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A method for the decrease of phenolic content in commercial canola meal using an enzyme preparation secreted by the
1Department of Chemical Engineering, University of Ottawa, 161 Louis Pasteur Street, P.O. Box 450, Ottawa, Ontario K1N 6N5, Canada.
Abstract:
An enzymatic process for upgrading the quality of canola meal (CM) by decreasing its phenolic content was investigated. The new method was based on the addition of the enzyme preparation from white-rot fungus Trametes versicolor to the meal-buffer slurry. A 98% decrease in the concentration of SAE was observed after 1 h of the treatment. The following process variables were considered for optimizing the process: pH, temperature, enzyme, meal, and oxygen concentrations. It was found that: (1) the natural buffering capacity of CM resulted in a negligible effect of the pH of the buffer, which was used as the continuous phase in the process, on the extent of decrease in sinapic acid esters (SAE); (2) the system was saturated with the enzyme when its concentration was 4 nkat/mL of the continuous phase; and (3) the optimum temperature was 50 degrees C. The process could be carried out even at higher temperatures due to the protective action of CM, which resulted in an increase in the thermal stability of the enzyme. The particle size influenced the extraction of the SAE from the meal, indicating that, at lower SAE concentrations, the process became diffusion limited. This result, together with those showing no effect of the intensity of agitation, indicated that the enzymatic process can be characterized by high Biot numbers. During the enzymatic process, the molar concentration of available oxygen can become a limiting factor when it is more than four times lower than the molar concentration of phenolics in the treated meal. The new enzymatic method was compared with other methods reported in the literature for the decrease in the phenolic content of rapeseed meals. It was found that, among the methods tested, the enzymatic treatment was the most effective, followed by the lime treatment. The enzymatic process did not reduce the quality of the protein isolates prepared from the CM. After the addition of a simple acetone-washing step, the isolate from the enzymatically treated meal had even better properties. Copyright 1999 John Wiley & Sons, Inc.