Lactobacillus sp. H7 isolado de kefir na produção e caracterização de leite fermentado com a adicão de Bifidobacterium animalis subsp. lactis Bb-12 e amora-preta

Abstract

Fermented dairy foods have been increasingly associated with health and well-being, and the addition of fruits and probiotics bacteria make them more nutritious and appealing to the consumer. Thus, in this study the objective was to evaluate the technological potential of Lactobacillus sp. H7 isolated from kefir in the production of fermented milk added with Bifidobacterium animalis subsp. lactis Bb-12 and blackberry. From four kefir samples, 40 isolates were obtained using the selective medium (MRS agar) for lactic acid bacteria (BAL). Gram stain and catalase tests were performed, evaluation of microbiological safety aspects including tests such as Dnase enzyme activity, hemolytic activity, gelatinase enzyme activity, susceptibility to antimicrobials of clinical use and evaluation of the presence of plasmid. The technological and probiotic potential and its molecular identification were analyzed. The isolate identified molecularly as Lactobacillus sp. H7 showed technological and probiotic potential, demonstrating values of self-aggregation and co-aggregation, respectively of 67.69% and 39.33% and hydrophobic capacity of 12.67%. Among the two isolates, H7 was selected for the elaboration of fermented milk, due to its ability to synthesize exopolysaccharides. Two treatments of the fermented milk were elaborated, starting from the basic formulation, being one of them kept in the form of gel (LF) and the other submitted to the process of lyophilization (LFLR), both kept in refrigeration. The freeze-dried fermented milk was always reconstituted before performing the analyses. In the analysis of fermented milk, in the gastrointestinal transit simulation, the isolate H7 presented a count of 5.99 log CFU.mL-1 for LF and 5.93 log CFU.mL-1 for LFLR, while the probiotic bacterium Bb-12 had a count higher than 6 log CFU/mL for both. The viability of these bacteria during the storage time of the fermented milk in refrigeration was also evaluated, obtaining for the isolate Lactobacillus sp. H7 and the probiotic bacterium Bb-12, at the end of the 35 day period, 7.28 log CFU.mL-1 and 7.46 log CFU.mL-1 for LF and 7.21 log CFU.mL-1 and 6.74 log CFU.mL-1 for LFLR, respectively. The treatments showed no significant difference regardings the pH, humidity, ashes, lipids, proteins, anthocyanins, phenolic compounds and antioxidants. The treatments LF presented acidity higher than or equal to LFLR. The addition of blackberry pulp contributes with the anthocyanins, phenolic compounds and antioxidants in the dairy product. Both treatments showed good sensory acceptance, however the LF was the preferred sample among the evaluators. Thus, it can be concluded that the isolated Lactobacillus sp. H7 demonstrated technological potential for the elaboration of a fermented milk and, together with Bb-12, guaranteed a probiotic product, and maintained a viability higher than 6 log CFU.mL-1 , during the 35 days of storage, regardless of the lyophilization process.