Multipurpose 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
time parameters. Free fatty acid (FFA) content, oxidation stability
index (OSI), peroxide value (PV), total polar compounds (TPC),
tintometric redness, fatty acid composition of every deodorized canola
oil sample was measured. Deodorization parameters were optimized using
only responses with good model fit by aiming lowest free fatty acid and
trans-linolenic acid (tr-C18:3) contents and highest OSI value and
polyunsaturated fatty acid (PUFA) content via Response Surface
Methodology. Optimum temperature, pressure, stripping steam, and time
were predicted as 228.8°C, 1.4mBar, 1.25 gr/min and 80 minutes,
respectively and the optimization model has predicted the FFA level to
be 0.044%, OSI as 10.65h, tr-C18:3 content as 0.21% and PUFA content
as 30.50%. Results of the validation experiments at this optimum point
were close to the those predicted and the relative differences between
predicted and validation results were within the variance coefficients
of each model. Temperature and time of deodorization were found
significantly effective on trans isomerization of linolenic acid on
ANOVA, therefore the reaction rate constants of tr-C18:3 formation and
cis-linolenic acid (cis-C18:3) degradation were calculated together with
Arrhenius’ equation constants using graphical method. Cis-C18:3
degradation rate was higher than that of tr-C18:3 formation showing;
besides isomerization, different decomposition mechanisms took place for
possibly not only for linolenic acid but also for all polyunsaturated
fatty acids of canola oil during deodorization.