# Edible Films Based on Ovine Second Cheese Whey with Oregon Essential Oil
###### Abstract
These products contain valuable essential amino acids and are useful to produce edible films and coatings [2, 9, 10, 11]. These edible films can reduce food waste and act as barriers against oxygen and aromatic compounds with good mechanical properties [9]. It has also been indicated that WPI films in substitution of fossil polymers could be useful to reduce environmental contamination due to the reduction of electricity consumption [10]. These studies have been done with protein films obtained from bovine whey. We have not found works related to the application of ovine whey in edible films. The second cheese whey (SCW) is a by-product generated in the whey cheese production. Whey cheese is obtained by heating whey at 85-90 \({}^{\circ}\)C for 20-30 min to facilitate the denaturation of whey proteins, which results in their aggregation; SCW is the liquid remaining after protein aggregates recovery [9]. Although a high proportion of this product is discarded without treatment, it contains proteins, mainly in a denatured state, that are beneficial to human health, can be used in the manufacture of foods such as fermented drinks or dressings, and can also be useful in the production of edible films and coatings with excellent nutritional and functional properties [9]. However, the use of SCW in the production of edible coatings and films has been mostly ignored, and its potential as a sustainable packaging material has remained unstudied. To date, only one study has been found referring to the use of SCW as a material for the production of edible films [12]. [PERSON] et al. investigated the use of buffalo second cheese whey (SCW) to obtain films. They treated buffalo SCW with microfiltration and ultrafiltration and obtained two retentates of 100 kDa and 10 kDa. They obtained removable and reusable film with a thickness of 100 \(\upmu\)m only with the retenate of 10 kDa, using glycerol as plasticizer. The characteristics of the films are not described in this study [12]. There are no studies of films obtained with ovine SCW. In one article of our research group, [PERSON] et al. [13] used sheep SCW in a mixture with WPI with 8% (\(w/v\)) protein (in the proportion 2:1 SCW/WPI) and with glycerol as plasticizer in order to prepare cheese coatings with or without oregano or clary sage essential oils. To obtain SCW powder, ultrafiltration (10 kDa cutoff), diafiltration, reverse osmosis and lyophilization processes were used. Cheeses with SCW/WPI coatings had higher water activity, higher moisture content (due to prevent high evaporation), lower titratable acidity and lower chewiness, hardness and gumminess at the end of ripening than cheeses without coating or with commercial coating with natamycin. Additionally, it was concluded that coatings made with SCW and WPI can successfully replace commercial coatings [13]. The addition of essential oils, such as oregano essential oil, to films manufactured with WPC or WPI has been investigated due to their antimicrobial and antioxidant effects [14; 15; 16; 17]. However, this incorporation has some effects on some of the properties, such as water permeability and the flexibility of the films [16; 17; 18]. The development of edible films with a mixture of SCW and WPI and the addition of essential oils could also be interesting for food packaging. However, their properties are different to those of the coatings and must be studied before application in the food industry because the proportion of SCW, WPI and essential oils can influence their efficiency. One objective of this work was to develop edible films based on ovine SCW powders, alone or combined with different proportions of bovine WPI, and to compare the water vapor permeability, solubility, color, opacity, antioxidant activity, mechanical properties, structure (by FTIR), thermal stability (by TGA), microstructure and crystallinity (by XRD) of the films. The second aim was to study these properties in films obtained with ovine SCW and WPI incorporating oregano (_Origanum compactum_) essential oil (EO) in two different percentages.