Title: Utilisation of cod processing side streams (heads and backbones) for improved fishmeal production

Abstract

Zhang Hanbing's final project will be published in due time. Until then we share the abstract and a link to a poster.

Cod, as a vital resource in Iceland’s fisheries, has an annual production of approximately 210,000 tonnes. During processing, side streams (including heads and frames) account for 30–40% of the total weight. Traditional dried export methods offer low economic value and are susceptible to market fluctuations. This study explores high-value utilisation pathways for cod side streams, focusing on the impact of storage conditions and processing techniques on fishmeal quality. Storage at 0°C significantly suppresses the accumulation of Total Volatile Basic Nitrogen (TVB-N), with a daily increase of only 3.6 mg/100g, whereas storage at 5°C accelerates TVB-N growth by 2.1 times. Mechanical grinding increases the spoilage rate of cod heads by 24%, suggesting that processing should be completed within three days. The raw material characteristics of cod heads and frames significantly influence fishmeal quality. Their fat content (1–2%) is much lower than that of salmon (8–12%), while their ash content is higher (15–18% in heads, 18–20% in frames). A bone-meat separation process is required to reduce ash content to ≤5%. The crude protein content reaches 83–88%, outperforming freshwater fish species (12–15%) and exhibiting excellent thermal stability. The high ash (18–20%) and salt-free ash (15–18%) content in cod frames present potential for mineral extraction, such as calcium and phosphorus. The inherent salt content (3–4%) makes them suitable for marine feed production, avoiding osmotic pressure risks in freshwater feed. After washing, the ash content in fish bones decreases from 18.9% to 2.1%, with protein retention exceeding 80%, providing a foundation for developing nutritional supplements and bio-calcium sources. The study confirms that optimising storage temperature and processing timelines enhances fishmeal stability, while separated bone components hold high-value potential. These findings provide key technical support for the resource-efficient use of fishery side streams and the development of a circular economy.