Location: Food Processing and Sensory Quality Research
2020 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 l.A: Define, measure and preserve/enhance/reduce attributes that impact quality and marketability and l.C: New and improved food processing and packaging technologies.
This is the final report for the project 6054-44000-078-00D which terminated in July 2020. All planned field experiments were completed by ARS researchers at New Orleans, Louisiana, prior to termination with the exception of the validation of the pass/fail instrumental method by industrial flavor checkers.
Objective 1A, Many of the needs of catfish flavor checkers were identified in a workshop lead by ARS researchers at New Orleans, Louisiana. One project was to standardize the nomenclature for catfish flavor attributes. In another, off-flavor catfish fillets were collected from the USDA/ARS Warm Water Aquaculture Center in Stoneville, Mississippi. These samples were used by ARS researchers at New Orleans, Louisiana, to determine how different cooking and evaluation procedures currently used by different flavor checkers. A sensory panel was trained to detect different levels of off-flavors in catfish fillet and was used to evaluate the different cooking procedures and evaluation procedures. Results indicated off-flavored fish that were breaded and oil fried were significantly less intense in dirt/earthy/musty flavor than the fish microwaved. However, using a microwave was a much simpler method. In order to provide this information to the industry a technical bulletin titled “Effects of Cooking Methods on Catfish Flavor Using a Trained Sensory Panel” was provided to all catfish processing plants to help them evaluate the flavor checking procedures used by their plant. Follow-up discussions with flavor checkers and others at each processing plants are ongoing to clarify the study as needed and listen to their ideas for future studies. The sensory panel was also employed 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 ng/kg while in catfish detection levels ranged from 50 to 100 ng/kg.
Objective 1B, variation of the concentration of the off-flavor compounds geosmin and 2-methylisoborneol in different parts of the fillet was investigated by ARS researchers at New Orleans, Louisiana. Previous work has shown that there is little difference in concentrations in the fillet when cut into vertical portions, but there was a need to evaluate fillets cut into horizontal portions and correlate concentrations with the fat content of the potions. Fillets were tagged, frozen and then each fillet was cut vertically and horizontally into four portions and analyzed for the off-flavor compounds and fat content. Results indicated no trend was observed to support the hypothesis that one portion of the fillet had higher concentrations of off-flavor compounds than another. Machine vision methods for sorting catfish products by color were evaluated. However, it was apparent that rather than develop a system for sorting catfish fillets it would be advisable to adapt a currently available machine vision system used for color evaluation of other food products.
A non-invasive headspace sampling instrument was evaluated by ARS researchers at New Orleans, Louisiana, for use in detecting off-flavor compounds in raw fillets. But unfortunately, the system was found to be insufficiently sensitive and time consuming. Working with a collaborator, an evaluation by ARS researchers at New Orleans, Louisiana, 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 in conjunction with a producer. 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 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. ARS researchers at New Orleans, Louisiana,working with a industrial collaborators, 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. Collaborators designed purging experiments to remove off-flavor compounds from contaminated fish, which were then analyzed. Optimum conditions of time and water usage were determined no achieve a quality product.
Objective 2, a set of experiments were initiated by ARS researchers at New Orleans, Louisiana, to evaluate the texture properties of both channel and hybrid catfish. Fillets from both hybrid and channel catfish similar in age, diets, and growing conditions were obtained and after freezing were analyzed. Differences in color and texture were determined between channel and hybrid catfish, and between male and female gender. In addition, both fresh and individually quick frozen channel and hybrid catfish fillets were obtained from a commercial processor. Fresh fillets were analyzed immediately and the individual quick frozen fillets remained frozen until analyzed. Fillet texture was analyzed using both a texture analyzer and a trained sensory panel. In addition fat, protein, ash and moisture content of all fillets were analyzed, and the color distribution within fillets and between channel and hybrid catfish fillets are analyzed. Computer programs were written to calculate texture attributes and convert data. There are few U.S. catfish products designed to be microwave cooked or reheated. A study to examine the properties of raw frozen catfish fillets microwave cooked or precooked fillets reheated by microwave cooking was conducted, with a second goal to evaluate the effect of adding phosphate on properties of microwave cooked or precooked frozen catfish fillets. Both fresh and individually quick frozen fillets containing phosphate were evaluated. After microwave cooking, sample analysis included weight loss, moisture content, color, pH, mechanical texture (hardness) and fat oxidation. Pilot microwave cooking studies determined that cooking at 870 W for 2.5 minutes was best for a uniform cooking condition. Both cooked and precooked samples showed less moisture loss and lower levels of fat oxidation when they contained phosphate. Color analysis showed an increase in yellow color after cooking for fillets without phosphate. This study will be used to develop precooked catfish products that can be reheated in a vacuum sealed bag placed in boiling water. The quality and storage stability of the frozen precooked product was evaluated during frozen storage for up to 10 months. Other catfish products developed included battered products designed to be baked rather than fried or par-fried. Also, marinated products were made using fillets that had more of the skin-fat layer removed. Another approach used in this objective was to develop a masking agent that would reduce detection of the undesirable earthy/musty off-flavor compounds. The precooked products were analyzed for proximate, mineral, amino acid, and fatty acid composition and a marketing study was conducted by a collaborator. All five products were found to be acceptable and marketable, with the three breaded products scoring higher than the two marinated products. A consumer sensory panel evaluated the appearance, taste, and texture of the products and a willingness-to-pay was determined using an experimental auction, showing the Panko-breaded Delacata fillet was the most preferred, but varied with socioeconomic factors. However, the marination process may serve as a masking agent for off-flavor fish.
Accomplishments
Review Publications
Chen, M., Bergman, C.J., Grimm, C.C., McClung, A.M. 2019. A rice mutant with a giant embryo has increased levels of lipophilic antioxidants- E vitamers and gamma-oryzanol fraction. Cereal Chemistry. https://doi.org/10.1002/cche.10242.
Mattison, C.P., Vant-Hall, B., Bren-Mattison, Y., Grimm, C.C. 2019. A cashew specific monoclonal antibody recognizing the small subunit of Ana o 3. Toxicology Reports. 6:736-744. https://doi.org/10.1016/j.toxrep.2019.06.018.
