Investigation on the usage of UV-C irradiation process in onion juice pasteurization

Onion (Allium cepa L.) juice is a by-product of onion paste production and onion roasting processes. After the size reduction and grinding steps of these processes, 10-40 % (w/w) of onion is extracted and discarded as onion juice. On the other hand, it can be freshly prepared and used as marinade by the large-scale producers of meat products such as doner kebab. However preparation of onion juice is a time and manpower consuming process requiring a temperature controlled storage space for onions. The continuous supply of onion is also a problem because it is a seasonal plant. With the aim of solving these problems and adding value to a by-product this study aims to pasteurize the onion juice and extend its shelf life by means of ultraviolet (UV-C) irradiation. For this purpose, irradiation time, UV incident intensity, and juice depth factors on the microbial inactivation parameters were optimized using experimental design and statistical analysis which was resulted in 4.02 ± 0.17 log inactivation of E. coli K-12 with the UV dose of 6374.5 mJ/cm2. This part was followed by studies on the effect of UV-C irradiation on the microbial shelf life, textural, sensorial and some physicochemical properties of onion juice.