Nonthermal pasteurization of onion juice by continuous UV‐C reactor

Abstract

AbstractThe objective of this study is to investigate the continuous pasteurization of onion (Allium cepa L.) juice by ultraviolet (UV‐C) irradiation by a designed coiled‐tube type UV‐C reactor. System is composed of four vertical low‐pressure mercury lamps (20 W/lamp, 254 nm) coiled using a PTFE tube. A secondary eddy flow effect was achieved with a Dean number of 0.073. The Escherichia coli K‐12 count in onion juice was reduced by 4.83 log after exposure to UV‐C light for 8.13 min at an estimated UV‐C dosage of 38.1 J/mL with the flow rate of 1.26 L/min. After UV‐C treatment, the total color change (ΔE) of the onion juice was recorded as 1.15 which can be referred as slightly noticeable. Total aerobic mesophilic count of UV‐C irradiated samples was below acceptable limits after 6 weeks of storage. Meat marination in UV‐C‐treated onion juice reduced the hardness of meat by 78%.Practical applicationsCurrently, many of the large‐scale processed meat producers prefer to marinate the meat directly in the onion juice or in a sauce formulation including onion juice. Therefore, they are the major end‐users of this product. In addition, onion juice has a large potential to be used by the catering industry providing food service for relatively large number of people. If the storage space for onions, the preparation, and service time for the meals are taken into consideration, catering services may highly benefit from the pasteurized onion juice products. Conventional heat treatment is the most common method to extend shelf‐life of vegetable juices. The results of this study indicated that continuous UV‐C irradiation can successfully be used to pasteurize onion juice. The outcomes will also serve the basis to technical knowledge for designing the pilot‐scale production of onion juice processed by nonthermal treatments.