Small amounts of low cost carob flour do not change the colour, aroma or taste characteristics of cocoa powder. Therefore, Spanish researchers have developed a NIR (near infra-red) method combined with chemometrics to determine that adulteration with carob flour has taken place, and the amount of carob flour that has been used. Data sets using cocoa powders with different alkalisation levels, carob flours with three different roasting degrees, and adulterated samples prepared by blending cocoa powders with carob flour at several proportions, were obtained. For qualitative results, a principal component analysis (PCA) and a partial least squares discriminant analysis (PLS-DA) were used, giving a 100% classification accuracy to distinguish pure cocoa powders from adulterated samples. For quantitative analysis, a partial least squares (PLS) regression analysis was performed giving a root mean square error of prediction of 3.2%, thus making the method fit for purpose for determining the amount of carob flour in cocoa powder within this error.
Read the abstract at: cocoa powder adulteration with carob flour