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United States Department of Agriculture

Agricultural Research Service

Title: Extruded Corn Meal and Whey Protein Concentrate: Effect of Particle Size

Authors
item Onwulata, Charles
item Konstance, Richard - RETIRED-USDA-DPPRU

Submitted to: Journal of Food Processing and Preservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 29, 2005
Publication Date: N/A

Interpretive Summary: Previous attempts to use milk proteins such as whey to fortify extruded snack foods made from corn meal have not been successful. In this research, a new way of adding whey proteins to corn has been discovered. When whey protein is blended with corn and extruded, the products are frequently denser, have a harder bite and do not expand to the same extent as snacks made from corn meal alone. One of the contributing factors to this problem may be the differences in the particle size of the corn meal and the protein. Our studies evaluated the impact of various particle size distributions of the corn meal blended with whey protein concentrate and extruded into a snack. The addition of the protein resulted in a significant decrease in the viscosity in the extruder, but this reduction was minimized when corn meal, similar in size to the whey protein, was used. By more closely matching the particle size, the processing progressed with more uniform heating and moisture uptake and allowed for the creation of an extruded product that exhibited properties very similar to the corn snack.

Technical Abstract: Blends of whey protein concentrate (WPC) and corn meal, which were separated into four particle fractions (residual on a #30 screen, #40 screen, #60 screen, and through a #60 screen), were extruded at two moisture conditions (23 and 28%) to determine the effects of particle size on the extrudate properties. Smaller particle size fractions exhibited significantly higher viscosity both with and without added protein. When WPC was added to the corn meal, a large reduction in paste viscosity was observed regardless of the particle size. The blend with similar particle size distributions of corn meal and WPC had a significantly higher viscosity than the other blends. The expansion ratio, porosity, breaking strength of this blend, when extruded at the lower moisture content, was improved to the extent that it behaved similarly to extrudate made from corn meal alone.

Last Modified: 7/22/2014
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