Production of lactic and acetic acids during fermentation of milk fortified with kiwi juice using Saccharomyces boulardii and lactobacilli

Purpose: To investigate the synergistic effect of Saccharomyces boulardii and lactobacilli on lactic and acetic acids produced during fermentation of milk fortified with kiwi juice, relative to fermentation of unfortified milk. Methods: Skimmed milk was fortified with kiwi juice (4 % v/v) and fermented for 12 h at 37 °C by a combination of S. boulardii and lactobacilli strains. Lactic and acetic acids were determined using gas chromatography-mass spectrometry (GS-MS). Results: The presence of kiwi juice in the milk stimulated the production of lactic (1.35 g/100g) and acetic (0.29 mg/g) by S. boulardii in the absence of lactobacilli. When S. boulardii was inoculated with Lb. casei 20975, the production of lactic acid and acetic acid increased to 2.36 g/100 g and 0.71 mg/g, respectively. Furthermore, acid production increased when Lb. plantarum RS (35-11), Lb. casei LCS, and Lb. plantarum JXJ (6 - 12) were inoculated into milk free of kiwi juice in which S. boulardii was grown. Saccharomyces boulardii resulted in marginal production of acids by Lb. fermentum F9. Conclusion: These results show that acid production is positively affected by some lactobacilli strains in the milk whether fortified with kiwi juice or free of this juice. However, fermentation of these formulations for a period longer than 6 h may result in losses in acid yield.