Submitted to: American Association of Cereal Chemists Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 4/10/2005
Publication Date: 9/11/2005
Citation: Robertson, G.H., Cao, T. 2005. Protein solubility considerations for low temperature processing with aqueous ethanol. American Association of Cereal Chemists Annual Meeting, September 11-14, 2005, Orlando. FL. Paper No. 0-76.
Technical Abstract: Wheat protein solubility in aqueous ethanol is reduced by the use of low temperature as in the cold ethanol method for separation of gluten and starch. Protein functionality is altered in this technical separation method. One reason for the change may be differential solubility of protein subfractions. Capillary zone electrophoresis was applied to identify the temperature-solubility of wheat flour albumin/globulin and gliadin component protein in aqueous ethanol (0 to 100 vol%, 22C, to -12C). The amount of total protein solubilized (as absorbance at 200nm) at the peak solubility of 64% at 22C ethanol declined to 70% of the peak value as the temperature was reduced to 0C, rapidly declined to less than 5% of the peak at -7C and 3 % at -12C. The peak solubility for the above-zero data was at 60% ethanol, but for sub-zero data it shifted to 70% . There was a narrowing of the absorbance concentration data: some solubility at all concentrations between 0 and 90% at 22C, between 40 to 90% at 10C or 0C, but only from 50 to 90% at -7C to -12C. The beta, gamma, and omega gliadins had similar patterns as the total protein. Albumin/globulin proteins at 22C were most soluble at 0% and less soluble at all higher concentrations of ethanol, and at -12C were most soluble at 55% ethanol. At -12C the alpha gliadins and albumins were the most soluble forms of protein extracted up to 50%; but at 55 to 85% beta-gliadins were most soluble. The shifts in the proportion of protein extracted relate directly to changes in the insoluble protein remaining and hence may contribute in complex ways to the functionality of the insoluble gluten. These data for dry flour conservatively estimate processing extraction to hydrated and developed batter.