| Gelatin film has good biocompatibility and degradability, but it also has some disadvantages, such as inferior strength, low barrier capacity and so on. So in this paper, the effects of three kinds of corn starch with different amylose content on gelatin and collagen were studied respectively, and the effect of different gelatinization degree of high amylose starch on the properties of gelatin film were studied.First, In order to find new reinforcing bio-fillers to improve gelatin films'performance, the gelatin films were composited with three types of maize starches:waxy maize starch (Ap), normal starch (Ns), and high amylose starch (Al), and their properties were investigated, focusing on the impact of amylose content. The thickness,opacity and roughness of gelatin films increased depending upon amylose content and additive amount of starch. Effects of three starches on mechanical properties of gelatin film were governed by amylose content, starch concentration, as well as environment humidity. At 75% RH, the addition of A1 and Ns into gelatin matrix increased film strength but decreased elongation except for Ap, which had an inverse effect. The addition of all starches decreased film oxygen permeability, with the lowest value at the amount of 20% Al and Ns. All starches, notably when the starch content are 30%led to a decrease in water vapor permeability of the composite films at 90% RH,especially Ns starch. Furthermore, starches improved film's thermal stability to some extent. The FTIR spectra indicated that some weak intermolecular interactions such as hydrogen bonding occurred between gelatin and starch. Moreover, a high degree of B-type crystallinity of starch was characterized in the Gel-Al film by X-ray diffraction.Tailoring the properties of gelatin film by the incorporation of different types of maize starch provides the potential to develop and extend its new applications in edible food packaging, especially for high humidity environment.Second, this study investigated the possibility of enhancing the properties of collagen with three different maize starches: waxy maize starch, normal starch, and high amylose starch. Scanning electron microscopy images revealed that starch-collagen films had a rougher surface compared to pure collagen films which became smoother upon heating. Amylose starch and normal starch increased the tensile strength of unheated collagen films in both dry and wet states, while all starches increased tensile strength of collagen film by heating. Depending upon the amylose content and starch concentrations, film solubility in water decreased with the addition of starch. DSC thermograms demonstrated that addition of all starches improved the thermal stability of the collagen film. Moreover, X-ray diffraction results indicated that except for high amylose starch, the crystallinity of both starch and collagen was significantly decreased when subject to heating. FTIR spectra indicated that intermolecular interactions between starch and collagen were enhanced upon heating.Lastly, in order to study the impact of starch in film performance, high amylose corn starch was composited in gelatin films under different gelatinization conditions and, in high and low concentrations (10 and 50 wt.%). It was found that hot water gelatinized starch (Gel-Shw) increased film mechanical strength and was dependent upon the starch concentration. The addition of an alkali component to the starch significantly enhanced the swelling of the starch granules and expedited the gelatinization process. Incorporation of starch, especially the alkalized starch (Sha),into the gelatin films decreased film solubility which improved its water resistance and water vapor permeability (WVP). Multiple techniques (DSC, TGA, FT-IR, and XRD)were used to characterize the process and results, including the crosslinking of the dissolved starch molecules and the particles formed from gelatinized starch during retrogradation process, which played an important role in improving the thermal stability of the composited gelatin films.Overall, the starch provides a potential approach to improve gelatin/collagen film performance and benefit their applications in the food industry. |
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