The Effect of Roasting on the Health-Promoting Components of Nuts Determined on the Basis of Fatty Acids, Polyphenol Compounds, and Antioxidant Capacity

This study focused on analyzing the direction of changes in recognized health-promoting fatty acids, antioxidant activity, and total polyphenolic compound in the three most popular types of nuts, hazelnuts, walnuts, and peanuts, before and after roasting under various conditions. The roasting process caused changes in the content of selected health-promoting fatty acids in the tested nuts, which depended on both the type of nut and the roasting conditions used. The main fatty acids in walnuts are linoleic acid and α-linolenic acid, while in peanuts and hazelnuts, oleic acid was the main fatty acid. The highest losses of these acids were observed after convective roasting, and the lowest after microwave roasting with a protective coating, which promoted better preservation of these acids in the nut fat. Walnuts exhibited a relatively high antioxidant potential, which was greater than the level in peanuts and hazelnuts. Roasting (regardless of its type) increased the antioxidant potential of all tested nuts. Microwave roasting seems to be a good option in the search for optimal process conditions for the protection of health-promoting ingredients, especially since the processing time is significantly shortened.