Formulation of Probiotic Mango Juice and Assessment of Physicochemical Characteristics, Nutritive Quality, Culture Viability and Storage Stability

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Mwanzia, Margaret M.
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Kenyatta University
Probiotics are live microorganisms added to food products to confer health benefits such as gut health, cancer protection and improved immunity when consumed. Fruits juices, particularly mango (Mangifera indica l.) fruit juice, are considered as potential channels for delivering probiotics as they contain essential nutrients suitable for the growth of probiotics and are free from allergen as opposed to milk based products. There is limited information on the processing and stability of probiotic fermented mango juice in Kenya. The study was undertaken to formulate, evaluate the nutritive value, physicochemical, sensory acceptability and storage stability of a fermented probiotic mango fruit juice for the Kenyan market. Mature ripe apple mango variety were sourced from Masii in Machakos county, transported to Jomo Kenyatta University of Agriculture and Technology (JKUAT) Food Science Department and stored in a cold room (6-100C). Three different mixed probiotic cultures were used in this study (Abt-5® culture Streptococcus thermophillus, Bifidobacterium and Lactobacillus acidophilus); Fiti® culture (lactobacillus rhamnosus) and Yo-mix® culture (Streptococcus thermophillus and Lactobacillus delbruikii ssp bulgaricus). The viability of the cultures was also assessed. The mango juice was formulated using mango juice to water ratios of 100:0 (control), 25:75, 50:50 and 75:25 (v/v) and adjusted to 170brix using cane sugar. The formulated mango juice was pasteurized at 900C for 1 minute, cooled using ice water and refrigerated at 10°C. Sensory evaluation was carried out using a 9-point hedonic scale, a questionnaire was administered to a sample of 35 untrained panelists between 18-50 years of age randomly selected from the Food Science Department. The preferred mango juice samples based on overall acceptability were incubated at 42°C for 0, 12, 16, 24, 36, 48 and 72 hours. The final product was refrigerated at 4°C for analysis. There was a general increase in cell count in all cultures with mango juice fermented with Fiti® culture (Lactobacillus rhamnosus GR-1) for 48 hours recording the highest viable cell count of log10 9.14 CFU/ml. Fermentation significantly changed the final product's physicochemical, nutritional, and sensory acceptability (P<0.05). The highest pH decrease was observed in 50:50 formulation with a significant (p<0.05) increase in total titratable acidity from 0.15% to 0.69% using Fiti® culture (Lactobacillus rhamnosus GR-1) within 72 hours. Subsequently, the total soluble solids decreased from 17° Brix to 14.47° Brix. The decrease in pH and increase in viable count indicated that probiotic bacteria utilized the available sugars in the juice for cell synthesis. β-carotene levels increased by 3-8%, whereas vitamin C retention was >68%. The culture viability, pH and total soluble solids decreased during the four weeks of storage at 40C. The fermented mango juice was microbially stable during the four weeks of storage at 40C. The recommended storage period for the probiotic mango juice is four weeks and one week for the juice fermented using Fiti® culture (lactobacillus rhamnosus) and Yo-mix® culture (Streptococcus thermophillus and Lactobacillus delbruikii ssp bulgaricus) respectively. On the overall, mango juice fermented using Fiti bacterial culture for 48 hours was superior in quality based on sensory and culture viability. Therefore, the results of this study are beneficial to food industries, small and medium scale enterprises. The study recommends the popularization of probiotic fermented mango juice using Fiti culture® as a healthy drink.
A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science in Food, Nutrition and Dietetics, School of Public Health and Applied Human Sciences, Kenyatta University. May, 2022
Formulation, Probiotic Mango Juice, Assessment, Physicochemical Characteristics, Nutritive Quality, Culture Viability, Storage Stability