Impact of the film-forming dispersion pH on the properties of yeast biomass films

Abstract

BackgroundYeast biomass, mainly composed by proteins and polysaccharides (mannans and β‐glucans), has been proposed to develop films. pH can affect the solubility of polysaccharides, the structure of the cell‐wall and the interactions between proteins. Considering the potential impact of these effects, the pH of yeast film‐forming dispersions was studied from 4 to 11.ResultsIn tensile tests, samples increased their elongation by increasing pH, from 7 ± 2% (pH 4) to 29 ± 5% (pH 11), but Young´s modulus was not significantly modified. Regarding thermal degradation, the maximum degradation rate temperature was shifted 46 °C from pH 4 to 11. Differences in water vapour permeability, colour, opacity and roughness of films were also found. According to the results of differential protein solubility assay, at pH 4 hydrophobic interactions and hydrogen bonding were promoted but, at pH 11 disulphide bonds were benefited, in addition to partial β‐glucan dissolution and break‐up of the alkali‐sensitive linkage in molecules from the cell wall.ConclusionResults let to conclude that film‐functional characteristics were greatly benefited at pH 11 in comparison to the regular pH of dispersion (pH 6). These results could help to understand and select the pH conditions to enhance the desired properties of yeast biomass films.