91C-37 |
Incidences of corn drying on its quality for wet-milling process |
M. Bello1, M. C. Haros, and C. SUÁREZ1. (1) Departamento de Industrias, Facultad de Ciencias exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, 1428, Argentina Corn wet-milling is the largest commercial source of starch. Drying conditions may affect the protein and starch granules within the kernels, with resulting low recovery of starch and poor quality of the recovered starch. Our objective was to survey the potential effects of corn drying on starch recovery and physical and functional properties of wet-milled starch. Drying runs were conducted in a laboratory drier at 70, 90 and 110°C; flint corn (CARGILL T-42) was used for the experiments. The millability of grains was evaluated in terms of starch recovery, saturation moisture content after steeping and rate of waterabsorption during steeping in 0.25% SO2 aqueous solution. A laboratory wet-milling process was used for starch recovery. The quality of wet-milled starch was measured in terms of protein content, water vapour sorption capacity, swelling, solubility, color and DSC endotherm temperatures. Starch recovery drop from 96.5 to 82.0% when drying temperature was increased from 70 to 110°C, while saturation moisture content drop from 0.634 to 0.570 (dry basis). Such increase in drying temperature reduced moisture diffusivity from 5.6 to 4.7x10 –11 m2/s. Starch recovery from air-dried corn contained greater amounts of residual protein than did starch from undried corn, and was more yello in color. Sorptional characteristics of starch were unaffected by grain drying. Swelling power and solubility of starch was reduced by the increase of drying temperature. Such increase also increased the onset and peak temperatures of gelatinization. Heat of gelatinization decreased with the increase of drying temperature, probably due to the presence of remanent protein in starch granules. High drying temperatures reduce dramatically starch recovery, increasing protein content of starch because of the increased difficulty in starch-gluten separation and altering the functional properties of native starch.
Session 91C, Food Engineering: Food process engineering
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