Effect of ultrasound treatment in fresh apple juices from different cultivars

Abstract

The sonication process is based on the cavitation phenomenon, which allows the extraction of target compounds, homogenization of solutions, and breakdown of plant cells. Thus, this paper aimed to assess the effect of ultrasound treatment in fresh apple juice to control the enzymatic browning effect. Three different apple varieties, Gala, Fuji and Argentina, were used to extract the juices, and were then subjected to ultrasound treatment for 0, 5, 15, and 30 minutes. Total soluble solids, citric acid content, pH, phenolic compound concentration, and color aspects were evaluated. Argentina apple variety had higher total soluble solids and pH values, with no visual differences between treatments. In contrast, ultrasound treatment of the fuji apple had a statistical difference to the control sample, regarding citric acid content. The analysis of the L* parameter, representing luminosity, showed slight variations ranging from 24.78 to 28.27 in all samples, with no significant differences observed among different treatment durations. Furthermore, the a* parameter showed a significant difference only for the Gala apple in the 0 and 5 min treatment. The b* and Chroma value was higher in Argentina variety (5.78 to 7.05 and 6.08 to 7.42, respectively) than in Fuji and Gala. On the other hand, a statistical difference was observed in the °HUE in Gala variety, faced to Fuji and Argentina. The content of phenolic compounds in the apples’ varieties remained unaltered by ultrasound treatment, with values ranging from 52.47 to 116.23 mg of gallic acid equivalent L-1. These unexpected results indicated no significant variations between the sonification durations in the evaluated parameters. Thus, it is suggested that a new ultrasound procedure utilizing a probe and/or temperature control may be more effective in diminishing the enzymatic browning effect.