Location: Plant Polymer Research
2019 Annual Report
Objectives
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. As a result 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: Enable, from a technological standpoint, the commercial production of marketable products from the proteins in crops such as pennycress, camelina, soybean, cottonseed or corn. Sub-objective 1A. Establish pilot-scale extraction and biorefining techniques that generate protein-rich industrial feedstocks from plant crops, such as pennycress, camelina, soybeans, or cottonseed.
Sub-objective 1B. Determine ability to form solvent cast and melt processed films or articles, as well as surface and interfacial tension agents; determine if suitable chemical modifications of these proteins will provide products that can replace petroleum-based products.
Approach
Establish pilot-scale extraction and biorefining techniques that generate protein-rich industrial feedstocks from plant crops, such as pennycress, camelina, soybeans, or cottonseed. Determine ability to form solvent cast and melt processed films or articles, as well as surface and interfacial tension agents. Determine if suitable chemical modifications of these proteins will provide products that can replace petroleum-based products.
Progress Report
Significant progress was made on both objectives which fall under National Program 306: Quality and Utilization of Agricultural Products, specifically Component 2, addressing Objective 1.3 of the ARS Strategic Plan.
Under Sub-Objective 1A of this research project, the effects of genetic modification for oil quality (acetyl-triacylglycerols, acTAG) on the heat stability of camelina protein was evaluated and compared with wild camelina. Proteins from either source were only minimally affected by heat treatment. However, the protein isolated from camelina-acTAG was more heat-stable at all pHs than that isolated from wild camelina. The impact of mucilage removal (degumming) prior to protein extraction was evaluated for its effects on protein yield and properties. Mucilage was extracted using an aqueous technique developed by ARS scientists in Peoria, Illinois. Mucilage yield was as high as 42% of starting meal, indicating its potential as a major co-product. Camelina ac-TAG had greater mucilage yield than wild camelina. The mucilage from both sources had substantial amounts of co-extracted protein. Protein yield was significantly increased after degumming for the camelina acTAG only. The purity of the protein extracts from both camelina sources was improved after degumming. Protein extracts from the degummed samples showed markedly higher solubility than those from nondegummed camelina. Degumming did not affect the thermal stability of the camelina proteins.
Under Sub-Objective 1A of this research project, pilot-scale (5 kg) production of glandless cottonseed protein isolate was conducted using a method based on alkali extraction/acid precipitation. This process produced 1.5 kg of protein isolate (95% crude protein). The yield is 50% more than that obtained in previous runs done by ARS-SRRC collaborators. Water was removed from the protein isolate by freeze drying. The protein isolate that was quick-frozen and freeze-dried in flasks was off-white while the portion that was frozen in the freezer and placed in the tray freeze-dryer was light brown. Color differences were quantified using colorimetric procedure. The composition of both samples was the same, suggesting that these color differences are physical in nature and a result of the rate of cooling.
Under Sub-Objective 1B of this research project, efforts were carried out to evaluate films using glandless cottonseed protein isolate and to determine if fibers could be electrospun. In order to define the product value of glandless cottonseed protein, a proper solvent was required. After evaluating numerous solvents, formic acid was found to be suitable, generating solutions having up to 30% protein solids. While clear amber colored films could be produced, fibers could not be formed using electrospinning. From the evaluation of a variety of plasticizers, preliminary results suggest that levulinic acid and glycerol give the best overall physical properties. Optimization of the cottonseed formulation is in progress.
Under Sub-Objective 1B of this research project, pennycress protein isolates (PPI) produced by replicate runs of the pilot-scale (5 kg) processes (alkali extraction/acid precipitation or saline extraction) were evaluated for foaming and emulsification properties. Saline-extracted PPI had good foam capacity and excellent foam stability; these were near-identical to values obtained for the lab-scale protein isolate. Pilot-scale acid precipitated PPI had poor foam stability. Like the bench-scale findings, saline-extracted PPI had good emulsifying activity values which increased with pH. The saline-extracted PPI was a much better emulsifier than the acid-precipitated PPI. The emulsification properties of PPI extracted from either process were better at elevated pH. The pilot-scale PPI had poorer emulsifying activity compared with the lab-scale proteins. Efforts are underway to understand the source of this difference.
Previously it was determined that formic acid was the best volatile solvent for acid precipitated PPI. Electrospinning PPI formic acid solutions did not produce fibers. By combining PPI with corn protein (zein), ribbon-shaped fibers could be produced by electrospinning from formic acid solution. Centrifuging the PPI and zein solution before spinning gave fiber mats with fewer defects. Electrospinning an 80:20 blend of zein and PPI in the formic acid solution provided ribbon fibers having a diameter of ~0.5 micrometers. Currently, the value of PPI fibers is not significant enough to warrant additional research in this area.
