Characterization, stability and application in yogurt of a coloring food from Opuntia robusta fruits

Color is a discriminant factor in the food market regarding acceptancy by consumers. Synthetic colorants have been questioned in recent years due to their harmful effects on human health. Nowadays, consumers are looking for more natural and healthier colorants, while at the same time rejecting synthetic ones more and more. An alternative to supply this demand is the use of coloring foods, foods with coloring properties obtained by non-selective means. The EU and FDA regulations have classified them as ingredients, not additives. Furthermore, they are safer, covering a wide range of colors and providing, in many cases, functional properties to the products where they are applied. The aim of this study was to evaluate the potential of purple cactus pear fruits from Opuntia robusta as a coloring food. The fruit pulp was vacuum concentrated to obtain a concentrated colorant (CC). The CC was physically and chemically characterized. The betalains’ (betanin) stability and total color change (ΔE) of the CC was evaluated in a white commercial yogurt for 6 weeks at cold storage (5±2°C). A comparison with a beetroot commercial colorant (BC) was carried out. The CC shows 64.7±0.1 total soluble solids, pH 4.73, 3.560.46±0.25 mg GAE L^‑1 and 164.97±6.36 mg BE 100 g^‑1. Similar betanin degradation rates in CC and BC were observed (0.11±0.01 and 0.10±0.00 k(obs) week^‑1, respectively), without significant differences among treatments. There were no significant differences regarding CC and BC half-lives (45.77 and 46.40 days, respectively). Color in yogurt showed significant differences with the treatments; nevertheless, they obtained close values with respect to color parameters.