# Effect of Cooking Methods on Bioactive Pigments in Purple Carrots (_Daucus carota_ L.)
## 1 Introduction  
Carrots are one of most valuable vegetables in terms of commercial interest. Their nutritional value is widely known and is in part due to high content of carotenoids [1]. Conventional orange carrots contain \(\alpha\)- and \(\beta\)-carotene and a small amount of lutein [2]. Carotenoids not only are responsible for the colors of red- and orange-colored fruits and vegetables, but also play an important role in human nutrition. They possess provitamin A activity and they are regarded as potent antioxidants. In addition, they are widely used as food colorants and precursors of aroma compounds by the food industry [3]. In addition to carotenoids, carrots are also rich in phenolic compounds, including anthocyanins, which also contribute to a majority of their in vitro antioxidant capacity [4].  
In the last few years, awareness of the health benefits of anthocyanins has increased, resulting in the development of new vegetables enriched in anthocyanins, including purple carrots [5]. Among other benefits, anthocyanins have been linked to reduced risk of cardiovascular diseases [6] and cancer preventive properties [7]. The color of carrots indicates the different levels of carotenoids and anthocyanins occurring in them. Orange and yellow are usually related to the presence of \(\beta\)-carotene and lutein, respectively, whereas blue, purple and black are associated with anthocyanins. The more commonly known anthocyanins are based on six anthocyanins: cyanidin, delphinidin, malvidin, pelargonidin, peonidin and petunidin. However, more than 500 different anthocyanins have been isolated from plants [8]. In the case of purple carrots, the main anthocyanins are all derived from cyanidin being essentially acylated [9].  
Although carrots can be consumed fresh, they are frequently consumed cooked to extend their shelf-life and preserve their quality. Moreover, the high content of terpenes in carrots causes them to have a strong, harsh smell when consumed fresh [10], which is usually unacceptable, especially by children. Among the most common cooking procedures applied to carrots, the following can be highlighted\" freeze-drying, boiling, steaming and roasting. Bibliographic reports indicate that all these procedures lead to relevant improvements in the sensory quality since they reduce the brightness, redness or yellowness color saturation and taste, which has a direct influence on carrots' acceptability to consumers. However, these methods can in turn result in the loss and/or alteration of the most unstable constituents. In this regard, it is known anthocyanins are particularly temperature labile, and they are easily affected by exposure to heat and light. Several studies have demonstrated that anthocyanins occurring in pigmented foods other than purple carrots decrease by about 80% after cooking [11].  
In the present research, we evaluated the impact of cooking on pigmented bioactive constituents as well as on the AA in purple carrots (_Daucus carota_ L.). To that end, we studied the effects of freeze-drying, boiling, steaming and roasting on the content of carotenoids, phenolics and, particularly, anthocyanins. The impact on free radical scavenging activity as measured by DPPH and ABTS assays was also considered. Although the influence of different cooking methods on bioactive compounds including anthocyanins has been reported in other purple-pigmented foods [12; 13; 14], a very limited study has been carried out on carrots [15]. In this work, an extensive study considering various cooking methods as well as various parameters related to the health-promoting properties of purple carrots is, to our knowledge, addressed for the first time.