A new high molecular weight polymalate coating film on grape

Abstract

In this study, the high molecular weight (HMw) polymalate (PMA) film [10% glycerol (g/100 g of HMw PMA) and 90.0 g/L HMw PMA] as a coating material was used in protection of grapes for the first time. Based on tensile strength (TS) (5.94 Mpa), elongation at break (EB) (35.8%), oxygen barrier property (PV) and water vapor permeability (WVP) of the film, 10% glycerol (g/100 g of the HMw PMA) and 90.0 g/L of the HMw PMA were used to prepare the HMw PMA film. Under these conditions and at room temperature and relative humidity of 53%, PV and WVP values of the film were 2.2 meq/kg and 1.6 ng·m/m2·s Pa, respectively. When the HMw films were coated on the grapes, they effectively reduced weight loss, vitamin C loss, decay rate, respiration rate and relative conductivity of the grapes. Furthermore, they also could increase the textures (hardness, springiness, adhesiveness, cohesiveness, gumminess, chewiness) of the grapes and greatly improve appearance of grapes. The HMw PMA film as a digestible material could be hydrolyzed into malic acid in the in vitro simulated gastric fluid. Thus, as the new digestible material, the HMw PMA film coated on grapes was a sustainable packaging technique and the HMw PMA was one of the good materials in food industry compared to the conventional ones.