METHODS FOR DETERMINING THE CONCENTRATION OF LACTIC ACID IN FOOD PRODUCTS
Abstract
Abstract. At the present stage, the addition of lactic acid in the process of food production is extremely common not only in Ukraine but also around the world. High bioavailability and versatility of technological actions determine the demand for this additive in various sectors of the food industry. Thus, lactic acid is used as a preservative, antioxidant and acidity regulator under the additive code E 270 and is an important component of many foods. To determine it’s concentration, colorimetric, spectrophotometric, fluorometric, enzymatic methods as well as high-performance liquid chromatography are currently used. As lactic acid itself is present in all fermented milk products (due to lactic acid fermentation), and it is actively used by most manufacturers of these products to maintain acidity balance for an optimal period, it is advisable to investigate its concentration in these products. For this purpose, 5 samples of yogurt with 2,5 % fat content were taken, and the amount of lactic acid was determined by a two-stage enzymatic-chemical method with the formation of Berlin Blue (BB). This method is patented by the staff of the Department of Analytical Biotechnology of the National Academy of Sciences of Ukraine and is used to measure the level of this compound in various foods and biological fluids. The method is based on the use of FC b2, its substrate (lactate) and ferricyanide (Fe3+). The highest concentration of L-lactate was found in Polish strawberry yogurt with fruit slices TM Mlekovita – 125,6 mmol/l, and the lowest in yogurts with filler “Strawberry” TM Dolce Lactel and with fruit filler “Strawberry” TM Prostokvashino 64,75 and 64,0 mmol/l. It should also be noted that after analyzing the composition of selected samples of yogurt, it was found that to regulate the acidity, manufacturers use citric acid and its salts, namely sodium citrate. Thereby a certain amount of lactic acid in the selected samples of yogurt accumulated during lactic acid fermentation. Thus, as a result of experimental research, we have proved that the FC b2-BB method is accurate and cost-effective, as it does not require large costs for reagents and is convenient to use in analytical practice. In the future, it is advisable to study the concentration of lactic acid by this method in other foods, the technological scheme of production of which provides for the need to assess the course of lactic acid fermentation and, accordingly, to test the quality of finished products.
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