Development of Bioactive Edible Coatings and Biodegradable Packaging Using Gamma Irradiation

Gamma irradiation was used to cross-link milk proteins in order to enhance the physico-chemical properties of edible films made of calcium caseinate, whey protein isolate and glycerol. Fourier Transform Infrared analysis was used to characterize the conformation of proteins adopted after irradiation. The molecular weight of cross-linked proteins was measured by Size-Exclusion Chromatography. Furthermore, the effect of the addition of methylcellulose to the irradiated protein matrix on the rheological properties (puncture strength, puncture deformation and water vapor permeability) of films was also studied. Moreover, cross-linking of polysaccharides under paste-like state was investigated and the cross-linking degree of the gel products was determined by gel fraction measurements and solubility percentage. In order to prepare bioactive coatings, several antifungal compounds were evaluated as bioactive compounds in order to select one of them to prepare an antimicrobial solution to spray onto strawberries or to encapsulate them in film formulations composed of milk proteins and methylcellulose based films. In addition, the bioactive coatings containing the antifungals were used to increase the radiosensitivity under air of moulds and total flora in strawberries and the relative sensitivity of selected formulations was calculated from their D10 value. The film formulation selected was used as a bioactive edible coating in order to determine their efficiency to increase the shelf life of fresh strawberries and to preserve their quality during storage. (author)