Research Project: Improving the Product Value of Catfish

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 catfish industry by improving product quality and developing greater utilization of catfish byproducts. To achieve this overall goal we will pursue the following objectives: Objective 1: Characterization of off-flavors and color in catfish and, Objective 2: Enhance the utilization of byproducts from aquaculture product processing.

Approach
The approach objective 1 research will evaluate the incidence and diversity of off-flavors and fillet color in hybrid and channel catfish throughout the year across several locales. This information will be useful in devising new strategies to improve the quality of products entering the market place by reducing the incidence of off-flavor and color variation in catfish products. In addition, improved methods for determining the incidence of off-flavors prior to harvest would be developed. The approach for objective 2 higher valued products can be made from some catfish processing byproduct components. This research will identify and quantify the composition of the catfish processing byproduct streams and its seasonal variation. This information will be used to identify opportunities to add value to selected byproduct components.

Progress Report
This is the final report for the project 6054-43440-049-00D, which was terminated on May 18, 2020, being replaced with project 6054-43440-050-00D, titled “Improving Product Quality in Farm-Raised Catfish”. Progress was made on one objective, with two subobjectives, which falls under National Program 106, Aquaculture, Component 5, Product Quality and New Products. Under Objective 1, significant progress was made on the validation of the new method used to quantify the spatial fat content of catfish fillets and its variability. Sample numbers were increased by a factor of 100, while sample size was reduced by a factor of 8. Also under Objective 1, significant progress was made on the development of a method for the separation, identification, and quantification of eleven B-vitamins. Enzymatic extraction protocols were determined. The new method was further improved with enhanced equipment with the speed of analysis increasing by a factor of ten. Objective 2 milestones were not met because of reduced manpower, due to retirement of team member; and it was decided to postpone the objective. This project is related to NP 306 Project No: 6054-44000-078-00D, titled “Postharvest Sensory, Processing and Packaging of Catfish” and significant progress was made on new ready-to-cook catfish products that were developed and analyzed by ARS scientists at New Orleans, Louisiana, in collaboration with researchers at the University of Arkansas, Pine Bluff and Texas State University. Three types of Panko-breaded samples (fillets and strips) and two marinated products (ginger and sriracha) that had been produced in New Orleans, Louisiana were analyzed for nutritional content. 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. Substantial results were realized over the 5 years of the project. Under Objective 1, U.S. catfish processing plant flavor checkers in Louisiana, Mississippi, and Alabama were visited and surveyed to examine variations in their methods to assess off-flavor as a means to control the harvesting of off-flavor ponds. A workshop was presented in 2015 to discuss the survey results and to examine off-flavor perception thresholds of flavor checkers, with a large percentage of the commercial processors represented. Research based on these interactions, using trained sensory panels and instrumental methods, determined how the different catfish off-flavor detection methods used by the different processors affect detection of off-flavors in catfish fillets. New methods were developed to identify and quantify the xanthophylls responsible for the yellow off-color of catfish fillets. The variability of yellow off-color of catfish fillets between species, gender, geographical location, and harvest seasons was determined. A difference in yellow color was seen between hybrid and channel species, with channel having a larger amount of yellow color, and between male and female gender. The spatial variability of off-flavor and yellow color in relation to the fat content was studied and results indicated that although certain areas tended to have a higher concentration of off-flavor and off-color compounds than average values, a specific optimal area could not be identified. Therefore, the recommendation for flavor checkers at processing plants is to sample additional areas if no off-flavor is detected. The technology used for the quantification of yellow colored xanthophylls was transferred to the ARS salmon research at the National Cold Water Marine Aquaculture Center, Franklin, Maine, for use in evaluating salmon fillet color. The measurement of spatial fat content of catfish fillets, in relation to off-flavor and off-color content, was examined by near infrared (NIR) spectroscopy, pressurized solvent extraction, and time-domain nuclear magnetic resonance (TD-NMR) methods, with increases in sample throughput and decreases in sample size found for the NMR method. Methods for determining textural differences between catfish fillets samples, according to species, gender, geographical location, harvest season, and processing methods, for both raw and cooked samples were developed by instrumental methods and a trained sensory panel. Differences were determined between channel and hybrid catfish, and between male and female gender, but the largest difference was correlated to the processing method of addition of polyphosphate. However, this correlation was only found for hybrid catfish. Because of the greater ease of the instrumental texture analysis over the trained sensory panel, the correlation between the two was determined, with predictive equations developed between the two methods. Results also indicated that the instrumental texture evaluation was more successful for identifying differences between sample types. With collaborators from the University of Arkansas, Pine Bluff and Texas State University, new convenient, read-to-cook catfish products were developed. They were analyzed for nutritional content and by a consumer panel to evaluated their appearance, taste, and texture, as well as undergo an experimental auction to determine the price they would be willing to pay for each product. The results showed the baked, breaded Delacata fillet was the most preferred, but varied with socio-economic factors. Under Objective 2, the major byproducts from farmed catfish including heads, inner organs, frames, and skin were collected along with fillet and the yield of the individual byproducts as a percent of fish weight was determined. The major off-flavor compounds in the individual byproducts and fillets was determined. Physical and enzymatic methods were evaluated for their effect on the production of powdered bone products from the catfish frames and heads. The channel and hybrid catfish bone samples were characterized for color, proximate composition, composition of major elements and amino acid composition. Collaboration with ARS, New Orleans, Louisiana, scientist studied the adhesive properties of catfish skin protein and gelatin. Scientists at Mississippi State University, in collaboration with a scientist from the ARS in New Orleans, Louisiana, extracted proteins from catfish byproducts for potential utilization in surimi (fish protein gel)-like gel products. Results indicated that yield of protein extracted from catfish frames was higher than that from the heads. Texture analysis showed gel made from heads was similar to that made from frames. The composition of extracted protein was similar to that from the fillet, indicating integrity of muscle proteins during the extraction process. Results indicated it was possible to extract proteins from catfish byproducts that could be used for making surimi. The use of different proteolytic enzymes to digest protein from catfish heads and frames for potential use as food, feed, and industrial ingredients was also evaluated. Results indicated that enzyme activity varied significantly among different enzymes and ficin was the most efficient in hydrolyzing the ground catfish by-product. Louisiana State University scientist, in collaboration with scientist from ARS in New Orleans, Louisiana, evaluated the effects of a coating material containing hydrolyzed catfish skin on improving the quality of blast frozen shrimp. After 60 days frozen storage, shrimp coated with the hydrolyzed skin treatment had slightly lower lipid oxidation. Additionally, the potential to increase shelf life of catfish fillets with a coating of chitosan was evaluated. Chitosan is produced from the chitin of shrimp, crawfish, and crab shell, and has good antioxidant and antimicrobial properties. Catfish fillets treated with chitosan had the lowest lipid oxidation and inhibited yeast and mold counts more than the other treatments during the 20 days in refrigerated conditions. Catfish fillets that were vacuum tumbled with chitosan solution had an eight-day shelf life increase and sprayed or dipped fillets had a four-day increase compared to untreated fillets. Texture was also impacted, with vacuum tumbled catfish fillets having a more rapid decrease in hardness than the other treatments. The study suggests that vacuum tumbling with chitosan solution can increase the shelf life of catfish fillets under refrigerated storage.

