Antimicrobial potential of unstressed and heat stressed Allium sativum

Garlic (Allium sativum) is generally known to be of medicinal value, possessing potentials that include antimicrobial activity, but are often consumed in foods after subjection to cooking heat. The antimicrobial potential of heat stressed garlic may become decreased or lost when cooked, making its medicinal benefit unavailable to consumers. The potential of uncooked and cooked extracts from garlic imported to Jamaica, to inhibit the growth of eight microbes of clinical significance was investigated. Aqueous extracts of fresh garlic of 15 g/100 ml (fw), and dried and pulverized garlic cloves of 12.5 g/100 ml, 25 g/100 ml, 50 g/100 ml, and 100 g/100 ml (dw), were tested for inhibition of microbial growth. Extracts were tested uncooked, and cooked by boiling for 5, 10, and 15 min respectively. Of all the microbes studied, C. albicans incurred the largest zone of inhibition (57.7 ± 0.6 mm at the 100 g/100 ml of the dried extract, F(3, 8) = 51.778, p < 0.001, ω² = 0.93). Cooking of garlic extracts resulted in statistically significant decreases in zones of inhibition of microbes, as evident in the linear regression and one-way ANOVA analyses, and/or complete loss of microbial inhibition. C. albicans was the most inhibited microbe, followed by E. coli, and Salmonella sp., respectively. The use of uncooked garlic may be the best route for obtaining the greatest antimicrobial potential of garlic against susceptible bacteria and fungi because cooking heat stress resulted in the decrease and complete loss of the antimicrobial potentials of the garlic.