The Role of Microwave and Oven Roasting on Oil Contents, Bioactive Properties, Phenolic Components, Fatty Acids and Mineral Contents of Grape (Vitis spp.) Seeds

In this study, the role of roasting on the total phenol, antioxidant capacity, phenolic constituents and fatty acid profile of the grape seeds was investigated. Total phenolic and flavonoid quantities of the grape seeds roasted in microwave (MW) and conventional oven (CO) systems were recorded between 673.57 (control) and 713.57 (MW) to 7121.67 (MW) and 7791.67 mg/100 g (CO), respectively. Antioxidant activities of the grape seeds varied between 6.57 (MW) and 7.24 mmol/kg (control). Catechin and rutin quantities of the grape seeds were recorded to be between 435.30 (CO) and 581.57 (control) to 94.94 (CO) and 110.53 mg/100 g (MW), respectively. While gallic acid amounts of the seed samples are established between 21.06 (control) and 101.79 (MW), quercetin values of the grape seeds were assigned to be between 56.59 (control) and 77.81 mg/100 g (CO). In addition, p-coumaric acid and resveratrol quantities of the grape seeds were recorded between 15.43 (control) and 22.98 (CO) to 12.50 (CO) and 29.57 mg/100 g (MW), respectively. The main fatty acids in oil samples were linoleic, oleic, palmitic and stearic acids in decreasing order. Linoleic and oleic acid values of the oils provided from grape seeds were recorded to be between 72.75 (control) and 73.33% (MW) to 14.79 (CO) and 14.87% (MW), respectively. It was observed that the element results related to the grape seed differed based on the roasting type when compared to the control. The most abundant elements in the grape seed were K, P, Mg, S, Na, Fe, Ca, Zn, and K and P amounts of the grape seeds were reported to be between 6706.93 (MW) and 7089.33 (control) to 2764.27 (CO) and 2927.97 mg/kg (control), respectively. It is thought that it would be beneficial to add grape seeds to foods as an ingredient by taking into account these phytochemical components as a result of the applied heat treatment.