A capillary sieving electrophoretic method for protein analysis and molecular weight determination was used to characterize ciders from Asturias, northern Spain. The total protein content (Bradford method) and the foam parameters (Bikerman method) were also analyzed to complete this characterization. The polypeptide profile, based on the molecular weight, together with exploratory and classification techniques, that is, principal component analysis (PCA) or linear discriminant analysis (LDA), allowed ciders to be differentiated on the basis of their foam assessment and the apple juice extraction technology used in the cidermaking process. In addition, the application of correlation analysis, that is, canonical correlations (CCA) or partial least-squares (PLS), revealed that the proteins with higher molecular weight were more relevant with respect to cider foamability. PLS analysis also provided a mathematical equation that is able to predict the stabilization time of foam from the polypeptide profile of the cider, because this is the foam parameter most influenced by these compounds.

a b s t r a c tThis paper describes the characterisation of sparkling ciders from Asturias, northern Spain, by means of the analysis of their protein content and their foam characteristics. A capillary sieving electrophoretic method was used in the protein analysis to determine molecular mass and the Bradford method to determine total protein content. The foam parameters were measured using the Bikerman method.Chemometric techniques, such as principal component analysis (PCA) and soft independent modelling of class analogy analysis (SIMCA), allowed the sparkling cider to be differentiated on the basis of the yeast strain used in their manufacture. As a result, feasible models for classifying sparkling ciders were computed (classification hits higher than 96%). Furthermore, the relationship between polypeptides and foam was demonstrated with a prediction equation of foam stability time, which was computed using the partial least square (PLS) regression technique. This mathematical equation confirmed that the polypeptides of high molecular mass are especially related to this foaming parameter.