Multi-factor optimization of canola oil deodorization parameters and evaluation of linolenic acid isomerization kinetics during pilot-scale deodorization

Abstract

In this study, neutralized and bleached canola oil, deodorized according to the central composite design consisting 30 experiments with differing levels of deodorization temperature, pressure, stripping steam rate and duration to optimize process parameters and evaluate isomerization kinetics of linolenic acid. Free fatty acid (FFA) content, oxidation stability index (OSI), peroxide value, total polar compounds, tintometric redness, fatty acid composition of every deodorized canola oil sample were measured. Deodorization parameters were optimized by aiming the lowest FFA, trans-linolenic acid (tr-C18:3) content, highest OSI value and polyunsaturated fatty acid (PUFA) content via response surface methodology. Optimum temperature, pressure, stripping steam, and duration were calculated as 228.8 °C, 1.4 mBar, 1.25 g/min and 80 min, respectively. FFA level, OSI, tr-C18:3 content, and PUFA content was predicted as 0.044%, 10.65 h, 0.21% and 30.50% by the optimization model. The relative difference between the results of the validation experiments and optimization model predictions was differed between 7.04 and 14.49%. Temperature and duration of deodorization were found significantly effective (p < 0.05) on trans isomerization of linolenic acid according to ANOVA, therefore reaction rate constants of tr-C18:3 formation and cis-linolenic acid (cis-C18:3) degradation were calculated with Arrhenius’ equation using graphical method. Activation energies were calculated with Arrhenius’ equations as 346 kJ/mol for cis-C18:3 deterioration (R2 = 0.92) and 183 kJ/mol for tr-C18:3 formation (R2 = 0.99). Cis-C18:3 degradation and tr-C18:3 formation rates were found as 0.0032 min−1 and 0.0014 min−1 at 220 °C, 0.0049 min−1 and 0.0024 min−1 at 225 °C, 0.0172 min−1 and 0.0034 min−1 at 230 °C, respectively.