Preparation and Property Comparison of Four Modified Starches and Gelatin Blended Films
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Abstract:
Gelatin-blend films with four modified starches (hydroxypropyl distarch phosphate, hydroxypropyl starch, oxystarch, and oxidized hydroxypropyl starch) were analyzed in terms of solubility, swelling potential, pasting characteristics, and aging value. Starch with high solubility, low swelling potential, good gelatinization characteristics, and low aging value is more suitable for preparing blend films. For this, glycerol or polyethylene glycol 400 (PEG400) was addedas bulking agent to prepare starch-gelatin blend films, and the proportions of water and glycerol in the formula were tested. Ultraviolet (UV) spectroscopy, scanning electron microscopy (SEM), and tensile testing were used to determine the light transmittance, water vapor transmission, microscopic morphology, and mechanical properties of the blend films. The results showed that hydroxypropyl starch had the highest solubility (86.42%). Its swelling potential of 0.086% was the lowest, compared to those of the other three starches, while the stability was higher. Its low viscosity provided good fluidity and enabled easier film formation. It had a larger aging value as well. All these properties indicate that among the four modified starches, hydroxypropyl starch is the most suitable for blending with gelatin. Specifically, we report that the blend film with hydroxypropyl starch has higher transmittance than pure gelatin, good water vapor permeability, and mechanical properties. The micromorphology, as shown by SEM, shows good compatibility. Compared to PEG400, glycerol provides a more uniform and smoother cross-section for the blend film. The gelatin: glycerol: water mass ratio of 1:9:3:13 produced a blend film with the highest light transmittance, highest water vapor permeability, and best mechanical properties. Hence, this blend film has good potential for practical applications.
