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ABSTRACT:The present investigation dealt with the mechanical properties, water-vapor transmission behavior at different relative humidity conditions, and DSC thermograms of edible films formulated using various proteins (casein, gelatin, albumin) in combination with starch and nonthermal as well as intense thermal blending. Nonthermal blended film showed in the DSC thermogram a double T g , indicating poor miscibility of the components and, hence, a poor film-forming property. However, the DSC thermogram of all the films based on intense thermal blending showed a single T g , indicating the complete molecular miscibility of the components. Casein-based film showed a lower watervapor transmission rate, water gain at different relative humidity conditions, and higher tensile strength compared to its counterparts containing gelatin and albumin. Since the casein-starch blend gave better film properties, a blend of hydrophobic carnauba wax and casein was prepared to compare the properties of hydrophilic-hydrophilic and hydrophobic-hydrophilic blends. Both these blends compared well with respect to the water-vapor transmission rate. Waxbased film showed multiphased behavior in the DSC thermograms and the percent elongation was lower as compared to the casein-starch blend.

Wide angle X-ray scattering (WAXS) was used to follow the development of crystal size and strain during the staling of bread containing different additives. In this it was observed that one can classify the good anti-staling additives as gelatin, propylene glycol, maltodextrin and anti-staling enzyme corresponding to the order of increasing crystal size for a particular Bragg reflection in all the samples and correlate using DSC (differential scanning calorimetry) studies of all the bread compositions containing different additives.

Differential scanning calorimetry (DSC) and positron annihilation lifetime measurements have been carried out to study the effect of the compatibilizer maleic anhydride grafted ethylene propylene copolymer (EPM-g-MA) in poly trimethylene terephthalate and ethylene propylene diene monomer (PTT/EPDM) immiscible blends. The DSC results for the blends of 50/50 and 30/70 compositions show two clear glass transition temperatures, indicating that the blends are two-phase systems. With the addition of compatibilizer, the separation between the two glass transitions decreased, suggesting an increased interaction between the blend components with compatibilizer. At 5 wt % of compatibilizer, the separation between the T g s reduced in both 50/50 and 30/70 blends. The positron results for the blends without compatibilizer showed an increase in relative fractional free volume, as the EPDM content in the blend is increased. This suggests the coalescence of free volume of EPDM with the free volumes of PTT due to phase separation. However, the effect of compatibilizer in the blends was clearly seen with the observed minimum in free volume parameters at 5% of the compatibilizer, further suggesting that this percent of compatibilizer seems to be the optimum value for these blends.

An edible coating was formed by blending turmeric (Curcuma longa) and casein in equal proportions at 95°C for 12 h. Small quantities of polyvinyl alcohol and propylene glycol were added to encourage film formation and plasticizing respectively. The blend was removed from the reaction vessel and homogenized using Tween-80 as emulsifier. The homogenized blend was sampled at 2-h intervals for stability by means of the Ôkeeping propertyÕ and Ôaccelerated stabilityÕ tests. Stability was also determined by differential scanning calorimetry in which a singlet endotherm indicated molecular mixing (miscibility window) of the components. All three tests indicated that the emulsion was stable after 12 h of blending. Colour, carotenoid content, texture retention and antimicrobial properties remained satisfactory for 10 days in the stable emulsion-coated carrot whereas the control spoiled after 3 days. Thus turmeric and casein based-emulsion coating could extend the shelf-life of carrots by 7 days.