71A-53 |
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V. M. HERNANDEZ, Dept. of Biological and Agricultural Engineering, Univ. of California-Davis, 1 Shields Ave., 126 Cruess Hall, Davis, CA 95616 and J. M. Krochta, Dept. of Food Science and Technology, Univ. of California-Davis, 1 Shields Ave., 237 Cruess Hall, Davis, CA 95616. In the manufacturing of pouches and sachets, sealability of the material and the formation of an adequate seal are important. The seal must have sufficient strength to hold the product in the package and keep its integrity during handling and storage. Proper seal formation requires the correct combination of heat, dwell time, and pressure. We hypothesized that thermal transitions of whey protein films can be used to guide the selection of heat-sealing temperatures. The objective of this research was to determine the conditions necessary for efficient heat-sealing of whey protein-glycerol films obtained by solution casting. Differential scanning calorimetry (DSC) was used to identify the thermal transitions in heat-denatured 60%-whey protein-40%-glycerol films (d.b.). The films were heat-sealed using an impulse heat sealer with an effective jaw pressure of 293.31 kPa, 4 sec cooling time, and a voltage of 15 V. Three different impulse times were used to seal the films. A thermocouple was used to measure the temperatures reached by the sealing jaws at each impulse time. Seal strengths were determined using an Instron Universal Testing machine. DSC showed the existence of endothermic peaks starting at 155±2 °C and ending at 189±5 °C. Optimum seal appearance and strength were achieved at 2 sec impulse time, which corresponded to a temperature of 166±20 °C as indicated by a thermocouple. Analysis of variance and multiple comparison tests indicated that films sealed at 1.5 sec had significantly lower (P <=.05) seal strength than films sealed at 2 and 2.5 sec. Although some degradation of the films occurred at 2.5 sec impulse time, seal strengths between films sealed at 2 and 2.5 sec were not significantly different from each other (P > 0.05). These results are important in the development of whey protein-based packaging materials. Whey protein pouches could be used for milk powders and other dry foods and ingredients.
Session 71A, Dairy Foods: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |