Location: Functional Foods Research2013 Annual Report
1a. Objectives (from AD-416):
The overall project goal is to develop new technologies for producing amylose helical inclusion complexes on a large scale that provide new biobased applications to replace existing petrochemical-derived products, covalently modified starches, and natural gums using energy-efficient, green manufacturing techniques. Helical inclusion complexes of amylose and various ligands have been described in the literature, but they are typically produced in small quantities using various solvents and alkaline solutions. The goal of this project is to characterize thermomechanically-produced amylose helical inclusion complexes and investigate commercial applications based on their chemical and physical properties. Specific objectives are: Objective 1. Develop biobased, environmentally friendly technology for producing amylose helical inclusion complexes with anionic ligands which are functional in applications such as water-dispersible surfactants and lubricants. Objective 2. Develop biobased, environmentally friendly technology for producing amylose helical inclusion complexes with cationic ligands which are functional in applications such as papermaking retention aids and flocculating agents. Objective 3. Develop biobased, environmentally friendly technology for producing amylose helical inclusion complexes and spherulites with uncharged ligands which are functional in applications such as controlled-release agents, microbial production substrates and dispersants.
1b. Approach (from AD-416):
Steam jet cooking technology will be investigated as an efficient method for producing amylose helical inclusion complexes with functional properties relevant to a wide range of food and industrial applications. Whereas many types of such complexes have been prepared in small quantities under laboratory conditions, this research will focus on developing thermomechanical production methods using only starch, water, and specific ligands of interest to form complexes that can be used for applications currently employing covalently modified starches, expensive natural gums, and other materials. Preliminary experiments with high amylose starch and sodium palmitate have demonstrated that amylose inclusion complexes could be readily formed in high yields in jet cooked starch dispersions. A series of anionic, cationic, and uncharged ligands will be investigated in terms of ability to form complexes thermomechanically with various commodity starches such as normal dent, high amylose, and waxy cornstarch, and their morphological, chemical, and physical properties will be determined. Specific ligands will be chosen for particular end-use applications, including surfactants, lubricants, papermaking retention aids, flocculating agents, and controlled release agents for food and non-food products. The complexes possessing crystalline spherulite morphology will be investigated as solid supports for the growth of microbes in liquid culture and as a dispersal medium for microbial products. For each application, the best ligands will be selected from available candidates, sufficient quantities of amylose inclusion complexes will be prepared using steam jet cooking methods, and laboratory tests will be performed to determine the performance of the complexes for the specific end use. As the efficacy of these products are successfully demonstrated, prototype products will be prepared and collaboration with the private sector will be sought for transfer of the technology to the private sector for field testing and market development.
3. Progress Report:
New applications for amylose inclusion complexes were investigated and their efficacy and performance in different applications were determined. (1) Uniform, resilient aerogel beads were prepared by injecting amylose-sodium palmitate complexes into dilute acid solutions. Beads dried with supercritical carbon dioxide had surface areas of 360 m2/g, compared with 100-250 m2/g for starch-based aerogels previously reported in the literature. The internal structure of the beads was characterized by light and electron microscopy. (2) The formation of nanometer-size spherulites from amylose-oleic acid complexes was accomplished by collecting the jet-cooked product directly onto crushed ice. The spherulites formed were 100-200 nm in diameter. The nanoparticles were characterized by light and electron microscopy, laser light scattering, and X-ray diffraction. Similar nanoparticles were obtained from larger, micron-sized spherulites by either sonication or homogenization treatments. (3) Amylose-sodium palmitate complexes were acidified in the presence of a styrene-butadiene rubber (SBR) latex, and the precipitate formed was dried to a powder with the SBR encapsulated by starch complexes. When subjected to high temperature, high shear extrusion processing, a phase inversion occurred yielding rubber with starch inclusions of various sizes. (4) Using high amylose starch plus palmitic acid, complexes prepared using microwave processing produced