Avaliação do potencial funcional de bebida láctea de soro em pó de queijo de cabra

Abstract

The goat whey is considered a byproduct of the cheese production and is often discarded as effluent without any treatment, becoming a source of pollution. Alternatively, the use of whey for the production of dairy beverages has been a very attractive option, especially due to its nutritional value. Probiotic cultures are composed of microorganisms that confer health benefits for the host, can be used in fermented beverages. Several food proteins contain physiologically active peptides, known as bioactive peptides. Milk proteins are considered a major source of potentially inhibitory peptides on the activity of the angiotensin-converting enzyme (ACE). This study aimed to prepare fermented dairy beverages produced with goat cheese whey powder considering the addition of a probiotic microorganism and its viability in the product, as well as, to evaluate bromatological, microbiological and physicochemical properties during the storage, and also to investigate the inhibitory activity on the ACE. The fermentation process was performed for the beverages of the control trial (BLC), added with Streptococcus thermophilus TA 40, and the probiotic trial (BLP), added with Streptococcus thermophilus TA 40 and Lactobacillus casei BGP 93. The chemical composition of the whey powder and the final milk beverages was evaluated, as well as the pH, titratable acidity and viability of the microorganisms in the reconstituted whey after the addition of the cultures, before fermentation (T0), after fermentation (TF), and after 1, 7, 14 and 21 days of storage at 4 °C. The instrumental texture for both beverages was analyzed during the storage period. The sensory analysis was performed on D7, D14 and D21 sampling periods. The protein content was analyzed for the reconstituted whey (SR) and for beverages on D1, D7, D14 and D21 sampling periods. The degree of proteolysis by the o-ftaldialdeíde (OPA) method and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis were carried out to evaluate the protein degradation in samples during the processing and storage. The inhibitory activity on the angiotensin converting enzyme (ACE) was measured in order to obtain the bioactive potential of the product. The pH during fermentation (T0 and TF) and storage decreased from 5.71 to 4.92 and from 5.72 to 4.97 for BLC and BLP, respectively. The acidity for both trials increased significantly (p<0.05) between T0 and TF and showed significant differences neither between storage periods nor between trials (p>0,05). The viability of S. thermophilus was in accordance with the levels required by the Brazilian legislation for fermented dairy beverages, showing populations higher than 10 CFU/ml in the final product, during the whole storage period. Viable L. casei cells in the probiotic trial were consistent with the recommended levels by the literature (above 10 – 10 CFU/ml) for products with probiotic benefits. The final products were in accordance with the Brazilian legislation for microbial contaminants, which present less than 3 most probable number (MPN)/ml to 100 MPN/ml for coliforms at 30/35 °C and at 45 °C. The texture parameters did not differ significantly (p>0.05) between the trials and the storage period. The presence of the probiotic microorganism did not result in significant differences between trials in the sensory evaluation. The protein content of the SR was significantly higher (p<0.05) than that verified in the dairy beverages during the storage periods for the two trials, which showed values of 2.2 g/100 g for BLC and of 2.1-2,17 g/100 g for BLP. Both beverages showed, during the whole storage, protein levels higher than the minimum of 1.0 g/100 g required by the Brazilian legislation for dairy beverages with added ingredients. Although the degree of proteolysis did not differ significantly between trials and storage time (p>0.05), there was a tendency for the increasing of this parameter during the storage period, as well as a trend of higher proteolysis in the probiotic trial, suggesting that the addition of L. casei promoted the release of peptides, since it was also found electrophoretic bands with larger size ranges for BLP in relation to those verified for BLC. For the ACE assay, both BLP and BLC were able to inhibit the enzyme under study, with increased values for BLP on D1, close to that found with captopril (reference medicine to treat hypertension).