Methods of colour measurements of vegetable raw materials

Beside sensoric tests colour measurements of vegetable raw materials used for food production belong to the most important quality approvements. Whereas theses measurements have been performed in the past by visual comparison with glass colour standards, nowadays more and more objective methods are applied. Colour ist mostly measured according to the L*a*b* colour space defined in DIN 6174; by this method the subjective human colour impression is adapted in the best way. The colour-bearing substances present in vegetable food as for instance chlorophylls, carotenoids, betalains, and anthocyanins are predominantly determined by HPLC/UV-Vis measurements. Based on this quantification in most cases it is possible to monitor ripeness as well as influences of storage or processing in the sample material.