"Previously, an acidified, thermally treated whey protein concentrate (mWPC) was developed to produce a cold-set thickening ingredient. Mass spectroscopy revealed an approximate 2.5-fold decrease in the lactosylation of beta-lactoglobulin in mWPC starting materials compared with commercial whey protein concentrates, manufactured at a higher pH. Potentially, this should increase the number of reactive sites that remain available for carbohydrate attachment. With this study, the formation of glycoprotein complexes was demonstrated between the mWPC ingredient and lactose, naturally occurring in mWPC powders, or between mWPC protein components with dextran (35 to 45 and 100 to 200 kDa) materials at low pH. In fact, additional dry heating of mWPC powders showed a 3-fold increase in the amount of lactosylated beta-lactoglobulin. Evidence of Maillard reactivity was suggested using colorimetry, o-phthaldialdehyde assays, and sodium dodecyl sulfate PAGE followed by glycoprotein staining. Resultant glycoprotein dispersions exhibited altered functionality, in which case steady shear and small amplitude oscillatory rheology parameters were shown to be dependent on the specific reducing sugar present. Furthermore, the emulsion stability of mWPC-dextran fractions was 2-3 times greater than either mWPC or commercial WPC dispersions based on creaming index values. The water-holding capacity of all test samples decreased with additional heating steps; however, mWPC-dextran powders still retained nearly six times their weight of water. Scanning electron microscopy revealed that mWPC-dextran conjugates formed a porous network that differed significantly from the dense network observed with mWPC samples. This porosity likely affected both the rheological and water-binding properties of mWPC-dextran complexes," wrote J.S. Lillard and colleagues, North Carolina State University.
The researchers concluded, "Taken together, these results suggest that the functionality of mWPC ingredients can be enhanced by conjugation with carbohydrate materials at low pH, especially with regard to improving the emulsifying attributes."
Lillard and colleagues published their study in the Journal of Dairy Science ("Glycosylation and expanded utility of a modified whey protein ingredient via carbohydrate conjugation at low pH." Journal of Dairy Science, 2009;92(1):35-48).
For additional information, contact C.R. Daubert, North Carolina State University, Dept. of Food Bioproc & Nutrition Science, Raleigh, NC 27695.
From the February 2, 2009, Prepared Foods E-dition