The effects of pasteurization on caseinate-based edible film solutions

Edible films based on the dairy protein casein have been developed, but widespread adoption will require pasteurization, and nothing is known about the effects of pasteurization on properties of the film solutions or their resulting films. This study investigated alterations in calcium and sodium caseinate-based film solutions due to commonly used pasteurization techniques: low temperature, long time; HTST; and UHT. All pasteurization conditions resulted in films with most textural properties and water vapor permeabilities having no significant changes in comparison to those made from nonpasteurized solutions; the only exceptions were films made from the UHT-processed calcium caseinate and HTST-processed sodium caseinate solutions having increased tensile strength and decreased yield stress, respectively. The solutions themselves, however, changed dramatically after higher temperature pasteurization conditions, with reduced viscosity (resistance to flow), and a weakened storage and loss moduli. The pasteurized solutions would thus be easier to process, except more complications may arise during casting. The particle size distribution of the solution based on calcium caseinate, but not the sodium caseinate, changed with all pasteurization techniques to become more polydisperse. Whereas lower temperature processing did not change solution stability, UHT increased stability of the sodium caseinate film solution, but decreased the suspension stability of the calcium caseinate film solution. Processing with UHT was the only pasteurization technique that proved effective in reducing microbial counts to below the limit of detection (1 log₁₀ cfu∙mL^-1). Overall, we demonstrated that caseinate-based film solutions may be pasteurized without concern of obvious changes to properties of resulting films; however, considerable rheological changes to the film-forming solutions are likely to occur.