Abstract
With the increasing demand of health promoting food products, formulations of yoghurts are changing more towards live probiotic starter culture milk fermentation and fortification with plant-based food ingredients to improve the flavour and nutrition composition. Synbiotic yoghurts fermented with probiotic microbes and fortified with prebiotic food ingredients have become very popular as functional foods due to their scientifically proven bioactive compounds that promote human gut health and alleviate dysbiosis. The aim of the current study therefore, was to assess the physiochemical, nutritional proximate composition and viability of probiotics in formulated yoghurt fortified with a novel purple-leaf tea (Camelias sinensis) puree that is rich in anthocyanins, bioactive polyphenols. Whole milk was fermented with probiotic starter culture (Lactobacillus acidophilus (LA-5), Bifidobacterium animalis subsp. lactis -ABT 5) from CH Hansens Limited. Subsequently, the yoghurt was fortified with a novel purple tea puree at the Food and Tea Science Workshop of Karatina University, Kenya. Proximate composition and physiochemical properties (pH and mineral salts profile) were analyzed both in the formulated probiotic yoghurt (PYFPT) and control yoghurt without the tea puree. The viability of the probiotic colony forming microbes was determined using the De Man, Rogosa and Sharpe (MRS) anaerobic bacteria selective culturing agar media. The pH results of PYFPT (4.24 ± 0.04) was not significantly different (p< 0.05) to that of the control yoghurt even after 28 days of refrigerated storage. However, proximate composition recorded significant differences except for the crude fiber content (0.01 ± 0.01 %). A higher percent moisture content and crude lipid was recorded in the control yoghurt (88.18±0.01 and (2.11 ± 0.02) than the PYFPT (78.14±0.04 and 1.33 ± 0.09). Inversely, higher percentage of crude protein, carbohydrates and crude mineral salts were recorded in the formulated PYFPT (7.96±0.27, 11.17±0.25; 0.81±) than control yoghurt (4.23±0.01, 5.44±0.04, 0.59±0.01). A profile of ash content of the added purple tea puree recorded 16 different mineral salts. The macro minerals were the major, with potassium recording the highest content (282 ppm), followed by sodium (121 ppm), magnesium (97.2 ppm) and calcium (96.4 ppm). The microbial anaerobic probiotic count (6.14 - 6.80 log CFU/ml) was not statistically and significantly different between the PYFPT and the control yoghurt after 28 days of refrigerated storage. In conclusion, the study demonstrated that it is feasible to formulate nutritious probiotic yoghurt fortified using purple-leaf tea puree with potential for commercialization. Key words: Probiotic yoghurt, purple-leaf tea, physiochemical property, proximate composition, probiotics viability
Published Version
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