spherulites similar in size and abundance to those obtained with steam jet cooking. Adjustment of the heating protocol and holding times resulted in an increase in spherulite yield. Using defatted high-amylose starch supplemented with various fatty acids revealed the limitations of microwave processing in terms of mixing intensity and degree of starch solubilization. (5) Complexes were prepared with high amylose starch and hexadecyl amine (HDA), the amine analog of palmitic acid. Spherulites obtained upon cooling were similar to those obtained with palmitic acid. Using the HCl salt of HDA as the ligand, solutions were obtained that had low viscosity at low pH and thickened upon adding NaOH solution. The cationic complexes were found to precipitate suspended kaolin, indicating their potential for use as biobased flocculants. (6) Spherulites prepared with neutral ligands were initially found to have very low resistance to enzymatic degradation. However, further experiments revealed that they may exhibit a “slowly digestible” behavior and therefore could serve as a source of lower glycemic index starch with a sustained release of glucose. (7) Amylose complexed with potassium oleate was used as gum alternative in low-fat yogurt. Fermentation rate was not affected, texture was similar to a higher fat yogurt, and syneresis was reduced during storage. (8) Soybean-oil-derived lubricants were encapsulated into drum-dried starch-lipid composites, and independent laboratory tests showed substantially enhanced lubrication performance with less lubricant.
1. Comparison of starch spherulite production by microwave versus steam jet cooking technology. In order to provide new opportunities for biobased product development using green technology to replace synthetic or petrochemical-based materials, starch-based amylose inclusion complexes produced by steam jet cooking are being investigated. One type of these complexes is microscopic-sized crystalline particles called spherulites that form when cooked starch is cooled in the presence of a building block of vegetable oil (fatty acid). Due to their large surface area, these spherulites are suitable as biobased, biodegradable substrates for the synthesis, delivery, or dispersal of active agents for many different applications. Agricultural Research Service scientists in the Functional Foods Research Unit at the National Center for Agricultural Utilization Research, Peoria, Illinois, discovered that microwave processing could be used to increase the yield of spherulites, enable the production of spherulites of uniform morphology, and investigate alternate complexing agents for specific applications. Adjustment of the heating and cooling protocol in the microwave increased yield of spherulites from non-defatted, high amylose corn starch. Experiments with solvent-defatted starch revealed that the absence of shear forces in the microwave procedure inhibited spherulite growth, while the shear provided by steam jet cooking enabled uniform spherulite production from defatted starch. These results provide evidence that steam jet cooking remains the most appropriate approach for large-scale production, but will allow researchers to utilize microwave heating for some aspects starch spherulite investigations. The ability to use either microwave or jet cooking to produce starch spherulites will enable application research by a broader range of investigators and industry product developers.
2. Positively-charged starch complexes as replacements for chemically modified starch. Commercially available cationic (positively charged) starch is used as an additive by the paper industry to improve retention of added substances during processing and to improve overall paper quality. Cationic starches also serve as flocculating agents for various industries to treat wastewater by aggregating fine particles so they settle out or can be filtered. The current process for making cationic starch is costly and produces toxic waste; therefore, a more cost effective process that eliminates hazardous waste is needed. Agricultural Research Service scientists in the Functional Foods Research Unit at the National Center for Agricultural Utilization Research, Peoria, Illinois, discovered that cationic charges can be conferred to starch by complexation of alkaline fatty acid derivatives of vegetable oils with the amylose component of starch through a simple jet cooking process in water that eliminates hazardous waste output. The physical and chemical behavior of these cationic complexes was characterized and these materials were found to precipitate suspended clay particles, suggesting their potential for use as biobased flocculating agents. This information will be beneficial both to manufacturers of positively charged, chemically modified starch products and to the various industries that use such starches in large quantities.
Byars, J.A., Fanta, G.F., Kenar, J.A. 2013. Effect of amylopectin on the rheological properties of aqueous dispersions of starch-sodium palmitate complexes. Carbohydrate Polymers. 95:171-176.