Multitasking food dyes could reveal clues about food quality

Friday, 13 February, 2015

Food dyes tend to be somewhat one-dimensional - they serve only an aesthetic purpose. But what if they could multitask?

Measuring light emissions from fluorescent particles is commonly used as a form of non-destructive testing. Many fluorescent dyes are toxic or expensive, making them unsuitable for use in food. However, Rutgers University researchers think common food dyes could be used in a similar manner to test the quality of edible goods.

They have discovered that the fluorescence of five common food colours increases as the viscosity of the surrounding fluid increases. This means that dyes could potentially act as embedded sensors for food’s physical consistency in products such as yoghurt or flavoured milk. Changes in consistency could point to issues like food spoilage.

The researchers tested the fluorescent properties of five commonly used edible food colours: Allura Red, Sunset Yellow, Brilliant Blue, Fast Green and Tartrazine. These were mixed with different components to create liquids with a range of viscosities. The fluorescent characteristics of each colour were measured under varying conditions.

They found that all five dyes fluoresce at a significantly different colour than the light used to excite them or the fluorescence of other components in the environment, meaning the emitted signal can easily be distinguished from the background.

In addition, they found that although the food colours emitted virtually no light when mixed with pure water, the light intensity increased as the solutions thickened.

The change in the dyes’ fluorescence could give clues about the consistency and molecular arrangement of the fluid surrounding the dye particles, said Sarah Waxman, an undergraduate student working on the research project.

“A viscometer, which is a typical instrument to test the thickness of food, requires separating and ultimately discarding a large sample size and could report distorted numbers due to factors like the slippage of layers in the fluid,” Waxman said.

“Using food dyes, which are already present in many food products, as probes could be a less invasive and more accurate way to test food’s physical properties.”

Waxman and colleagues presented their research at the 59th Annual Meeting of the Biophysical Society in Baltimore. The research abstract is available from

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