Influence of dried Hokkaido pumpkin and ascorbic acid addition on chemical properties and colour of corn extrudates Valentina Obradovic ´ a,⇑ , Jurislav Babic ´ b , Drago Šubaric ´ b , Antun Jozinovic ´ b , Ður - dica Ac ˇkar b , Ilija Klaric ´ c a Agricultural Department, Polytechnic of Poz ˇega, Vukovarska 17, 34 000 Poz ˇega, Croatia b Subdepartment of Technology of Carbohydrates, Faculty of Food Technology, Josip Juraj Strossmayer University of Osijek, Franje Kuhac ˇa 20, 31 000 Osijek, Croatia c Departmant of Public Health, R. Dz ˇ. Cauševica 1, 76 000 Brc ˇko DC, Bosnia and Herzegovina article info Article history: Received 28 November 2014 Received in revised form 5 March 2015 Accepted 13 March 2015 Keywords: Extrusion Pumpkin powder Ascorbic acid Carotenoids Polyphenols Crude fibre abstract The influence of Hokkaido pumpkin powder (PP) addition to corn grits at levels 4%, 6%, and 8% and ascor- bic acid (AA) addition at levels 0.5% and 1% was evaluated. Extrusion was done using a single-screw extruder at two temperature regimes: 135/170/170 °C (E1) and 100/150/150 °C (E2). Mathematical mod- els that describe the influence of additives on the colour of extrudates were determined. Raw extrusion mixtures as well as obtained extrudates were tested for ascorbic acid, polyphenol, proteins, fat, crude fibre, ash and carotenoids content, and antioxidant activity. E1 extrusion regime acted favourably on polyphenols, crude fibre content, and antioxidant activity. It also caused higher fat degradation than E2 extrusion. Xanthophylls (lutein and zeaxanthin) were less sensitive to extrusion than carotenes (a-carotene, 9-cis-b-carotene and 13-cis-b-carotene). Ascorbic acid was more sensitive to higher extru- sion temperatures (49–76% degradation). It provided protection to carotenoids and consequently the colour of the extrudates. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction During recent decades consumer requirements in relation to food quality and safety have significantly changed. Consumers are increasingly interested in high-value food products, especially fruit, vegetables and other functional foods (Bisharat, Oikonomopoulou, Panagiotou, Krokida, & Maroulis, 2013). Therefore, food manufacturers are facing the challenge to create new products which, beyond basic nutrients, also provide certain health-promoting properties. In this context, extrusion is particu- larly interesting because it belongs to HTST (high temperature short time) processes, so it restricts the unwanted effects on pro- teins, amino acids, vitamins, starch, and enzymes. Besides, it can be used in the production of a wide range of products such as snack-foods, baby foods, breakfast cereals or pasta (Jozinovic ´ et al., 2012). Enrichment of extruded snacks with nutritionally valuable ingredients is increasingly practised by many studies, wherein the addition of protein and fibre rich ingredients like legumes or whey protein is leading, and the addition of fruits and vegetables is studied to a lesser extent (Obradovic ´, Babic ´, Šubaric ´, Ac ˇkar, & Jozinovic ´, 2014). Still, more needs to be done in terms of producing snacks, especially since snacking is part of day-to-day lives of children (Potter, Stojceska, & Plunkett, 2013). Pumpkins are particularly interesting since they are rich source of fibre and bioactive substances like carotenoids and polyphenols. Besides the pro-vitamin A activity of some carotenoids such as b- carotene and a-carotene, studies have also indicated that the con- sumption of carotenoids lowers the risk of degenerative and car- diovascular diseases, cataracts, and certain types of carcinomas (Provesi, Dias, & Amante, 2011). Only several studies are dealing with the influence of the extrusion on carotenoids, primarily b-car- otene (Berset, Trouiller, & Marty, 1989; Emin, Mayer-Miebach, & Schuchmann, 2012; Waramboi, Gidley, & Sopade, 2013) and lyco- pene (Deghan-Shoar, Hardacre, & Brennan, 2010). Considering the complex composition of extruded products, ingredients undergo changes and mutual interactions. In order to create prod- ucts of satisfying quality and nutritional value, it is necessary to understand those changes. Therefore, the objective of this study was to utilise different levels of dry Hokkaido pumpkin in corn grits. The effect of extrusion processing on the nutritional and functional properties and colour attributes of raw materials and extruded samples was evaluated. In this research, strong antioxi- dant ascorbic acid was also added to the extrusion mixture. Ascorbic acid can function as an acidulant and vitamin in foods, thus could improve pigment retention (Camire, Chaovanalikit, Dougherty, & Briggs, 2002; Chaovanalikit, Dougherty, Camire, & Briggs, 2003). Previous research has shown ascorbic acid retention http://dx.doi.org/10.1016/j.foodchem.2015.03.045 0308-8146/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +385 34 311 463. E-mail address: vobradovic@vup.hr (V. Obradovic ´). Food Chemistry 183 (2015) 136–143 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem