Location: Functional Foods Research Unit
Title: Comparison of microwave processing and excess steam jet cooking for spherulite production from amylose-fatty acid inclusion complexes Authors
Submitted to: Starch/Starke
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2013
Publication Date: March 30, 2013
Citation: Felker, F.C., Kenar, J.A., Fanta, G.F., Biswas, A. 2013. Comparison of microwave processing and excess steam jet cooking for spherulite production from amylose-fatty acid inclusion complexes. Starch/Starke. 65(9-10):864-874. Interpretive Summary: 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 spherulite particles that form when cooked starch is cooled in the presence of a native or added fatty acid ligand (guest molecule). This study was made to determine whether microwave processing technology could be used to increase the yield of spherulites, enable the production of spherulites of uniform morphology, and investigate alternate ligands 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. Controlled, bulk production of starch spherulites will enable their characterization and evaluation for use in applications such as microbial substrates, delivery systems, functional foods, or controlled release agents.
Technical Abstract: Helical inclusion complexes of amylose with fatty acids can form spherulites of various morphological types. Previous studies have described the spherulites obtained by cooling dispersions of steam jet cooked corn starch either by itself or supplemented with various fatty acids. In light of potential advantages of microwave processing, we investigated the use of a laboratory microwave instrument as an alternative method for spherulite production. With native high amylose corn starch (HAS), spherulites were formed with morphology similar to those observed previously by steam jet cooking. Adjustments to the reaction conditions led to slight improvement in yield over jet cooking. Using solvent-defatted HAS supplemented with straight-chain fatty acids (C10:0 to C22:0), microwave processing produced only small, disc-shaped spherulites in a gel matrix. However, when defatted HAS was supplemented with either capric or palmitic acid and processed by steam jet cooking, a uniform dispersion of toroidal spherulites was obtained. These results show that although jet cooking is not required for spherulite formation when native HAS is used, defatted HAS requires the high-shear steam jet cooking method of heating for optimal spherulite growth. Microwave experiment results could be adapted to jet cooking methods for large scale spherulite production.