A Rapid tool for the stability assessment of natural food colours

Natural food colours lack stability under a number of conditions such as pH variation, oxidation, hydration, heat treatment and, most importantly, exposure to daylight. Stability tests to assess shelf life of natural colours under light irradiation can be time consuming. Thus, an accelerated test carried out under high light intensity irradiation that can be related to normal daylight irradiation conditions is highly desirable. Samples of various natural colouring solutions were prepared in aqueous model matrices at a range of pH values to mimic the majority of food matrices, pasteurised and irradiated under normal D65 light (0.2 W/m2) at 25 °C, and in parallel under high light intensity irradiation (30 W/m2) at 3 different temperatures (25, 35 and 45 °C). Similarly to the already known Q10 parameters for temperature, acceleration factors QL for irradiation, were determined and used for the first time to obtain a link between colour degradation under normal and accelerated conditions. It was possible, using these acceleration factors, to greatly reduce the time required to predict and compare the shelf life stability for a series of natural colours in aqueous model systems.