Encapsulation of a proteolytically active novel bioproduct; controlling the release of proteinous components

Abstract

Low trophic level organisms like zooplankton not only represent a valuable and unutilized 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 diffusion 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 2 h, no further 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.