Optimization of water chestnut (Trapa bispinosa) starch, fructo-oligosaccharide and inulin concentrations for low-fat flavoured yogurt consisting of a probiotic Lacticaseibacillus rhamnosus strain†

Water chestnut (Trapa bispinosa) starch has technical and functional qualities that are mostly comparable to those of traditional sources. In this study, low-fat flavoured probiotic yogurt was prepared with the addition of Lacticaseibacillus rhamnosus (ATCC 7469), mango pulp and water chestnut starch as a fat replacer as well as a biothickener. A central composite face centered experimental design (CCFD) optimization study was carried out using different combinations of fat (0.5–1.5%), starch (1.0–3.0%), fructo-oligosaccharides (0.5–1.5%) and inulin (0.5–1.5%). L. rhamnosus exhibited resistance to simulated gastric fluid, intestinal fluid and hydrogen peroxide, along with good cell surface hydrophobicity and antimicrobial properties against Escherichia coli, Bacillus subtilis, Salmonella typhimurium and Staphylococcus aureus. Water chestnut starch was found to have a characteristic A-type crystalline pattern with 28% crystallinity, and it was smooth with oval to irregular in shape. The proximate, texture, color, and sensory properties and the viability of L. rhamnosus in yogurt did not vary significantly during a 15 day storage period. Thus, the starch from water chestnuts can be explored as a possible fat substitute for formulating low-calorie food products.