Characterization of the Physical and Mechanical Properties of Sugary Kefir Polysaccharide/Wheat Starch Edible Films by Using Response Surface Methodology

• Main Authors: Lin Shih-Han, 林詩涵
• Other Authors: Lih-Shiuh Lai
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/19515448216021463546

碩士 === 國立中興大學 === 食品暨應用生物科技學系所 === 102 === The sugary kefir polysaccharide (K) was extracted from sugary kefir grains and mixed with wheat starch (S) to form composite edible films. The effect of total solid, K/S ratio and glycerol content in the mixed system on the mechanical and other physical properties as well as water vapor permeability (WVP) of the resulting films were investigated by using Box-Behnken design of response surface methodology. The results revealed that the mechanical strength (including tensile strength and puncture force) of K/S films was enhanced with increasing total solid content and decreasing K/S ratio or glycerol content, accompanied with a decrease in elongation and puncture deformation. Moreover, the WVP of edible films decreased with increasing total solid content or decreasing glycerol content. However, the WVP of composite films decreased when K/S ratio decreased from 75/25 to 50/50, then increased when K/S ratio further decreased to 25/75. Edible films with lower total solid and glycerol content and higher K/S ratio generally showed larger water contact angle. Moisture sorption isotherm results revealed that edible films with a total solid-K/S ratio-glycerol value of 1.25-50-20 and 0.75-50-10 had the highest and lowest equilibrium moisture content among the treatments, respectively. Edible films with higher glycerol content and lower K/S ratio generally showed higher moisture content and solubility, accompanied with enhanced opacity and lightness. Microstructural examination by using scanning electron microscopy (SEM) revealed that films prepared under lower K/S ratio showed grainy surface and occasional pores. However, films with different glycerol content did not show a significant difference in terms of microstructure. Optimization analysis based on the mechanical strength and WVP results revealed that the optimal film forming condition could be obtained under a total solid content of 1.25%, K/S ration of 37/63, and glycerol content of 10%. Validation test revealed that films prepared under the optimal condition showed a tensile strength of 20.60±2.19 MPa, puncture force of 3.01±0.40 N and WVP of 3.86±0.18×10-11 gm-1s-1Pa, which were not significantly different from the prediction results by response surface model. Such results implied the appropriateness of the response surface model obtained.