|De Carvalho, Carlos-piler|
Submitted to: Journal of Food Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2009
Publication Date: 12/16/2009
Citation: De Carvalho, C.W., Takeiti, C.Y., Onwulata, C.I., Pordesimo, L.0. 2010. RELATIVE EFFECT OF PARTICLE SIZE ON QUANTITATIVE AND QUALITATIVE FEATURES OF CORN MEAL EXTRUDATES. Journal of Food Engineering. 98:103-109. Interpretive Summary: To use milk products such as whey proteins successfully to fortify extruded snack foods, the particle sizes of the whey proteins and corn meal must be taken into account. In this research, the effect of different corn meal sizes on the extent of expansion of puffed snack was investigated. When whey protein is blended with corn and puffed, the products are frequently denser, have a harder bite and do not expand to the same extent as snacks made from corn meal alone. We found that the best expanded products are made from corn meal with larger particle sizes, and that whey proteins must be made in a way so that the particle size of the whey proteins matches that of corn meal, to obtain the best puffed product. This information can be used by food manufacturers to make healthier corn snacks containing nutritious whey proteins.
Technical Abstract: Corn meal of various particle sizes ranging from 180 to 710 µm was processed in a twin-screw extruder at 16% moisture content, screw speed (300 rpm), and fixed temperature profile, to produce directly expanded extrudates with different physical properties. The extrusion process effects on the specific mechanical energy (SEM), expansion indices (radial, longitudinal and volumetric), pasting viscosity, water absorption index (WAI) texture properties, and microstructure were determined. Results show that increasing the particle size decreased the SME input. Extrudates produced with corn meal of higher particle sizes expanded more than extrudates produced with smaller particle sizes. For all treatments there was no peak viscosity at 95°C, and no evidence of gel formation. But expanded corn meal extrudate from the 180 µm fraction showed a discontinuous gel matrix phase. Also, it was observed that increasing corn meal particle size decreased WAI values. The mechanical resistance of the extrudates from the smallest particle size (180 µm) was significantly higher (p<0.05) than that of the largest particle size (710 µm). The microstructure of raw corn meal revealed large fractured particles with small rounded particles adhering to the surface.