Location: Plant Polymer Research
2022 Annual Report
Objectives
Objective 1: Increase the value of amylose inclusion complexes (AICs) produced from various carbohydrates and ligands for use as emulsifiers, film blends or surface treatments for paper products.
Sub-Objective 1A: Develop effective emulsifiers based on AIC using high-amylose corn (HAC) or other polysaccharides, complexed with the salts of fatty acids or amines, using economical manufacturing techniques.
Sub-Objective 1B: Produce higher value polymer blends or cellulosics using amylose inclusion complex materials made with lower-cost starches, such as normal corn food-grade starch (FGS) or corn flour, and fatty acids/amines or their salts.
Objective 2: Resolve the underlying lab and pilot-scale extraction and biorefining techniques that generate protein-rich industrial feedstocks from plant crops, such as camelina or sorghum, define their functional properties, and enable industrial production and commercialization.
Approach
This project plans to increase the value of existing and new crops by developing higher value amylose and protein products. Recent research has shown that starch processed from corn can provide high-value amylose inclusion complexes with vegetable oil derivatives (ex. fatty acid or amine salts) in excellent yield and at low cost. To transfer this technology to industry, it is critical to determine the impact of the amount and source of amylose on the attributes of the resulting complex. Protein-rich crops such as camelina or sorghum, which are not produced in high quantities in the U.S., have the potential to provide additional higher revenue streams to U.S. farmers. While the U.S. is the world’s leader in sorghum production, the use of sorghum is currently generally relegated to feed uses. Given the similarities between sorghum and corn, it is expected that sorghum value can be increased by utilizing its component fractions, as has been done to corn. Camelina has shown value as a winter-grown oilseed crop, but new uses are needed for the components of the resulting seed press cakes. Improved extraction techniques are needed to increase the value of both crops. This research will: 1) enable new approaches to produce and use amylose complexes and establish their physicochemical properties, and 2) innovate and evaluate extraction techniques, as well as identify uses for proteinaceous materials from crops such as sorghum and camelina. Improved utilization of current and future crops will enhance the value of these crops in new and existing markets.
Progress Report
Objective 1. Emulsifiers are used to combine materials that normally do not mix well (such as oil in water) into one blended product. There are food (salad dressing) and non-food (paint) applications. Surfactants are materials that make water, or other liquids, ‘slicker.’ The presence of a bio-based surfactant will allow products such as cleaners, adhesives, foams, food products (For example, mayonnaise) and others to provide valued product performance while avoiding petroleum-based options. Continued progress has been made on developing high performance industrial and food grade emulsifiers and surfactants using amylose inclusion complexes (AIC) made from corn. An AIC is formed from starch, which can be from corn, and a vegetable oil derivative (called a ligand). This ligand can be a fatty acid salt or a fatty amine salt. The starch part of the AIC is the carrier, and the ligand provides the performance. The emulsifier/surfactant market is valued at tens of billions of dollars and uses billions of pounds of petroleum-based chemicals. Relative to traditional uses of corn starch, as a food product or in paper, the AICs in these markets will increase revenue to for corn starch producers and processors. The AICs were, in general, non-foaming emulsifiers. AICs made using fatty amine salts have shown value in emulsifying essential oils (such as garlic oil) to control mosquitos. Ligands that were fatty amine salts were found to have improved performance relative to the fatty acid salt AICs.
Given that amines and acids will be altered by pH, it has been shown that pH (how acidic or basic a solution is) can affect the performance of the AIC emulsifier/surfactant. The fatty amine salt AICs, in general, performed well in acidic solutions. Certain ammonium salts, called quaternary ammonium salts, are not affected by pH. When didecyldimethylammonium chloride (DDAC), a fatty quaternary ammonium salt, is used as the ligand in an AIC (DDAC), the material can produce be used to emulsify pinewood oil. The resulting emulsified system is a very effective termiticide, killing 100% of termites exposed to the treated wood. The advantage of the DDAC is that the performance of the AIC is less dependent on pH.
While corn starch has often been used as the carrier in an AIC, other carbohydrates can be used. Corn starch has a very large molecular structure while that of another tested carbohydrate, called dextrin, is on the order of 20 times smaller. This great reduction in size allows dextrin AICs to modify the properties of a solution more quickly. When a corn starch fatty amine salt AIC is used as a surfactant, it takes more than 30 minutes for the water system to reach equilibrium. When dextrin is substituted for corn starch, the same system reached equilibrium in three minutes, a 10-fold improvement. Shorter times to reach equilibrium has value. Relative to the industry standard sodium dodecylsulfate, the dextrin AIC is a better surfactant (increased value), but still takes longer to reach equilibrium (lower value). The ability of the dextrin to act as an emulsifier is more sensitive to changes in pH than the corn starch versions. All of the fatty amine salt AICs kill microbes, which may have great value, depending on the desired end-use.
