Abstract
The content of anthocyanins in fruits (Sambucus nigra. Vaccinium myrtillus. Aronia melanocarpa) and in some fruit (berry) products was determined by differential spectrophotometry, a method recommended by AOAC International (former Association of Official Analytical Chemists). The method takes advantage of the reversible pH-dependent transformation of the colour to the colourless form of anthocyanins. The procedure and evaluation were refined to allow measurements of incompletely specified anthocyanin mixtures. Parameters of the determination (buffer composition, pH, stabilisation of samples, reference standards) were optimised. Using the modified method, anthocyanins in various matrices (fruits, syrups, wines) were measured with the aim to explain possible losses of these active substances during processing and/or storage of fruit products. Real samples of commercial products recommended conventionally as a valuable source of antioxidants were analysed and in some of them, only low levels of anthocyanins were found. In a model arrangement, anthocyanins in the skin and the pulp of Sambucus nigra fruits were extracted separately. In all samples of various cultivars, anthocyanins were present predominantly in the skin (up to 90% of the total content). Considering this, among other factors, a suitable extraction technology might improve the quality of berry products substantially.