Controlling of geosmin and 2‐methylisoborneol induced off‐flavours in recirculating aquaculture system farmed fish—A review

Abstract

Recirculating aquaculture system (RAS) is an increasingly popular alternative to open aquaculture production systems. However, off-flavours and odours can accumulate in the fish flesh from the circulating water and decrease the fish meat quality. Offflavours are typically caused by geosmin (GSM) and 2-methylisoborneol (MIB) that are lipophilic compounds formed as secondary by-products of bacterial metabolism.Even though GSM and MIB are not toxic, they often are disliked by consumers, and both have very low human sensory detection limits. Multiple methods have been suggested to remove or decrease GSM and MIB in fish, including ozonation, advanced oxidation processes (AOP)s and adsorption removal from water using activated carbon and/or zeolites. So far, purging with fresh water is the only efficient method available to remove the off-flavours. There are multiple analytical methods available for the extraction and separation of GSM and MIB from fish flesh and water. This review discusses the current knowledge of GSM and MIB formation, the challenges faced by RAS farms due to these compounds and process solutions available for their removal. K E Y W O R D S2-methylisoborneol (MIB), geosmin (GSM), off-flavours, purging

Seasonal dynamics are the major driver of microbial diversity and composition in intensive freshwater aquaculture

“…These conditions are prevalent during the summer months in Israel. Certain cyanobacteria can produce metabolites that cause undesirable flavors to the fish products (Lee et al, 2017; Lindholm-Lehto and Vielma, 2019; Mares et al, 2009; Paerl and Tucker, 1995; Schrader and Dennis, 2005; Tucker and Schrader, 2020), and/or various toxins that can kill both invertebrates and fish (Oberemm et al, 1999; Smith et al, 2008). Over the course of this study, cyanotoxins (microcystins or nodularins) were repeatedly observed in the particulate fraction of the reservoir and the fishponds during summer, at concentrations that, at times, were above the recommended limit for drinking water of 1 µg microcystins L -1 (according to guidelines set by the World Health Organization (WHO, 2019).…”

Metabarcoding profiling of microbial diversity associated with trout fish farming

“…Fish malodor is routinely observed in several cultivated fish species 18 . This problem is frequently associated with the exogenous accumulation of the earthy and musty off-flavors (2-methylisoborneol and geosmin) from water in fish 19 , 20 .…”

“…This problem is frequently associated with the exogenous accumulation of the earthy and musty off-flavors (2-methylisoborneol and geosmin) from water in fish 19 , 20 . These compounds' primary producers are species belonging to Actinobacteria and Cyanobacteria phyla 6 – 8 , 18 , 19 . Recent reports indicated that other species might also contribute to fish malodor (e.g., members of the genera Myxobacteria and Sorangium of the phylum Proteobacteria; 21 ).…”

The Fate of Bacteriophages in Recirculating Aquaculture Systems (RAS)—Towards Developing Phage Therapy for RAS

“…Furthermore, by selecting phages targeting unwanted contaminants (pathogens or other bacteria), this approach could be used in developing phage-based techniques in managing the RAS biofilter microbiome. For example, geosmin compounds accumulate in fish tissue, causing unwanted earthy taste and odor [27]. Phages infecting geosmin-producing Streptomyces species have already been shown to be capable of reducing geosmin production [28] and could be used in RAS systems to control product quality.…”