High-conversion hydrolysates and corn sweetener production in dry-grind corn process.

Authors: WANG, ZHAOQIN - University Of Illinois; SHARMA, VIVEK - Dupont Industrial Biosciences; Dien, Bruce; SINGH, VIJAY - University Of Illinois

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2017
Publication Date: 1/22/2018
Citation: Wang, Z., Sharma, V., Dien, B.S., Singh, V. 2018. High-conversion hydrolysates and corn sweetener production in dry-grind corn process. Cereal Chemistry. 95:302-311. https://doi.org/10.1002/cche.10030.
DOI: https://doi.org/10.1002/cche.10030

Interpretive Summary: Each year, the U.S. produces over 15 billion gallons of ethanol, which consumes 6.4 billion bu of corn. Eighty-five percent of this corn is converted to ethanol by saccharifying and fermenting whole dry ground corn. Dry grinds processes are favored over competing wet mill technologies because they cost less to construct and are very efficient at producing ethanol. However, unlike wet mills, they only produce animal feed as a co-product and low-grade corn oil suitable for biodiesel production. In response to volatility in the ethanol market, there is an interest in diversifying to higher value co-products, especially suitable for food and chemical markets. This paper seeks to bridge the gap by developing technology suitable for producing a commercially suitable glucose stream at a dry grind facility. Specifically the paper demonstrates that concentrated glucose syrup can be recovered from dry ground corn, the product meets industrial purity standards, it can be converted to high fructose corn syrup (a widely used sweetener), and recovered (non-starch) corn residues is suitable for use as animal feed. This technology is expected to be of considerable interest to corn processors, auxiliary suppliers, and more broadly food manufacturers.

Technical Abstract: Most corn is processed to fuel ethanol and distillers’ grain animal feed using the dry grind process. However, wet milling is needed to refine corn starch. Corn starch is in turn processed to numerous products, including glucose and syrup. However, wet milling is a capital, labor, and energy intensive process compared with the corn dry grind process. The liquefaction and saccharification steps of the corn dry grind process are similar to those used for processing wet milled extracted starch. Production of refined corn starch from the dry grind process would be advantageous for expanding the number and value of possible co-products. The objective of this study was to determine the feasibility of adapting the corn dry-grind process for high conversion hydrolysates production. After purification (refining processes), the glucose conversion efficiencies were similar between dry-grind processed corn (95.69 ± 0.29%) and wet milled corn starch (95.05 ± 0.88%). Soluble protein content is an important specification for starch hydrolyates because it affects its conversion to syrup. The protein content of hydrolysates from the dry grind process was 0.4%, which is higher than the maximum concentration (0.3%) specified by the food industry. Therefore, a thermal treatment was developed to remove soluble protein. The results showed that the thermal treatment did not affect the high sugar conversion efficiency (94.61 ± 1.34%) and removed the soluble protein, demonstrating that the modified dry grind process presented herein can be potentially used to produce corn sweeteners.