Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem Fried potatoes: Impact of prolonged frying in monounsaturated oils Carla S.P. Santos a , Lucía Molina-Garcia a,b , Sara C. Cunha a , Susana Casal a,c, ⁎ a REQUIMTE, Laboratory of Bromatology and Hydrology, Faculty of Pharmacy, University of Porto, Rua Jorge de Viterbo Ferreira 228, 4050-313 Porto, Portugal b Department of Physical and Analytical Chemistry, Faculty of Experimental Sciences, University of Jaén, Campus las Lagunillas, E-23071 Jaén, Spain c EPIUnit - Instituto de Saúde Pública, Universidade do Porto, Rua das Taipas, nº 135, 4050-600 Porto, Portugal ARTICLE INFO Keywords: Deep-frying White potatoes Nutritional and sensory quality Acrylamide Ascorbic acid Oxidation Monounsaturated fats ABSTRACT Fresh potatoes were intermittently deep-fried up to recommended limits (175 °C, 8 h/day, 28 h) in extra-virgin olive oil (EVOO), peanut oil (PO) and canola oil (CO), and compared for diverse chemical components and sensorial attributes, aiming to quantify the impact of prolonged frying on potatoes nutrients, and the potential alterations resulting from the use of different monounsaturated-rich oils. Independently of oil type, its degradation promotes time-dependent losses of important potato nutrients, as vitamin C. Regarding the monounsaturated-rich oils tested, potatoes fried in CO had more equilibrated fatty acid profiles, but higher amounts of aldehydes derived from PUFA oxidation, while in EVOO were enriched with phenolic compounds. Acrylamide amounts were not affected by oil type or frying hours. Sensory degradation was gradually perceived by the panellists, except in PO. Prolonged frying should not be studied only on the basis of oil degradation because, even if within regulated limits, it induces loss of important food compounds. 1. Introduction Deep-frying is among the most popular cooking methods world- wide. Several studies comparing performances of different vegetable oils during prolonged frying are found in the literature, as recently reviewed (Hosseini, Ghorbani, Meshginfar, & Mahoonak, 2016; Nayak, Dash, Rayaguru, & Krishnan, 2016), but when searching for the nutri- tional impact from the consumer’s perspective, on the fried food, data on nutritional and sensory changes during prolonged frying are scarce (Boskou, Salta, Chiou, Troullidou, & Andrikopoulos, 2006; Carlson & Tabacchi, 1986; Han, Kozukue, Young, Lee, & Friedman, 2004; Romano, Giordano, Vitiello, Grottaglie, & Musso, 2012; Salta, Kalogeropoulos, Karavanou, & Andrikopoulos, 2008; Zhang, Zhang, Cheng, Wang, & Qian, 2015). Fried food incorporates fat in variable amounts, while being enriched in oil components, as fatty acids and vitamin E (Casal, Malheiro, Sendas, Oliveira, & Pereira, 2010; Chiou, Kalogeropoulos, Boskou, & Salta, 2012). Simultaneously, some food components are loss by evaporation or leaching, as moisture itself, or degraded, as ascorbic acid, while new compounds are formed during these hot oil-food interactions, including highly pleasant ones, as the typical fried volatile flavors, or unhealthy ones, as degraded lipids and acrylamide (Camire, Kubow, & Donnelly, 2009). Potatoes (Solanum tuberosum L.) are regarded as an excellent source of carbohydrates, supply protein of high relative biological value (90–100), while being very low in fat (0.1%) (Camire et al., 2009). They are also rich in several micronutrients, as essential minerals, carotenoids, phenolic compounds, and vitamin C (Camire et al., 2009). However, to increasing its digestibility, potatoes are consumed only after cooking, by boiling, roasting, frying, among others (Decker & Ferruzzi, 2013). Therefore, together with the agronomic practices, postharvest storage methods and potato varieties, known to influence potatoes composition, the cooking method and, in the parti- cular case of frying, the cooking oil determines the nutrients truly available to consumers. From the vegetable oil perspective, many types of vegetable oils are available for deep-frying purposes, highly based on availability, tradi- tion, and thermal resistance. Soybean and sunflower are more generally accepted worldwide, canola oil is common in various European coun- tries and Canada, peanut oil is also used in several countries, while olive oil is more traditionally used around the Mediterranean Sea (Hosseini et al., 2016). While the health impact of saturated fats is still under discussion, and hydrogenated ones are fading out, vegetable unsaturated fats have moved to the forefront, and among them, monounsaturated fats (MUFA) are increasingly providing a broader spectrum of functionality and health benefits (Gillingham, Harris- Janz, & Jones, 2011), with an inherent higher thermal oxidation stabi- lity than polyunsaturated fats (PUFA). Several “high-oleic” vegetable oils, both natural (as olive oil and peanut oil) or “modified” (high-oleic http://dx.doi.org/10.1016/j.foodchem.2017.09.117 Received 2 June 2017; Received in revised form 11 September 2017; Accepted 22 September 2017 ⁎ Corresponding author at: Laboratory of Bromatology and Hydrology, Faculty of Pharmacy, University of Porto, Rua Jorge de Viterbo Ferreira 228, 4050-313 Porto, Portugal. E-mail addresses: csps.santos@gmail.com (C.S.P. Santos), lucymolgar@gmail.com (L. Molina-Garcia), sara.cunha@ff.up.pt (S.C. Cunha), sucasal@ff.up.pt (S. Casal). Food Chemistry 243 (2018) 192–201 Available online 27 September 2017 0308-8146/ © 2017 Elsevier Ltd. All rights reserved. MARK