Decomposition of Food Dyes by Oxidation Products of Oil

Decomposition of added phloxine (Food red No. 104) and β-carotene in oils (olive, soybean and whale oils), and its extent in oils with different degrees (peroxide value 2, 98, 292 and 695 meq/kg) of oxidative deterioration were investigated. Oils containing 0.01% phloxine and 0.1% β-carotene were placed in a beaker (4×5.5cm, oil: 10g) and oxidized at a window (room temperature: 25±2°C). Oxidative deterioration of oils and the decomposition of phloxine and β-carotene in oils during storage were determined by Oven test (at the window) and a Lovibond colorimeter, respectively. Phloxine and β-carotene with oxidative products (oxidized fatty acids [OFA]; fatty substances insoluble in petroleum ether) separated from oxidized soybean oil in ethanol were placed in a test tube (10ml), and decomposition of phloxine and β-carotene during storage at the window were determined by absorption spectrometry at 548.5 and 470nm, respectively. The degree of decomposition of β-carotene in oils was observed to be much higher in whale oil than in soybean and olive oils during storage, and it depended on the degree of oxidative deterioration of oils. On the other hand, no significant large difference could be found in the decomposition of phloxine among the three kinds of oils. The decomposition of phloxine and β-carotene in an ethanol solution was apparently promoted by OFA, and it increased with increasing concentration of OFA.