Anthocyanin and antioxidant activity of snacks with coloured potato Agnieszka Nems ´ a,⇑ , Anna Pe ˛ksa a , Alicja Z. Kucharska b , Anna Sokół-Le ˛ towska b , Agnieszka Kita a , Wioletta Dro _ zd _ z a , Karel Hamouz c a Department of Food Storage and Technology, Faculty of Food Science, Wroclaw University of Environmental and Life Sciences, Poland b Department of Fruit, Vegetable and Cereals Technology, Faculty of Food Science, Wroclaw University of Environmental and Life Sciences, Poland c Department of Plant Production, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Czech Republic article info Article history: Received 2 July 2014 Received in revised form 5 September 2014 Accepted 6 September 2014 Available online 16 September 2014 Keywords: Coloured potatoes Snacks Antioxidant activity Polyphenols Anthocyanins abstract Coloured-fleshed potatoes of four varieties were used as raw material for coloured flour and fried snack production. The effects of thermal processes traditionally used in dried potato processing and in snack pellet manufacturing on anthocyanin profiles, total polyphenols and antioxidant properties of obtained half- and ready products were studied. There was a significant influence of potato variety on the exper- imental flour and snack properties. Flours with the highest antioxidant activities were obtained from Salad Blue and Herbie 26 potatoes; however, the flour prepared from the Blue Congo exhibited a much higher total polyphenol and anthocyanin content. Snacks produced with coloured flour had 2–3 times higher antioxidant activities, 40% higher contents of polyphenols, attractive colour and better expansion compared to control samples. The lowest losses of anthocyanins during snack processing were in snacks with flour from the purple-fleshed Blue Congo and red-fleshed Herbie 26. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Pellet snacks are well-known within the world market of food products for having huge versatility regarding taste, raw materials used and some sensory characteristics. Pellet snacks are typically small, have large expansion, a porous structure and a crispy tex- ture; however, these properties can differ depending upon the raw material used. The specific physical and sensory features of these popular snacks are the effect of starch transformation during processing. In the manufacturing of pellet snacks, a raw material containing starch, such as potato starch, flakes, granules or grits, are mixed with water, salt and optionally with other dough com- ponents, such as vegetable, cereal or legume flour, semolina or grits, and pellets are formed, usually with the use of low shear extrusion technology. Pellets of approximately 20–30% moisture content are subjected to a drying process under mild temperature conditions to obtain a half-product of approximately 11–12% mois- ture equally dispersed throughout the pellet’s volume. To obtain ready-to-eat products a thermal process, such as frying or baking, is necessary. During that process, the pellets expand, increasing their volume 3–8 times and the typical porous, light structure and crispy texture of the final product is created (Lusas & Rooney, 2001). There is suggested by different authors (Brown, 2005; Lachman, Hamouz, Orsák, & Pivec, 2000; Yen & Chen, 1995) that antioxidants naturally presented in food have health-promoting and antiaging effects in the human body. However, depending on the type of bio- active compounds they can be well absorbed and act as antioxi- dants within the organism or can be abolished during first-pass metabolism in the intestine and liver. Among antioxidants ascorbic acid and a-tocopherol preserve their properties in the organism but another phytochemicals, like polyphenols lose this function as a result of the attachment of a functional group at exactly those positions of the molecule that are responsible for its antioxidant activity. This is one of the reason why the referring total antioxi- dant capacity (TAC) of food, measured by different in vitro assays, to its importance for human health is to be discouraged (Pompella et al., 2014). However, antioxidants can also play an important role in food technology by contributing to food quality, for instance by the preventing fat deterioration in fried products. Potatoes are known as one of the richest sources of antioxidant compounds in the human diet. The main antioxidants are polyphe- nols, ascorbic acid, a-tocopherol and b-carotene. In addition, the antioxidant activity of patatin, a tuber storage protein, has been investigated (Hillebrand, Naumann, Kitzinski, Kohler, & Winterhalter, 2009; Lachman, Hamouz, Orsák, Pivec, & Dvor ˇak, 2008). Polyphenols are the largest group of plant components and can be divided into phenolic acids, flavonoids, stilbenes and lignans (Manach, Scalbert, Morand, Remesy, & Jimenez, 2004). In http://dx.doi.org/10.1016/j.foodchem.2014.09.033 0308-8146/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: agnieszka.nems@wnoz.up.wroc.pl (A. Nems ´). Food Chemistry 172 (2015) 175–182 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem