Canola proteins and glucosinolates : effect of protein isolation and post-isolation processing
Ser. Wan Yuin
Knowledge of the behavior of problematic factors, including the glucosinolates and their degradation products, is important if increased utilization of canola protein in human food is to be realized. Using a series of samples representing various stages in the protein micellar mass (PMM) process, the goals of this work were to determine how effective this process is in recovering protein and removing glucosinolates from low-temperature heated canola meal. Furthermore, the effects of post-isolation processing on the residual glucosinolates and glucose, and how these influence isolate color were examined. In addition to the standard gas chromatography (GC) technique, the thiocyanate (SCN-) ion determination and a diabetic test kit technique were used and evaluated as methods for assessing the glucosinolate levels in canola protein isolates. These latter two are based on the measurements of free SCN- ions and the glucose released upon the glucosinolate decomposition, respectively. Our results showed a good agreement (R2 = 0.93) between the GC method and the estimate of total glucosinolates from the diabetic test kit technique although an overestimation of glucose was observed possibly due to the presence of free glucose from other sources in the canola samples. Ultrafiltration was an important stage in recovering canola protein, as well as reducing the glucosinolates. The Vivaflow 200 tangential ultrafiltration system was significantly better than the Amicon stirred cell system in achieving both functions, although removal of glucosinolate was not as great. Poor protein recovery (<12%) from canola meal has suggested that the PMM process is a selective technique for isolating only 12S salt-soluble globulins...