Studies were carried out to investigate the main fermentation microorganisms and their flora changes during Korean native soy-sauce fermentation.
Korean native Maeju loaves collected from 5 Do´s were separated into surface and inner parts.
Four different soy-sauces-the surface part Maeju fermented soy-sauce, the inner part, the surface and inner part combined Maeju fermented soy-sauce, and the semi-Japanese type soy-sauce were fermented and the changes of fermentation microorganism flora and the various chemical components during the period of their fermentations were studied.
Besides, 14 home-made soy-sauces collected from 14 different places all over Korea were examined in comparison with the laboratory soy-sauces and to determine the characteristics of Korean native soy-sauce.
The results were as follows:
1. The main microorganisms in Korean native soy-sauce fermentation were determined as;
Aerobic bacteria: Bacillus subtilis, Bacillus pumilus
Lactic acid bacteria: Pediococcus halophilus, Leuconostoc mesenteroides
Yeasts: Torulopais datila, Saccharomycea rousii
2. Microflora changes during Korean native soy-sauce fermentation were as follows; Aerobic bacteria increased until the 2nd week of fermentation and then gradually
decreased.
The lactic acid bacteria increased until the 3rd week, after which decreased.
When the lactic acid fermentation lowered the pH value to below the 5.4, yeasts were able to grow and participate the fermentation.
As the production of organic acids amounted, to a certain height, the growth of all microorganisms lead to the period of decline or death at about the 2nd month of fermentation.
After boiling of soy-sauce most microorganisms except a few of Bacillus sp. disappeared. Occosionally yeasts and lactic acid bacteria survived depending upon the composition of soy-sauce.
3. Changes of general chemical components influencing the microflora were investigated for the period of Korean native soy-sauce fermentation.
Tetal acidity, salt concentration and total nitrogen were increasing steadily over the entire period of fermentation. pH values were dropping to a certain degree of about 4.5. Salt concentration and pH value seemed to be the important factors influencing the microflora.
4. The microflora were influenced by chemical components of soy-sauce. Aerobic bacteria were able to survive in all soy-sauce as they made spores.
Growth of lactic acid bacteria was inhited at 23-26% of salt concentration and pH 4.8. Soy-sauce yeasts storied to grow only at pH below 5.4 and seemed to be inhibited at around 26% of salt concentration under pH 4.5-4.7.
5. The open kettle boiling of soy-sauce, the characteristic process of Korean native soy-sauce manufacturing, was effective to sterilize microorganisms, increase the salt concentration, and coagulate proteins.
6. The average viable cell counts of microorganism found in collected samples of home-made Korean native soy-sauces were;
Aerobic bacteria: 53×10² cell/㎖
Lactic acid bacteria: 34 cell/㎖
Yeasts: 14 cell/㎖
The average values of chemical compositions of samples of home-made Korean native soy-sauce were;
Salt concentration: 28.9%
pH value: 4.79
Total acidity(lactic acid): 0.91g/100㎖
Total nitrogen: 1.09g/100㎖
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