SOLID PHASE ASSAYS TO DETERMINE THE BINDING TO PROTEINS OF SOME FOOD DYES CONTAINED IN COMERCIAL DRINKS OR IN BAKERY/PATISSERIE COLOURING ADDITIVES

ASENSIO CRISTIAN JORGE ALEJANDRO; SANTA COLOMA T. A.

MAR DEL PLATA

Congreso; REUNION SAIC 2018; 2018

saic

Drinks, foods, candies, cosmetics and medicines are coloured with different artificial anionic sulfonated azo dyes. There is a long standing discussion concerning the toxicity of these dyes and their effects on food digestibility as well as if they are really edible and safe. After many worrying research reports, some countries banned certain dyes while they are still allowed in others. Simple methods to compare the protein binding capacity and optimal pH or concentration of different dyes would be a step forward to determine their binding constants/parameters and possible toxicity. Some dyes might bind proteins in the stomach at acid pH by electrostatic interaction of basic residues with the sulfonic groups while others might also bind proteins in the lower tract even at neutral pH through hydrophobic and/or non-ionic interactions. Dyes might also access the bloodstream during gastrointestinal pathologies. Thus, we implemented solid phase assays to quickly assess the effects of incubating milk proteins, BSA and bovine gamma-globulin directly with drinks and beverages including isotonic drinks. 1μl of serially diluted protein samples was spotted on different surfaces in an arrayed manner. Dye binding was imaged and densitometrically quantified. Commercial isotonic drinks coming at a pH of 2.6-2.9 were able to stain quickly, sensitively and linearly the proteins regardless of the many other additives or preservatives present in the drinks (sucrose, citrate, benzoate, salts, etc). Besides, dyes commercialized for cooking, bakery or patisserie as pastes or solutions were also able to stain proteins. Altogether, our solid-phase assays are a simple, promising way to compare the binding of different food dyes dissolved in drinks or commercialized in pastes or solutions. The effects of pH, solvents, additives, dye concentration and protein types on dye-protein affinities/bonding can be compared as a step previous to the evaluation of dye toxicity by other analytical methods.