Composite films based on sodium caseinate, plasticized with glycerol and incorporating oil bodies recovered by applying ultrafiltration on maize germ aqueous extract were stored at 25 °C and relevant humidity 53% and the changes in their physicochemical and mechanical properties were monitored over a storage period of 2 months. The rearrangement of the protein matrix molecules, oil droplet reorganization and movement during ageing was revealed through the generalized 2D correlation FTIR spectra analysis. Both the control and the oil bodies-containing caseinate films showed marked alterations of their mechanical and optical characteristics upon storage, mainly due to water uptake and glycerol or oil bodies movement, as the application of 2D correlation of the FTIR spectra time series revealed. The fact that the films become less transparent and, in addition, lose and then regain their mechanical strength during ageing for 70 days is essential information for the development of edible films and their commercial applications in the food industry.
Keywords: 2D correlation; Edible films; Oil bodies; Sodium caseinate; Storage; Tensile properties.
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