Musty Off-flavors Research Articles

Metabarcoding profiling of microbial diversity associated with trout fish farming

Earthy and musty off-flavors are routinely observed in farmed trout worldwide. The microbial association to the production of those off-flavors was previously reported. The current manuscript aimed to catalog the microbial enrichment (eukaryotes and prokaryotes) in semi-intensive aquaculture freshwater sources that might influence the trout aquaculture quality production. The 16S rRNA and ITS metabarcoding analyses were applied on the inflow- and pond-water samples from trout farms previously recorded a malodor fish products and located alongside Moosach and Sempt Rivers in Bavaria province, Germany. The results showed that more than 99% of the detected prokaryotic OTUs (Operational Taxonomic Unit identification) were bacteria as of ~ 75.57% were Proteobacteria, and ~ 14.4% were Bacteroidetes. Meanwhile, 118 out of 233 of the eukaryotic OTUs were known species. Of these, ~ 45% were plant pathogens, and ~ 28% were mushroom/yeasts. Based on the comparative analysis between inflow- and pond-water samples, several pro- and eukaryotic microorganisms that affect the trout aquaculture water quality and industry have been detected, including the malodor-producing microorganisms, e.g., Cyanobacteria and Actinobacteria, along with fish infectious microorganisms, e.g., Chilodonella cyprinid, Metschnikowia bicuspidate. Additionally, the effect of the human- and industrial-related activities around the sampling area on the microbiota of the investigated farms were highlighted.

Use of a plastic film to eliminate the cork taint of a contaminated wine – improvement of organoleptic quality

Cork taint, generally recognized by a musty or moldy off-flavor, is a serious problem facing the industry today when putting wines on the market. To assess the effectiveness of a food-grade plastic film in removing the compounds concerned, trials were carried out under real conditions. It was found that enological parameters as well as color are maintained, and there is no absorption of phenolic compounds or oak aromas. The plastic film improves the organoleptic quality of wines contaminated with haloanisoles, by reducing the concentration of compounds that give the cork taint and mask oaky and/or fruity aromas.

Culture environment and the odorous volatile compounds present in pond-raised channel catfish (Ictalurus punctatus)

A headspace solid-phase micro-extraction (SPME) coupled with GS-MS method was used to measure volatile compounds in fillets from musty off-flavor, muddy off-flavor, and on-flavor channel catfish (Ictalurus punctatus), along with water and soil samples from the farm ponds in which the fish had been raised. Two ponds of each type of flavor were selected, and five fish, water, and soil samples were collected from each pond. Linear and multiple linear regression analyses were carried out between/among off-flavor strength and volatile compound contents to investigate their possible correlations. The combination of two strong off-flavor compounds, 2-methylisoborneol (MIB) and geosmin (GSM), was probably mainly responsible for the musty off-flavor in the catfish fillets, and an odorous alcohol, 1-hexanol, was correlated with muddy off-flavor (p = 0.015). There was a strong correlation between beta-cyclocitral and MIB in a pond that gave musty off-flavor catfish contents (p = 0.006), suggesting that these compounds might be generated by similar cyanobacteria. The contents of GSM, MIB, and beta-cyclocitral were high in the water of ponds that yielded off-flavor fish, indicating that catfish might acquire these compounds from pond water.

Exploration of volatile compounds causing off-flavor in farm-raised channel catfish (Ictalurus punctatus) fillet

Off-flavor is a major challenge to the quality of farm-raised catfish fillet. In this work, headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS) was employed to analyze volatile compound profile of catfish fillet to find the volatiles which might be responsible for the off-flavor. Ten volatile compounds were identified, and their concentrations in on-flavor and musty off-flavor fillets were compared. The off-flavor fillet contained significant larger amount of geosmin (GSM), 2-methylisoborneol (MIB), hexanal, 1-octen-3-ol and nonanal, indicating they might be related to the musty off-flavor. Sensory evaluation of the five compounds and their combinations suggested that GSM and MIB might be mainly responsible for the musty off-flavor, while the presence of hexanal or 1-octen-3-ol might notably intensify the off-flavor. This research suggested that besides GSM and MIB, some small aldehydes and/or alcohols might also need to be considered for controlling off-flavor in catfish fillet. This work also provided a useful chemistry-based objective method to evaluate the effects of treatments and/or managements in reducing catfish off-flavor.

