Protein and Long-Chain n-3 Polyunsaturated Fatty Acids Recovered from Herring Brines upon Flocculation and Flotation─A Case Study

Abstract

A novel integrated process for recovery of protein-enriched biomasses from 5% presalting brines and spice brines of herring (Clupea harengus) was investigated by combining carrageenan- and/or acid-driven flocculation (F) plus dissolved air flotation (DAF). The F-DAF technique with carrageenan resulted in protein and lipid recoveries from 5% presalting brine of 78 and 38%, respectively. Without flocculation or with only acidification, protein and lipid recoveries in DAF were only 13 and 10%, respectively. Low protein and lipid recoveries, 8-12 and 1.8-8.2%, respectively, were also obtained when spice brine was subjected to only acidification and DAF. The protein content in dry biomasses from 5% presalting brine and spice brine was 36-43 and 13-16%, respectively. The corresponding lipid levels were 23-31 and 9-18%, respectively, with ash levels of 11-20 and 38-45%, respectively. Biomass proteins contained ≤45% essential amino acids, and the lipids had ≤16% long-chain n-3 polyunsaturated fatty acids. Freeze-dried spice brine biomasses were characterized by anchovy- and spice-related sensory attributes. 5% presalting brine biomasses were connected to fish and seafood attributes and showed gel forming capacity. The outlined F-DAF recovery system can thus recover both nutrients and interesting flavors from the herring process waters, which are currently lost from the food chain.