Impact of process conditions on probiotic survival and physicochemical characteristics of fermented milk containing functional vaginal strains

Functional foods are considered a promising dietary strategy to reduce incidence of human illness thanks to their active components. The project FUNPRO-L wants to develop a probiotic fermented milk designed to be good, from a sensory perspective, healthy and functional since made with exopolysaccharides-producing lactic acid bacteria and vaginal probiotics. First, acidification kinetics were determined by applying 1 or 3U of the commercial starter Lyofast ST440 (Sacco) in skimmed milk incubated at 45°C for up to 24h. 4.5 and 7h of fermentation already dropped the pH to around 5 and 4.5, respectively. Therefore, these two incubation times and 1U of the starter culture were independently tested with 5 different vaginal probiotics (Lactobacillus crispatus BC1, BC4 and BC5; Lactobacillus gasseri BC9 and BC12), previously characterized for their functional properties, supplemented at 7 and 8 Log CFU/ml. pH, starter culture and probiotics viability, water holding capacity (WHC), and volatile molecule profiles of the fermented products were evaluated after 0 and 28 days of storage at 5°C. After 28 days of storage, control samples which underwent to 7 and 4.5h of fermentation showed a pH of 4.0 and 4.5, respectively. Addition of vaginal strains, especially at 8 Log CFU/ml, determined a further reduction of the pH up to 3.84 (7h) and 4.07 (4.5h) with BC5 and BC9, respectively. A drop of about 1 and 0.5 Log CFU/ml of the probiotics and the starter culture were observed in all the samples fermented for 7h and 4.5h, respectively. WHC increased after fermentation with vaginal strains, while it was maintained or reduced upon 28 days of storage, depending on the probiotic applied. The analyses of the volatile compounds showed specific fingerprints for each strain and concentration used. This preliminary screening provided the basis for the production and formulation of a fermented milk, containing functional probiotics, intended to promote female well-being.