Cactus Betalains Can Be Used as Antioxidant Colorants Protecting Food Constituents from Oxidative Damage

In recent years, growing concerns about food safety and the strong consumer demands have induced many food manufacturers to review the formulation of their products and to make efforts to replace synthetic colorants by natural ones, when this is technologically feasible. Among the water-soluble natural pigments, betalains present significant advantages as they have good chemical stability in a wide pH range facilitating its application in low-acidic foods such as dairy products. These pigments can be obtained from cactus pear fruits. Our main aim was to evaluate the protective effect of cactus betalains against lipid oxidation when these compounds are added to yogurt and milk cream as functional colorants. Betalains were purified from cactus fruits. Betacyanins and betaxanthins were extracted from Opuntia ficus-indica (purple pulp) and Opuntia megacantha (yellow-orange pulp), respectively; betanin and indicaxanthin being the major ones. Different betalain concentrations were assayed in both foods. Food oxidation process was induced by a free radical generator azocompound AAPH in order to accelerate the reaction. Lipid oxidation products were determined by the method of thiobarbituric acid reactive substances (TBARS). This spectrophotometric technique measures the formation of final stage products of lipid oxidation taking as reference malondialdehyde (MDA). The control system consisted of food without pigment additions. The highest concentrations of betacyanins and betaxanthins to be assayed were selected considering pink and pale yellow color intensities similar to those of commercial strawberry and peach yogurts; foods where synthetic colorants are regularly used. The results show that both kinds of pigments significantly reduced the lipid oxidation products formation compared with the control system. The effect increased, the higher the applied concentration. Betanin was more efficient than indicaxanthin protecting yogurt and cream from oxidation damages. Results indicate that cactus betalain can be used to replace the synthetic coloring food improving oxidative stability of food.