| Summary: | 碩士 === 國立中興大學 === 食品暨應用生物科技學系所 === 105 === Development of biodegradable films has a highly practical and environmental value due to the limited resources. Therefore, the objective of this study is to investigate the properties of sugary kefir polysaccharide/starch edible films as a function of types of plasticizers (sorbitol, xylitol and glycerol) and starch (potato, tapioca and wheat). Specifically, the thickness, opacity, microstructure、hydrophobic/hydrophilic properties and mechanical properties of the films would be determined.
Physical properties of sugary kefir polysaccharide/starch edible films showed strong dependency on the types of plasticizers and starch. Generally, the thickness of the films was in the order of 30%>15% plasticizer and wheat>potato>tapioca starch. Films formed with tapioca starch and more plasticizer generally showed more transparent appearance. Microscopic examination revealed that films with wheat starch was much smoother at the cross-section, in contrast to those with the other two types of starch, which showed obvious porous structure at the cross-section.
Moisture content increased with increasing glycerol concentration, but had no significant effect with increasing sorbitol and xylitol concentration. Water vapor permeability and water solubility increased with increasing plasticizer concentration. Under side of edible films had smaller water contact angle than upper side of edible films. Most of sample groups had smaller water contact angle with higher concentration of plasticizer. The sorption isotherms of sugary kefir polysaccharide/starch edible with any type of plasticizer showed typical behavior of water-vapor-sensitive hydrophilic biopolymers.
Mechanical test results revealed that a higher concentration of plasticizer would increase the elongation at break and puncture deformation, decrease the tensile strength, but had no significant effect on the puncture strength of the films, probably related to the thickness and structure of the films.
These results implied the diverse potentials for biodegradable films and edible coating applications by adjusting the types of plasticizer and starch.
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