Sucrose and D-tagatose fermentation profile by different probiotic strains and its effect on physical properties of chocolate milk

Chocolate milk is one of the most popular non-fermented dairy products, while, due to its higher sugar content than white milk, it has been lately criticized for its contribution to diabetes, child obesity and tooth decay. Therefore, our aim in this study was to investigate the substitution of D-tagatose with sucrose in chocolate milk product and if it can be also a probiotic carrier. We studied the effects of different ratios of the sucrose/D-tagatose (100:0, 0:100 or 50:50) as well as the type of probiotic culture (L. acidophilus, L. casei, L. rhamnosus or B. lactis) on the microbiological characteristics (by MRS agar medium) of the chocolate milk. Also, the percentage of the sugar residue (by HPLC) and color properties (by Hunter Lab colorimeter) of the synbiotic chocolate milk were studied at (5°C) during 21 days. The control samples were not incubated with probiotics. The greatest vitality rate at the end of storage was related to the treatment of L. rhamnosus (T-R) and L. casei (T-C) with D-tagatose. Both L. acidophilus and L. casei showed high inclination for D-tagatose, lactose and sucrose fermentation, respectively. However, L. rhamnosus mostly fermented D-tagatose, sucrose and lactose, respectively, while, this order for B. lacti was sucrose, lactose and D-tagatose. B. lactis did not significantly consumed D-tagatose. The treatments inoculated with L. acidophilus, L. casei, L. rhamnosus and B. lactis, orderly showed significant higher color changes in compare to non-probiotic ones. D-tagatose as a natural sugar may make a suitable substitute for sucrose in chocolate milk, while preserving the functional probiotic properties; enhances the health benefits of dairy chocolate milk products. Nevertheless, the right selection of sucrose/D-tagatose ratio and type of probiotic strain has high importance in probiotic biological sustainability and the quality of the final product