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A Salem, Ind., utility devised a generic, widely applicable approach to taste‐and‐odor control that paved the way to site‐specific treatment, resulting in higher quality water and fewer customer complaints. [ABSTRACT FROM AUTHOR]

Abstract: Over the past decade in the United States, there has been increased interest in the establishment and use of land-based, closed-containment systems [e.g., recirculating aquaculture system (RAS)] for salmonid culture. These culture systems have unique challenges compared to net pen culture of salmonids, including maintenance of pumps and filters as well as the potential growth of certain bacteria within the systems that can render fish off-flavored. The purpose of this study was to determine the impact of implementing a depuration process to purge the “earthy” and “musty” off-flavor compounds geosmin and 2-methylisoborneol (MIB) from Atlantic salmon fillets on fillet quality characteristics (e.g., lipid content, color). During two depuration trials, salmon were depurated without feed in a flow-through tank, a recently “cleaned” RAS system or the originally stocked grow-out tank for up to 20 days. Results from both trials determined that the salmon required depuration in odor-free water for 10–15 days in either a flow-through system or a recently cleaned RAS to obtain the lowest residual levels of geosmin and MIB in the fish flesh. In trial 1, after 20 days, fish had lost significantly more weight (5.8%) compared to day 5 (3.8%). In the second trial, lipid content of the fillet also significantly dropped from 8.2% to 5.1% and moisture content increased from 69.3% to 71.1%. Fillet color quality was not compromised during the 20-day depuration periods. In trial 1, MIB was the main off-flavor compound present in salmon fillets while geosmin was at higher levels than MIB in fish flesh in trial 2. During the second depuration study, three geosmin-producing species of actinomycetes were isolated from the recirculating system and were attributed as the likely sources of geosmin in the salmon fillets. Because fillet color quality was not compromised during the depuration periods used in these studies, the main fillet quality concerns for producers of RAS-cultured salmon are flavor, texture and lipid levels during the pre-harvest purging process. [Copyright &y& Elsevier]

A guide to confirmed geosmin- and MIB-producing cyanobacteria isolated in the United States is being prepared. This document will include 41 different species or morphologically distinct types from eight states and diverse aquatic sources isolated over a 22-year period. The organisms comprised by this guide demonstrate the importance of attached cyanobacteria as off-flavor agents, the strain specificity of MIB production, the existence of unicellular MIB producers, the occurrence of multiple geosmin and MIB producers in reservoirs, and the relationship of certain planktonic odor producers to species in other countries. [ABSTRACT FROM AUTHOR]

The article discusses on the detection of off-flavor in channel catfish, Ictalurus punctatus Rafinesque, fillets by trained dogs in the southern U. S. Off-flavor is a problem for producers of channel catfish which is caused by the accumulation in the catfish flesh of the metabolites geosmin (GSM) and 2-methylisoborneol (MIB). These compounds grow in the catfish aquaculture ponds and are abundants during summer. It produces unpleasant taste which must be detected by the processors to prevent unpalatable catfish. Both GSM and MIB are detected with the use of analytical/chemical methods. The solid phase microextraction-gas chromatography with mass spectrometry detection is used to identify and quantify the compounds in water and fish tissue, but these methods is expensive and time consuming. However, trained dogs could be used to detect GSM and MIB in pond water. And so the study aims to determine if trained dogs could also be used to detect off-flavor compounds in the processed products.

Three odorants, geosmin (earthy), MIB (2-methylisoborneol) (musty), and IPMP (2-isopropyl-3-methoxypyrazine) (decaying vegetation/musty) were spiked into raw water taken from the Detroit River and subjectedto bench-scale ozonation (with and without hydrogen peroxide). Statistical experiment design was employed to investigate operating variables such as ozone dose, ozone addition point, temperature, odorant spike level, and presence of hydrogen peroxide. Two additional odorants, cis-3-hexenyl acetate (grassy) and trans,trans-2,4-heptadienal (fishy) were also tested. Results showed that ozonation was capable of mitigating the spiked odorants in the Detroit source water. Ozone dose was the single most important factor in removing the odorants. Presence of hydrogen peroxide (without dose optimization) had a limited effect on odorant removal at tested pH and alkalinity conditions. Ozone application point and water temperature had significant impacts on ozone residual, but not on odorant removal. MIB was most difficult to remove by ozonation among the five spiked odorants. [ABSTRACT FROM AUTHOR]