Abstract
The phenomenon and kinetics of the ethanol extraction of canola oil from microwave-pretreated seeds was studied using a Fick’s diffusion model. The extraction was performed in a batch system at constant temperature (313–333 K) at different times (300–64 800 s); then the total solvent-free extracts (SFE) were washed with hexane, obtaining oil as a hexane-soluble fraction (HSE) along a hexane-insoluble fraction. The values of the fitted parameters were different from those obtained by hexane extraction, showing an influence of the solvent on the kinetic parameters. A comparison of SEM images of pre-extracted, post-extracted with ethanol and post-extracted with hexane meals showed a dilution of the structural matrix with ethanol, not observed in post-extraction samples with hexane. This would indicate that a microwave-pretreatment is not necessary for the ethanol extraction of canola oil under the studied conditions, although it is important for breaking seed structures to facilitate the conventional extraction with hexane.
Highlights
Canola oil is a vegetable oil considered nutritionally balanced, with a good linoleic/linolenic acid ratio (2:1), and healthy due to its high content of phenolic compounds (6.3– 18.4 mg/g in defatted meal; Kozlowska et al, 1990)
At a temperature of 313 and 323 K, the oil yields extracted with hexane were significantly higher than the hexane-soluble fraction (HSE) fraction extracted with ethanol for all times, whereas at 333 K no significant differences were detected after 7200 s
Extraction capacity for ratios lower than 1:10 (Thobani and Diosady, 1997). These results show that using an adequate solid:solvent ratio for the extraction with ethanol can allow to obtain yields equivalent to those obtained with hexane from microwave-pretreated samples, without the need to apply any microwave pretreatment
Summary
Canola oil is a vegetable oil considered nutritionally balanced, with a good linoleic/linolenic acid ratio (2:1), and healthy due to its high content of phenolic compounds (6.3– 18.4 mg/g in defatted meal; Kozlowska et al, 1990). The used solvent in the industry is hexane, since it is stable, and presents a high solubilizing power and a convenient boiling point that favors its recovery (Sicaire et al, 2015). This solvent obtained from fossil fuels is highly flammable, and causing negative effects on health and the environment (Sánchez et al, 2018a, b). The meal obtained after the extraction must be desolventized for later use (protein concentrates, animal feed), a process that involves solvent losses and a high energy cost
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