Location: Food Processing and Sensory Quality Research
2017 Annual Report
Objectives
The overall goal of this research project is to stimulate consumer demand for catfish products and increase the profitability of the U.S. catfish industry through improved product quality.
Objective 1: Generate new processed catfish definitions for uniform sensory quality and grading standards and enable economical, accurate and real-time commercial methods to monitor sensory attributes of processed catfish.
Sub-Objective 1.A: Develop a set of guidelines for the evaluation of off-flavors in farm raised catfish and provide them to the industry through a set of workshops.
Sub-Objective 1.B: Develop instrumental methods for the economic rapid determination of color and off-flavors in farm raised catfish for use by the industry.
Objective 2: Enable new commercial value added postharvest processes and innovative packaging technologies that maintain/improve the sensory qualities and shelf life of processed catfish.
Approach
Consumption of U.S. grown catfish has dwindled from its maximum in 2003 to almost half that in 2014. There are multiple reasons for decreased catfish consumption including reduced production, imports and variability in product quality. The most pressing quality problem, as identified by the catfish industry, is the incidence and intensity of off flavors. Consumer demands in the dinner protein market are high quality products, free of defects.
This project will develop a set of guidelines for the evaluation of off-flavors in farm raised catfish and provide them to the industry through a set of workshops. A survey of existing flavor checkers at catfish processing plants will be conducted to determine the best practices currently used in the industry. Individual processors will be surveyed with regard to their flavor checking practices. Different practices will be subjected to laboratory testing to determine the most effective protocols. Once the best practices have been determined, a series of workshops will be provided to the industry to standardize the analysis of off-flavors.
Instrumental methods will be developed for an economical and rapid determination of color and off-flavors in farm raised catfish for use by the industry. In line instrumentation for color evaluation is widely used for quality assessment in a variety of agricultural products and this technology will be adapted for use by the catfish aquaculture industry. Initial experiments will focus on documenting the degree of color variation and identifying strategies to minimize variation. Currently the analysis of off-flavors for individual fillet does not appear to be economically feasible even if it were technological possible. However, a detailed evaluation of test samples may suggest procedures that could effectively assist existing flavor checker protocols to reduce variation in off-flavor. The adoption of improved analtyical methods by the industry will depend upon need, cost and effectivness. Efforts will be made to demonstrate the benefits of improved methods.
This project will develop new and improved processes, products and packaging systems that will enrich the sensory qualities and improve the shelf life of processed catfish. Marination, the process of soaking foods in seasoned, often acidic, liquids before cooking and may offer an opportunity for modulating the off-flavors found in some farm raised catfish fillets. In addition, frozen precooked catfish products will be developed that are designed to be heated in a microwave or conventional oven before serving. Studies will be conducted on precooking methods, packaging, and product quiaty duign storage. Efforts will be made to deveolop new products and extend product lines of frozen catfish products using processing equipment commonly found in the industry.
Progress Report
This project is related to NP 106 Project No: 6054-44000-077-00D, titled “Postharvest Sensory, Processing and Packaging of Catfish” and annual reports share some progress and accomplishments.
Progress has been made on Objective 1, Sub-Objective 1.A. The flavor checkers from catfish processing plant in Mississippi, Alabama, and Louisiana were visited to learn about the flavor checking process and differences in the procedures. The objective of this project was to evaluate the flavor of catfish prepared by methods commonly used by the “flavor checker”. Catfish fillet samples were collected from the USDA/ARS Warm Water Aquaculture Center in Stoneville, Mississippi. These samples had detectable levels of the off-flavor compounds 2-methylisoborenol and geosmin and were used to determine how different cooking and evaluation procedures currently used by different flavor checkers affect detection of off-flavors in catfish fillets. A sensory panel was trained to detect different levels of off-flavors in catfish fillet. Descriptive sensory evaluation was performed on off-flavor and on-flavor catfish prepared as follows: microwaving in ceramic dishes, brown lunch bags, paperboard serving boats, foam trays, plastic food bags. In addition, descriptive sensory evaluation was performed on off-flavor and on-flavor catfish prepared by deep fat frying. Data has been collected and is currently being statistically analyzed. The cooking methods may have had a slight effect on off-flavor perception, and may have contributed flavor to the cooked catfish. Further analysis will determine if differences were significant and interferes with off-flavor perception. This information will be presented at the Fall 2017 workshop for catfish processors.
Research studies on the distribution of off-flavor compounds in fish tissues focused on refining the methodology. Previous research has shown variations in concentration when measured longitudinally from head and tail as well as from the top of the fillet to the bottom. In addition off-flavors were shown to be found in higher concentrations in fatty parts of the fish. However, in some previous experiments it was determined that fat was carried over during the microwave desorption step in the method. In the present study fillet tissue was removed from four selected sites and samples were prepared by microwave desorption and analyzed. Concentrations of the off-flavor compounds, 2-methylisoborenol and geosmin, were detected in all fish and varied significantly between sites within a single fillet. It was determined that inconsistency stemmed from the variation in fat within each sample. By selectively choosing fatty tissue concentration of off-flavor compounds were two to three times higher relative to leaner portions of the fillet. A manuscript detailing these results is in preparation.
