Germ soak water as nutrient source to improve fermentation of corn grits from modified corn dry grind process

Abstract

Corn fractionation in modified dry grind processes results in low fermentation efficiency of corn grits because of nutrient deficiency. This study investigated the use of nutrient-rich water from germ soaking to improve grits fermentation in the conventional dry grind and granular starch hydrolysis (GSH) processes. Comparison of germ soak water with the use of protease and external B-vitamin addition in improving grits fermentation was conducted. Use of water from optimum soaking conditions (12 h at 30 °C) resulted in complete fermentation with 29 and 8% higher final ethanol yields compared to that of control in conventional and GSH process, respectively. Fermentation rate (4–24 h) of corn grits with germ soak water (0.492 v/v-h) was more than double than that of control (0.208 v/v-h) in case of conventional dry grind process. The soaking process also increased the oil concentration in the germ by about 36%, which would enhance its economic value.

Improving dry‐fractionated corn fermentation by supplementation of corn germ meal and pasta mill feed from agro‐food industries

“…The results are in agreement with those reported by Juneja et al. () during complete fermentation of corn grits due to the addition of excess B vitamins or protease enzymes. The essential coenzymes present in B vitamin complex are involved in carbohydrate metabolism and provides important metabolic precursors for yeast growth.…”

“…() and Juneja et al. () with the use of germ soak water (2‐hr soaking) as a nutrition supplement. The residual glucose concentration was reduced by almost 50% (4.31%–2.3% w/v ).…”

“…Juneja et al. () observed that the addition of protease enzymes resulted in complete fermentation and increased conversion efficiency from 62.4% to 82.8%. However, the use of expensive vitamins, lipids, and protease enzymes increases the operating cost of the process and counters the benefits of fractionation.…”

“…Dry fractionation technologies, such as quick germ-quick fiber (QGQF), dry degerm, defiber process (3D process), require less capital investments compared to wet fractionation technologies and produce germ and pericarp fiber as additional co-products (Bothast & Schlicher, 2005;Murthy, Singh, Johnston, Rausch, & Tumbleson, 2006a;Taylor et al, 2001). Separation of pericarp at front end would reduce the fiber content in DDGS and widen its market utilization because it can be used as food for nonruminants such as poultry and swine (Juneja, Kumar, & Singh, 2017;Murthy et al, 2006a). High-value co-products, such as corn oil and corn fiber oil, can be recovered from separated germ and pericarp, respectively, which would improve the overall profitability of the dry-grind process.…”

“…Removal of germ leads to nutrient deficiency to yeast and results in sluggish and incomplete fermentation of dry-fractionated corn (Murthy, Singh, Johnston, Rausch, & Tumbleson, 2006b;Murthy et al, 2006a;Ponnampalam et al, 2004;Ramchandran et al, 2015;Vidal et al, 2011). Various approaches, including partial germ removal (Ramchandran et al, 2015), lipid supplementation (Murthy et al, 2006b), B vitamin supplementation (Murthy et al, 2006a), germ soak water addition (Juneja et al, 2017), and protease enzyme use (Juneja et al, 2017), have been investigated to address this issue of lack of nutrition. Ramchandran et al (2015) reported that leaving 20% germ behind can result in complete fermentation and high ethanol concentration.…”