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EUROTIER: Preventing An Off-Taste In Fish


GERMANY - A musty or earthy off-flavour can be a problem in farmed fish, regardless of the water type in which they were grown. The economic impact of a poor consumer experience can only be guessed, but it is known that the pre-harvest purification practised on farms is a significant added cost.

Unfortunately, according to aquaculture scientist Edward Schram at the IMARES unit of Wageningen University in the Netherlands, the processes employed in purification of the fish before sale are also unreliable and therefore they need to be optimised.

Good knowledge exists already on the basic mechanisms by which off-flavours occur, Mr Schram told an aquaculture forum held during the EuroTier 2010 exhibition in Germany. We know the undesirable taste starts with two lipophylic compounds (Geosmin or GSM and MIB) being produced by bacteria and reaching the fish through the culture water. But there are vital aspects of this that remain unknown at present, not least why the microbes produce the compounds and the conditions under which the production arises or accelerates.

“I do not believe that the microbiota produce GSM and MIB for no reason,” he declared. “These compounds must have a biological function, which means there are conditions conducive to their production. If we can understand the reason then this should give us clues on how to prevent the microbes doing it.

“It will need some fundamental research, of course, so other actions need to be considered in the short term. One of these may be to find ways of promoting the excretion of the compounds from the body of the fish during purification before harvesting. For example, we know that a higher water temperature leads to a faster excretion rate, although there would obviously be an extra cost to be taken into account.”