Recipient Organization
VIRGINIA POLYTECHNIC INSTITUTE
(N/A)
BLACKSBURG,VA 24061
Performing Department
(N/A)
Non Technical Summary
Off-flavor--the presence of musty or earthy odors or flavors caused by geosmin (GSM) and 2-methylisoborneol (MIB)--is an issue for farmed fish. Off-flavors can reduce product value and/or increase production costs by necessitating operational changes or technologies to prevent or correct off-flavor.Studies have been conducted to assess strategies to address off-flavors, but experiments are generally conducted opportunistically with fish known or assumed to be off-flavor. In some cases, the starting tissue levels of GSM and MIB are too low to be practically relevant; in other cases, extremely wide variation in starting levels complicates interpretation and application. Hypothesis testing and innovation to address off-flavors in farmed fish is constrained by the absence of predictable experimental models.We propose to refine a prototype model of off-flavor we developed in Rainbow Trout (RBT) and extend this model to Atlantic Salmon (ATL). Using these models, we will assess dietary and water treatment-based strategies to address off-flavor in flow-through and recirculation aquaculture system (RAS) environments.Objective 1: Further develop and validate flow-through models of off-flavor in RBTObjective 2: Develop and validate RAS model of off-flavor in ATLObjective 3: Using these models, optimize purging strategies and assess emerging technologies for mitigation/correction of off-flavor in RBT and ATLThe proposed work will address Program Area Priority "c. Improving the quality and efficiency of producing meat, milk, eggs, fish, and animal fiber" by informing off-flavor research broadly and demonstrating how researchers and farmers can address the problem of off-flavor more rigorously and effectively.
Animal Health Component
90%
Research Effort Categories
Basic
10%
Applied
90%
Developmental
(N/A)
Goals / Objectives
Off-flavor--the presence of musty or earthy odors or flavors caused by geosmin (GSM) and 2- methylisoborneol (MIB)--is an issue for farmed fish. Off-flavors can reduce product value and/or increase production costs by necessitating operational changes or technologies to prevent or correct off-flavor.Studies have been conducted to assess strategies to address off-flavors, but experiments are generally conducted opportunistically with fish known or assumed to be off-flavor. In some cases, the starting tissue levels of GSM and MIB are too low to be practically relevant; in other cases, extremely wide variation in starting levels complicates interpretation and application. Hypothesis testing and innovation to address off-flavors in farmed fish is constrained by the absence of predictable experimental models. We propose to refine a prototype model of off-flavor we developed in Rainbow Trout (RBT) and extend this model to Atlantic Salmon (ATL). Using these models, we will assess dietary and water treatment-based strategies to address off-flavor in flow-through and recirculation aquaculture system (RAS) environments.Objective 1: Further develop and validate flow-through models of off-flavor in RBTObjective 2: Develop and validate RAS model of off-flavor in ATLObjective 3: Using these models, optimize purging strategies and assess emerging technologiesfor mitigation/correction of off-flavor in RBT and ATL
Project Methods
In a series of experiments, Riverence, US Department of Agriculture / Agricultural Research Service / Fish Processing and Sensory Quality Research Unit(FPSQRU), and the Virginia Tech / Virginia Seafood Agricultural Research and Extension Center (VSAREC) will continue to refine our existing experimental model of off-flavor induction in RBT raised in flow-through raceways via dietary exposure to off-flavor inducing compounds. Refinements will address the influence of dietary lipid levels, fish size, and duration of exposure. Using the information developed for Rainbow Trout (RBT), we will extend this model to Atlantic Salmon (ATL) reared in the same flow-through conditions. We will also develop experimental models of off-flavor induction in ATL reared in recirculation aquaculture systems (RAS). These experiments will build on the prior work done in flow-through conditions and assess the implications of exposure to off-flavor inducing compounds via the diet and/or rearing water. Using the models of off-flavor induction in RBT and ATL raised in flow-through raceways or RAS, we will assess the effectiveness of promising dietary and water treatment-based strategies to prevent or correct off-flavor in salmonids. The following experiments will be conducted to addressObjectives 1-3:1.1: Factorial experiment to evaluate effect of dietary exposure to GSM and/or MIB in RBT, building on existing flow-through experimental model1.2: Side-by-side comparison of RBT and ATL of different sizes using existing flow-through experimental model1.3: Factorial experiment to evaluate effect of dietary exposure to GSM in RBT in the context of feeds with different lipid levels, building on existing flow-through