Objective 2. Sorghum is a high-volume, heat- and drought-resistant ancient grain that is used as a staple food and animal feed around the world. Sorghum also has value as a source for bioethanol. Current interest in sorghum is a result of the steep growth of alternative plant-based proteins market, such as gluten-free products. Sorghum value can be further increased but would require improved methods for utilizing each component of the seed including the starch, protein, oil, and fiber. The extraction and use of sorghum protein has been a challenge to processors because of the highly water-repelling nature of the protein. This attribute will impact sorghum protein extraction, recovery, and the final protein properties. Progress was made to develop bench-scale protein extraction methods for sorghum. Improved processing methods are needed to extract a unique mixture of sorghum protein fractions that may have novel or enhanced characteristics. In the current work, sorghum grain was processed, on a pilot scale (40 pounds), by wet-milling in a fashion similar to corn and from which three multi-pound fractions were obtained. The protein-rich fraction, called sorghum gluten meal, will be subjected to many protein extraction methods in the upcoming year’s research to define protein yield, purity, and value. In addition, sorghum starch was isolated and will be used to produce AICs. Finally, sorghum fiber was obtained, and it will be used to increase the value of polymer composites such as those using corn-based polylactic acid. Sorghum oil can also be obtained from the same fiber co-product, given that the oil-rich germ is recovered with the fiber.
It has been shown in previous year’s research that plant-based proteins have great value and can be an acceptable replacement for animal-based proteins for animal or human consumption. In additional research under Objective 2, considerable progress was made to develop environmentally friendly or ‘green’ methods for isolating proteins from new pennycress varieties and study their properties. Pennycress is a high oil (useful as a biodiesel source), high protein winter annual crop that can serve as feedstock for new farm products that increase revenue to farmers without impacting current corn/soybean production. New pennycress-derived varieties with specialized traits have been developed to establish the plants as unique cover crops and as cash crops for oil and protein. However, no research has been done to assess the new specialty varieties’ protein extractability and properties of protein or oil. Additionally, alternatives to petroleum-based solvents for defatting are being sought to better align with consumer preferences for ‘clean’-labelled products. Through a collaboration with an industrial partner, we developed an improved method for isolating protein from a new high value pennycress variety and assessed protein yield and properties. We produced high purity proteins (85-95% protein) through this ‘green’ technique that involved cold pressing, alcohol defatting and saline extraction. These proteins are highly soluble, and display notably improved foaming, emulsification, and water-holding properties. Solubility dictates a protein’s other functional properties (that is, being insoluble is usually not beneficial) and thus will drive value. Foaming properties are important in products such as shaving creams, foamed glues or whipped dairy products. Emulsification, the blending of incompatible liquids (example, oil and water), is a critical attribute for products like dairy beverage alternatives, protein shakes, salad dressings, facial creams, or paints. In baked goods, meat products, soups and gels, the ability to hold water will affect the texture of the product. These results showed that high purity pennycress protein with excellent properties can be isolated from specialty golden pennycress by using this newly developed environmentally friendly protein isolation method.
Accomplishments
1. Developed an environmentally friendly process for pennycress protein isolation. Pennycress is a winter annual that is being established as a cover crop and as a cash crop for oil (biofuel) and protein. Not only will pennycress provide an additional revenue stream to farmers, but its use as a cover crop can also increase soil quality while reducing runoff. New and improved pennycress varieties have been developed as a novel source of plant-based protein; however, no research had been done to determine if these new varieties have improved protein extractability and if the protein had market-valued properties. In addition, alternatives to petroleum- based solvents for defatting are being sought to better align with consumer preferences for ‘clean’-labelled products. ARS researchers in Peoria, Illinois, developed an environmentally sustainable method for extracting protein from the new pennycress varieties. The newly developed method produced a high-purity, highly soluble protein isolate with excellent foaming (important in whipped dairy products or dairy beverage alternatives), emulsifying properties (useful in salad dressing or paints), and water-holding properties (improving the texture of food products), thus increasing the value of recovered protein. These new protein products will increase value and acceptance of pennycress crops and subsequently benefit farmers, downstream processors, and consumers.
2. Improved biobased emulsifiers. Emulsifiers are used to combine two liquids that are not compatible (for example vinegar and oil). Current commercial emulsifiers include octenylsuccinic anhydride-starch’ (a commercially available chemically altered starch with usage limits), gum Arabic (which experiences large pricing swings and is not a domestic product), soy protein (which has allergenicity concerns) and sodium lauryl sulfate (made from toxic agents). Emulsifiers made from renewable materials can have great commercial value. ARS researchers in Peoria, Illinois, have demonstrated that amylose inclusion complexes (AIC) made from starch and vegetable oil derivatives are very effective emulsifiers. There are roughly 3 billion bushels of corn which are available for export, future use or the development of new products. An AIC is made from corn starch, and a ligand, a derivative of vegetable oil. All of the raw materials are commercially available in large quantities. The AIC produced from these materials uses a process commonly used in the food and paper making industries called steam jet cooking. The AIC is made in near 100% yield, essentially no lost material, and can be used as produced or after removal of water using common industrial techniques. Some AICs may be generally recognized as safe, and others will have pesticidal activity, which will increase their value in certain markets. This new high value domestic biobased/biodegradable emulsifier will benefit corn growers, processors and the consumer.
