Evaluation of Ethiopian Thyme (Thymus Schimperi R.) Antioxidant Activity and Its Preservative Effect on Some Food Products
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Date
2012-06
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Addis Ababa University
Abstract
The study was conducted with the objective of evaluating antioxidant activity of Thymus Schimperi and its preservative effect on oil, butter and meat. Thyme was prepared by investigating the effect of ethanol concentration (0-97%), extraction time (180-240 min) and extraction temperature (20-40℃) on its antioxidant activity and extract yield. Based on ANOVA analysis, extraction parameters have significant effect (P<0.05) on thyme antioxidant activity and its extract yield. The best levels of extraction parameters for higher antioxidant activity and extract yield were distilled water (0% ethanol concentration) for 210 min at 20℃. Antioxidant activity of thyme was evaluated by adding 0.1% thyme crude extract to refined soybean oil and butter. For comparison, 0.05% α-Tocopherol was added as positive control and none thyme extract was used as negative control. The results were expressed as induction time determined by Rancimat (hr) and Schaal Oven Test (day) methods. Induction time of thyme was 3.25±0.02 hr and six day when determined in soybean oil. But, α-Tocopherol has 4.98±0.10 hr and seven day induction time. Thyme has 5.28±0.08 hr induction time when evaluated in butter. The preservative effect of thyme was also studied by performing free fatty acid, Peroxide value, Acid value (on oil and butter); Aerobic plate count, Aerobic Mold & Yeast count and Enterobacteriaceae count on butter and meat. In the study, all samples were treated with 0, 0.1% and 0.2% levels of thyme extract and analysis were performed in weekly basis. Compared to thyme extract treated samples of oil and butter, control sample showed higher lipid oxidation rate in each storage weeks. Highest microbial load was obtained in controlled samples of butter and meat. Samples containing 0.2% thyme extract have lower count of total viable microbes, mold & yeast and enterobacteriaceae. Based on the results, samples with 0.2% thyme extract significantly (P<0.05) improved both the oxidative and microbial stability. Hence, Ethiopian thyme has antioxidant activity and preservative effect as evaluated on soybean oil, butter and meat. The preliminary techno-economic feasibility study also showed good profit margin and financial feasibility for crude thyme extract production.
Keywords: antioxidant activity, induction time, thyme extract, thymus schimperi, preservative effect, protection factor.
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Keywords
Antioxidant Activity, Induction Time, Thyme Extract, Thymus Schimperi, Preservative Effect, Protection Factor