Effect of thyme (Thymus vulgaris L.) essential oil on the quality parameters of stirred yoghurt

Abstract

Aim Stirred yoghurt was supplemented with thyme essential oil in an attempt to enhance its quality. Materials and methods Thyme (Thymus vulgaris L.) essential oil concentrations (0, 2, 4, 6, 8, and 10 μl/ml) were added to the prepared stirred yoghurt and then examined for microbiological count and mycotoxin quality during storage intervals following the Egyptian standards. Results Samples contained ≥ 6 μl/ml oil showed significant increase (p<0.05) of total viable bacterial count and lactic acid bacteria, whereas mold and yeast count was decreased. Pathogenic bacteria including Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Salmonella spp., Escherichia coli, and coliform group were not detected in any of the samples, which complied with the standards. Moreover, aflatoxin M1 content was reduced by time in direct proportion to the thyme essential oil concentration. Conclusion The bioactive components in thyme act as a natural preservative in stirred yoghurt throughout the storage interval when the yogurt is fortified with hydro-distilled thyme essential oil.

Keywords

• stirred yoghurt
• thyme essential oil
• microbiology