Turning Waste into A Resource: Isolation and Characterization of High-Quality Collagen and Oils from Atlantic Bluefin Tuna Discards

Neil Cutajar,Johann Galdies,Marion Zammit Mangion,Vincenzo Arizza,Frederick Lia,Alan Deidun

doi:10.3390/app12031542

Abstract

At the behest of the Green Deal, circular economy concepts are currently being widely promoted, not least within the aquaculture sector. The current study aims to demonstrate the technical feasibility of extracting collagen and fish oils from waste Atlantic bluefin tuna biomass originating from the Maltese aquaculture industry. For collagen, a three-stage methodology, consisting of pre-treatment, extraction, and retrieval, was applied to biomass originating from bone, skin, muscle, and internal organs (offal) in order to extract both acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC). The chemical identity of the extracted collagen was confirmed through the conduction of hydroxyproline and SDS-PAGE tests as well as through FTIR, whilst the extracted collagen was also tested for its microbiological and heavy metal profiles. The collagen yield was found to be highest for skin tissue and for PSC-based protocols and is comparable to the yield cited in the literature for other tuna species. Oils were extracted through low temperature, high temperature, and enzymatic means. The fatty acid profile of the extracted oils was assessed using GC-FID; this indicated high proportions of EPA and DHA. Yield indicated that the enzymatic extraction of oil is most effective. High heat and the presence of iron-containing muscle starting material promote oxidation and rancidity. Further effort into the optimization of both collagen and lipid extraction protocols must be invested, with a special focus on the production of high-value fractions that are much closer to the quality required for human use/consumption.

Highlights

Worldwide, the volume of fish hailing from the aquaculture industry (80 million tons) is rivaling that hailing from wild-capture fisheries (98 million tons), with global fish demand increasing annually [1]
The collagen yield was found to be lower for all acid-soluble collagen (ASC)-tissue extracted, ranging from 1.2 g/100 g of collagen derived from general waste to 1.64 g/100 g from bone to 4.9 g/100 g from skin, compared to 3.3, 2.01, and 16.6 g/100 g, respectively, for the pepsin-soluble collagen (PSC) components
The increased yield noted for PSC extraction occurred as the proteases used to cleave the telopeptide cross-linking regions of the collagen structure that represent the main sites of intra- and inter-molecular cross-linkage in the collagen structure, effectively exposing further collagen for extraction

Summary

Introduction

The volume of fish hailing from the aquaculture industry (80 million tons) is rivaling that hailing from wild-capture fisheries (98 million tons), with global fish demand increasing annually [1]. The sanctioned disposal at sea within Maltese territorial waters of vast volumes (estimated at an annual figure of 3000–5000 metric tons) of non-commercialized Atlantic bluefin tuna biomass (e.g., fish heads, tails, fins, and offal) represents a missed opportunity in terms of an under-exploited resource as well as an environmental hazard (mainly in terms of degraded water quality), given the importance to the local economy represented by the tourism industry These aforementioned problems and their persistence indicate that the Atlantic bluefin tuna capture-fisheries industry is not entirely sustainable; one must note how the ongoing initiative to increase the sustainability of this industry by ICCAT in the last 20 years has led to the species no longer being considered endangered [4].

Objectives

Methods

Results

Discussion

Conclusion