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Aquaculture, VA 2008

Flick Jr, George
Virginia Polytechnic Institute and State University
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The overall objective of this research project is to improve the economic feasibility of recirculating aquaculture systems. Specific objectives involve identifying value-added products from the fish produced in recirculating aquaculture systems to maximize economic return to the aquaculture venture and finding a use for the effluent discharged from a production facility.

Two specific objectives are as follows:

  1. Determine the effects of the following: a) natural oxidation inhibitors on extending the shelf-life and quality of frozen rainbow trout and Atlantic salmon mince; and b) varying high pressure processing times and temperatures on shelf-life, quality, and lipoxygenase activity on minced rainbow trout and minced Atlantic salmon.
  2. Investigate ways to utilize effluent, generated as a by-product of yellow perch production at the Southwest Virginia AqREC in Saltville, Virginia, in conjunction with aquaponics, to produce food safe for human consumption.
Expected outputs include activities such as conducting experiments, analyzing data and publishing results in scientific journals and trade magazines.
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NON-TECHNICAL SUMMARY: To make salmon and trout production in recirculating aquaculture systems profitable in the United States and competitive in world markets, the conversion of current waste products into higher valued products is essential. The cost of salmon production in South America will be substantially less than in the United States due to lack of environmental requirements and the availability of lower cost labor. Additionally, the methods of domestic salmon production available do not include net pens or flow-through systems. Net pens have not been well received by government or communities due to visual degradation of the ocean, escapees, parasites, and pollution emanating from feces and waste feed. Flow-through systems are not available since there are insufficient sources of water available for this type of fish culture. Furthermore, firms currently using flow-through systems are making capital investments in other countries in order to increase their production volume. In a typical filleting operation, filet yields range from 35 to 45 percent. Once the filet has been produced, a substantial amount of usable meat remains on the frames and in the belly flaps. One method of meat recovery is to obtain a minced product through the use of a meat bone separator. Mince meat can be of high quality if processed properly and stored under appropriate refrigerated conditions. Mince fish flesh has been incorporated into many types of products such as surimi, nuggets, fish sticks, portions, and pate's. There has been little information published on the production of mince meat obtained from salmon processing operations. The research described in this proposal will provide sufficient information on the processing and storage of the salmon mince for use in further processed products. The use of natural oxidation inhibitors will permit the product to have greater appeal since it could be labeled as natural or carry a statement that no artificial antioxidants were added. The Southwest Virginia AqREC in Saltville, Virginia produces yellow perch, Perca flavescens, in recirculating aquaculture systems (RAS). An issue with production in RAS is the disposal of fish waste, or effluent. A single tank at the AqREC produces nearly 300 gallons of effluent each day which must be disposed of by some means; currently it is going to the municipal sanitary sewer system. Effluent at the AqREC at full production, with only a 5% daily removal of water with the waste can reach 2,000 gallons per day. This effluent is nutrient rich, suggesting a possible use as a fertilizer for plants. However, there are challenges with its use. Yellow perch produced at the AqREC are grown in water kept at low salinity to improve fish health. Even low salt levels can adversely effect plant growth. Additionally, the effluent contains microorganisms that could present a food safety issue, so without proper consideration and treatment, its use as a nutrient source for plant production could be problematic.

APPROACH: Fresh rainbow (Oncorhynchus mykiss) trout and Atlantic salmon (Salmo salar) will be minced using a mechanical meat/bone separator. Four natural oxidation inhibitor blends will be prepared and randomly assigned to one of five groups (control, and four products). All samples will be stored at -29C. At 0, 6, 12, 18, and 24 weeks, samples will be evaluated for percent drip loss, pH, 2-Thiobarbituric Acid Reactive Substances, and sensory evaluation. All measurements will be made in triplicate. The extent of oxidation among samples will be assessed at each testing period by a trained sensory panel. Paired comparison tests will be used to assure that panelists can differentiate between higher levels of oxidation. To determine the effect of high pressure treatments on shelf life of trout and salmon mince, both will be subjected to varying high pressure treatments (275 and 310 MPa) for 2 and 5 min at 5C and ambient temperature. The minces will be stored at 0, 4, and -20C. The refrigerated product ( 0 and 4C storage) will be sampled for quality after 4, 8, and 12 days of storage using a sensory panel to compare a refrigerated sample to a sample that has been frozen during the same period. The frozen samples will also be evaluated after 2, 4, and 6 months of storage. Waste water (effluent) will be collected from the aquaculture center and diverted to a collection tank equipped with an agitation system to prevent the settling of the solids for increased nutrient content of effluent. Municipal water will be added to the effluent as needed to prevent over-fertilization of plants, if phosphate levels exceed 6.0 mg/L. An ultraviolet (UV) filter (Emperor Aquatics, Pottstown, PA, USA) will be installed in the effluent line between the culture room and the greenhouse, and its effectiveness in destroying any bacteria present will be evaluated. Waste water will be analyzed for nutrient content and pathogens. Microbiological tests to be performed include total aerobic plate count, fecal coliform, a total vibrio, and tests for the presence or absence of Listeria monocytogenes and Salmonella. Two identical ebb and flood irrigation systems have been installed. One system receives municipal water; the other fish effluent. A timer activates submerged pumps in both the effluent and municipal water reservoirs, filling the ebb and flood trays in both systems simultaneously. The pumps run for 20 minutes. When the timer turns off the pumps, water from the trays drains back into the reservoir tanks. Bibb lettuce, Lactuca sativa, will be sown in rockwool cubes in the ebb and flood trays. Municipal water will be augmented using a commercially available liquid fertilizer to achieve a target phosphate level of 4.0 mg/L. Phosphate levels will be used as the limiting factor as 4.0 mg/L of phosphate has been found to be relatively stable within the effluent. From each system, five randomly selected heads of lettuce will be harvested at approximately six weeks. Results of microbiological tests will be reviewed to determine if harmful pathogens are present and to determine if the UV filter successfully destroyed microbes present in the effluent, or if other adjustments are needed.

Funding Source
Nat'l. Inst. of Food and Agriculture
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Natural Toxins
Viruses and Prions
Bacterial Pathogens
Chemical Contaminants