Development Of A Potential Functional Ready To Drink Rice Beverage Using Amylolytic Lactic Acid Bacteria

Rice is one such important cereal crop and staple food for over half of the world’s populationthat is a potential vehicle for probiotics and other functional compounds. Lactic acidfermentation generally leads to improvement in the shelf life, texture, taste and aroma of thefinal product. However, very few amylolytic multifunctional lactic acid bacteria have beenreported that can be used as starter cultures in the fermentation of cereal products giving riseto consistent acceptable product quality. The aims of this research were therefore to screenlactic acid bacteria for amylolytic activity in rice starch, apply the successful strains in thedevelopment of a ready-to-drink functional rice beverage, evaluate nutritional compositionand consumer acceptability of the beverages.Twenty-nine Lactobacillus Plantarum strains potentially useful in the development of afunctional ready to drink rice beverage were screened for amylolytic activity by investigatingtheir capacities to utilize rice starch, using the known amylolytic L. plantarum A6as areference strain. Among these strains,21were capable of degrading rice starch,10showedextracellular amylase activity greater than0.30μ Units/mL. The microbial growth, titratableacidity, pH, reducing sugars and organic acids were measured respectively. Only4strainswere able to grow substantially in the liquid medium, reaching maximum cell count after12hfermentation (7.0-10.6log cfu/mL), with a pH below4.5. Lactic acid was produced inamounts ranging from5.98mg/mL to8.16mg/mL and acetic acid ranged between3.47mg/mL to5.90mg/mL. Some strains produced more acetic acid than lactic acid between12-24h of fermentation. L. Plantarum Z4showed highest residual reducing sugars content.Two of the strains tested (L. plantarum Z4and L. plantarum CS) that showed the highestgrowth and amylase activity were used to ferment beverages containing white rice flour,supplemented with soy protein concentrate (SPC). The strains were applied as single startersinoculated at10%levels; to obtain approximately6log cfu/mL in each beverage at0h. Thebeverages were mainly differentiated based on the concentration of organic acids, viable cellcounts, nutritional composition, amino acids, mineral content, viscosity, syneresis, volatilecompounds and sensory profiles.Most strains reached maximum cell count after12h of fermentation (8.5–10.9log cfu/mL),with a pH below4.5. Both L. plantarum Z4and A6utilised maltose and glucose ascarbohydrate sources, while L.plantarum CS utilised only glucose. Nutritional compositionresults varied greatly with L. plantarum Z4and A6having better protein, energy, and sugar content. The essential amino acids especially lysine and methionine were highly augmented.Sensory profiles using both quantitative descriptory analysis and9-point hedonic scalerevealed that the beverage made with L. plantarum Z4had better appearance and viscositythan other beverages. Panelists preferred beverage fermented with Z4and rejected samplefermented with strain CS due to its thickness and grumpiness on the tongue. The samebeverage inoculated with strain Z4, also survived with a cell density of log5x108cfu/mLthroughout storage at4C for30days. Among the exploited biotechnological options, thisbeverage could be considered as a promising novel functional food and L.plantarum strain Z4as a functional starter culture.