Contact heat transfer coefficient during double-sided cooking of hamburger patties

Contact heat transfer coefficient values during double-sided contact cooking of hamburger patties were calculated from grill plate temperatures, patty surface temperatures, and heat flux values. The patties were cooked for 130 s using different top and bottom grill plate temperatures (171C, 191C, or 204C) and gap thicknesses between plates (10.0 mm, 10.5 mm, or 11.0 mm). Heat transfer coefficient values obtained were in the range of 250 to 650 W/m2C, depending on the cooking conditions. After reaching a maximum value, the coefficient decreased and reached an asymptotic value at the end of the cooking cycle. The maximum heat transfer coefficient values depended on top or bottom grill plates and gap thicknesses between plates. Average heat transfer coefficient values during 80 to 130 s of cooking depended on top or bottom grill plates and set grill temperatures.Fil: Wichchukit, S.. University of California; Estados UnidosFil: Zorrilla, Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Singh, R.. University of California; Estados Unido

Whey protein/alginate beads as carriers of a bioactive component

Bioactive components encapsulated in gel particles offer a means to deliver these components in a time release fashion to improve health through daily diet. The objective of this work was to evaluate the physical/mechanical properties of a release system consisting of whey protein/alginate gel beads in a model beverage. Riboflavin, vitamin B-2, was incorporated in the gel beads as a model bioactive compound. Gel beads were formed both with and without riboflavin and then added to a xanthan/sucrose suspending medium. Both the beads and the polymer solutions from which they were formed were characterized by standard rheological methods. An absorbance method was used to monitor riboflavin release over time. NMR and MRI (magnetic resonance imaging) methods characterized bead integrity and the state of protons in the gel beads. The combination of whey protein and alginate formed beads with good integrity and zero order rate kinetics for the release of riboflavin. The release rate of the bioactive component was more rapid that the typical shelf life of a bottled beverage however, the work represents a step toward the design of this type of functional food through characterization of the encapsulation medium