Determination of food colouring candies: implementation of a new activity in an experimental subject

Abstract

Motivation plays a fundamental role in a student’s learning. In experimental subjects, it has been seen over the years, that what creates a certain interest and motivation in students is working with real samples that are present in our daily life. In the Analytical Chemistry Laboratory subject, students already work with motivational samples for other techniques, but there are few determinations of them that use the UV – Vis Spectrometry technique. Therefore, it is proposed to develop a new activity to enhance the learning of this technique. It is proposed to make the determination of food colorants present in candies. Food colorants are additives that make foods more attractive, enhance their colour, or give them colour if they are colourless. The presence and concentration of colorants in food is regulated by law and their determination is interesting. The aim of this work is to develop a new activity for the measurement of the different food colorants that give colour to the analysed candies: E100 (yellow), E120 (red), E133 (blue), E160a and E160e (orange). To carry out the determination, first the extraction medium was found for each one, making studies of solubility, degradation and pH influence. For E100 and E133 an EtOH/H2O 70:30 mixture, for E120 a phosphate buffer solution at pH 7.5, and for E160 an EtOH/H2O/CH2Cl2 50:25:25 mixture. The wavelengths of the corresponding maximum absorbances were established, the linearity intervals of each of the dyes were found and the samples were extracted. Absorbance measurements were carried out and the amount of colorant of each colour sample was found: 0.05 mg/g in yellow samples, 0.09 mg/g in blue ones, 0.07 mg/g in red ones, 0.017 mg/g in orange ones, and in the green samples 0.025 mg E100/g and 0.013 mg E133/g. It is concluded that an activity for the determination of food colorants in candies has been satisfactorily developed