Oxidative stability of crude oils relative to tocol content from eight oat cultivars: Comparing the Schaal oven and Rancimat tests

Abstract

Oats are a good source of oil containing polyunsaturated fatty acids and natural antioxidants such as tocols. This study investigated tocol composition relative to oxidative stability in crude oils from eight oat cultivars. Tocol content in the cultivars was as follows: Santini > Saul > Korok > Atego > Kamil > Patrik > Oliver > Marco Polo. Santini had the highest tocol content (155.3 mg/kg of oil), whereas Marco Polo contained only 62.0 mg/kg of oil. Extracted oat oils were subjected to the Schaal oven test at 60 ± 2 °C and the Rancimat test at 100 °C and 110 °C to determine oxidative stability. The induction period of oat samples ranged from 51 to 56 days in the Schaal test, with a protection factor of 7.8–8.6. The Rancimat test yielded induction periods ranging from 3.78 h to 9.31 h at 100 °C and 1.11 h to 4.25 h at 110 °C. Both tests revealed remarkable stability against oxidation. Therefore, oat oil, particularly from the Santini cultivar, could be a valuable and stable source of natural antioxidants for the food and pharmaceutical industries. However, a significant correlation between Schaal-derived induction period and tocopherols or tocotrienols was not identified. This outcome indicates that oil stability is due to more than tocol presence, with other antioxidants in the crude oil likely playing important roles. In contrast, the Rancimat test revealed that β-tocotrienol content was correlated with induction period at both temperatures 100 °C and 110 °C.