In collaborative research with Purdue University scientists, ARS scientists in Peoria, Illinois, produced electrospun zein fibers or zein extrudates that were evaluated for their ability to produce high-quality gluten-free bread. The preferred starch used to produce the bread was made from rice. Zein fibers, having certain plasticizers, were found to provide bread doughs with high elasticity, comparable to wheat-based doughs. However, the zein doughs do not undergo strain hardening (the property which allows wheat-based bread to maintain its loaf shape). Zein extrudate was prepared at temperatures from 90–160°C. As determined in earlier research by ARS, zein processed at elevated temperatures can undergo molecular weight gain due to disulfide bond formation. When zein extrudate (160°C) was incorporated into bread dough using rice starch, doughs of similar quality to wheat were produced. Additional testing is underway to assess bread production.
Amylose inclusion complexes (AIC) formed from high amylose corn starch and fatty ammonium salts (obtained commercially from vegetable oil) have been found to be an effective pesticide. To be used commercially, it must be determined if the use of AIC has a detrimental effect on plant growth and health. Three corn trials were carried out in the greenhouse using control corn seed, corn seed coated with AIC, and corn seed being watered with an AIC aqueous solution. These tests were run in soil from a local farmer's field or in potting media, and growth was monitored for four weeks. Plant health (emergence and leaf color) and growth rate (plant height and final whole plant biomass above/below ground) were measured. Within experimental error, the presence of AIC had no impact on corn plant health and growth. There were no beneficial or adverse effects observed when AIC aqueous solutions were also applied to wheat, soybean, cabbage, and tomato plants in the absence of pests.
At a local orchard, various solutions of AIC with polyvinyl alcohol (PVOH) were applied to the pruning wounds of apple, cherry, pear, apricot, and peach trees to form protective films over the wound. In lab testing, these same films were found to have antimicrobial properties. In most samples, the AIC/PVOH films were found to last several months on the pruning wounds in the orchard. Some individual samples lasted one year in the orchard. The presence of these films may reduce infection of the tree through the pruning wound.
Accomplishments
1. Pilot-scale production of pennycress protein isolate. Pennycress, an annual winter crop with seed oil being developed as a biodiesel source, has other seed components that must also be utilized to maximize the value of pennycress. ARS scientists in Peoria, Illinois, have determined the conditions for pilot-scale extraction and purification of pennycress protein. Two industrially friendly processes were developed to provide high purity pennycress protein isolate (PPI). Protein recovery and purity are comparable to those of typical industrial processes. The pilot processes produced 0.6 kg of high purity PPI which can be used by ARS scientists or researchers from other institutions. The PPIs were highly soluble in water, had excellent emulsifying activity, and produced substantial and stable foams. These attributes will broaden its possible end-uses. The PPI from this work was found to make quality films and was an effective suspending agent for vanilla extracts. Producing larger amounts of high purity PPI provides confidence to potential pennycress converters, and this material may be transferred to other researchers to develop new high-value markets for pennycress. These efforts will result in increased worth of a pennycress crop and may generate additional revenue streams for farmers and downstream processors.
2. Improved food-grade emulsifier. There is a need for improved food-grade emulsifiers that do not have limits on their use in foods. ARS scientists in Peoria, Illinois, have developed an economical food-grade emulsifier that uses high amylose corn starch and fatty acid salts (obtained from vegetable oil). When these two materials are processed using an industry standard technique, an amylose inclusion complex (AIC) forms. In the AIC, the amylose corn starch is wrapped around the fatty acid salt. The AIC can interact with oil to allow the formation of a suspension in water (the AIC acts as an emulsifier). This would have value in salad dressing, ice cream, sodas, baked goods, and other products. This technology will be able to replace imported emulsifiers or those that have limits on their usage. These new products will result in new applications for corn starch benefiting corn producers, processors, and consumers.
Review Publications
Hay, W.T., Fanta, G.F., Felker, F.C., Peterson, S.C., Skory, C.D., Hojilla-Evangelista, M.P., Biresaw, G., Selling, G.W. 2019. Emulsification properties of amylose-fatty sodium salt inclusion complexes. Food Hydrocolloids. 90:490-499. https://doi.org/10.1016/j.foodhyd.2018.12.038.
Moser, B.R., Doll, K.M., Peterson, S.C. 2019. Renewable poly(thioether-ester)s from fatty acid derivatives via thiol-ene photopolymerization. Journal of the American Oil Chemists' Society. 96(7):825-837. https://doi.org/10.1002/aocs.12244.
