Abstract
In chemical education, it is often a challenge to understand the basic principles of spectroscopic techniques due to missing connections to the real world. Therefore, the present contribution offers context-based applications of UV/Vis spectroscopy for analytics of food colorings with which learners can improve their skills regarding this method. The spectroscopic determination of food colorings seems to be a promising approach due to the long tradition and omnipresence of dyes in supermarket products. The therefor-required spectral data for commonly used dyes are provided for educational usage. Qualitative and quantitative analytics of food colorings in four different lemonades and chocolate beans have been used to introduce learners to important analytical techniques like sample preparation or elimination of confounding factors. These analytics also display the limitations of the method in the visible range of light in the case of tartrazine and curcumin. By applying Lambert-Beer-Bouguer’s Law in different variations, typical calculations of concentrations can be studied in quantitative analyses. The studied food samples demonstrate the different usage of food colorings depending on the country of sale. Finally, a 3D-printable low-cost photometer suitable for the discussed quantitative analytics in educational contexts is presented.
Highlights
In the field of chemical education, the understanding of individual topics of physical chemistry in general and of modern spectroscopic methods in particular are highly demanding challenges
We studied carotenes, chlorophylls, and curcumin in food
The yellow chocolate beans purchased in the European Union (EU) are colored with the natural dye curcumin (E100), whereas the United States (US) version is colored with the azo dye tartrazine (E102)
Summary
In the field of chemical education, the understanding of individual topics of physical chemistry in general and of modern spectroscopic methods in particular are highly demanding challenges. There, natural products like saffron or plant extracts were used as dyes [12] This type of natural food coloring was not affordable for common people, which changed initially with industrialization. A milestone was a new synthesis technology based on the invention of the first synthetic dye “mauveine” by William Henry Perkin in 1856 which lead to a wide range of synthetic coal-tar colors [12]. These new artificial food dyes replaced hazardous inorganic salts and natural colorants due to their low manufacturing costs, superior coloring properties, and economical usage in products [11]
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