Chemical Treatments to Reduce Off-Flavor in Farm-Raised Channel Catfish (Ictalurus punctatus ) Fillet

The efficacy of chemical treatments on reducing musty off-flavor in catfish fillets was evaluated in this work. Two ingredients, tea polyphenols and acetic acid, were found effective on removing the off-flavor. Three treatments, i.e., 0.40 g/L tea polyphenols, 0.50% acetic acid and 0.40 g/L tea polyphenols + 0.50% acetic acid, presented significantly better results than water wash (the control). Mechanism study indicated that the three treatments were able to reduce the contents of geosmin and/or 2-methylisoborneol which are the two major off-flavor causing compounds in catfish fillet. The treatment with both of the ingredients showed slightly better results than the treatment with only one ingredient. Practical Applications Off-flavor is a major quality concern to farm-raised catfish fillet. Major revenue lose could be caused by delay of harvest and/or defective products due to off-flavor. This study offers a novel strategy to reduce the musty off-flavor by chemical treatment, which could help the catfish industry improve fillet quality and lower production cost. The research indicated that tea polyphenols and/or acetic acid were effective to reduce/remove musty off-flavor in farm-raised catfish after harvest. The two chemicals could reduce the contents of geosmin (GSM) and/or 2-methylisoborneol (MIB), which are the two major off-flavor causing compounds in various fish fillets. Therefore, the treatments developed in this work may also be effective for other seafood products.

Evaluation of a Modified pH‐Shift Process to Reduce 2‐Methylisoborneol and Geosmin in Spiked Catfish and Produce a Consumer Acceptable Fried Catfish Nugget‐Like Product

Muddy and/or musty off-flavors in farmed-raised catfish occur as a result of the absorption of geosmin (GEO) and 2-methylisoborneol (MIB), compounds produced by algae. Previous research suggests the acid pH-shift method may be able to reduce off-flavors to produce a consumer acceptable product. The objective of this research was to evaluate application of the acid pH-shift method using a shaker sieve for protein recovery and to evaluate consumer acceptability of a resultant batter-coated fried nugget-like catfish product. Farm-raised catfish were either allowed to depurate (control) or treated with 1 ppb GEO or MIB. Fillets from each replicate were collected and ground and treated by the acid pH-shift process. Samples from all treatments and replicates were evaluated for residual GEO and MIB. In addition, batter-coated fried catfish samples were prepared for a consumer sensory evaluation. Results demonstrated that the pH-shift process decreased moisture, ash, and collagen content of catfish fillet tissue (P < 0.05). Flavor of control samples was preferred (P < 0.05). Texture of catfish samples treated by the pH-shift process was preferred (P < 0.05). Results demonstrate the pH-shift process can be utilized to reduce off-flavors and increase the acceptability of a processed catfish product. Use of a sieve as an economic alternative for the pH-shift process was evaluated for removing off-flavors from catfish. Difficulties were encountered with regard to protein recovery using the sieve and suggestions are made to, perhaps, make the process more applicable for a sieve-based recovery step. The process as described reduced off-flavors, but only 2-fold suggesting the process would work best on catfish near or just over off-flavor thresholds. Results also indicated the pH-shift process could be used to improve texture of a fried catfish product designed to be similar to chicken nuggets.

New Class of Algicidal Compounds and Fungicidal Activities Derived from a Chromene Amide of Amyris texana

A chromene amide, N-[2-(2,2-dimethyl-2H-1-benzopyran-6-yl)ethyl]-N,3-dimethylbutanamide, was isolated from the EtOAc extract of the leaves of Amyris texana and found to have moderate antifungal activity against Colletotrichum spp. and selective algicidal activity against Planktothrix perornata, a cyanobacterium (blue-green alga) that causes musty off-flavor in farm-raised channel catfish (Ictalurus punctatus). To improve the selective algicidal activity and provide water solubility, a series of chromene analogues were synthesized and evaluated for algicidal activity using a 96-well microplate rapid bioassay. In addition, the chromene analogues were evaluated for antifungal and phytotoxic activities. Hydrochloride salts of a chromene amine analogue showed improved water solubility and selectivity toward P. perornata with activity comparable to that of the naturally occurring chromene amide.

