Microwave heating induces changes in the physicochemical properties of baru (Dipteryx alata Vog.) and soybean crude oils

Baru oil is extracted from baru nuts (Dipteryx alata Vog.) by cold mechanical pressing, and is exploited as a source of vitamins, fatty acids and antioxidants in the Brazilian food and pharmaceutical sectors. No information is available on this oil under domestic culinary processes and thermal conditions. So, in the present study we evaluated the response of crude baru oil under microwave heating (0, 1, 3, 5, 10, and 15min), using crude soybean oil as comparison. Physical and chemical parameters were evaluated (free acidity, peroxide value, specific extinction coefficient at 232 and 270nm, K and color by CIELAB method), fatty acid profile, tocopherol composition, antioxidant activity, and oxidative stability. Until 3min (1000W) no significant adverse changes were observed in either oil. However, higher exposition times are more adverse to baru oil than to soybean oil. Tocopherols, oils stability and antioxidant activity drop abruptly. The typical yellow coloration is lost with heating, giving a less appealing appearance to the oils. By a principal component analysis, it was verified that microwave heating differently influenced each oil, and within the same oil, exposure time also caused distinct effect on properties, quality, and composition. Based on the obtained results, we discourage the use of baru oil for culinary process. Practical applications: The use of baru oil for prolonged culinary processes is discouraged due to lower stability and low content in antioxidants. Baru oil is more suitable for seasoning for usage in domestic consumption at RT. Exposure to microwave heating is completely discouraged at an exposure higher than 3min.