Pigmentos Naturais em Diferentes Variedades de Batatas-doces

Abstract

The sweet potato (Ipomoea batatas L.), rustic, rich in carbohydrates, functional phytochemicals, natural pigments, antioxidants and pro-vitamins A, has great potential to bring social and economic development for the most needy and distant of urban centers populations. It can aid in the prevention of diseases related to malnutrition, vitamin A deficiency and oxidative stress. It is an option to boost organic production systems and generate healthier foods with higher levels of nutrients and functional substances in a sustainable way. Their natural pigments (carotenoids and anthocyanins) can replace the synthetic dyes used in industrialized foods with functional advantages. The carotenoids and anthocyanins profile of many sweet potato varieties are still being published in recent works, as many of these molecules have not yet been elucidated. The functional potential of these phytochemicals depends on their stability to heat treatments and bioavailability after the digestive process. The objective of this work was to characterize and quantify the carotenoids and anthocyanins of four varieties of sweet potatoes grown in the organic system and to evaluate retention in the most common forms of consumption. Four organic sweet potato varieties were cultivated for this purpose and prepared in fresh, cooked and fried forms for evaluation of the contents, retention and profiles. The analytical techniques used were spectrophotometry, High Performance Liquid Chromatography with Diode Array Detector (HPLC-DAD) and High Resolution Mass Spectrometry with Electrospray Ionization (ESI-QToF-MS2). The carotenoids and anthocyanins present in the studied varieties were quantified and characterized. Most of the carotenoids and anthocyanins were identified and some were detected for the first time in the matrix, such as 6 acylated anthocyanins, among the 22 detected in the variety of purple skin and flesh, most of them derived from peonidin, justifying the purple color with red tint, acilated with caffeic, phydroxycinnamic and mainly ferulic acids. In the variety of white skin and purple flesh, 14 known anthocyanins have been identified, most of them derived from cyanidin, justifying the purple colour with blue tint and, acylated with the same acids, mainly caffeic. Two of them diacilated, rare in sweet potatoes, derived from pelargonidin were only identified in sweet potatoes by Lee et al. (2013). Unacylated anthocyanins were not detected. The anthocyanin profiles of these sweet potatoes differentiate them from other varieties. Anthocyanins were stable to cooking and frying, which facilitated their desorption from the starch of the matrices during the extraction, resulting in levels three times higher than in fresh sweet potatoes, indicating that heating should be inserted in their preparation before lyophilization, which also increases the extraction of anthocyanins, without degrading them. The carotenoid profile of the IAPAR 69 cultivar, with orange flesh due to b-carotene as a major (> 90%) and zeinoxanthin as a minor presented total contents of almost 65 mg 100-1 g-1 on dry basis (BS) with isomerization after cooking and frying with retentions around 55%. The yellowish flesh variety, with 2 mg 100-1 g-1 BS of unidentified total carotenoids, presented a rare profile characteristic of new xanthophylls similar to those found by Maoka et al. (2007), with degradation after cooking and frying, and retentions around 82%.