Evaluation of Diquat as a Potential Algicide for Controlling the Musty-Odor-Producing Cyanobacterium, Oscillatoria perornata, in Catfish Aquaculture Ponds

ABSTRACT The synthetic herbicide diquat was applied to a catfish aquaculture pond containing a heavy bloom of the cyanobacterium Oscillatoria perornata(a major contributor to musty off-flavor in farm-raised catfish) in order to determine the effectiveness of diquat as a selective algicide to prevent musty off-flavor in cultured catfish. Levels of the musty-odor compound 2-methylisoborneol (MIB) and numbers of O. perornata were monitored. Results indicate that diquat is not useful as an algicide for controlling O. perornata in catfish aquaculture ponds, despite its usefulness in controlling other aquatic weeds.

Novel derivatives of 9,10-anthraquinone are selective algicides against the musty-odor cyanobacterium Oscillatoria perornata.

Musty "off-flavor" in pond-cultured channel catfish (Ictalurus punctatus) costs the catfish production industry in the United States at least 30 million US dollars annually. The cyanobacterium Oscillatoria perornata (Skuja) is credited with being the major cause of musty off-flavor in farm-raised catfish in Mississippi. The herbicides diuron and copper sulfate, currently used by catfish producers as algicides to help mitigate musty off-flavor problems, have several drawbacks, including broad-spectrum toxicity towards the entire phytoplankton community that can lead to water quality deterioration and subsequent fish death. By use of microtiter plate bioassays, a novel group of compounds derived from the natural compound 9,10-anthraquinone have been found to be much more selectively toxic towards O. perornata than diuron and copper sulfate. In efficacy studies using limnocorrals placed in catfish production ponds, application rates of 0.3 micro M (125 micro g/liter) of the most promising anthraquinone derivative, 2-[methylamino-N-(1'-methylethyl)]-9,10-anthraquinone monophosphate (anthraquinone-59), dramatically reduced the abundance of O. perornata and levels of 2-methylisoborneol, the musty compound produced by O. perornata. The abundance of green algae and diatoms increased dramatically 2 days after application of a 0.3 micro M concentration of anthraquinone-59 to pond water within the limnocorrals. The half-life of anthraquinone-59 in pond water was determined to be 19 h, making it much less persistent than diuron. Anthraquinone-59 appears to be promising for use as a selective algicide in catfish aquaculture.

High-affinity monoclonal antibodies for detection of the microbial metabolite, 2-methylisoborneol.

The production of 2-methylisoborneol (MIB) by certain fungi and algae can contribute musty off-flavors to foods and water supplies if uncontrolled. The goal of this research was to develop a nonsensory simple method for the detection of MIB. Anti-MIB monoclonal antibodies were produced by immunizing mice with borneol-conjugated protein and selecting positive clones with an MIB-protein conjugate. An indirect competitive immunoassay developed using this antibody had a detection limit of 0.6 microg L(-)(1) and an I(50) value of 5 microg L(-)(1). Detection was relatively specific for MIB and showed 20% cross-reactivity with borneol or isoborneol and 4-5% cross-reactivity with camphor. No cross-reactivity to geosmin was observed.

Evaluation of Ferulic Acid for Controlling the Musty-Odor Cyanobacterium, Oscillatoria perornata, in Aquaculture Ponds

The cyanobacterium Oscillatoria perornata f. attenuata, a common inhabitant of channel catfish, Ictalurus punctatus, aquaculture ponds, produces the musty compound 2-methylisoborneol that causes fish to become off-flavor and unmarketable. Previous laboratory studies suggest that the natural compound trans-ferulic acid (4-hy-droxy-3-methoxycinnamic acid) is selectively toxic against O. perorna-ta. The present study was conducted to determine the effectiveness of the compound for controlling the growth of O. perornata under field conditions. The study was conducted in 12 0.1-ha earthern ponds in northwest Mississippi. Ponds contained 20,000 catfish/ha and were managed according to commercial culture practices. Half of the ponds were treated six times over a 2-month period with 5μM (0.97 mg/L) trans-ferulic acid, and the other half were untreated controls. Water samples obtained from all ponds preceding and following treatment were analyzed for phytoplankton community structure and concentrations of chlorophyll a, ferulate, and 2-methylisoborneol. Abundance of cyanobacteria, including O. perornata was not consistently affected by applications of ferulic acid. Only one of the six ferulic acid applications resulted in a decrease in abundance of O. perornata in treated ponds relative to untreated ponds (P <0.1). The ineffectiveness of trans-ferulic acid as a cyanobacterial algicide in catfish ponds appears to be caused by rapid dissipation of ferulic acid from pond waters. Use of trans-ferulic acid was neither an effective nor an economical approach to preventing musty off-flavor in pond-cultured channel catfish.

Investigations into the Origin of Chloroanisoles Causing Musty Off-Flavor of Raisins

The formation of chloroanisole in commercially processed and nonprocessed dried-on-the-vine (DOV) raisins under sterile, nonsterile, and low-moisture conditions was determined. The chloroanisoles of raisin samples were steam−solvent extracted using a modified Likens−Nickerson glass distillation apparatus and the concentrated extracts analyzed by gas−liquid chromatography and mass spectrometry. Processed raisins with low water activity (Aw) of 0.48 or 0.80 formed 2,4,6-trichloroanisole (TCA) when incubated during a 3−4 week period. TCA was formed by raisins partially sterilized with propylene oxide or completely sterilized with hydrogen peroxide. Nonprocessed DOV raisins incubated at an Aw of ≤0.80 also formed TCA. Although the amounts of TCA formed in raisins vary greatly from batch to batch, it is demonstrated that sterilized raisins formed TCA under low water activity nonconducive for microbial activity. Keywords: Biogenesis; chloroanisole; raisins

Comparative physiology of geosmin production by Streptomyces halstedii and Anabaena sp.

Geosmin and 2-methylisoborneol (MIB) are microbial metabolites that can cause earthy or musty off-flavors in aquatic food animals as well as seasonal taste and odor episodes in drinking water. This paper compares effects of selected environmental factors on biomass and geosmin production by the actinomycete Streptomyces halstedii and the cyanobacterium Anabaena sp., isolated from an aquaculture pond and from a source-water reservoir, respectively. For S. halstedii, optimal biomass production occurred at pH 6-7 and 30°C, and optimal geosmin synthesis occurred at pH 9 and 35°C. Low concentrations of both nitrate- and ammonium-nitrogen favored geosmin production, with higher concentrations stimulating biomass production. For Anabaena sp., optimal biomass production at 20 days occurred at 15°C and a light intensity of 17 μE/m2/s; optimal geosmin synthesis occurred at 20°C and 17 μE/m2/s. Chlorophyll a (chl a)/biomass varied inversely with light intensity. Maximal geosmin/biomass occurred at 20°C (17 μE/m2/s), and geosmin/chl a varied inversely with temperature. It was concluded that at 20°C, increasing light intensity favors lower chl a and greater geosmin synthesis by Anabaena sp.; at 17 μE/m2/s, increasing temperature stimulates chl a production (to 25°C) but represses geosmin synthesis (above 20°C).

Comparative physiology of geosmin production by Streptomyces halstedii and anabaena sp.

