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ARS Home » Research » Publications at this Location » Publication #168982


item Rosentrater, Kurt
item Flores, Rolando

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2005
Publication Date: 5/1/2005
Citation: Rosentrater, K.A., Richard, T.L., Bern, C.J., Flores, R.A. Small-scale extrusion of corn masa byproducts.2005. Cereal Chemistry, 82(4):p.436-446.

Interpretive Summary: Masa is a corn dough that is used to make corn snacks, chips, and tortillas. Byproduct streams are generated in the production of corn masa. These streams are of little value and a source of contamination that frequently ends up in landfills. A potential use for the suspended solids of the byproduct streams is in livestock feed rations. This study looked at blending the suspended solids of the masa byproducts with another agricultural product, i.e. soybean meal, to develop a feed ingredient using extrusion processing. To determine the optimal extrusion conditions and their impact on the extrudates, extrusion tests were conducted in a laboratory-scale extruder by blending the suspended solids with soybean meal at four levels (0, 10, 20 and 30% wet basis) under two extruder screw speeds (50 and 100 rpm) and two temperature profiles of the extruder barrel sections (80-90-100 and 100-110-120 ºC). The resulting extruded products were subjected to physical and nutritional characterization. Laboratory-scale extrusion produced extrudates with nutritional properties similar to those of the raw ingredient blends, with improved protein digestibility, which was due to the thermal effects of the extrusion cooking. The results indicated that the final product's physical properties were dependent on the screw speed and extrusion temperature and not on the blending ratio with soybean meal. This study has provided new information essential in the development of valuable livestock feeds and feed ingredients from low-value corn masa byproducts. Use of this technology will reduce waste and improve profitability of corn masa producers and feed manufacturers.

Technical Abstract: Corn masa byproduct streams are high in fiber and are amenable for utilization in livestock feed rations. This approach is a potential viable alternative to landfilling, the traditional disposal method for these processing residues. Suspended solids were separated from a masa processing waste stream, blended with soybean meal at four levels (0, 10, 20 and 30% [wet basis]), and extruded in a laboratory-scale extruder at screw speeds of 50 rpm (5.24 rad/s) and 100 rpm (10.47 rad/s) with extruder temperature profiles of 80-90-100 ºC and 100-110-120 ºC. Processing conditions, including dough and die temperatures, drive torque, specific mechanical energy consumption, product and feed material throughput rates, dough apparent viscosity, and dough density, were monitored during extrusion. The resulting extruded products were subjected to physical and nutritional characterization, in order to determine optimal processing conditions for the blends under investigation. Extrudate analysis included moisture content, water activity, crude protein, in-vitro protein digestibility, crude fat, ash, product diameter, expansion ratios, unit and true density, color, water absorption and solubility, and durability. All blends studied were suitable for extrusion at the processing conditions used. Blend ratio had little effect on either processing parameters or extrudate properties; extrusion temperature and screw speed, on the other hand, significantly affected both processing and product properties,