Executive Summary: Scoping Project: Value from aquaculture nuisance species. Blue Mussels

Summary of Project and Key Findings:
Blue mussels (Mytilus edulis/galloprovincialis) are a major nuisance species for Greenshell mussel (Perna canaliculus) farmers. The ‘blues’ grow on the Greenshell lines, competing for available space and food with the ‘greens’, and adding significant sorting and disposal costs. Although blues are one of the main edible species worldwide, in New Zealand there are few commercial products made from them, and they are usually dumped over the side of the barge. Those that make it to the factory are sorted, then often sent to land-fill. Despite considerable efforts to reduce growth on the lines, in the worst cases they can cover up to 40% of the line space.

The 2006-2008 project team successfully developed a blue mussel stock with a characteristic fresh mussel flavour, made by enzymatic hydrolysis from a mussel slurry. The mussel slurry was made using the same first steps as used in the nutraceutical mussel process (i.e., crushing, then centrifuging to remove beard and shell). Various trials were carried out to establish the best enzyme system, effects of: freezing, membrane concentration and freeze-drying on the flavour and performance in foods, and how to pack and stabilise. Although it was shown that freeze-drying made an excellent product, the final version was packed in a UHT brick, with the intention to perhaps move on to a freeze/spray/belt dried product at a later date. Several factory-scale runs were carried out at Nutura. These were followed by shelf-life testing and demonstration of the product in foods.

This BPA blue mussel hydrolysates project was an opportunity to revisit this raw material for a food product and reassess whether the stock and flavouring might be worth pursuing in a new commercial environment.

The BPA project has verified that a well-flavoured stock can be made from a blue mussel slurry, but also that it could be made from heat-shucked mussels although process optimisation would be required for this raw material. Heat-shucked may be more convenient for many raw material suppliers and/or processors, and removes the need for expensive crushing equipment. It has indicated that freezing is a viable route for liquid product delivery as well as showing that a freeze-dried powder retains good flavour.