Geosmin and 2-methylisobomeol (MIB) are microbial metabolites that can cause earthy or musty off-flavors in aquatic food animals as well as seasonal taste and odor episodes in drinking water. This paper compares effects of selected environmental factors on biomass and geosmin production by the actinomycete Streptomyces halstedii and the cyanobacterium Anabaena sp., isolated from an aquaculture pond and from a source-water reservoir, respectively. For S. halstedii, optimal biomass production occurred at pH 6-7 and 30°C, and optimal geosmin synthesis occurred at pH 9 and 35°C. Low concentrations of both nitrate- and ammonium-nitrogen favored geosmin production, with higher concentrations stimulating biomass production. For Anabaena sp., optimal biomass production at 20 days occurred at 15°C and a light intensity of 17 µE/m2/s; optimal geosmin synthesis occurred at 20°C and 17 µE/m2/s. Chlorophyll a (chi a)/biomass varied inversely with light intensity. Maximal geosmin/biomass occurred at 20°C (17 µE/m2/s), and geosmin/chl a varied inversely with temperature. It was concluded that at 20°C, increasing fight intensity favors lower chi a and greater geosmin synthesis by Anabaena sp.; at 17 µE/m2/s, increasing temperature stimulates chi a production (to 25°C) but represses geosmin synthesis (above 20°C).

Geosmin-producing species of Streptomyces and Lyngbya from aquaculture ponds

Water and sediment samples collected monthly from six aquaculture ponds in east-central Alabama were analyzed for the presence of actinomycetes and cyanobacteria capable of producing geosmin and (or) 2-methylisoborneol, which cause earthy–musty off-flavors in fish. Six actinomycetous isolates were identified as geosmin producers, five of which were capable of producing 2-methylisoborneol. The one actinomycetous isolate producing geosmin but not 2-methylisoborneol was identified as Streptomyces halstedii. Only one of several cyanobacterial isolates was found to produce geosmin. This isolate was identified as Lyngbya cf. subtilis and was prevalent throughout the sampling period in a pond with a history of off-flavor problems. None of the cyanobacterial isolates produced 2-methylisoborneol in laboratory culture.Key words: geosmin, Streptomyces, Lyngbya, off-flavor, aquaculture.

Qualidades organolépticas de purês de batatinhas procedentes de culturas tratadas com inseticidas

Resultados significativos foram obtidos na análise do sabor de amostras de purês preparados com batatinhas procedentes de ensaios de aplicação de vários inseticidas no solo, na folhagem e em batatas-semente. Em 1959, dos inseticidas aplicados no solo (BHC, Heptaclor, Aldrin, Parathion e Lindane) apenas o BHC imprimiu sabor estranho bastante pronunciado semelhante a môfo, diferindo da testemunha ao nível de 1%.Para Heptaclor e Aldrin não foram verificadas alterações de sabor; Lindane e Parathion apresentaram leves odores estranhos, semelhantes a medicamento. Disyston, aplicado nas batatas-semente, e Metasystox, na folhagem, imprimiram ao purê sabor ardido e odor a remédio, mostrando-se inferiores, respectivamente, aos níveis de 5 e 1%. tanto à testemunha, tratada com carvão, como ao item sem qualquer tratamento. Parathion, aplicado na folhagem, comparado com as mesmas testemunhas, não apresentou diferenças significativas. Em 1960, dos inseticidas aplicados no solo, apenas Lindane, em dose normal e dobrada, diferiu da testemunha ao nível estatístico de 1%, apresentando sabor estranho, semelhante a môfo. Heptaclor, Aldrin e Toxafeno. em doses normal e dobrada, não diferiram da testemunha. classificando-se o sabor do primeiro como regular e dos dois últimos como bom.

Yield and Quality of Mushrooms from Beds Treated with Lindane

Studies were made of the tolerance of mushrooms to lindane applied in a water suspension to the bearing beds for the control of mushroom files, chiefly the sciarid fly, Bradysia fenestralia (Zett.), and the phorid fly, Megaselia agarici Lintner. Dosages of 0.5 pound per acre or less did not affect the yield, but 1 pound or more tended to depress yield. Neither dosage left appreciable residues on mushrooms harvested 5 day after application. Only slight occasional off-flavors were found in canned mushroom pieces and cream of mushroom soups made from mushrooms from beds treated with 0.25, 0.5, and 1 pound of lindane per acre 7 days or more before harvest. Samples from mushrooms harvested 3 days after treatment had musty off-flavors, which made both the pieces and the soup inferior in eating quality.