Desenvolvimento de leite fermentado por Lactobacillus helveticus adicionado de extrato de hibisco encapsulado

Abstract

Functional dairy food consumption has expanded rapidly due to its quality and high biological value. Among these products, milk fermented by lactic acid bacteria (LAB) stands out, which increase the improvement of sensory and nutritional characteristics. Another factor that has been showing visibility is the application of plants that can provide technological and sensorial characteristics in substitution of synthetic compounds, in addition to providing an increase in nutritional value due to the presence of bioactive compounds. Therefore, this work proposed to develop a milk fermented with the culture L. helveticus (LH) and S. thermophilus (ST), added with free hibiscus extract (LHExL and LHSTExL) or encapsulated with PVP and Tween 80 (LHExE and LHSTExE), which were evaluated for pH, titratable acidity, antioxidant activity (DPPH and FRAP), protein profile by electrophoresis, LAB count and color over 30 days of storage at 4 ± 1 °C. The association of cultures made it possible to improve technological performance by reducing time and fermentation. The pH of LHExL and LHExE fermented milk was lower compared to the other treatments at the initial time, and after 15 days there was a significant reduction in milks fermented by both BALs. Regarding the antioxidant activity against the DPPH radical, the fermented milks showed significant values, however, these results obtained were developed exclusively by the high proteolytic activity of L. helveticus, so that the addition of hibiscus extracts did not provide any difference between the samples. The FRAP assay also showed a positive effect on the antioxidant capacity in all samples, the results showed that the application of hibiscus extracts contributed to the stability of the activity during storage. The study of the protein profile showed that after 15 days of storage, there was a probable synergistic relationship between the cultures contributing to the reduction of the α-casein and β-casein protein band of the samples and that the caseins were hydrolyzed in all treatments at 30 storage days. The texture parameters showed that all treatments presented a soft and fragile gel structure. The LHST fermented milks with or without hibiscus extracts showed color changes in the first 15 days of storage. LH did not change this parameter along the storage time. When comparing the color difference between the fermented milks, it was observed that the LH showed significant differences, in which the addition of the encapsulated extract resulted in greater color intensity compared to the milk without addition over the 30 days of storage. While the LHST treatment showed significant differences in color intensity with the hibiscus extracts only at 30 days of storage. Finally, in the results on the coloring potential of the hibiscus extract, it was possible to observe that the tendency to a more intense red color is proportional to the concentration of extract added. With this, it is possible to conclude that the culture of L. helveticus can develop antioxidant activity in fermented milks, and hibiscus extracts can be an alternative to synthetic dyes.