Strengthening the Growth of Probiotic Lactobacillus casei subsp. rhamnosus TISTR 047 and Texture of Pressurized Corn-Milk Yoghurt using Whey Protein Concentrate and Xanthan Gum

Abstract

The objective of this research was to investigate the effects of whey protein concentrate (WPC; 3.5%, 7%, and 14%, w/v) and xanthan gum (0.05, 0.1 and 0.2%, w/v) supplementation on the promoting of probiotic growth and the improving of texture characteristics of corn-milk yoghurt treated with ultra-high pressure (HPP). The corn-milk with WPC were HPP treated at 500 MPa for 10 min at room temperature, then inoculated with 5% (w/v) of yoghurt starter culture (a mixed culture of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) and 5% (w/v) of probiotic Lactobacillus casei subsp. rhamnosus TISTR 047 cells, and then incubated at 43 °C for 48 h. Each treatment was taken for microbiological and physicochemical qualities at 0, 2, 4, 6, 8, 10, 12, 24 and 48 h. A control corn-milk yoghurt was prepared as described, but without addition of WPC. Increasing amount of WPC led to the increase in viscosity, total titratable acidity and the viable number of L. casei subsp. rhamnosus TISTR 047. The optimum incubation time for corn-milk yoghurt production was 6 h. Addition of 7% WPC to corn-milk was selected to incorporate with different levels of xanthan gum. The results indicated that, after fermentation, the optimum level of xanthan gum addition should be 0.1%, since this level could improve syneresis and water holding capacity as well as appropriate viscosity. Results obtained suggest that a novel yoghurt produced from HPP corn-milk added with WPC (7%) and xanthan gum (0.1%) could be considered as one of the potential probiotic foods which could deliver benefits to consumers.