Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2014
Publication Date: 7/21/2014
Citation: Hojilla-Evangelista, M.P. 2014. Improved solubility and emulsification of wet-milled corn germ protein recovered by ultrafiltration-diafiltration. Journal of the American Oil Chemists' Society. 91:1623-1631. DOI: 10.1007/s11746-014-2503-5.
Interpretive Summary: Ultrafiltration-diafiltration (UFDF) is a standard technique that concentrates desired components in a solution while also filtering out undesirable elements. We used UFDF for isolating proteins from wet-milled corn germ so that we may recover protein with higher purity and hopefully improved properties. Our research crafted a viable technique for corn germ protein recovery and generated new fundamental data on functional properties that provide direction for end-use industrial applications. Corn germ protein products (approx. 500 million pounds of corn gluten feed and 250 million pounds of corn germ meal/cake per month in the United States) are utilized mainly as animal feed. Developing new uses/markets for corn germ protein will enhance its value and generate additional income for corn growers. We found that, while our UFDF method gave marginally higher protein yields and purities (from 30% to 40%), our recovered proteins had unusual and remarkable solubility properties. The UFDF germ proteins were much more soluble than germ proteins isolated by the standard method. In addition, unlike most proteins, our UFDF proteins had nearly the same solubility at all pH conditions, which indicate easier dispersion in many applications of varying pH that, in turn, broaden their usefulness. UFDF germ protein extracts also had excellent emulsifying capacities and water-holding capacities. Based on these functionality results, the potential uses of the UFDF germ protein may be as emulsifier, thickener in pastes and facial creams, or viscosity and clarifying agent in beverages. Our research findings will benefit corn producers, corn biorefiners, and researchers on protein-based or bio-based products in academia and industry.
Technical Abstract: This study evaluated ultrafiltration-diafiltration (UFDF) as a means to improve the extractability of wet-milled corn germ protein and determined its effects on the functional properties of the recovered protein product. Wet germ (WG) and finished germ (FG) proteins (Pr) were extracted by using 0.1M NaCl at 50°C. Major steps in the method were stirring, centrifugation, UFDF, and freeze-drying. UFDF marginally increased protein extraction efficiency of FG while that of WG remained similar to what we observed for the baseline method (saline extraction without UFDF). UFDF protein extracts from both germ samples were significantly more soluble than extracts recovered by the baseline method and showed atypical solubility profiles; i.e. the amount of soluble protein was essentially unchanged under acidic, neutral, and alkaline pH. FGPr-UFDF was markedly more soluble than WGPr-UFDF (80% vs. 50% soluble protein, respectively) at pH 2-10. Both WGPr-UFDF and FGPr-UFDF also had emulsifying capacities and water-holding capacities that were superior to those of WGPr and FGPr, but this favorable effect by UFDF was not observed for emulsion stability, foaming properties, and heat stability.