Alkali debranning for corn wet and dry milling and characterization of the end products
Mistry, Atulkumar
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https://hdl.handle.net/2142/22625
Description
Title
Alkali debranning for corn wet and dry milling and characterization of the end products
Author(s)
Mistry, Atulkumar
Issue Date
1991
Doctoral Committee Chair(s)
Eckhoff, Steven R.
Department of Study
Food Science and Human Nutrition
Discipline
Food Science and Human Nutrition
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Engineering, Agricultural
Language
eng
Abstract
The objectives of this investigation was to develop an alkali based corn process that requires less processing, is easy to control, is more time and cost effective than current industrial corn processes and to obtain corn products in higher yields with better quality that is beneficial for various food applications than existing commercial corn products from yellow dent corn. The developed process is outlined in Figure A and includes debranning, dry milling, and flour steeping processes to extract corn starch.
The alkali debranning process, which included soaking corn in alkali solution, rendered 4.68% (corn dry basis) corn bran without disintegrating the kernel. The effect of process variables on bran yield were studied and found that maximum value of bran yield occurred at 6% alkali concentration, 9 minute treatment time and 57$\sp\circ$C. Corn bran contained 92.12% dietary fiber, constituting 95.5% of the dietary fiber present in the pericarp. The bran obtained by this process was more clarified than commercially available corn brans.
The dry milling process developed for alkali debranned corn was short, required less conventional equipment and degermed much faster with less product loss and resulted in cleaner and easier separation of all fractions compared to untreated corn. The yields of No. 5, 7, and 10 grits were much higher and the milling evaluation factor was 454 for debranned corn compared to 277 for untreated corn. Debranned corn germ would obtain 35% more oil and the crude fiber content of all fractions was 40-50% less than the corresponding untreated corn fractions.
The starch extracted from corn flour by steeping the flour in alkali solution was affected by three process parameters: alkali concentration, steep time and temperature. The main and interaction effects of all the parameters significantly affected the three measures of starch extraction efficiency: starch yield and protein and sodium content. The conditions identified that simultaneously extracted more starch with lower protein and sodium content were: 0.1% alkali concentration, 30 minutes and 55$\sp\circ$C.
The alkali extracted corn starch had low initial pasting temperature, high peak viscosity, no shear-thinning, high energy of gelatinization and absorbed more moisture at a given water activity. The X-ray diffraction, birefringence, granule morphology, and enzymatic hydrolysis characteristics of alkali starch were not significantly different than commercial corn starch obtained by conventional wet milling process.
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