Effects of thermosonication pretreatment on the physicochemical and sensory properties of grape juice obtained from Kösetevek grapes

Kösetevek grape is a significant indigenous black grape variety with colored pulp, grown in the Eastern Anatolia Region of Türkiye. Mash heating (MH) is commonly used in grape juice production. However, to better preserve phenolic, aroma, and nutritional components, Thermosonication (TS) process is utilized as an alternative technique. The aim of this study was to determine the effects of TS conditions on the physicochemical and sensory properties of grape juice obtained from Kösetevek grapes. Grape juice underwent TS at various temperatures and ultrasound energy density (UED) levels, followed by an optimization study using Response Surface Methodology (RSM). Grape juice samples were analyzed for total phenolic content (TP), total monomeric anthocyanins (TMA), antioxidant activity (FRAP and DPPH), polymeric color ratio (PCR), color difference (ΔE*), and extraction yield. The optimum TS conditions were determined as 801.99 J/g UED and 43.5 °C (desirability value = 0.595). Under optimal conditions, anthocyanin profiles were characterized by HPLC, aroma compounds were identified using GC–MS, and sensory properties were evaluated by descriptive analysis. TS resulted in a significant increase in TP and TMA content. The ΔE* value was lower, suggesting that the product's natural color was better preserved. TS enhanced the phenolic content and yield of the grape juice while also contributing to the preservation of color and sensory properties. TS juice contained the highest concentrations of aroma compounds, particularly C6 compounds and higher alcohols. This characteristic made TS more effective at preserving fresh aromas compared to MH, which generated cooked odors. Overall, TS has the potential to be applied as an alternative to or together with traditional thermal processes in industrial production.