Researchers from the University of Copenhagen have made a significant breakthrough in addressing the persistent issue of muddy off-flavours in farmed fish, a problem that has plagued the aquaculture industry for two decades. The discovery allows for precise identification of when these undesirable flavours emerge, opening the door to effective solutions.
The off-flavour, often described as musty, earthy, or muddy, has been a deterrent to the consumption of otherwise healthy and sustainable fish, particularly in species like trout, carp, pangasius, and tilapia—key players in global aquaculture.
The culprit behind the muddy taste is Geosmin, a compound produced by aquatic microorganisms in the water where fish are raised. While Geosmin is harmless to humans, its presence hampers fish production, affecting a crucial protein source globally.
Associate Professor Mikael Agerlin Petersen of the Department of Food Science explains, “Geosmin is the compound that gives a beetroot its characteristically earthy flavor. In fish, it is an undesirable off-flavour that discourages people from eating an otherwise healthy and often sustainable food.”
The researchers have, for the first time, determined the precise amount of geosmin needed to affect the flavour of tilapia, using advanced measurement techniques. The studies conducted in aquaculture facilities in Sao Paolo, Brazil, revealed that even extremely low concentrations of geosmin in the water could result in muddy-flavoured fish.
Niels O. G. Jørgensen, Associate Professor emeritus at the Department of Plant and Environmental Sciences, highlighted the significance of the findings, stating, “Our study shows fish take up an off-flavour from geosmin, even when extremely low concentrations of it are present in the water.”
The researchers employed a combination of advanced chemical analyses and human sensory perception to identify and measure geosmin and other compounds in both water and fish. The results indicated that geosmin is the primary culprit, but 2-methylisoborneol also plays a significant role in the off-flavour, along with other volatile organic compounds that are harmless to humans.
The breakthrough not only provides a deeper understanding of the issue but also offers practical tools for producers to ensure the quality of their fish. By determining exact concentrations of off-flavour compounds, producers can now take measures to prevent the development of undesirable tastes in farmed fish.
The study emphasizes the role of water quality in the development of these compounds, particularly in aquaculture farms with limited water circulation. The findings have broader implications for the aquaculture industry, which plays a vital role in global food supply and sustainability.
Niels O. G. Jørgensen notes, “Foul-tasting farmed fish doesn’t just impact aquaculture industry revenue—it also affects the promotion of a more sustainable protein source.”
This breakthrough research comes at a crucial time as the focus on sustainability in aquaculture continues to grow, and challenges such as water management and feed sourcing are being addressed to make the sector more environmentally friendly and acceptable to consumers worldwide.
Source: University of Copenhagen
