Location: Plant Polymer Research
2024 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
ARS researchers in Peoria, Illinois, have found that amylose inclusion complexes (AICs) derived from corn starch and vegetable oils can produce effective food and industrial emulsifiers and surfactants. Food applications include salad dressings, while industrial applications include cleaning solutions and personal care products (e.g. shampoos, cleansers, etc.)
All previous work with AICs utilized a special grade of corn starch referred to as high amylose corn starch. While this grade of corn starch provided AICs with excellent performance as a bio-based surfactant/emulsifier, as well as an antimicrobial and pesticidal agent, it is relatively expensive compared to other grades of starch obtained from corn and other plants. In support of Objective 1, significant progress was made to investigate the performance of AICs obtained from lower cost sources of starch, including normal corn starch, waxy corn starch, potato starch, and sorghum starch. AICs from these lower cost types of starch were successfully produced and are being characterized and evaluated for performance as a surfactant/emulsifier. Interestingly, simple visual observation of dispersions of these different AICs in water showed that two starches with the lowest amylose content (potato and waxy corn) were much less hazy than the others, suggesting much lower particle size of the AICs, which may enable improved performance as a surfactant/emulsifier.
In addition to understanding the effect of the nature and source of starch, research is being conducted to understand the effect of the vegetable oil component of the AIC on performance, specifically, emulsification properties, antimicrobial activity, and pesticidal activity. A series of AICs possessing systematic variations in the chemical composition of the vegetable oil-derived component of the materials were produced and characterized. All samples formed AICs without issue using steam jet cooking and all showed emulsification potential. The AICs are currently being evaluated for potential to replace a common petroleum-based surfactant, sodium dodecyl sulfate, in shampoos. In addition, the AICs are being evaluated for antimicrobial properties and pesticidal activity toward nematodes, a class of pests that cause crop damage.
Improved techniques for extracting proteins from sorghum and other crops are needed to maximize the amount and quality of the protein product. Plant-based proteins continue to have high demand for the alternative protein markets (2024 global market=US$14.2B). Sorghum’s major proteins have posed challenges for extraction, recovery, and protein quality using conventional extraction methods. In support of Objective 2, substantial progress was made to develop and assess a blended solvent approach (ethanol/alkali) to improve sorghum protein yield and properties. The baseline extraction method using 45% ethanol/55% 0.1 N NaOH at 50°C was applied to ground undefatted or defatted pearled sorghum and wet-milled sorghum protein meal. Protein yield, purity/composition and functional properties were then determined. The baseline ethanol/alkali method had high protein recoveries (78- 83%) and produced high-purity (87-97%) protein extracts. Protein isolates and spent solids of ground pearled sorghum had much lighter color than sorghum protein meal from conventional wet milling. Protein solubility index (PSI) values of pearled sorghum starting meals were low (30%), but five-fold greater than that of wet-milled sorghum protein meal. The protein isolates of the pearled sorghum samples and wet-milled sorghum protein meal showed markedly improved solubility, with PSI of 99% (practically fully soluble) and 20%, respectively. All the sorghum protein isolates produced substantial foams, but only the protein from defatted pearled sorghum showed moderately stable foam (64% remaining foam after 15 min). The defatted pearled sorghum protein isolate showed notable emulsification properties that were superior (five-fold greater emulsifying activity and two times more stable) to those reported for soy protein isolate. When the proportion of ethanol in the blend was changed to 35% or 55%, protein yield and isolate purity were essentially the same as that of 45% but using 15% ethanol in the blend reduced protein yield by 50% and purity by 33%. This work demonstrated the significantly enhanced yield, solubility, and emulsifying ability of sorghum protein obtained by using ethanol/alkali for extraction.
In further support of Objective 2, research was conducted on agricultural hemp seeds to evaluate the effects of seed maturity and variety on protein quality. Through a research collaboration with a university and other ARS researchers in Peoria, Illinois hemp seeds from Henola variety were analyzed for protein extractability, soluble protein classes, and polypeptide size. Protein recovery from mature seeds was greater than that from immature seeds (68-73% versus 60%). Seed maturity also notably affected the proportion of soluble protein groups, with the alkali-soluble glutelins being dominant in mature seeds, while the water-soluble, saline-soluble, and alcohol-soluble proteins were abundant in immature hemp seeds. Additionally, 16 established and new varieties of hemp grain provided by an industry partner were analyzed for soluble protein classes and protein recovery to determine varietal differences.
Overall, total protein content among the varieties were similar and within a narrow range, 24-27%; however, the amount of each soluble protein group varied greatly. This work demonstrated the notable effects of seed variety and maturity on the amount of each soluble protein group, which will impact the method of hemp seed protein extraction and subsequent yield.
Accomplishments
1. Expanded utilization and value of sorghum. Sorghum is an ancient grain with potential for significant use as a staple food and biofuel source, but its current market is limited to mainly livestock feed. One of the key barriers to expanding the use of sorghum is the challenge related to protein extraction and utilization via conventional methods. ARS researchers in Peoria, IL, developed an environmentally friendly method for extracting sorghum protein with improved yield and properties. This industrially relevant method used ground pearled sorghum and produced high-purity protein isolate that has potential to be useful in both food applications, such as yogurt, dairy alternative beverages, salad dressings, baked goods, and alternative meat products, and industrial applications, such as adhesives for wood-based products. The new protein products serve as an additional revenue stream for sorghum, will increase the crop’s value, and consequently benefit farmers, downstream processors, consumers, and the environment.
2. Biobased products to control harmful microbes and insect pests. ARS researchers in Peoria, IL, have developed new antimicrobial and insecticidal materials from corn starch and vegetable oils that are referred to as amylose inclusion complexes (AICs). One class of pests that can cause considerable damage to crops are nematodes. A collaboration with ARS researchers in Corvallis, OR, demonstrated that specific AICs are highly effective toward combating nematodes. This result indicates that the AIC technology will benefit not only starch and seed oil producers and processors, but also growers that have a need to combat nematodes.
Review Publications
Hojilla-Evangelista, M.P., Evangelista, R.L., Selling, G.W., Ulmasov, T.N. 2024. Cold-pressing, ethanol defatting, and saline extraction enhances properties of protein products from new pennycress varieties (covercress). Sustainable Food Proteins. https://doi.org/10.1002/sfp2.1029.
Selling, G.W., Hay, W.T., Peterson, S.C., Hojilla-Evangelista, M.P., Kenar, J.A., Utt, K.D. 2024. Structure and functionality of surface-active amylose-fatty amine salt inclusion complexes. Carbohydrate Polymers. https://doi.org/10.1016/j.carbpol.2024.122186.
Selling, G.W., Cermak, S.C., Kenar, J.A., Finkenstadt, V.L. 2024. Preparation of starch coconut fatty acid inclusion complexes by twin-screw extrusion. Starch. https://doi.org/10.1002/star.202300228.