Thesis (M.Sc)--University of Limpopo, 2010. / Black tea (Camellia sinensis) and black tea combined with bush tea (Athrixia
phylicoides) were analyzed for their polyphenol content, antioxidant activity and
tannin content. Solvent extraction methods were used for extracting polyphenols,
antioxidant activity and tannin content. Total phenols were determined using the
Folin-Ciocalteu method, antioxidant activity using Trolox Equivalent Antioxidant
Capacity (TEAC) assay and tannin content using vanillin-HCl method.
Polyphenol content, antioxidant activity and tannin content were calculated using
regression equation Y=MX+C, where C=intercept, Y= Absorbance of the sample
and M= Gradient.
Results of black tea in this study showed that total polyphenols, antioxidant
activity and tannin content decreased with decrease in temperature and time and
this was attributed to the release of polysaccharides at 90°C. At 90°C for 3
minutes 7.68mg/100g of total polyphenol, 3.85μmol/g of antioxidants and
2.81mg/100g of tannin were obtained and this amount decreased to
5.50mg/100mg for total polyphenols, 1.31μmol/g for antioxidant activity and
0.72mg/100mg for tannin content at 30°C for 10 minutes.
Combining the two tea types (50:50) resulted in a significant (p<0.005) decrease
in total polyphenols, antioxidant and tannin content. Results of this study showed
that at high temperature of 90°C for 3 minutes 2.64mg/100g for total polyphenol,
2.48μmol/g for antioxidants and 1.8mg/100g for tannin were obtained and these
amounts decreased to 1.39mg/100mg for total polyphenols, 0.35μmol/g for
antioxidant activity and 0.64mg/100mg for tannin content at 30°C for 10 minutes.
Thus high brewing temperature causes increase in total polyphenols, antioxidant
activity and tannin content of the combined teas. This study showed that black
tea and combined black tea and bush tea solutions had large TEAC radical
scavenging activity which can be related to total polyphenols and catechins. The
antioxidant activity of the tea solution increased with increase in extraction
temperature and duration of soaking. It is recommended that 3-min soaking
temperature of 90 °C of black tea and combined bush tea and black tea can be
used due to the highest total polyphenols and antioxidant activity obtained.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/382 |
| Date | 12 1900 |
| Creators | Negukhula, Shonisani |
| Contributors | Mudau, F.N, Mariga, I.K, Liphadzi, K.B |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | vii, 41 p. |
| Relation |
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