Location: Food Processing and Sensory Quality Research
2019 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
The project objectives fall under National Program 306, Product Quality and New Uses, Component 1 Foods. Progress on this project focuses on Problem Statements 1.A: Define, measure and preserve/enhance/reduce attributes that impact quality and marketability and 1.C: New and improved food processing and packaging technologies. Substantial progress was made under Objective 1A, Objective 1B, and Objective 2, notwithstanding the retirement of two of the three scientists on the project, at the beginning of FY 2019. Under Objective 1. A, a sensory panel was conducted to determine the human detection threshold for the two off-flavor compounds most commonly found in farm raised catfish. There was noted variation in the abilities of the panelists to detect these compounds. Using a forced choice method consisting of one off-flavor sample and two on-flavor samples, panelists were asked to select the sample different from the other two. In water, detection levels for the majority of panelists ranged from 1 to 10 parts per trillion (ng/kg) while in catfish detection levels ranged from 50 to 100 parts per trillion (ng/kg). The goal is to determine if human sensory evaluation is sufficient to identify off-flavor fish by sampling a limited number of fish from ponds prior to harvest, as is the common practice. Flavor training for other off-flavors has been delayed one year due to the retirements of two ARS scientists on the project. Under objective 1B, a rapid high throughput analytical method was developed for the detection of off-flavors found in farm raised catfish as well as other aquaculture products. The method uses one gram samples and can detect the two most common of-flavors at concentration levels of 50 parts per trillion (ng/kg), which is on par with human sensory detection levels. This method will allow screening for off-flavor in large numbers of samples, permitting the evaluation of flavor checkers and estimating the actual proportion of off-flavor fish reaching the consumer. A non-invasive headspace sampling instrument was evaluated for use in detecting the presence of off-flavor compounds in raw fillets. The system was found to be insufficiently sensitive and time consuming in its present configuration with detection limits at the low parts per billion level. Further efforts are underway to try and improve the sensitivity by 1 to 2 orders of magnitude. Working with a collaborator, an evaluation of a treatment process for the removal of off-flavor compounds from the water used in aquaculture facilities was found to reduce the concentration levels but not at a rate sufficient to preclude uptake by the fish. Purging experiments designed to remove off-flavor compounds from contaminated fish were run to determine optimum conditions for time and water usage were run in conjunction with a producer. Under Objective 2, precooked catfish products developed by ARS researchers in New Orleans, Louisiana, were evaluated in a marketing study conducted by a University collaborator. All five products were found to be acceptable and marketable, with the three breaded products scoring higher than the two marinated products. However, the marination process may serve as a masking agent for off-flavor fish.
Accomplishments
1. Development of a high throughput analytical method for detection of the major off-flavors in farm raised catfish. Off-flavor in farm raised catfish is a major problem with product quality, particularly in late summer and early fall. Although samples from ponds are checked prior to harvest, by professional flavor checkers, off-flavor fish still find their way to the market. Analytical methods are available to measure the concentration levels of off-flavor compounds but are expensive and time consuming, requiring specialized instrumentation and skilled technicians. An improved analytical pass/fail method that decreases sample preparation time by nearly an order of magnitude from the previous method, has been developed by ARS researchers in New Orleans, Louisiana, which is as sensitive as the human flavor checkers. Although this new analytical method will not replace the need for the flavor checkers, it will allow the analysis of large numbers of samples. We anticipate using this method to evaluate the flavor checkers and to determine the proportion of off-flavor fish reaching the market from each processing plant. This information will be supplied back to the individual plants and should have the direct benefit of reducing the proportion of off-flavor fish reaching the consumer.
2. Development of precooked catfish products. In order to increase the demand for U.S. farm raised catfish, five precooked products were developed to expand the consumer options beyond basic fresh and frozen fillets. Fifty samples of each product were produced at the Research Center’s pilot plant. The samples consisted of three Panko-breaded fish samples using different cuts from the fillet (strips, regular cuts, or delacata cuts) and two marinated products, a sirachi and a sesame ginger marinade. The breaded products were prepared by baking, while the marinated products were microwaved. Samples were evaluated by a test panel run by a university collaborator. Experimental auctions and sensory evaluation by ARS researchers in New Orleans, Louisiana, found the products to be acceptable based on appearance, color, serving size, smell, taste, and texture, with the baked products preferred, especially for the delacata fillet cut. The market analysis found a willingness to purchase for all five products.
Review Publications
Bechtel, P.J., Watson, M.A., Lea, J.M., Bett Garber, K.L., Bland, J.M. 2019. Properties of bone from catfish heads and frames. Journal of Food Science and Nutrition. 7:1396-1405. https://doi.org/10.1002/fsn3.974.
Davidson, J., Plautz, C., Grimm, C.C., Jorgensen, N.G., Podduturi, R., Raines, C., Snader, R., Good, C., Summerfelt, S. 2018. Evaluating the microbial effects of stocking freshwater snails (Physa gyrina) in water reuse systems culturing rainbow trout (Oncorhynchus mykiss). Journal of Applied Aquaculture. 31(2):97-120. https://doi.org/10.1080/10454438.2018.1541771.
