Studies on the stability of an edible film and its use for the preservation of carrot ( Daucus carota )

Summary 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 ‘keeping property’ and ‘accelerated stability’ 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.