Comparing the Oil Extraction and Refining Methods for Muscadine Grape Seeds of Noble and Carlos Cultivar

Abstract

Muscadine is a native grape species in the southeastern United States. It has a distinct nutrient composition compared to Vitis vinifera grapes. Most Muscadine grapes are made into wine due to the lack of seedless cultivars, which results in a large amount of Muscadine seeds in the pomace. Muscadine pomace from purple Noble grapes and bronze Carlos grapes are dried and seeds are separated. Seed oils are extracted using a Soxhlet extractor by hexane, mechanical pressing, or enzyme‐assisted aqueous extraction. Oil extraction efficiencies are assessed using yield by dry weight. Oil quality is evaluated by peroxide content, free fatty acid content, fatty acid composition, and tocopherol and tocotrienol content. Extracted seeds oils are refined by degumming, neutralizing, and bleaching. Hexane extraction gives significantly higher yield from both Noble and Carlos seeds followed by mechanical expression and enzyme‐assisted aqueous extraction, respectively. Linoleic acid accounts for 72–79% total fatty acid for all oils. Concentrations of tocopherol and tocotrienol in Noble seed oil ranges from 29.4 to 53.8 mg 100 g−1 and 25.3–44.3 mg 100 g−1, respectively. Concentrations of tocopherol and tocotrienol in Carlos seed oil range from 11.8 to 31.9 mg 100 g−1 and 25.3–33.4 mg 100 g−1, respectively. Refining the oil removes peroxides and free fatty acids without altering fatty acid composition but eliminates 44–100 and 11–95% of tocopherols and tocotrienols, respectively.Practical Applications: Muscadine grape seed oil is high in linoleic acid and antioxidant components, making it an ideal product for culinary, and cosmetic purposes. The unrefined oil is high in tocopherol and tocotrienol, shown to have anti‐adipogenic and anti‐inflammatory capabilities. Grape seed oil is ideal for cooking at high temperatures, with a smoking point of about 190–230 °C being reported before. Grape seed oil is also useful in cosmetics where its hydrophobic nature and antioxidant components could be utilized in skin care products.In this study three different extraction methods are used to obtain oil from muscadine grape seeds of the Noble and Carlos cultivar. In this work, the oil yield efficiencies, peroxide values, free fatty acid content, fatty acid composition, and tocopherol and tocotrienol content are measured in the oil before and after a refining process. In this study, it is found that different extraction methods as well as the refining process, affect the tocopherol and tocotrienol content of the muscadine grape seed oil.