| Maize is one of the most widespread food crops in the world. It not only has some effect in the prevention and treatment of hypertension, arteriosclerosis, coronary heart disease, and cancer, but also has taller nutrition value and action of apparent health protection. Food products that are made by maize fermentation are not much in China, including sour maize pancake, which is staple food for the middle south plain area in Shandong province. The sour maize pancake is made from naturally fermented maize mash. At present the production of the sour maize pancake are subject to hand-workshops and short of professional criterions or regulations, which result in differences in quality of products and restrict development. In this research, pH value, total acid content, organic acids content, population of the dominant microorganisms, antimicrobial effect, and change of starch, fat, and true protein contents of the fermented maize mash at different temperatures were studied. Moreover, the dominant microorganisms were isolated and preliminarily identified. The main results were as follows:1. The pH value, total acid content, and ten kinds of organic acids content were studied at 15oC, 20oC, 25oC, 30oC, and 35oC. The results showed that the initial pH value was from 5.62 to 6.94, and the lowest pH value was from 3.30 to 3.80. As the fermentation temperature increased, the pH value reduced quickly; the initial total acid content was from 3.89g/kg to 16.14g/kg. The optimum fermentation time for maize mash were 72~84h, 72~108h, 48~72h, 21~27h, and 24~27h according to that the optimum total acid content in sour maize pancake was about 20.00g/kg. With the increase of the fermentation time, the organic acids content increased, and its changing tendency was similar to that of the total acid content. By correlation analyzing, lactic acid content had significantly positive correlation with the organic acids content at the five temperatures (P=0.000). The lactic acid was the main organic acid whose content accounted for about 80% in the fermented maize mash; the acetic and malic acids content accounted for about 12% and 5%; the other seven organic acids content accounted for about 3%. The lactic, acetic, and succinic acids content increased, while the fumaric acid content decreased, and the changing tendency of the other six organic acids were not obvious.2. The population of the lactic acid bacteria, yeasts, and the aerobic plate count were studied at 15oC, 20oC, 25oC, 30oC, and 35oC. The results showed that the changing tendency of the lactic acid bacteria were similar at 15oC, 20oC, and 25oC, while that of the yeasts were different. The maximum population of the lactic acid bacteria was 9.06~9.29lg cfu/g and that of the yeasts was 6.75~7.67lg cfu/g, which lagged behind the lactic acid bacteria. The period of logarithmic phase for lactic acid bacteria was 0~12h at 15oC, 20oC, and 25oC. The population of the lactic acid bacteria kept stable or had descendant tendency after 12h. The yeasts had lag phase at not 20oC but 15oC and 25oC. The changing tendencies of the lactic acid bacteria were similar at 30oC and 35oC with the maximum population 9.20lg cfu/g and 8.94lg cfu/g. The period of logarithmic phase for the lactic acid bacteria was 0~8h at 30oC and 35oC, then the population of the lactic acid bacteria kept stable and had descendant tendency. The changing tendencies of the yeasts were different at 30oC and 35oC, and the population of them decreased after 30h and 33h when they got in attenuative phase. During the whole fermentation, the population of the yeasts was much smaller than that of the lactic acid bacteria.3. The starch, fat, and true protein contents were studied at 15oC, 20oC, 25oC, 30oC, and 35oC. The results showed that when the fermentation time were 72h at 15oC, 20oC, and 25oC, and 27h at 30oC and 35oC, the starch content was 71.08%~73.23% initially, and that was 72.06%~75.35% after fermentation. The starch and amylase content increased, while amylopectin content decreased. The ratio of the amylopectin content to the amylase content was initially from 2.05:1~2.23:1 finally to 1.62:1~1.69:1. The fat contents increased or didn't change obviously. The fat content was initially from 3.33%~3.44% to 3.53%~4.46%, while the true protein content increased obviously from 9.73%~9.75% to 9.85%~9.93%.4. The antimicrobial effect of fermented maize mash in different periods on Staphyloccocus aureus and Escherichia coli were studied. The results showed that the fermented maize mash didn't have inhibitory effect on them. For both Staphyloccocus aureus and Escherichia coli, no bacterial inhibition ring formed on the plate with the supernatant of fermented maize mash in 0h and 24h. Bacterial inhibition ring formed with supernatant of fermented maize mash whose total acid content was 19.45±0.21g/kg by fermenting 48h. The inhibition zone in 72h was significantly lager than that in 48h (P<0.05), while it had no significant change among 72h, 96h, and 120h (P>0.05). No significant difference between the inhibitory effects by the same supernatant of the fermented maize mash on the two kinds of bacteria (P>0.05).5. Sequence analysis of 16S rRNA, physiological and biochemical experiments were used to identify the lactic acid bacteria which were isolated from the fermented maize mash. Cultural characteristic observation, physiological and biochemical experiments were used to preliminarily identify the yeasts. The results showed that the main lactic acid bacteria were Leuconostoc citreum, Lactobacillus sakei, Lactobacillus curvatus, and Lactobacillus brevis. The main yeasts were Hansenula jadinii, Candida apicola, Wickerhamiella domercqiae, Hansenula anomala, Candida magnollae, Meischmkowia pulcherrima, Debaryomyces hansenii, and Pichia pastoris.
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