Colour reduction in canola protein isolate

#The present invention relates to the recovery of canola protein isolate from canola seed meals.

#In U.S. Pat. Nos. 5,844,086 and 6,005,076 (“Murray II”), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described a process for the isolation of protein isolates from oil seed meal having a significant fat content, including canola oil seed meal having such content. The steps involved in this process include solubilizing proteinaceous material from oil seed meal, which also solubilizes fat in the meal, and removing fat from the resulting aqueous protein solution. The aqueous protein solution may be separated from the residual oil seed meal before or after the fat removal step. The defatted protein solution then is concentrated to increase the protein concentration while maintaining the ionic strength substantially constant, after which the concentrated protein solution may be subjected to a further fat removal step. The concentrated protein solution then is diluted to cause the formation of a cloud-like mass of highly associated protein molecules as discrete protein droplets in micellar form. The protein micelles are allowed to settle to form an aggregated, coalesced, dense amorphous, sticky gluten-like protein isolate mass, termed “protein micellar mass” or PMM, which is separated from residual aqueous phase and dried.

#The protein isolate has a protein content (as determined by Kjeldahl nitrogen or other convenient procedure N×6.25) of at least about 90 wt %, is substantially undenatured (as determined by differential scanning calorimetry) and has a low residual fat content. The term “protein content” as used herein refers to the quantity of protein in the protein isolate expressed on a dry weight basis. The yield of protein isolate obtained using this procedure, in terms of the proportion of protein extracted from the oil seed meal which is recovered as dried protein isolate was generally less than 40 wt %, typically around 20 wt %.

#This Example shows the effect of various parameters on protein extraction and protein solution colour.

#A series of experimental runs was performed in which 37.5 g of commercial canola meal (AL-016) was mixed with water containing NaCl of desired concentration at the desired pH, at a meal concentration of 7.5% w/v at 20° C. Sodium chloride concentrations employed were 0, 0.05, 0.10, 0.15 and 0.25 M and pH values used were pH 6.3, 8.0, 9.8 and 11.0. A sample of about 30 mL of extract was taken every 10 minutes during the 60 minutes extraction period and centrifuged at 10,000×g for 5 minutes. The supernatant of each sample was analyzed for protein concentration at the end of the extraction period. The entire batch was centrifuged at 10,000×g for fifteen minutes and the supernatant was vacuum filtered using a 0.45 μm micro filter. The filtered supernatant was analyzed for protein content and for free phenolics concentration (absorbance at 330 nm).

#A 100 ml aliquot was drawn from the clarified supernatant for ultrafiltration (UF) by a concentration factor of 4 using an Amicon 8400 unit with a membrane of 10,000 molecular weight cut-off. The protein concentration and A330 absorbance of the 25 ml retentate and pooled permeate were determined. The ultrafiltered solution was subjected to diafiltration (DF) by a diavolume of 6, using 150 mL of solution with the same salt concentration and same pH as used for the extraction. At the end of the diafiltration both the retentate and pooled permeate from the diafiltration were analyzed for protein concentration and A330.