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K. LIU1, H. E. Huff2, and F. Hsieh2. (1) Dept. of Food Science, Univ. of Missouri, Columbia, 124 Eckles Hall, Columbia, MO 65211, (2) Dept. of Biological Engineering, Univ. of Missouri, 254 Ag. Eng. Bldg., 1406 E. Rollins St., Columbia, MO 65211-5200 Recent development in extrusion technology has focused on high moisture (40-80%) texturization of vegetable proteins, using twin screw extruders fitted with a long cooling die. The resulting products resemble more like whole muscle meat as compared with those obtained by thermalplastic extrusion under low moisture conditions (<40%). Thus the technology shows a great promise. Yet, our knowledge on mechanism of fiber formation and protein changes during extrusion is rather limited. In particular, with regard to the nature of protein-protein interactions responsible for the fiber formation and texture stabilization, controversy still exists in the literature. This study was aimed at elucidating protein changes at the molecular levels as a result of high moisture extrusion, using one of proteomics techniques -- two-dimensional gel electrophoresis. Soy protein, wheat gluten and modified starch were mixed well before extruded in a twin screw extruder. The extruder temperature was set at 165°C and moisture was set at 60% by adjusting a water pump. Raw mixture and extruded product were then extracted with a phosphate buffer and an isoelectric focusing (IEF) buffer. The later contained chemicals that can break hydrogen bonds, hydrophobic interactions, and disulfide bonds. The protein content in the extracts was determined. Then, 750 micro grams of protein in the IEF extract was loaded on two-dimensional gels. Following SDS-PAGE in the 2nd dimension, the gels were stained with colloidal Commassie blue. The images were captured into a 16-bit TIFF format. By comparing the images between the raw ingredient mixture and extruded samples, we found that the protein patterns were identical. Furthermore, their protein extractability by the IEF buffer was basically the same and both reached to a maximum level as compared with that by the phosphate buffer. Results indicate that beside disulfide bonds and such non-covalent bonds as hydrogen bonds and hydrophobic interactions, no other covalent bonds formed during high moisture extrusion.
Session 94, Food Chemistry: Chemical effects of food processing, preservation and formulation
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