food and bioproducts processing 87 (2009) 40–45 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/fbp Encapsulation of a proteolytically active novel bioproduct; controlling the release of proteinous components Geir Solgaard ∗ , Kaspar H. Thorsen, Kurt I. Draget Norwegian Biopolymer Laboratory, Department of Biotechnology, The University of Science and Technology NTNU, Sem Sælands v 6/8, 7491 Trondheim, Norway article info Article history: Received 10 January 2008 Accepted 12 March 2008 Keywords: Marine bioproduct Alginate Protein release Protein–alginate interactions Protein conservation methods abstract Low trophic level organisms like zooplankton not only represent a valuable and unuti- lized source for marine proteins and lipids, but are also challenging with respect to high post-mortem protease activity. As an example, Ca–alginate encapsulated homogenized fresh zooplankton (Calanus finmarchicus) exhibited a high release of protein components when immersed in water due to diffusion of proteolytically degraded proteins. Initial dif- fusion rates at pH 7 increased with temperature up to 60 ◦ C. Above 50 ◦ C, the release was reduced because of protease instability after 12 h. The release of protein also increased with increasing ionic strength, most likely due to decreased electrostatic interaction between the alginate matrix and protein. As function of pH, the release of both amino groups as well as larger protein entities was apparently highest under alkaline conditions. Encapsulated heat- treated or alkali treated zooplankton had a high degree of release, the first 2 h reflecting the presence of osmoregulating amino acids as well as pre-digested proteins. After 2h, no fur- ther release of protein was observed, which can be attributed to protease inactivation caused by these treatments. The present data show that all studied parameters (temperature, pH and ionic strength) have a profound impact on protein loss from the encapsulated model feed particles. Therefore, possible conservation methods to control the observed protein loss from marine raw materials in, e.g. marine feed formulations are suggested. © 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction Calanus finmarchicus is a low trophic level zooplankton species, which easily can be harvested and is present in massive amounts in the northern oceans (Melle and Olsen, 2002). This species has a high-protein content and a beneficial fatty acid profile (Solgaard et al., 2007), and may therefore be a new, useful resource in human and animal nutrition. For example, Ca–alginate-gelled particles containing C. finmarchicus may be used as, e.g. feed for marine juveniles as a replacement for Artemia and Rotifers. The zooplankton may also be an appro- priate fish meal substitute on a general basis. At present, however, most of the protein in fish feed comes from fish and other high trophic level sources (Adelizi et al., 1998; Millamena and Golez, 2001), which is becoming an increasingly limited resource for this purpose. More generally, protein and lipids ∗ Corresponding author. Tel.: +47 735 91685; fax: +47 735 91283. E-mail address: geir.solgaard@biotech.ntnu.no (G. Solgaard). derived from C. finmarchicus may also serve as useful additives in food and neutraceutical products to improve their nutri- tional value (e.g. functional foods). Thus, C. finmarchicus, as a low trophic species, could be considered to be an attractive resource in a world with a growing demand for marine pro- teins and lipids; both for human consumption as well as for feed to farmed animals. However, a high catabolic activity was observed in crude extracts of C. finmarchicus post mortem (Solgaard et al., 2007) resulting in a high degree of protein loss as function of time. Most of the water-soluble protein is rapidly digested and turned into small peptides and amino acids. Some enzyme activity may, however, be beneficial under certain circum- stances as it, e.g. facilitates digestion in juvenile marine larvae (Kolkovski, 2001; Dabrowski and Glogowski, 1977). Thus, the primary goal for the exploitation of these bioproducts is to be able to control the overall proteolytic activity; both through a 0960-3085/$ – see front matter © 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.fbp.2008.03.003