| The effect of plasticizer (glycerol), gelatin type (Type A B240 and Type B B240) and mixture ratio of type A and B on mechanical properties, oxygen and water vapor permeabilities of gelatin films were measured. To analyze the behavior of protons in gelatin films, a Low Field NMR relaxation study was performed as a function of glycerol concentration, relative humidity and temperature. The thermal and mechanical properties of gelatin films, plasticized with 30% glycerol and modified with a series of organic acids (malic, citric and phytic acid) were measured as a function of acid type and concentration from 0.2 to 1.0%. Finally, the effects of different antioxidants incorporated into gelatin films on mechanical properties, oxygen permeability and antioxidant activity were investigated using a model food system which was made of agar, emulsifier, soybean oil and pH indicator. Gelatin films containing antioxidants were produced by melt extrusion and film casting. Variables such as the die and heating zone temperatures, and mesh size of the screen in the extrude exit were investigated.; When glycerol content was increased from 0 to 40%, tensile strength (TS) and energy to break (EB) of type A and type B gelatins systematically decreased, while the elongation at break (EB) increased up to 65% and 72%, respectively. At 30% glycerol concentration, type B gelatin film showed higher TS and EB than type A gelatin film. Tensile strength and energy to break values of mixed gelatin films with Type A and B were basically related to the characteristics of Type B, whereas the elongation properties depended on the mean elongation values of types A and B. Water vapor (WVP) and oxygen permeabilities (OP) of gelatin films were significantly affected by gelatin type, plasticizer content and relative humidity (RH). Consequently, gelatin films plasticized with 20∼30% of glycerol showed high oxygen and water vapor barrier properties compared to others, as well as stable mechanical properties for handling. For acid-modified gelatin films, increasing acid concentration in citric acid and malic acid films lowered the tensile strength compared with control. At 0.6% phytic acid, the tensile strength was highest and elongation was lowest among all gelatin films due to the cross linking effect of phytic acid. (Abstract shortened by UMI.)... |
