The effect of potassium sorbate on microorganisms in fermenting corn
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"Introduction: Food is the source of energy for the maintenance of life. The primary concern of all civilizations was to produce adequate supplies of food. Current estimates place the world population growth rate at about 2% per year, and this population will increase 50% by the year 2000 (Global 2000, 1980). The world food needs for 1985 are estimated to be 44% greater than that required in 1970. It is further estimated that approximately 70% of these needs will be to feed the third world (Global 2000, 1980). Cereals contribute over half of man's directly consumed food energy. In developing countries, 95% of the population consume cereals as their dietary staple (Abbott, 1969). For the most part, people in the developing countries will depend upon plant rather than animal sources of protein. Because of its availability, low cost and acceptability, corn (Zea mays L.) will play an important role in man's future. Corn is a staple food in the diet of many countries in Asia, Africa and Latin America (Johnson et al., 1978). However, present day varieties of corn cannot qualify as a complete food source for humans or animals, due to deficiency in niacin and the essential amino acids, lysine and tryptophan (Robinson, 1972). Some alternative ways to improve the nutritional quality of corn and corn products are fortification, blending with legumes, germination, and genetic experimentation. Another method that is being explored for nutritional improvement is fermentation, either by pure cultures or by the natural flora. Fermentations are inexpensive and simple methods for improving nutritive value of corn (Lay and Fields , 1981). According to Frazier (1967), a wet mash of grains undergoes a lactic acid fermentation, chiefly by the lactic acid bacteria and coliforms normally present on plant tissue. A natural lactic acid fermentation occurs when the mixture of corn meal and water was incubated at 37°C. Tongnual et al. (1981) found that % Relative Nutritive Value, lysine and tryptophan were all significantly increased by fermentation. Other than research by Kratochvil (1984), there has been only limited research on the effect of potassium sorbate on the natural lactic acid fermentation, especially on the fermentation of corn meal. Potassium sorbate has been widely used as a food preservative to prevent the growth of undesirable yeasts, molds and many bacteria. The fermentation of corn meal usually takes three or four days of fermentation. During this time, undesirable microorganisms, especially molds, may cause undesirable changes of flavor, nutritive value and vitamin content of the corn meal. The principle purpose of this study was to determine the influence of potassium sorbate on the microflora in the fermentation of corn meal. The secondary objective was to determine the effect of potassium sorbate on the growth of vitamin producing bacteria. In this study, the growth of microorganisms, plate count, pH and titratable acidity were important factors to be evaluated. Since potassium sorbate might remain in the corn meal after drying and since information on the sensitivity of Tetrahymena furgasoni (organism used to test the protein quality) to sorbate is not available, the last factor to be evaluated was the effect of sorbate on the growth of Tetrahymena furgasoni."--Page 1.
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