Effect of Cooking Methods on Bioactive Pigments in Purple Carrots (Daucus carota L.)

Carotenoids and anthocyanins are plant-based molecules that have shown potent antioxidant and anti-inflammatory activities contributing to human health. Purple carrots contain not only the carotenoids occurring in the typical orange carrots, but also a high content of anthocyanins, which makes them nutritionally more interesting. However, most of these bioactive compounds are partially lost during cooking. This study aimed to determine total carotenoid content (TCC), total anthocyanin content (TAC), total phenol content (TPC) and antioxidant activity (AA) in terms of DPPH and ABTS radical scavenging activity in cooked purple carrots. The identification of the main anthocyanins was also performed by HPLC-DAD. With a view to evaluating the effect of cooking, purple carrots were subjected to freeze-drying, boiling, steaming and roasting. To our knowledge, this is the first extensive study about the effect of various cooking methods on different parameters related to the beneficial health properties of purple carrots. As a result, freeze-drying brought about significant loss of carotenoids (TCCs 554.90 µg·g−1 vs. 1136.66 µg·g−1 in fresh carrots) whereas boiling resulted in a significant decrease of polyphenols (TPCs 15.71 µg·g−1 vs. 66.71 µg·g−1 in fresh carrots) and anthocyanins (TACs 1.41 µg·g−1 vs. 4.83 µg·g−1 in fresh carrots). The results in this paper can be used by the food industry to elaborate more nutritious purple-carrot-based products.