17G-18 |
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C. PANCHAPAKESAN1, C. I. Moraru2, H. Dogan1, and J. L. Kokini1. (1) Dept. of Food Science, Rutgers, The State Univ. of New Jersey, Center for Advanced Food Technology, 65 Dudley Rd., New Brunswick, NJ 08901-8520, (2) Dept. of Food Science, Cornell Univ., Stocking Hall, Ithaca, NY 14853 Atomic Force Microscopy (AFM) has been recognized as an important characterization technique for macromolecules and polymer materials. AFM is a powerful, revolutionary technique that enables surface morphology of the sample to be analyzed in addition to being a force analysis tool and molecular organization characterization tool. Our objective was to explore and understand the possible applications of this nano-tool in food biopolymer systems, primarily involving films of zein, a maize protein. Zein films were solvent cast and analyzed for physicochemical characteristics by using Atomic Force Microscope (Veeco Instruments, CA). The contact mode of operation was used and typical scan sizes ranged between 2-10 nm and scan rates of 1 Hz were employed. For additional information about the surface properties line analysis, bearing analysis etc were conducted. Force measurements were made on the film to study the effect of plasticizer content on the molecular mobility of the film at nano-scale levels. The zein films were equilibrated to varying water activity levels (0.12-0.97) and the adhesive force was measured at each point. The results were then compared with traditional techniques (DSC). Structural details were visible at scan sizes of 5 microns and surface analysis yielded an average roughness of 21.878 nm. Line analysis and bearing analysis provided an insight into the characteristics of the pinholes and aggregations seen on the surface of the biopolymer matrix at micrometer levels. Adhesive force measured at each point yielded information about the increase in plasticization and thus mobility in the sample. Comparison with DSC provided a better understanding of the properties of the biopolymer films at nanoscopic level and correlated the properties to the behavior at the macroscopic levels. This allowed us to characterize, for the first time, the dependence of the nano-forces responsible for surface adhesiveness, on the moisture content of a food biopolymer matrix.
Session 17G, Food Engineering: Physical, chemical and electrical properties
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