Use of ultrasonication assisted ultraviolet-C light treatment for microbial inactivation in apple juice and its effects on some quality attributes of the product

In this study, use of ultrasonication (US) assisted ultraviolet (UV-C) light treatment instead of tarditional pasteurization process for microbial inactivation in apple juice and determination of its effect on some quality parameters of apple juice [pH, °Bx, total antioxidant activity value, total phenolic compound and total flavonoid content, color (L*, a*, b*, C, C, Hue angle° and E) and browning index (BI) value] were aimed. To determine the effectiveness of combined US(Continue+Pulsed)+UV-C treatment on microbial inactivation, commercially available apple juices were inoculated with Escherichia coli O157:H7 at a ratio of 10:1 and the microbial inactivation level was determined after the treatment. In the study, a reduction of 5,04±0,66 log units was obtained in the number of E.coli O157:H7 by consuming 224255 J US energy as a result of 40 minutes of US (C+P)+UV-C treatment at 140W power. Application of US(C+P)+UV-C treatment for 40 min caused a decrease in pH values of apple juice samples (p<0,05). It was found that US(C+P)+UV-C application at 140 W power in two different times (35 and 40 minutes) caused a decrease in the total antioxidant activity value, total phenolic and total flavonoid compound contents of apple juices (p˂0,05). The application of US(C+P)+UV-C treatment at different times did not cause a significant change on the L* values of the apple juice samples (p>0,05), while it caused a negative increase in the b* values of the samples. With the application of US(C+P)+UV-C treatment for 40 minutes, the C* and BI values of the samples increased significantly (p˂0,05). The application of US(S+V)+UV-C treatment to apple juice samples did not have a statistically significant effect on the hue angle values of the samples. In this study, it was observed that the ΔE value of apple juice samples that were treated with US(C+P)+UV-C at different times was at a level (below 1) that could not be perceived by consumers. The results of the study show that the combined use of US(C+P) (140 W) and UV-C light for 40 minutes can be an important alternative for the pasteurization of apple juices.