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Films prepared from poly(vinyl alcohol) and amylose-fatty acid salt inclusion complexes with increased surface hydrophobicity and high elongation

Fanta, George F., Felker, Frederick C., Selling, Gordon W.
Starch/Stärke 2016
amylose, composite materials, contact angle, cooking, corn starch, droplets, films (materials), glycerol, hydrophobicity, microscopy, polyvinyl alcohol, salts, sodium, steam, surface roughness, tensile strength
Water-soluble amylose-inclusion complexes were prepared from high amylose corn starch and the sodium salts of lauric (C(12)), palmitic (C(16)), and stearic (C(18)) acid by steam jet cooking. Cast films plasticized with glycerol were prepared by combining solutions of the amylose complexes and poly(vinyl alcohol) (PVOH) at ratios varying from 100:0 to 0:100. All amylose complex formulations up to 60% incorporation had percent elongations equivalent to or greater than the PVOH control. Tensile strength was similar to control films up to 40% incorporation of the C(16) complex. All films prepared from these amylose complexes had tensile properties superior to composite films containing uncomplexed corn starch. Contact angles of water droplets showed that incorporation of as little as 20% amylose complex yielded films with increased surface hydrophobicity. Microscopy of iodine-stained films showed that the films contained a starch-rich phase and a continuous unstained background of PVOH. Surface roughness and the close proximity of the micron-sized areas of starch complex may contribute to the high contact angles observed at low concentrations of complex. This study enables production of PVOH films containing substantial levels of biobased starch, a good balance of physical properties, and greatly increased surface hydrophobicity relative to the PVOH control.