Viabilidade celular e atividade antioxidante de leite fermentado por Lactobacillus helveticus e Enterococcus faecium

Abstract

There is an increase in demand for food that appeal to healthiness, which in addition to nutrition brings benefits to their consumers, called functional foods. This class includes foods with bioactive compounds, such as antioxidants, probiotic microorganisms, and others. Seeking to diversify its products, the dairy industry researches the use of different species of probiotic bacteria, which can produce different compounds with antioxidant activity. The objective of this work is to formulate a skim milk fermented by the microorganisms Lactobacillus helveticus and Enterococcus faecium and to evaluate the proximate composition of the treatments, the viability of these microorganisms and the antioxidant activity of the product during the storage period (28 days). Three formulations were made: LH containing L. helveticus; EF containing E. faecium; and LHEF joing the two microorganisms. Fermented milks were kept at refrigeration temperature (5°C) for a period of 28 days. Proximate composition analyzes were performed on the first day and on days 1, 7, 14 and 28, plate cell count and antioxidant activity were performed by the DPPH and FRAP methods. Fermented milks are in accordance with the Brazilian legislation, being classified as skimmed because they have a fat content lower than 0.5%. They also have cell count above the required (min. 106 UFC/mL), with viability values higher than 8 log UFC/mL in all treatments throughout the experiment. In the antioxidant analysis, activity stability was observed for the LH and EF samples for the DPPH and FRAP analyses, with no significant difference during storage. The LHEF samples showed a decrease in the percentage of inhibition between days 14 and 28 for DPPH analysis, reaching values from 12.05 to 17.36 % of inhibition. The same occurred in the FRAP analysis, with the decrease in the Trolox equivalent activity, indicating a decrease in the antioxidant activity of the bioactive compounds present in the sample during storage. In this way, the formulated product fulfills the requirements of the legislation in relation to its composition and showed maintenance of cell viability. However, the use of the two cultures together can interfere in the production of compounds with antioxidant activity during the storage period.