Edible films with high oxygen-barrier properties, previously developed from a variety of casein sources and glycerol (Gly) as a plasticizer, were further enhanced with the addition of an alkali to modify the intra- and inter-molecular electrostatic interactions that form the films, and with the optional addition of citric pectin (CP) as a strengthener. Sodium hydroxide, NaOH, and calcium hydroxide, Ca(OH)<sub>2</sub>, had very different effects on the Casein/Gly/CP colloidal suspensions and on the resulting solvent-cast films’ properties, due to the dissolution or formation of calcium bridges by the two alkalies, respectively.  Several different combinations of casein sources, type of alkali, pH value, and CP content were investigated, both as  colloidal film-forming suspensions and as dried films, using optical microscopy, dynamic rheology, texture analysis (TA), humidity-controlled dynamic mechanical analyses (DMA-RH), vapor-sorption thermogravimetric analysis (VSA), oxygen permeation (OP) and water-solubility.  For most of the formulations investigated, the alkali addition moderately to strongly enhanced the appearance (clarity and homogeneity), the tensile strength, the environmental stability (higher humidity resistance), the flexibility (with up to 67% elongation at break), the water-resistance (greatly reduced solubility) and the shelf-life of the films ( reduced brittleness with time) by visibly restructuring the molecular network and forming whole new types of bonds. These findings further broaden the range of physical and functional properties that may be obtained with milk-based edible films, to enable numerous new food and non-food applications.

Flexible and more water-resistant edible films from caseinate, milk and alkali

256th National Meeting (2018)

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