Operational parameters of the Rancimat method, including oil sample size, airflow rate, and temperature, were evaluated to determine their effects on the oxidative stability index (OSI), temperature coefficient, Q10 number, and shelf-life prediction for soybean oil. Operational parameters of the Rancimat method had statistically significant effects (P < 0.05) on the OSI. Whenever the oil sample size and airflow rate at a given temperature were such that the airsaturated condition could be established, the OSIs showed no statistically significant differences. As temperature increased, OSIs decreased, while their average coefficient of variation (CV) increased. In general, the conditions where the sample was saturated with air and had a relatively lower CV were an oil sample size of 6 g at all temperatures and airflow rates, then 3-g oil sample size at low temperatures (100 and 110 C) and low airflow rates (10 and 15 L h–1). The temperature coefficient and Q10 number were found to be independent of the oil sample size and airflow rate, and their mean values for soybean oil were calculated to be –3.12 · 10–2 C–1 and 2.05, respectively. Oil sample size and airflow rate showed a significant effect on shelf-life prediction for soybean oil. Therefore, choosing the right levels of these operational parameters in the Rancimat method may produce the least possible difference between predictions from long-term storage studies and the OSI test.

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