Intermittent milling and dynamic steeping process for corn starch recovery
Lopes, Filho Jose Francisco
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Permalink
https://hdl.handle.net/2142/23432
Description
Title
Intermittent milling and dynamic steeping process for corn starch recovery
Author(s)
Lopes, Filho Jose Francisco
Issue Date
1995
Doctoral Committee Chair(s)
Eckhoff, Steven R.
Department of Study
Agricultural Engineering
Discipline
Agricultural Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Language
eng
Abstract
A laboratory-scale procedure of Intermittent Milling and Dynamic Steeping (IMDS) for corn wet milling was developed and evaluated. Soaking of the kernel, kernel cracking, and dynamic steeping are parts of the process.
The first study determined the effects of soaking temperatures (52, 60 and 68$\sp\circ$C) on the hydration of germ and endosperm of the kernels during 2 hr. The hydration rates increased with increasing temperature for both germ and endosperm. Germ hydrated faster than endosperm and moisture absorption was a logarithmic function of soak time for both corn fractions. In a 2 hr soak time the germ hydrated to 38.8, 42.0, and 42.7% and the endosperm to 26.4, 28.4, and 30.2% moisture for the three temperatures, respectively.
The second study investigated the effect of soak time, soak temperature, SO$\sb2$ and lactic acid concentrations, on corn fraction yield and quality and the effect of kernel cracking method. There were no advantages of using SO$\sb2$ or lactic acid in the soak water. Starch, gluten, and germ yields and the protein content in starch were not affected by soak temperature (52-68$\sp\circ$C) or soak time (1-3 hr). One and 3 hr of soaking time resulted in either more fiber with the germ or more damaged germ which difficulted germ recovery. Based upon the degree of germ damage and particle size distribution of resulting mash, the Bauer mill was the best method for kernel cracking among the methods tested: roller mill, Bauer mill, and Commercial grade Waring blender.
The third part evaluated the steep time required for dynamic steeping of the IMDS process, the level of SO$\sb2$ needed and if lactic acid was required during steeping. The use of lactic acid during dynamic steeping enhanced starch yield and decreased fiber fraction by 4 percentage points. Starch yield obtained with 3 hr steeping in 0.15% SO$\sb2$ and 0.55% lactic acid was not different from starch yield obtained with 7.5 hr dynamic steeping. Increasing SO$\sb2$ level from 0.05 to 0.15% increased starch yield by an average of 2 percentage points. The IMDS process produced, on an average, 1 percentage point more starch when compared with the 36 hr batch steeping process. The steep time was reduced from 24-40 hr for the conventional process to 5 hr for the IMDS process.
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