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United States Department of Agriculture

Agricultural Research Service

Research Project: Improved Utilization of Proteinaceous Crop Co-Products and Residues

Location: Plant Polymer Research

2013 Annual Report

1a.Objectives (from AD-416):
The long-term objective of this project is to develop novel products utilizing current and new co-products from the industrial processing of agricultural materials. By accomplishing this, our research will reduce dependence on non-renewable materials and produce higher value products that will benefit a large segment of our economy. Objective 1: Develop technologies that enable commercially viable biobased materials from the proteinaceous co-products produced during cereal and soy processing. Objective 2: Develop novel extraction techniques that enable the commercially viable biorefining of new protein-rich industrial feedstocks such as alfalfa and pennycress.

1b.Approach (from AD-416):
Improve extraction, isolation and derivatization techniques; develop new routes to isolate and characterize proteinaceous materials from corn, soy, pennycress and alfalfa. Proteins will need to be physically or chemically modified in solution and in melt state in order to impart valued properties required for the desired applications.

3.Progress Report:
The ultrafiltration-diafiltration (UF-DF) method using saline solution was used to extract protein from standard corn germ (CG). Relative to other types of CG protein, UF-DF finished CG protein had much higher solubility at all pH levels tested. This high solubility allows for easier dispersion in many applications. CG protein extract was also very stable to elevated temperature. By using UF-DF to extract the protein, the emulsifying capacity of the finished CG protein was improved by 40%. UF-DF extraction was also tested for soybean meal protein (SBM). While the amount and quality of the UF-DF SBM was not exceptional, it did produce more stable foam (100%) and was a better emulsifier (30%). The UF-DF SBM was more sensitive to heating. Solubility, emulsification, and foaming properties are important in products such as paints, shaving foams, and facial creams, both UF-DF CG and UF-DF SBM will find value in these applications.

The functional properties of the acid-precipitation (AP) and saline extraction (SP) pennycress protein isolates were determined. Both have sufficient solubility to be useful in various markets. AP had higher foaming capacity (20%), foam stability (30%) and was more resistant to heat than SP. SP had better emulsifying capacity (40%) and more stable emulsions (20%) than AP. AP and SP had highly desirable functional properties that varied somewhat with the isolation method. The amino acid scoring pattern of AP (39.6), SP (37.4) are superior or equivalent to those of soybean protein (37.4). The amount of sinigrin, a toxic material in pennycress (35 mg/g) was reduced to 0.3 mg/g for AP and 0.0 mg/g for SP - suggesting that they may be suitable food use.

Zein was successfully modified with poly(ethylenemaleic anhydride) [PEMA] via reactive extrusion processing. The extrudate obtained could be compression molded to give articles with tensile strengths similar to control processed under the same conditions. The compression molded samples had improved solvent resistance (46% soluble versus 100% for control). Processing conditions had to be adjusted to insure that the PEMA could be melted and react with zein, but not too high as to degrade the zein. A patent application was filed covering this technology.

Zein was shown to have improved properties after reaction with isocyanates (NCO) in solution and melt states. Modifications of zein with mono- and di-NCO in solution provided cast films that were more hydrophobic but had lower tensile strength/elongation than control. Molecular weight analysis confirms that when NCO was used molecular weight increased. This chemistry was also performed in the melt in the presence of a catalyst. Both as-is and dried zein were utilized (moisture can react with NCO) in this study. It was found when using dried zein, the temperature of the melt was higher and final viscosity of the melt was lower than the melt obtained when using as-is zein. Increased temperature results in increased protein degradation. Because of this, samples produced using as-is zein gave higher molecular weight material, with lower solubility and improved physical properties.

1. Defining the value of pennycress proteins. Pennycress seed oil is being developed as a biodiesel source, but little is known about the seed’s protein, which will be a co-product from oil processing. ARS Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, Illinois, have employed extraction methods that use simple solvents to produce high-purity protein extracts. The pennycress seed protein isolates have desirable properties that are affected by the method of extraction. Pennycress protein isolate produced by the traditional route had moderate solubility and excellent foaming capacity, foam stability and heat resistance. When salt-extraction was used to produce pennycress protein isolate, the resulting protein had excellent solubility and was a better emulsifier. Both isolation routes produced proteins that are expected to be safe for food use based on zero to trace amounts of sinigrin (an undesirable material in pennycress seed). The amino acid composition of both isolated proteins had equivalent to superior nutritional quality relative to soybean protein. Developing novel uses based on these properties will increase the value of the pennycress crops and provide another revenue stream for companies that will be processing pennycress seed.

2. Development of a new corn protein based product. Corn protein (zein) is a component in one of the main co-products of the bio-ethanol industry. Initial markets are those that are single use, such as plates, filters, and sheeting where limited solvent resistance is required. Zein requires chemical modification to deliver the needed resistance for products used in these markets. ARS Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, Illinois, have found that poly(ethylene maleic anhydride) [PEMA] can deliver this required resistance. PEMA delivers this improved performance by linking multiple zein proteins together resulting in improved solvent resistance. As a polymer PEMA is much safer than the alternative reagent - formaldehyde. Previously PEMA had been shown to give improvements after reaction in solution. It has now been demonstrated that this chemistry can be carried out in a continuous fashion using reactive extrusion techniques. By using extrusion techniques, the cost for processing is greatly reduced as solvents are not required. Molded samples have physical properties equivalent to control with improved solvent durability. These results will provide additional information so that companies will evaluate the use of zein in making ‘plastic’ articles which will increase the value of corn and the products made from corn. Developing higher value end uses for this material will benefit the agricultural economy and replace petroleum based products.

3. Improved corn germ protein emulsification product. Corn germ co-products are utilized mainly as high-energy/protein additives in animal feeds. While this takes advantage of corn germ protein’s excellent nutritional quality it does not make use of its equally desirable functional properties. ARS Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, Illinois, have found that it is possible to isolate substantial and functional protein from corn germ using uncomplicated methods and solvents that can be readily utilized by industry. Our extraction method using ultrafiltration-diafiltration has produced a corn germ protein product with high solubility in various liquids. This property is atypical for corn protein and is highly beneficial as the protein can be used in many products. Corn germ protein extracted using this method is an excellent emulsifier, highly stable to heat and retains water well. Companies that produce products that rely on emulsification and water-holding capacity, such as water-based paints, cosmetics and detergents as well as food products will benefit from this research.

Review Publications
Selling, G.W., Utt, K.D. 2012. Effect of multiple extrusion passes on zein. Polymer Degradation and Stability. 98(1):184-189.

Hojilla-Evangelista, M.P., Evangelista, R.L., Isbell, T., Selling, G.W. 2013. Effects of cold-pressing and seed cooking on functional properties of protein in pennycress (Thlaspi arvense L.) seed and press cakes. Industrial Crops and Products. 45(1):223-229.

Last Modified: 4/17/2014
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