Physical and functional properties of twin-screw extruded whey protein concentrate-corn starch blends
1997
Matthey, F.P. | Hanna, M.A.
Several physico-chemical and functional properties of corn starch-whey protein concentrate (WPC) extrudates were determined in the study. Blends of WPC and corn starch were extrusion-cooked with a co-rotating intermeshing twin-screw extruder at 220 g/kg moisture content, 140 rpm screw speed and 140 degree C barrel temperature. A split-plot experiment was conducted to investigate four levels of amylose in starch (main plots) with four levels of WPC in WPC-corn starch blends (sub-plots). The design was a randomized complete block with the three replications being three different WPC sources. Studied ranges were 0, 250, 500 and 700 g/kg for amylose and 0, 100, 200 and 300 g/kg for WPC. Measured properties were shear strength (5 1,4 to 361 kPa), radial expansion ratio (4.32 to 13.1), specific mechanical energy (SME) (240 to 383 J/kg), water absorption index (WAI) (1.98 to 8.57), % water solubility index (% WSI) 9.51 to 67,6 %, total color difference (8,08 to 35.9) and apparent amylose content (0-66 %) of extrudates. The WPC source affected several extrudate properties. Significant interactions between levels of amylose and WPC were found for radial expansion ratio, total color change and apparent amylose content. This suggested the presence of a physico-chemical interaction between amylose and WPC.
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