| Popis: |
Market today is overflowed with variety of food products and competition for consumers is high. As products need to be more attractive, appearance of food, especially colour, for consumers is the most important of all sensory properties that reflects the quality. Addition of synthetic food dyes is sometime justified to avoid the colour changes during storage especially when photosensitive vitamins and pigments are present, to correct the colour differences between plants regarding hue and intensity, to intensify naturally present colour or to colour products made of colourless components. Synthetic food dyes are not so harmless because degradation products are potentially toxic, mutagenic, teratogenic and carcinogenic, and interaction with some drugs may provoke allergic reactions. Since quality assurance is nowadays regulated by law, there has been a need for development of new simpler, faster and accurate methods for food analysis. To control food dye concentration UV/VIS spectrophotometry is a simple and rapid method of analysis but the major problem to be solved is lack of selectivity. Various algorithms and statistical methods can be used to avoid applying separation techniques, such as zero crossing derivative method, multivariate statistics and neural networks. In these work enhanced signals ratio resolution (ESRR) method as alternative to previously mentioned methods was applied. The main advantage of ESRR is that quantification of two analytes from global signal is obtained simultaneously only from one set of standard addition data. For resolving function any spectra from the calibration set can be used as long as absorption values are higher than 0.050. From the global signal, data with absorption less than 0.050 should be cut off, otherwise a large error in the calculated results (concentration) might occur. The method proposed is able to resolve two dyes with strongly overlapped spectra (Δλmax = 5 nm) and 10-fold excess of one component at micromolar concentration range with reproducibility better than 5 % on simulated signals. Real samples of strawberry aroma additive with two dyes E-110 and E-122 were analysed with reproducibility better than 10 %. |
