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Title:Factors influencing Beall degermination of corn for dry milling
Author(s):Mehra, Suhas K.
Doctoral Committee Chair(s):Eckhoff, Steven R.
Department / Program:Agricultural and Biological Engineering
Discipline:Agricultural and Biological Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Agriculture, Food Science and Technology
Engineering, Agricultural
Abstract:Pilot scale corn dry milling experiments were conducted to compare the throughput and the product yields obtained from the most widely reported procedure in scientific literature, 3-stage tempering, with those obtained from the most commonly commercially practiced procedure, 1-stage tempering. For certain conditions of temper duration and tail gate weight distance (tail gate loading), both procedures produced statistically similar results.
Based upon these results, further experiments were conducted to examine the factors influencing the optimum tempering for dry milling. Central composite design was used to study the effects of temper duration and the operating parameters of temperature (corn and water), moisture (initial corn and temper), and the Beall degerminator controls (rotor position and weight distance) on the throughput and product yields. A single set of conditions that would maximize the throughput and the yields of the prime products was not found. The water temperature had a stronger effect than the corn temperature on most of the product yields for shorter temper durations, while the inverse was true for longer temper durations. The yield of flaking grits increased with an increase in the initial corn moisture, though the storage of corn at high initial moisture may result in corn spoilage. The throughput was more dependent upon the rotor position than the tail gate weight distance at higher rotor positions (closed position), while the opposite was true at lower rotor positions (open position).
The effects of blocking certain sections of the degerminator casing and placing three different sized screens on the conical cage were also studied. Blocking section #3 alone (control condition) or together with any of the other sections, decreased the throughput and increased the flaking grits yield. Significantly higher flaking grit yield was also observed when the screen size was increased from 0.0056 (14/64 in) to 0.006 m (16/64 in) although the tail stock percentage was significantly reduced by 7% points when the screen size was increased.
Experiments were also conducted to study the effect of using steam for tempering corn at two different initial corn temperatures (5 and 30$\sp\circ$C). When steam and water were used together, the flaking grits yield from the corn at lower temperature (5$\sp\circ$C) showed a significant improvement, though at the expense of throughput. The milling action of the Beall degerminator and the horizontal drum degerminator were also compared. Poor correlations were observed for the yields of similar sized products from the two degerminators, however, the Beall degenninator produced higher yields of prime products.
All the experiments conducted in this study revealed inherent trade-offs in the recovery of the throughput and yields of prime products. The results clearly indicate that the selection of the levels and combinations of various operating variables depends on the overall milling objectives, since an increase in the yield of a prime product is often achieved at the expense of another.
Issue Date:1996
Type:Text
Language:English
URI:http://hdl.handle.net/2142/21619
ISBN:9780591198324
Rights Information:Copyright 1996 Mehra, Suhas K.
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9712375
OCLC Identifier:(UMI)AAI9712375


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