Efficacy of Probiotic Yoghurt Enriched With Purple-Leaf Tea on Gut Microbiota and Lipid Profile
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Date
2025-11
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Kenyatta University
Abstract
The gut microbiome has been found to have a significant impact on the health status
and diseases of humans. Dysbiosis increases gut permeability that subsequently lead to
increased gut inflammations and metabolic disorders such as obesity, type 2 diabetes
and inflammatory Bowel Diseases (IBD). These disorders cause chronic systemic
inflammation, which subsequently alters the lipid profile and gut microbiota
composition. The purple tea variety (TRFK 306/1) produced in Kenya is loaded with
polyphenols and more anthocyanins than the green tea showing great promise in
production of nutraceuticals and functional foods. Dairy products such as yoghurt have
been used as a vehicle for probiotic microbes delivery. Probiotics are living
microorganisms which provide health benefits to the consumer when taken in sufficient
amounts. However, limited intervention studies consider the impact of probiotics on
health outcomes. Therefore, the current study investigated the synergy of dual health
effects of a novel formulated probiotic yoghurt enriched with purple leaf tea (PYEPT)
against the control without the purple tea. The yoghurt was produced by fermenting
pasteurized milk with probiotic starter culture ABT 5. The benefits were assessed by
analysing the yoghurt nutritional properties (proximate composition, profiling of
minerals and anthocyanin content), consumer sensory acceptability, gut bacterial
community and diversity changes and lipid profile of Wistar rats fed on the yoghurt.
The study adopted a randomized control trial design using an in vivo animal model. A
total of 16 male white Wistar rats were used in the study whereby eight rats were the
control group, while the other 8 were the experimental group. The proximate results
showed significant differences (p<0.05) between the PYEPT and control yoghurt with
higher levels of protein and carbohydrates content. Moreover, the study found that the
mineral profile of the purple tea puree used in enrichment of the yoghurt potassium was
highest with 282 parts per million (ppm), and the total anthocyanin was 211.2 ppm. The
sensory evaluation showed that PYEPT had significantly higher scoring in terms of
appearance, colour, taste, odour and overall acceptability (p<0.05) than the control
yoghurt. The current study found that Bacteroidetes were the most dominant phyla at
the baseline, with 61% of all the bacteria. Moreover, after supplementation with
PYEPT, the level of Bacteroidetes reduced to 48.65%. At the baseline, the species level
of Lactobacillus helveticus was found to be at 0.1% while in the endline enriched group,
it was found to be at 0.8%. The current study found the baseline group had a species
richness of 49. After four weeks of the experiment, the control group increased the
species richness to 51, while the enriched yoghurt group reduced the richness to 45.
Both endline control and endline enriched yoghurt groups were associated with higher
levels of beneficial bacteria after the experiment. Particularly, there were significant
reductions in the pathogenic microorganism between endline control and endline
enriched yoghurt (p≤0.05). Independent sample t-test showed there was no statistically
significant difference between total cholesterol, serum triglycerides, serum high
density lipoprotein and serum low-density lipoprotein between the control yoghurt and
enriched yoghurt group (p>0.05). The current study concludes that the probiotic
yoghurt enriched with purple tea positively modulated the gut microbiota and can be
recommended as an avenue to provide a functional food for dietary intervention of
dysbiosis. However, further clinical studies with humans should be done to confirm the
conclusions and further in vitro studies for understanding the mechanisms of
interventions before releasing the yoghurt as a commercial product
Description
A Research Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Doctor of Philosophy in Food, Nutrition and Dietetics, in the School of Health Sciences of Kenyatta University. November, 2025
supervisors
Peter Chege
Mary Muchiri