Effect of sonication treatments on quality attributes of apple-carrot juice

In current study, a mixture of apple and carrot juice prepared at a ratio of 60:40 was processed with traditional pasteurization (PAS) at 90 °C for a min, ultrasonication (US) for 30 min and thermosonication (TS) at 40 °C, 50 °C and 60 °C for 30 min. The collected apple-carrot juice mixture were stored at both room temperature (25±0.5 ºC) and cold storage (4±0.5 ºC) for 28 days. The quality and microbiological analyses of control (untreated), PAS, US and TS-treated samples were performed on days 0, 14 and 28. It was determined that the shelf life of apple-carrot juice samples processed with different treatments at room temperature (25±0.5 ºC) and cold storage (4±0.5 ºC) enhanced at the end of storage period except for US-treated samples on 14th and 28th days and TS-treated samples at 40°C on 28th at room temperature. The initial total phenolic content of samples was increased compared to the control samples by sonication treatments. After 28 days of storage, a general decrease was observed in the total phenolic content of the samples and PAS samples were resulted with the lowest total phenolic content among the others. The antioxidant capacity of treated apple-carrot juices were shown an increase compared to the control samples. It was determined that TS-60 °C sample stored at both 4 °C and 25 °C after 28 days of storage preserved its antioxidant capacity (p>0.05). While the lowest total carotenoids were determined in PAS and TS-60 °C samples, the highest total carotenoid was found in US-treated sample. The total amount of carotenoids increased after 28 days of storage in all samples and the TS-60 °C sample showed the highest increase. There was a decrease in the ascorbic acid content of all samples compared to the control samples except for the US sample, and the most ascorbic acid loss was determined in PAS sample. While the highest HMF values were found in PAS samples, it was determined that the HMF values increased with higher temperature in sonication process. While the increase in HMF values of the samples during 28 days of storage at 4 °C was not significant (p>0.05), the increase at 25 °C was significant (p<0.05). It was determined that there was no significant change in the browning index of sonication (except TS-60 °C) and PAS samples compared to the control (p>0.05). L*, a* and b* values of treated samples showed a significant difference compared to the control samples (p<0.05). While the L* value of the samples decreased at the storage, the a* and b* values increased. Total color change (ΔE) was increased in all treatments compared to the control. It was determined that the color change in thermosonicated samples was less than PAS. While the brix values of sonication-treated apple-carrot juice samples were shown a significant increase (p<0.05), the pH values showed a decrease except for TS-40 °C. While the titratable acidity showed a decrease (p<0.05) in PAS and TS-40 °C samples, the differences in other treatments was not significant (p>0.05). While the pH values of PAS and thermosonicated samples showed an increase, brix values of theses samples showed a decrease at storage period. In addition, a decrease in titratable acidity of TS-50 °C and TS-60 °C samples was determined at storage. With the application of PAS and thermosonication (TS-40 °C, TS-50 °C, TS-60 °C) treatments, bacteria and yeast-mold were not observed in the samples on day 0. A significant level of inactivation was achieved. No significant differences were observed between sonicated samples and control (p>0.05) for sensory evaluation of apple-carrot juice samples while a significant difference was determined for PAS sample (p<0.05). While the TS-50 °C sample was determined as the most liked sample, the PAS sample was determined as the least liked sample.