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    Impact of UV-C and thermal pasteurization on bioactive compounds, sensory characteristics and aroma profile of traditionally produced koruk vinegar
    (M H Schaper Gmbh Co Kg, 2022) Gok, Sila Barut; Yikmis, Seydi; Levent, Okan; Karatas, Selen
    The aim of the study was to examine the effects of UV-C light applied by a designed reactor on bioactive components of traditionally produced koruk vinegar. Furthermore, microbial load, 5-HMF content, the volatile compounds, sensorial attributes and colour of vinegar were assessed. A reduction of 1.29-log CFUmL(-1) was achieved in total aerobic bacteria by applying a dose of 262.4 mJcm(-2). A total of 22 volatile compounds were determined in the traditionally produced vinegar. Among bioactive compounds, only total phenolic content changed significantly during UV-C treatment while antioxidant activity, total flavonoid and ascorbic acid content was not affected. Although the characteristic pungent sensation, aromatic intensity and richness in aroma of pasteurized vinegar significantly decreased, a non-significant difference in the sensorial properties was determined in all UV-C irradiated vinegar. UV-C treatment has potential for non-thermal pasteurization of koruk vinegar compared to thermal one due to the more preservative of its fresh-like characteristics.
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    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
    (Wiley, 2021) Yikmis, Seydi; Gok, Sila Barut; Levent, Okan; Kombak, Esengul
    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/cm(2) using a batch benchtop UV-C reactor and five different temperatures (40, 45, 50, 55, and 60 degrees 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 degrees C and 97.33 mJ/cm(2)) 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 (Delta E). 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.