Characterization of amylose lipid complexes and their effect on the corn dry grind process

The dry grind process is the most commonly used method for production of corn ethanol. Ethanol from corn is the biggest contributor to bioethanol produced in the US. In this study, effects of different parameters such as liquefaction temperature, solids content and particle size on formation of amylose lipid complexes (AML) were observed. This helps determine better methods of application in the dry grind industry by providing reasons for decreasing available starch. In the conventional dry grind process, starch in corn is liquefied to dextrins at high temperature, followed by simultaneous saccharification and fermentation (SSF), where dextrins are converted to monomers and are fermented simultaneously to ethanol by yeast. Prior to liquefaction, there is 73% starch available for enzymatic hydrolysis in ground corn. However, after liquefaction the available starch content decreases to 61%. This study aimed to identify decrease in available starch as being due to formation of AML. The ethanol concentration from utilizing granular starch hydrolyzing enzymes (GSHE), which is carried out at a constant temperature without a liquefaction step, is comparative to a conventional dry grind process. However, distillers’ dried grains with solubles (DDGS) obtained from the GSHE process contained 24% residual starch compared to a much lower 10% from the conventional process. This indicated that in addition to the loss of glucose to other streams during fermentation there was available starch lost during the liquefaction step. Addition of lipids to starchy food alters the physical and chemical composition due to formation of AML at high temperatures above 80ºC. These complexes decrease the water solubility and susceptibility of the starches to α-amylase digestion. AML content was found to decrease from 3.5 to 1.0% in post liquefaction solids (liquefact) as corn grind size was increased 0.5 to 2.5 mm. Across all solids content tested (25, 32 and 34%), the mean AML content was 0.61% lower when liquefaction temperature was increased to 105ºC, relative to the 85ºC liquefaction temperature. At 85ºC, liquefact from all three α-amylases, had similar AML content. However, when liquefaction temperature was increased to 105ºC, liquefact from enzyme AA2 had the lowest AML formation compared to other amylases. A differential scanning calorimetric (DSC) study was carried out to identify the formation of AMLs during liquefaction. The phase transitions that starch undergoes, including starch gelatinization and crystallization of AMLs, were identified in thermograms obtained from the DSC study. A starch standard containing soluble starch and linoleic acid, was made to undergo liquefaction. There was a 5% decrease in available starch content after liquefaction. In a control in which linoleic acid was taken with the same solid content and kept in an incubator to replicate a GSHE process without high temperature resulted in no change in available starch content. This confirmed AML formation during liquefaction in the dry grind process.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Agricultural & Biological Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2021

Author dc:creator

• Bhatia, Gitanshu

Contributors dc:contributor

• Singh, Vijay
• Johnston, David
• Juneja, Ankita
• Rausch, Kent D.
• Tumbleson, Mike E.

• Amylose lipid complex
• Available starch
• Dry grind ethanol process
• Liquefaction
• Starch estimation

Statement dc:rights

• Copyright 2021 Gitanshu Bhatia

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/110554

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/110554