Nutrient and polyphenolic composition of industrial strawberry press cake

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ORIGINAL PAPER

Nutrient and polyphenolic composition of industrial strawberry press cake Michał Sójka · Elz˙bieta Klimczak · Jakub Macierzyn´ski · Krzysztof Kołodziejczyk 

Received: 28 March 2013 / Accepted: 21 July 2013 / Published online: 9 August 2013 © The Author(s) 2013. This article is published with open access at Springerlink.com

Abstract  The objective of the present work was to determine the nutrient and polyphenolic composition of dried strawberry press cake (SPC), as well as that of its seedless fraction, termed exhausted strawberry flesh (ESF). The study materials were obtained over three consecutive years from an industrial facility manufacturing concentrated fruit juices. On average, SPC consists of 40 % seeds, 3.5 % sand, and about 55 % ESF. In the dry matter of SPC and ESF, the mean content of fat is 9.8 and 3.5 %, protein 17.3 and 20.4 %, and total polyphenols 3,449 and 5,410 mg/100 g, respectively. Both materials are rich in total dietary fiber, whose content amounts to 60 %. The predominant polyphenols in SPC and ESF are flavanols and ellagitannins, which collectively constitute over 95 % of the determined total polyphenol content. In ESF composition, of note is the high content of the strawberry ellagitannin, agrimoniin, which is approximately 1,000 mg/100 g DW (dry weight). SPC has the disadvantage of being highly contaminated with sand (3.4 %), which accumulates in ESF (5.6 %). However, as compared to SPC, ESF contains approximately 20 % more proteins and almost three times less fat. Based on our results, it appears that SPC may be considered a potential raw material for seed recovery. Moreover, dried strawberry press cake, and especially its seedless fraction (ESF), despite substantial contamination with sand, may be used as rich and widely available raw material for the extraction of proanthocyanidins and/or ellagitannins, and especially dimeric agrimoniin.

M. Sójka (*) · E. Klimczak · J. Macierzyn´ski · K. Kołodziejczyk  Faculty of Biotechnology and Food Science, Institute of Chemical Technology of Food, Lodz University of Technology, Stefanowskiego 4/10, 90‑924 Lodz, Poland e-mail: [email protected]

Keywords  By-products · Flesh · Flavanols · Ellagitannins · Agrimoniin

Introduction Strawberry (Fragaria  ×  ananassa Duch.) is one of the most important fruits, which adapts to various environmental growth conditions [1]. Strawberry fruits are not only attractive for their delicious taste and fresh aroma, but also for their nutritional values and antioxidant properties [2]. Their commercial production for the fresh fruit market and the processing industry has increased significantly in recent years, and in 2010, the world’s strawberry production was 4.4 million tons [3]. The future of strawberry production and sales is very promising. Poland, with its output of 176,000 tons, is a leading producer of strawberries in Europe [3]. Strawberries occupy an important position in the Polish frozen fruit industry and in industrial manufacturing of strawberry concentrates [4]. According to many