Impacts of exopolysaccharides producing probiotic bacteria on the physicochemical and sensory properties of fermented goat yoghurt under chilled storage

This study focused on the co-fermentation of goat milk with functional lactic acid bacteria (LAB) and traditional yoghurt starter culture. The fermentation process was optimised by single factor experiment and response surface methodology (RSM). The physicochemical and sensory properties of goat milk yoghurt were evaluated under chilled (4 °C) storage for 21 days. The optimised conditions were selected as the inoculum amount of Lactobacillus paracasei NM-8 (1.1 × 107 CFU.mL-1; CFU - colony forming unit), sucrose addition (6.8%) and fermentation temperature (41 °C). During milk coagulation, the pH declined to be 4.45 and the viable LAB number arrived at 8.77 log CFU.mL-1. The content of exopolysaccharides (EPS) increased to be 2.13 g.L-1. These changes led to the better viscosity (941.33-792.33 cP) and higher water holding capacity (63.24-56.20%) of yoghurt fermented using L. paracasei NM-8 in storage, compared with those of yoghurt without L. paracasei NM-8. This study provided a theoretical basis for eliminating the whey precipitation and rough texture of goat milk yoghurt.