experimental model1.4: Evaluate effect of dietary exposure to GSM and MIB in ATL using optimized flow-through experimental model developed for RBT.2.1: Evaluate effect of dietary exposure to GSM in ATL in RAS involving different levels of GSM and exposure periods.2.2: Factorial experiment to evaluate effect of optimized dietary exposure and/or water exposure to GSM in ATL in RAS3.1: Induce off-flavor according to optimized RAS model in ATL and evaluate depuration during purging and in association with water treatment-based technologies that may prevent/mitigate/correct off-flavor.3.2: Induce off-flavor according to optimized flow-through model in RBT and ATL and evaluate depuration during purging and in association with dietary technologies that may prevent/mitigate/correct off-flavor.Fish used in the proposed work will be sourced as eyed eggs from Riverence Brood LLC (Rochester, WA), a commercial salmonid genetics company with year-round availability of specific pathogen-free seedstock, including ATL and RBT. Eggs will be incubated, hatched, and reared according to typical trout and salmon rearing practices until they reach a suitable size for a given experiment.Experiments involving flow-through rearing systems will be conducted by Riverence at Riverence Holdings LLC R&D facilities (Buhl, ID). Experiments involving RAS will be conducted at VSAREC facilities (Hampton, VA). In all cases, treatments will be assigned to replicate compartments or tanks servingas experimental units (≥3 compartment or tanks/experimental units per treatment).Test diets will be prepared by Riverence. Commercially manufactured, extruded feeds suitable for trout or salmon and containing the desired amount of lipid will be purchased from a commercial supplier regularly used by Riverence (e.g., Rangen / Wilbur-Ellis, Optimal Aquafeed) and amended to contain the desired amounts of GSM/MIB according to a validated top-coating method used in our off-flavor research to-date.Fish will be fed assigned feeds at 1% bw/d, and rations will be adjusted weekly based on predicted weight gain, mortalities, and/or sampling. Feeding behavior will be recorded daily based on a 5-point ordinal scale, and any uneaten pellets will be removed from the compartments/tanks within 30 min of feeding and enumerated. Temperature and dissolved oxygen will be measured daily at the top and bottom of each raceway in trials involving flow-through systems or in ≥3 representative tanks in trials involving RAS systems. pH, alkalinity, and ammonia-nitrogen will be measured weekly in trials involving RAS systems or at the beginning and end of trials involving flow-through systems; nitrite-nitrogen and nitrate-nitrogen will also be measured weekly in trials involving RAS systems.Growth performance will be assessed at each sampling point in terms of weight gain (%), specific growth rate (SGR, % bw/d), feed conversion ratio (FCR), and feed intake (% bw/d). At each sampling point, 10 fish will be collected from each experimental unit and euthanized by single cranial percussion/disruption. Individual length/weight measurements will be taken and fish will be dissected to remove paired fillet samples from each fish for subsequent analysis. Fillet samples will vacuum sealed in plastic bags and stored frozen (-80°C) prior to analysis.To determine tissue GSM/MIB concentrations, fillet samples will be thawed, skinned, and minced prior to distillation and analysis by SPME-GCMS described for feed and water samples in our previous work/publications.Sensory tests will include paired preference tests and acceptability tests using both a 9-point hedonic scale and a binomial 'yes/no' scale. Collectively these tests will allow for both comparative and absolute measurements of fillet acceptability based on off-flavor levels. Rainbow Trout and Atlantic Salmon will be tested in separate studies. Fillets and treatment levels for each test will be selected based upon instrumentally obtained GSM and/or MIB concentration values.All growth performance data will be analyzed by one-way ANOVA to determine the significance of any differences between treatment groups. Raceway compartments/RAS tanks will be considered experimental units in all cases. Feeding behavior scores will be subjected to Chi-squared tests of equal proportions to determine the significance of differences in score frequencies among treatment groups. Linear mixed effects models and linear regression models will be used to explain relationships between effects of interest (GSM/MIB dose, exposure/induction/depuration times, dietary lipid, fish size, water geosmin) and GSM/MIB tissue concentrations. Repeated measures ANOVA will also be used to compare mean fillet GSM/MIB levels across repeated sampling events. In all cases, effects will be considered significant at critical values < 0.05. For consumer sensory data, Thurstonian 2-AC modeling will be used to analyze preference data; one-way and two-way ANOVA will be used to analyze mean liking scores from hedonic scales; and probit regression analysis will be used to model binomial acceptability responses.