The effect of batch system ultraviolet light application on the mold growth and the quality of yoghurt

Mold growth is an ongoing problem during the storage of yoghurt. In the study, it was aimed to determine the effect of batch system UV-C light application on the mold growth and the quality of yoghurt both after application and both during storage. The research was carried out in two stages. In the first stage, 0,321-19,26 kJ/m² doses of UV-C lights (254nm) were applied on homogenized and creamy yoghurt surfaces with the batch system. And their effects on mold inactivation, lipid oxidation level, color, hardness, and sensory properties were determined. In the second stage, UV-C light was applied to homogenized yoghurt surfaces at the doses determined in the previous stage (0,321-1,926 kJ/m²). The effects of batch system UV-C light application on the shelf life of yoghurts were determined by evaluating mold growth, lipid oxidation and sensory properties during 21 days of storage. UV-C light application was found to be effective on the mold count and 2,18 log decrease was obtained compared to the control group in homogenized yoghurt by application of 1,926 kJ/m² dose. And at the creamy yoghurt, 1,2 log reduction was achieved compared to the control group by application 5,778 kJ/m² dose. With UV-C light application, it was revealed that surface moldiness problem can be significantly reduced in homogenized and creamy yoghurts however high doses of UV-C light applications cause lipid oxidation and sensory foreign flavor. In this study, it is concluded that the UV-C light application dose is important because of the foreign flavor formation and this application will not be an alternative to good hygiene practices (GHP) and it will be appropriate to use it as a support.