The effects of starch source and various supplementary materials on the properties of starch based foam plates

The aim of this study was to produce a foam plate having low density, low water absorption and high mechanical resistance from glyoxal cross-linked corn, wheat, potato starches and their mix and various fibers, lipids and filling matters. In the first stage of the study, starch source was determined for production of ideal foam plate. For this purpose foam plates was produced from 0,126 g glyoxal/kg starch cross linked starches and their mixture. Thickness, density, water content and water absorption of the foams were measured. Mechanical properties of the foams were determined with flexural test. As results of analysis, the mechanical properties of the plates having enough foaming structure were similar to each other. However, density (0,17g/cm3) and water absorption (25.5%) of the foam plate produced from cross-linked wheat-potato starch (BP). were lower than that of other plates. Therefore, it was found that the most suitable starch source to produce a foam plate was the mixture of cross linked wheat-potato starch Three different fiber sources (wood, wheat and bamboo fiber), two different lipid types (beeswax and anhydrous hydrogenated margarine) and four different types of filling matter(kaolin, nanoclay (montmorillonite), silicon dioxide (SiO2), and zinc oxide (ZnO) nanoparticles ) was added to the mixture of cross-linked wheat-potato starch to improve plate properties additionally. Fiber type caused the most reduction on the water absorption of plates was wheat fiber (7 %) and lipid type was anhydrous hydrogenated margarine (10 %). Nanoclay increased the water absorption of the plates, silicon dioxide nanoparticles was not effect water absorption of the plates. It is found that the addition of kaolin (1% ) and zinc oxide nanoparticles (1% ) was decreased the water absorption of plates. The thickness, density, equilibrium moisture content, water absorption, color values and mechanical properties of the foam plates produced by adding the most appropriate kind and amount of the supplementary materials to wheat-potato starch were measured. Surface and cross-section of the plates were examined using a scanning electron microscope (SEM). The crystal structure of the plates was determined by the X-ray diffraction analyzes, and melting temperature and melting heat of them were determined by the differential scanning calorimeter (DSC). The thickness of the plates increased by the addition of all supplementary materials to cross linked wheat-potato starch. The plate which produced by the addition of 7% wheat fiber of the starch weight to cross-linked wheat-potato starch (BPL) and by the addition of 7% wheat fiber, 10% anhydrous hydrogenated margarine of the starch weight(BPLS) were have lower density than BP plate. The densities of these plates were 0.115 ± 0.013g/cm3 and 0.148 ± 0.005g/cm3 respectively. The density values of the plate which produced by the addition of 7% wheat fiber, 1% zinc oxide nanoparticles(BPLN) and by the addition of 7% wheat fiber, 1% zinc oxide nanoparticles, 10% anhydrous hydrogenated margarine(BPLNS) were the same as BP plate. Plates containing kaolin were found to have a higher density than the BP. While the water absorption content of BP plate was 25.50±0.74%, the water absorption of BPL, BPLS and BPLNS plates were decreased to 16.64±1.25%, 6.4±0.01% and 5.85±0.29% respectively. The surface micrographs of plates showed that the plates which were not include supplementary materials have more crack on the surfaces. But by the addition of supplementary materials the cracks were decreased evidently. The cross-sectional micrographs of the plates showed that BPL plate, having the lowest density, had thicker structure, smoother cell and greater cell size. L * value of the plates increased with the addition of all the supplementary materials. In the other words the color values of the plates were lighter with the addition of supplementary materials. And, BPLN and BPLNS plates had the lightest color. Fiber addition to cross-linked wheat-potato starch raised the melting temperature and the melting heat of the plate. Other supplementary materials (kaolin, nanoparticle, anhydrous hydrogenated margarine) affected differently the melting temperature of the plates but reduced the melting heat. The migration tests were conducted by BPLS and BPLNS plates which have less water absorption capacity. The glyoxal migration from plates to pure water was found lower than the upper level set by the Federal Institute for Risk Assessment (BfR). After antibacterial tests, it was found that zinc oxide nanoparticles showed antibacterial effect on E. coli XL 1-Blue, but silicon dioxide and the plates containing zinc oxide nanoparticles (BPLN and BPLNS) was not show antibacterial effect. Due to plates were not gain antibacterial effect by the addition of nanoparticles and also all filling maters did not affect positively other features of the plates, it was concluded there was no need to add filling matters (kaolin, nanoclay (montmorillonite), silicon dioxide and zinc oxide nanoparticles) while producing foam plates. As a result of this thesis study, it was determined that the most suitable plates can be produced by using cross-linked wheat-potata starch, wheat fiber and anhydrous hydrogenated margarine (BPLS) and it can be used safely for food packaging and servicing.