Rheological, Physico-chemical and Sensorial Attributes of Stirred Yoghurt with Irradiated and Autoclaved Thyme

In this study, T. vulgaris was disinfected, either with autoclave (A) and irradiation (I), and was added to stirred yoghurt with amount of 0 (as control), 0.25 and 0.50 g/100 cc as powdered (P) and granule (G). Sensorial attributes (3 and 15 days), physico-chemical characteristics, (1, 3 and 15 days) and Rheological parameters were evaluated. Statistical analysis showed that the addition autoclaved or irradiated Thyme, as powdered or granule, had no effect on physico-chemical properties. But, depend on the way of disinfection and the amount of added Thyme, sensorial attributes changed. Due to sensorial analysis, the samples IP1 and IG1 with 0.25 g Thyme were the best samples. Rheological test indicated that there were some differences between elasticity of samples with 0, 0.25 and 0.50 g Thyme/100 cc, but there was not any differences between powdered autoclaved and irradiated samples with the same amount of Thyme, such results was shown in the granulated autoclaved and irradiated samples. The type of Thyme, as powdered or granulated, the amount of Thyme, and the shelf life of samples had significance effect on the rheological parameters. In this respect, the viscose (G'') and elastic (G') moduli changed significantly and thus loss tangent (tan (δ)) decreased. In this regard, the addition of Thyme as IP (0.25) and IG (0.25) is recommended as the best treatment.