الملخص الإنجليزي
The anti-microbial activity of a range of garlic products including dried garlic powder produced by different methods, commercial garlic products, and garlic oil on selected bacteria was studied. The types of bacteria were foodborne pathogens and spoilage, and health-beneficial agents, namely Staphylococcus a ureus, Escherichia coli, Salmonella typhimurium, Bacillus cereus and a mixed lactic culture consisting of Lactobacillus bulgaricus and Streptococcus thermophillus. The dried powders were produced using air-drying at 60 and 80°C, vacuum-drying 50 and 60°C, and freeze-drying methods. Five commercial products were tested, two of which are used as spices, and three others that are used as food supplements. All the powder product's moisture contents were raised to the moisture content of fresh garlic before testing the inhibitory activity. Garlic oil was used without any addition of water. The results showed that growth of lactic culture was more sensitive compared to the other types of bacteria considered in this study. Bacillus cereus and Staphylococcus aureus appeared to be most sensitive while Salmonella typhimurium demonstrated the greatest resistance to garlic. In all cases fresh garlic showed highest inhibition followed by freeze-dried powder. The active components were above the concentration required for inhibition up to a 90% water content. The results showed that both drying temperature and time have major roles in retaining the active components causing the inhibition of microbial growth. The anti-microbial substances in the moist fresh garlic were also affected by heating temperature and time. Higher heating temperature caused faster reduction of the active components in fresh garlic responsible for anti-microbial activity. The decrease in growth inhibition zones was modeled with zero-order kinetics.
