Nutraceutical properties of bread obtained from a dough enriched with purple potatoes (cv. Vitelotte)

Although the partial substitution of wheat flour with potatoes in bread making (dough) is a traditional practice in various regions of Italy, potatoes of an ancient variety (cv. Vitelotte) with purple pulp are not usually used for the preparation of bread. Due to their high content in bioactive compounds, in particular phenolic derivatives of cinnamic acid and acylated anthocyanins, baking experiments on a small scale with the use of purple potatoes were made with the aim to investigate whether it was possible to transfer these compounds to the bread in order to improve its nutritional value. The potatoes were washed, boiled, peeled, sliced and air dried at 50 °C. The dried chips were then ground using an electric grinder and sieved. The powder obtained was finally used in baking after mixing with wheat flour using a 1:3 ratio. In the samples of bread total phenolic compounds, the antioxidant power (ABTS), and total anthocyanins were determined. Moreover, the composition of phenolic compounds was analyzed by HPLC. The powder from purple potatoes showed nutraceutical properties in comparison with that obtained from white potatoes containing total phenols at a value 35% higher. Among phenolic compounds, anthocyanins prevailed reaching a total phenols:total anthocyanins ratio of 3:1. To evaluate the phenolics losses during baking, data on bread were compared with those obtained on the powder from purple potatoes. Baking determined a loss of about half of phenolics and reduced the amounts of total anthocyanins as in bread the purple powder:wheat flour ratio passed from 1:3 (before baking) to 1:7 (after baking). These preliminary data appear to be promising as, notwithstanding the losses, the bread enriched with purple potatoes showed more nutraceutical properties than that obtained with white potatoes.