Response Surface Methodology (RSM) Optimization of the Physicochemical Quality Attributes of Ultraviolet (UV-C)-Treated Barhi Dates

Barhi date fruit is one of the most important fruits that has high consumer preference and market value at the Khalal maturity stage. However, this stage is very short and the fruit is vulnerable to decay and the ripening process under improper handling and storage conditions. Thus, the purpose of this study was to evaluate the feasibility of utilizing ultraviolet (UV-C) as a method to preserve the qualitative features of Barhi dates under various storage circumstances. The core of this study was defining the best conditions for UV-C treatment of Barhi dates, which was accomplished using a response surface methodology (RSM) model with a central composite, rotating four-factors-mixed-levels design (CCRD). The impacts of independent variables [UV-C exposure time (1, 2, 3, 4 min), UV-C dose (1, 3, 5, 7 kJ/m2), storage time (1, 6, 11, 16, 21 days) and storage temperature (1, 5, 15, 25 °C)] on the moisture content (MC), total soluble solids (TSS), total color changes (E), firmness, total phenolic content (TPC), total viable count (TVC), DPPH antiradical activity, fructose and glucose were investigated. The results revealed that the optimum UV-C treatment and storage settings for keeping the quality features of the dates were the UV-C exposure period and dosage of 1 min and 2.07 kJ/m2, and the storage time and temperature of 18 days and 12.36 °C, respectively. At the optimum conditions, the values of 59.66% moisture content, 38.24% TSS, 60.24 N firmness value, 48.83 ΔE, 0.07 log CFU/g TVC, 5.29 mg GAE/g TPC, 56.32% DPPH antiradical activity, 6.87 g/100 g fructose and 14.02 g/100 g glucose were comparable predicted values demonstrating the suitability of the used RSM models. Overall, the perfect UV-C treatment and storage circumstances for extending the storability and shelf life and maintaining the quality features of Barhi dates were identified in this study.