Antioxidant Activity and Preservative Effect of Thyme (Thymus schimperi R.)

Aims: To evaluate antioxidant activity and preservative effects of Thyme (Thymus Schimperi R.) on soybean oil, butter and meat food products.
Study Design: Complex factorial design.
Place and duration of study: Addis Ababa and Bahir Dar University, Ethiopia; between May 2010 to June 2012.
Methodology: Both leave and flower part of thyme was manually harvested, dried, milled, and sieved by 420-500µm mesh size. About 10g of prepared thyme was extracted and filtered using 125 mm diameter filter paper and stored at -18℃ till its antioxidant capacity and preservative effect of thyme was determined. Antioxidant activity of thyme crude extract was evaluated at 0.1% concentration as compared to 0.05% α-tocopherol and none-thyme extract treated soybean oil and butter samples using Rancimat and Schaal Oven test methods. The preservative effect of thyme was also studied by performing chemical and microbiological analysis on 0.1 and 0.2% thyme extract supplemented soybean oil, butter and meat for three consecutive weeks.
Results: Thyme extract increases the induction time of soybean oil from 1.92 to 3.25 hrs and five to six days as determined by Rancimat and Schaal Oven test; respectively. It also improves the induction time of butter to 5.28 hrs from 3.78hrs of control butter sample. Highest microbial load was obtained in controlled samples of butter and meat. Samples containing 0.2% thyme extract have lower value for all total viable microbes, mold & yeast and enterobacteriaceae counts of meat and butter.
Conclusion: Thyme extract significantly (P<0.05) improved both the microbial and oxidative stability of food samples. Thus, Thymus schimperi is a potential herb having antioxidant activity and preservative effect as it was evaluated on soybean oil, butter and meat. Thyme, which is abundantly available in Ethiopia, can be used as a source of antioxidant for production of shelf-stable food products via advance research and development activities.