Optimization of Microwave Pretreatment Variables for Canola Oil Extraction

Abstract

The influence of microwave pretreatment on the oil yield (solvent extraction) and oil quality of canola was studied. Response surface methodology was used to analyze the variables of microwave pretreatment, working with two microwave powers 80 and 100% (457 and 607 W, respectively, referred absorbed power of 1 L of water). The independent variables were initial moisture content (5–10% dry basis) and pretreatment time (10–350 s), considering five levels. Second-order polynomial equations were used for oil yield, and first-order polynomial for final moisture content. The response models obtained were validated with independent experiments. Under optimal pretreatment conditions, no significant differences were detected in acidity, fatty acid profile and tocopherol content between the unpretreated and pretreated samples. However, significant differences were observed for peroxide index. Practical Applications: Canola oil is classified as one of the healthiest vegetable oils due to its fatty acid composition (low in saturated fatty acids and high in essential fatty acids). Vegetable oils are conventionally obtained by pressing or solvent extraction, the latter being the more efficient method. However, the use of organic solvents has some disadvantages such as health and safety issues, emission of volatile organic compounds, high operating costs and poor oil quality caused by the high temperatures of the process. Microwave pretreatment applied to canola seeds is a new technique that offers shorter processing times and lower energy consumption and provides better yields within short times and with reduced solvent use in the extraction step, maintaining the quality of the oil.