Edible films based on ovine second cheese whey with oregano essential oil

Abstract

The aim of this study was to produce edible films using ovine second cheese whey (SCW) powder, alone or combined with whey protein isolate (WPI). SCW is a by-product obtained in the manufacture of ovine whey cheeses. In this instance, it was dehydrated after increasing the protein concentration by ultrafiltration/diafiltration. Furthermore, the effects of the addition of oregano (Origanum compactum) essential oil (EO) in two proportions to the films produced with a mixture of SCW powder and WPI were studied. The water vapor permeability, solubility, color, opacity, antioxidant activity, and the mechanical properties of the films were determined. In addition, we determined the films’ structure, by FTIR; thermal stability, by TGA; and microstructure and crystallinity, by XRD. SCW combined with WPI can be used to prepare edible films, but their properties were found to be affected depending on the proportion of each product. The substitution of WPI by SCW caused decreases in water solubility (from 81.44 to 66.49% D.M.), modified the color and decreased tensile strength (from 1.57 to 0.17 MPa), and decreased the elongation at break (from 52.17 to 3.57%), the puncture strength (from 2.40 to 0.20 MPa) and the deformation (from 18.92 to 0.93%) of the films. EO addition to the SCW–WPI films increased the antioxidant activity of the films (from 0.97 to 2.19 mg DPPH/g). It also modified other characteristics of the films such as the water solubility and the tensile strength. Both SCW and EO incorporations influenced the secondary structure of proteins and the thermal stability, microstructure and crystallinity of the films