Investigation of Antioxidant and Antimicrobial Properties of Garlic Peel Extract (Allium sativum) and Its Use as Natural Food Additive in Cooked Beef

Aims: To investigate the antioxidant and antimicrobial properties of garlic peel extract and its possible use as natural food additive in cooked beef
Study Design: Multifactorial Design
Place and Duration of Study: Department of Food Science and Technology, Federal University of Technology, Akure, Ondo State, Nigeria between August 2011-September 2012.
Methodology: Crude ethanolic extract from garlic peel was investigated for its total phenol content (TPC), according to Folin-Ciocalteu method and calculated as Gallic Acid Equivalent (GAE), while the flavonoid content was determined using the AlCl3 colorimetric method and expressed as Quercetin Equivalent (QE). In addition, antioxidant test was carried out using 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay. The crude extract at different concentrations (2.7mg/ml, 5.4mg/ml and 10.8mg/ml) were incorporated into minced beef, cooked in the microwave, inoculated with selected bacteria (Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Bacillus cereus, and Proteus vulgaris) and stored at 4°C for 9 days. The effects of garlic peel crude extract on lipid peroxidation and microbial growth was then evaluated.
Results: The results obtained showed that garlic peel extract added to the beef was able to lower the pH of the beef significantly when compared with the control. Furthermore, garlic peel crude extract demonstrated antioxidant activity which lowered thiobarbituric acid-reactive substances (TBARS) (mg malonaldehyde/kg muscle) from 11.23 in control meat sample to 2.62 in sample treated with 10.8mg extract on day 9. Antibacterial activity of the extract against tested bacteria inoculated into the cooked beef revealed that at a concentration of 10.8mg of extract/100g of meat, the extract reduced the bacterial population (Staphylococcus aureus, Escherichia coli and Proteus vulgaris), by at least one log compared to control at 9days of storage.
Conclusion: Garlic peel ethanol extract demonstrated both antioxidant and antibacterial activities in cooked beef.