POTENTIAL OF MILK FAT AS A PLASTICIZER IN BIODEGRADABLE MILK PROTEIN-BASED FILMS

This study aimed to evaluate the potential of anhydrous milk fat (AMF) and fully hydrogenated milk fat (FHMF) as a partial substitute for glycerol (GLY) used as a plasticizer in biodegradable milk protein-based films. The films were made from aqueous solutions at a fixed combination of 2.5% sodium caseinate and 7.5% whey protein isolate Plasticizers were added as a function of the protein concentration (50% w/w) and four film-forming solutions were prepared as follows: 100% GLY (F1); 40% AMF + 60% GLY; 20% AMF + 20% FHMF + 60% GLY; and 40% FHMF + 60% GLY. After the protein hydration and addition of plasticizers, the solutions were heat-treated (80ºC / 30 min) and subjected to homogenization (Ultra Turrax 22,000 rpm / 3 min) and microfluidization (Microfluidizer 600 bar / 3 cycles). The films were prepared by casting technique, conditioned at 25 ° C and 50% RH for 48 hours, and characterized for the visual aspect, thickness, grammage, density, morphology, and light transmittance. All films were flexible, easy to handle, with no rupture or brittle areas. The films containing AMF and FHMF presented whitish color and greater light barrier, with transmittance ranging from 60 to 66%, when compared to the films made with GLY alone, which presented 90% transmittance at 550 nm. All films provided approximately 100% UV radiation protection. Scanning electron microscopy revealed the formation of crack-free films, with fat globules homogeneously distributed within the polymer matrix. The addition of AMF and FHMF increased film thickness and grammage, probably due to the increase in molar mass of the plasticizers used. The partial replacement of GLY by AMF and FHMF led to the formation of homogeneous and flexible biodegradable films with greater visible light barrier, suggesting a potential application when a light barrier is needed food preservation.