Moderate temperature and UV‐C light processing of Uruset apple juice: Optimization of bioactive components and evaluation of the impact on volatile profile, HMF and color

In this study, the aim was primarily to optimize the process conditions for the enrichment of bioactive components in Uruset apple juice with UV‐C light and moderate heat treatment. UV‐C light was applied to Uruset apple juice at five different UV‐C doses between 84.6 and 169.1 mJ/cm² using a batch benchtop UV‐C reactor and five different temperatures (40, 45, 50, 55, and 60°C). Total phenolic content (TPC), total flavonoid content (TFC), total antioxidant capacity (1,1‐diphenyl‐2‐picrylhydrazyl [DPPH]), cupric reducing antioxidant capacity (CUPRAC), ascorbic acid and total anthocyanin content (TAC) were evaluated for optimization (response surface methodology) of process conditions. The effect of moderate temperature‐UV‐C light (40°C and 97.33 mJ/cm²) on the HMF (hydroxymethylfurfural) content, optical microstructure and color value of the Uruset apple juice (UUA), fresh Uruset apple juice (FUA) and pasteurized Uruset apple juice (PUA) were then evaluated. At the end of the optimization, TPC (852.83 mg GAE/L), TFC (539.91 mg CE/L), DPPH (71.97%), CUPRAC (79.17%), ascorbic acid (5.96 mg/100 mL), and TAC (211.71 mg/L) were determined. The PUA sample obtained a higher score than the UAA sample in terms of total color change (ΔE). As a result, UV‐C light and moderate heat treatment of Uruset apple juice was found to be successful. PRACTICAL APPLICATIONS: Fresh apple juices are important sources of bioactive components such as phenolics, carotenoids, vitamin C, and organic acids. The results provided in the study by the combination of moderate heat and UV‐C light could be suggested as an alternative pasteurization process in order to prevent and/or reduce the negative effect on nutritional and sensorial properties of juice of using the heat pasteurization process alone. The number of studies related to preservation of fresh apple juice in terms of Uruset apple variety is fairly limited. Furthermore, the reactor used in the study could be transferred to the fruit juice industry after a scaling‐up feasibility study.