11.4$ per cent 4 days after mashing, and were higher than those of the plots using malts powder. Their finished Takju was inferior in quality because of the lack of acid and being darkened gradually in process of time. 3) The kojies which were made of sweet potato chips powder with Neurospora sitophila or Aspergillus oryzae had good appearance, but the Takju mashes brewed with these contained remarkably less amount of ethanol. 4) Effect of the treatments of acid, alkali, polyphenol oxidase inhibitor and organic solvents such as ether and ethanol upon the prevention against coloring of sweet potato chips was not recognized. Alum and burnt alum were effective a little on the decolorization, and among the oxidizing and reducing agents tested, potassium permanganate was most effective. 5) Darkening of sweet potato chips powder in course of heating after mixing with water was not affected by pectin and amino acids, but by tannin. 6) Sweet potatoes were not peeled easily by friction after soaking in the boiling solution of 3 per cent alkali for 6 minutes and peeled in boiling water for 12 minutes. From the viewpoint of the results above mentioned, it seems to be necessary to study further on the isolation of microorganisms which are able to decompose the coloring substances and yeasts which are adequate for the fermentation of sweet potatoes in order to utilize sweet potatoes for Takju brewing, because brewing with raw sweet potatoes, sweet potato chips powder and its koji was unsuccessful, and effect of the various treatments on the decolorization of sweet potatoes was not recognized.

• Applied Biological Chemistry
• /
• v.19 no.2
• /
• pp.82-92
• /
• 1976

The study was carried out to investigate the changes of the various chemical components and the microflora during the aging period of Korean navive Kochuzang. (Red pepper soybean paste) Korean native maeju loaves were separated into surface and inner parts. Three kinds of Korean native Kochuzang were prepared from surface part, inner part, and ordinary of maeju. The selection and the indentification of the high enzyme producing strains from the microflora and characteristics of their enzymes were studied. I. The changes of the various chemical components during the aging period of Kochuzang. 1) The changes of pH in the 3 kinds of Kochuzang displayed rapid decrease for the first 10 days after preparing and gradual curve of decrease until 60 days, but slight increase for the next 30 days. The pH of the surface part Kochuzang was lower than that of inner part or ordinary Kochuzang. 2) The total acid contents in the 3 kinds of Kochuzang showed gradual increase until the 60 days but it slowly reduced after this time. 3) The total nitrogen contents in the 3 kind of Kochuzang showed gradual inerease up to the 60 days, but slight decrease after this time. 4) The changes of trichloroacetic acid soluble nitrogen in the 3 kinds of Kochuzang showed a remarkable increase for the first 10 days, however gradual increase after this time. 5) The increase of amino nitrogen contents in the 3 kinds of Kochuzang seemed to be remarkable until the first 30 days, however to be less remarkable after this time. 6) The contents of reducing sugar in the 3 kinds of Kochuzang showed remarkable increase until the first 50 days and it slowly reduced after this time. II. The changes of microflora during the aging period of Kochuzang. 1) Aerobic, anaerobic bacteria and mold in the 3 kinds of Kochuzang were increased until the first 30 to 40 days, but they were reduced after this time. 2) No yeast in the three kinds of Kochuzang appeared until the first 20 days. Yeast were proved to grow, when the pH value was decreased below 5.4 after the 30 days. Yeasts in the surface part and ordinary Kochuzang were gradually increased and those in the inner part Kochuzang were decreased as aging. III. The selection and identification of high amylase and protease producing strains from the microflora during the aging period of Kochuzang. 1) The amylase and protease highly producing strains from microflora were identified as Bacillus subtilis-P, Bacillus subtilis-G, Bacillus licheniformis-K, Aspergillus oryzae-B. 2) Amylase activity of Aspergillus oryzae-B was highest among the strains and the strains in order of the higher activity to the lower one were Bacillus subtilis-P Bacillus licheniformis-K, Bacillus subtilis-G. Protease activities of Aspergillus oryzae-B and Bacillus subtilis-P were about the same and the strains in order of the higher activity to the lower one were Bacillus licheniformis-K, Bacillus subtilis-G. 3) Amylase activity was inhibited more than protease activity was with NaCl concentration. Amylase activity was inhibited by 45 to 65 percent and protease activity by 40 to 46 percent at the concentration of 15 percent NaCl, which was the average concentration of NaCl in Kochuzang.