Lactococcus lactis GV103, potentially probiotic, applied in the development of lactose-free fermented milk

This study aimed to evaluate the effect of lactose and glucose on the viability of lactic acid bacteria (LAB) and assess the microbiological and technological characteristics of lactose-free milk fermented with the potentially probiotic strain Lactococcus lactis GV103. The viability of GV103, either alone or co-cultured with Streptococcus thermophilus STI-12, was evaluated in glucose (Glu), lactose (Lac), and glucose:lactose (Glu:Lac) media. After fermentation, pH, titratable acidity, syneresis, water-holding capacity (WHC), and LAB counts were monitored throughout 28 days of re-frigerated storage. Simulated gastrointestinal tract (GIT) conditions were also assessed for both LAB. When co-cultured, the Lac and Glu:Lac media reached pH 4.6 in approximately 480 min, while Glu required 703.5 min. As a monoculture, GV103 showed the highest counts in Glu:Lac, exceeding 10.50 log CFU/mL. After 28 days, the lactose-free fermented milk had a pH of 3.84 and a titratable acidity of 1.10 g lactic acid/100 mL. Syneresis and WHC were 42.32% and 34.62%, respectively. LAB viability remained above 10.50 log CFU/mL after storage, and both strains survived simulated GIT conditions with counts exceeding 9.00 log CFU/mL. The GV103 and STI-12 proved to be effective, supporting its potential for future probiotic applications in lactose-free dairy products, with attention to fermentation time. The results of this study are promising regarding the use of this microorganism to produce lactose-free fermented milk. However, further studies involving sensory analysis are recommended to assess consumer acceptance, as well as large-scale production to evaluate industrial feasibility.