Type of heat treatments on walnut fruits affects physicochemical content of walnut butter

The experimental material was walnut butter obtained from walnut fruits subjected to baking, roasting, and heating in the microwave field. It was found that heat treatment of walnut fruits increased the contents of fat, antioxidant capacity, total polyphenol content, color and tocopherol content in walnut butter. Butter prepared from the microwaved walnut fruits was characterized by the lowest hardness (0.16 N), adhesiveness (0.03 mJ), and gumminess (0.15 N). The content of total polyphenols was the highest in butter from the microwaved walnut fruits (970.2 mg GAE/100 g d.m.) and the smallest in the raw walnut butter (557.9 mg GAE/100 g d.m.). In the polyphenol profile, 18 compounds were identified, mainly from the ellagitannin class. Their content ranged from 2.68 mg/g DM (raw) up to 7.55 mg/g d.m. (microwayed) depending on the heat treatment applied. In turn, four tocopherol isoforms: α, β, γ, and δ were identified. Practical applications In the world, the raw material for the production of peanut butter are hazelnuts. In contrast, walnuts compared to hazelnuts are much more valuable under the nutritional value, and the cream based on them has interesting sensory properties. In addition, health-related properties and quality of walnut-based butter may depend to a large extent on the type of heat treatment the nuts have undergone. Therefore, the authors of the study decided to investigate this issue. The results of the research described in the article can be used to develop a new food product.