Continuous Gel Formation by HTST Extrusion‐Cooking: Soy Proteins

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Abstract
The continuous production of gels of high moisture content is carried out by extrusion‐cooking, with a residence time of 30‐100 sec, using soy protein isolate as a model ingredient. The hot viscous extrudate can be collected in a mold, and gels upon cooling. The best texture characteristics are obtained with protein and water concentrations of 18 and 80% (wet basis), respectively, and extrusion temperatures of 150‐160°C. The effects of acidification, addition of NaCl, CaCl2 or sucrose on gel texture are investigated. Extrusion‐prepared soy gels melt reversibly upon further heating (120°C) and withstand frozen storage. Their texture and micro‐structure are compared to those of soy gels prepared by conventional batch heating at 100‐120°C.