Defatted strawberry seeds as a source of phenolics, dietary fiber and minerals Katarzyna Grzelak-Blaszczyk a , El _ zbieta Karli  nska a , Karolina Grze˛ da b , Edward R  oj b , Krzysztof Kolodziejczyk a, * a Faculty of Biotechnology and Food Science, Institute of Food Technologyand Analysis, Lodz University of Technology, 90-924, Lodz, Stefanowskiego 4/10, Poland b Fertilizers Research Institute (FRI), 24-110, Pulawy, Aleja Tysia˛ clecia Pa nstwa Polskiego 13a, Poland article info Article history: Received 18 January 2017 Received in revised form 10 May 2017 Accepted 11 May 2017 Available online 19 May 2017 Keywords: Fragaria x ananassa Press cake Polyphenol Ellagitannin TDF abstract Strawberry seeds obtained from industrial press cake from three harvest seasons and defatted by su- percritical CO 2 were analysed for dry substance, protein, fat, ash, minerals, saccharides, total dietary fiber and polyphenols. The defatted seeds were composed mostly of dietary fibers (on average 728 g/kg dry matter) and proteins (167 g/kg dry matter). The sum of polyphenols determined by HPLC varied from 15.6 to 17.5 g/kg dry matter and did not vary significantly with production year. There are two main groups of polyphenols among determined compounds: ellagitannins and flavanols, which mean content are 8.50 and 5.82 g/kg dry matter, respectively. Total contents of ellagitannins in seeds varied signifi- cantly with production year, but not flavanols. High contents of dietary fiber, makes it reasonable to consider the use of degreased seeds in food production, as source of dietary fiber or polyphenol preparations. © 2017 Published by Elsevier Ltd. 1. Introduction Strawberry attracts much attention from consumers due to its high sensory values, rich composition in bioactive substances and proven health-beneficial properties. Both fresh and processed strawberries are rich sources of polyphenols e 95e788 mg/100 g, and the highest polyphenol contents were recorded in strawberries harvested in Poland (Aaby, Skrede, & Wrolstad, 2005; Cheel, Theoduloz, Rodríguez, Caligari, & Schmeda-Hirschmann, 2007; Klopotek, Otto, & B€ ohm, 2005; Oszmia nski, Wojdylo, & Matus- zewski, 2007; Roussos, Denaxa, & Damvakaris, 2009; Da Silva Pinto, Lajolo, & Genovese, 2008; Skupie n & W ojcik-Stopczy nska, 2006). The highest concentrations of polyphenols c.a. 1429 mg/100 g are found in strawberry seeds, while strawberry flesh contains only 375e998 mg/kg of polyphenols (Cheel et al., 2007). Proanthocya- nidins represent the highest share in strawberry flavonoids, and the predominant phenolic acid is ellagic acid, especially linked at form of ellagitannins, which make up 50% of polyphenols (H€ akkinen et al., 1999; Oszmia nski et al., 2007). The content of ellagic acid is ten times higher in seeds, comparing to pure flesh (Da Silva Pinto et al., 2008). Ellagitannins are esters of hexahydroxylodiphenyl acid (HHDPA) and a monosaccharide, usually D-glucose. Health- beneficial properties of ellagitannins are believed to be linked to the capacity of these molecules to deliberate free ellagic acid, and further metabolism of the acid in human and animal organisms. Hydrolysis of ellagitannins in a digestive tract results in prolonged liberation of ellagic acid to blood (Heber, 2008). The acid can be thus regarded as the chemical marker of hydrolysable tannins presence in fruit material, and also a biomarker in research on bioavailability of diet ellagitannins (Seeram, Lee, & Heber, 2004). Average yearly processing of strawberries into mash and concentrated juices in Poland is c.a. 30.000 tons. During processing, residual press cake represents 10e15% of initial fruit weight (Klimczak, Kr ol, & Rozpara, 2011). Press cake resulting from juice production and waste from mash preparation are characterized by relatively high share of fruit in total weight. Seeds (nuts) only represent 1% of fruit weight, but they contain up to 11% of total phenolics present in strawberry fruits (Klimczak & Kr ol, 2010). In accordance with environmental regulations all waste should be utilized or directed to recycling (Nawirska, 2007; Nawirska, Sok ol-Le˛ towska, & Kucharska, 2007). The waste from strawberry * Corresponding author. E-mail addresses: katarzyna.grzelak-blaszczyk@p.lodz.pl (K. Grzelak-Blaszczyk), krzysztof.kolodziejczyk@p.lodz.pl (K. Kolodziejczyk). Contents lists available at ScienceDirect LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt http://dx.doi.org/10.1016/j.lwt.2017.05.014 0023-6438/© 2017 Published by Elsevier Ltd. LWT- Food Science and Technology 84 (2017) 18e22