The Effectiveness of Extracts of Spent Grape Pomaces in Improving the Oxidative Stability of Grapeseed Oil

Spent grape pomace is a by-product of Grappa production that is usually considered waste. Therefore, in this study, in order to promote the sustainable use of by-products from the food industry, we aimed to optimize the extraction of antioxidants from spent grape pomace and their use to improve the oxidative stability of grapeseed oil. Ultrasound-assisted extraction maximized the total phenolic content and antioxidant activity, with the latter measured according to the ferric reducing antioxidant power. The best extraction conditions identified for spent grape pomace from red and white grapes were an amplitude of 40%, a duration of 22 min and a ratio of 1:37 and an amplitude of 40%, a duration of 25 min and a ratio of 1:45, respectively. Grapeseed oil, which is rich in polyunsaturated fatty acids and susceptible to rancidity, fortified with 10%, 20% and 30% of these extracts was evaluated in terms of its oxidative stability using the Rancimat method and compared with a control oil and an oil fortified with the synthetic antioxidant BHT at the highest legal level (200 ppm). For oil fortified with 30% of the extracts obtained from red and white pomace under the best conditions, increases in the induction time of 39% and 25% compared to the control and 23.01% and 10.62% compared to the BHT-fortified oil, respectively, were reported. This study highlights the potential of using grape pomace extracts as eco-friendly antioxidants to stabilize oil and contribute to the sustainability of the food industry at the same time.