Experiments were conducted to evaluate the texture properties of catfish fillets. Fillets from catfish similar in age, diets and growing conditions were obtained from the USDA/ARS Warm Water Aquaculture center in Stoneville, Mississippi. Differences in color and texture were determined between male and female gender. In addition, both fresh and individually quick frozen catfish fillets from a commercial processor were evaluated. Texture analysis of cooked fillets using both a texture analyzer and a trained sensory panel is under way. In addition color, fat, protein, ash and moisture content of fillets are being analyzed and the distribution within fillets. Computer programs were written to calculate texture attributes and convert data to graphical form for improved data analysis.
Progress has been made on Objective 1, Sub-objective 1.B. Methods for determining yellow off-color differences between catfish fillet samples were needed in order to evaluate variation resulting from differences in species, gender, geographical location, and harvest season. Using a color meter the yellow content of catfish fillets was analyzed that were obtained from processors in Mississippi and Alabama, for both hybrid and channel species, male and female genders, and at winter and summer harvest dates. A difference in yellow color was seen and may have implications on the management of the feeding regimen. Software and instrumental image analysis methods have been explored to analyze color variations of catfish fillet. Incidence and seasonality of fillet off-color has been measured.
Progress has been made on Objective 2. Frozen storage is widely practiced by the food industry and is one of the major ways to maintain product quality for an extended period of time; however, product quality slowly deteriorates with time during frozen storage. A study was completed to examine changes in quality of precooked catfish fillets during frozen storage for up to 10 months. The effect of two packaging materials on storage stability was also evaluated. Catfish samples were purchased from a commercial catfish processor, precooked and then packaged in poly-nylon vacuum pouches or sandwich bags. Samples were stored in a freezer for 0, 1, 6, 10 month(s) and analyzed. Fillet pieces were generally stable in terms of fat oxidation for up to 10 months of frozen storage. Texture profile analysis revealed no significant differences between storage times or packaging treatments. This study will be used by the catfish industry to develop precooked safe frozen catfish products for consumers.
A study has been initiated to evaluate the following marination treatments on the sensory perception of off flavor in catfish fillets and the chemical determination of the off-flavor compounds 2-methylisoborenol and geosmin. Catfish fillets containing known concentrations of off-flavor compounds were marinated overnight with food grade ingredients and examined immediately after cooking by a sensory panel trained to identify off-flavors and by chemical analysis gas chromatograh/maso spectrum (GC/MS) to detect the presence of the off-flavor compounds. The data has been collected and is being analyzed.
Accomplishments
1. Quality of catfish fillets after frozen storage. Frozen storage is one of the major ways to maintain product quality for an extended period of time; however, product quality slowly deteriorates with time during frozen storage. ARS scientists in New Orleans, Louisiana, developed a precooked catfish product; however, product quality during frozen storage needed to be determined. A study was completed to examine changes in quality of precooked catfish fillets during frozen storage using two packaging materials. Catfish fillets were purchased from a commercial catfish processor and fillet strips were precooked and stored in a freezer for 0, 1, 6, 10 months. Results indicated the quality of catfish fillet strips stored frozen for up to 10 months underwent little change in terms of fat oxidation and fillet texture measurements. This study will be used by the catfish industry to develop high quality new precooked safe frozen catfish products for consumers.
Review Publications
Li, C.H., Bland, J.M., Bechtel, P.J. 2017. Effect of precooking and polyphosphate treatment on the quality of microwave cooked catfish fillets. Journal of Food Science and Nutrition. doi:10.1002/fsn3.465.
Edwards, J.V., Fontenot, K.R., Haldane, D., Prevost, N.T., Condon, B.D., Grimm, C.C. 2016. Human neutrophil elastase peptide sensors conjugated to cellulosic and nanocellulosic materials: part I, synthesis and characterization of fluorescent analogs. Cellulose. 23(2):1283-1295.
Alfaro, L., Zhang, J., Chouljenko, A., Scott, R., Xu, Z., Bankston, D., Bechtel, P.J., Sathivel, S. 2016. Development and characterization of emulsions containing purple rice bran and brown rice oils. Journal of Food Processing and Preservation Research. doi:10.1111/jfpp.13149.
Bechtel, P.J., Bland, J.M., Bett Garber, K.L., Grimm, C.C., Brashear, S.S., Lloyd, S.W., Watson, M.A., Lea, J.M. 2017. Chemical and nutritional properties of channel and hybrid catfish by-products. Food Science and Nutrition. doi:10.1002/fsn3.483.
Li, C.H., Bland, J.M., Bechtel, P.J. 2017. Effect of precooking and polyphosphate treatment on the quality of catfish fillets cooked in pouch in boiling water. International Journal of Food Science and Technology. doi:10.1111/ijfs.13459.
Alfaro, L., Hayes, D., Boeneke, C., Xu, Z., Bankston, D., Bechtel, P.J., Sathivel, S. 2015. Physical properties of a frozen yogurt fortified with a nano-emulsion containing purple rice bran oil. LWT - Food Science and Technology. 62:1184-119.
Solval, K., Bannkston, D., Bechtel, P.J., Sathivel, S. 2016. Physical properties of microencapsulated gamma-3 salmon oil with egg white powder. Journal of Food Science. 81:E600-E609.
