Fast dissolving, hermetically sealable, edible whey protein isolate-based films for instant food and/or dry ingredient pouches

Abstract

The objective of this research is to develop edible, fast dissolving, sealable whey protein isolate (WPI)-based films for packaging premeasured dry foods/ingredients that will dissolve and release their contents upon contact with water. Modifications to the structure and properties of WPI films via heat-denaturation and plasticizers were determined. The structure-function relationship of the films was elucidated based on FTIR analysis. The developed water-soluble native WPI (NWPI) films had similar visual and barrier properties (oxygen permeability 4.74 × 10−4 to 12.26 × 10−4 cm3 μm/m2∙s∙kPa and water vapor permeability 0.0113–0.0148 g mm/m2∙s∙kPa) but lower mechanical properties (tensile strength 1.04–3.16 MPa, % elongation 7.45–15.31%, and elastic modulus 18.88–105.34 MPa) than the water-insoluble heat-denatured WPI films. The solution-sealed NWPI pouches of dry food models showed ready solubility. Heat denaturation strengthened the cohesion of the WPI films via the enhanced formation of the intermolecular β-sheet. Glycerol and atmospheric moisture showed plasticizing effects on both the barrier and tensile properties, which correlated well with the films’ moisture sorption isotherms. Solution-sealed NWPI pouches can be potentially used as leave-in packaging for portioned dry foods. The comprehensive understanding of the properties of glycerol-plasticized WPI films gained from this study is valuable in designing WPI-based packaging for commercial packaged food systems.