Accomplishments
1. Determined how the nutritional quality of catfish fillets differ between species and pond type. To ensure there are sufficient vitamins to meet the requirements for normal growth, health, and reproduction, catfish feed manufacturers add vitamin supplements, including most of the B-vitamins. Although, most vitamins may be acquired from algae and other natural sources. To determine the impact of species and pond management practices on catfish fillet vitamins, ARS scientists in New Orleans, Louisiana, have developed an improved method to quickly analyze the B-vitamins. The instrumental method is able to separate, identify, and quantify all B-vitamins (B1, thiamine; B2, riboflavin; B3, nicotinic acid; B5, pantothenic acid; B6, pyridoxine; B7, biotin; B9, folic acid; and B12, cyanocobalamin) 10-times faster than previous methods. This will allow the large number of catfish sample analyses needed in current research on parameters affecting catfish quality.

2. Improved catfish fat analysis. The major catfish quality issues, such as off-flavors and yellow-colored fillets, are related to the fat in the fillet. Present methods of fat analysis require a relatively large sample size and almost a week to analyze a small number of samples. The sample size limits the ability to determine the specific location or variation of fat in a fillet. To overcome this problem, ARS scientists in New Orleans, Louisiana, developed and validated a new method of fat analysis that uses an instrument similar to a medical MRI. Sample size is reduced in the new method about 5-times, but more importantly, the time for analysis is reduced about 100-fold and could be decreased almost 400-fold, if automated. This will greatly enhance the number of catfish samples that can be analyzed in current research on parameters affecting catfish quality.

3. New, convenient, ready-to-cook catfish products. ARS scientists in New Orleans, Louisiana, with University of Arkansas and Texas State University collaborators recently developed new catfish products to enhance the marketability of catfish fillets. As an addition to the traditional deep-fried catfish, five, more healthy and convenient products were developed. Three products were a breaded fillet, similar to the fried catfish, but designed to be crunchy when baked. Three sizes were made: strips, standard fillets, and Delacata fillets. Also, two marinated products (ginger and sriracha), using Delacata fillets, were developed. All five were analyzed for nutritional composition and a consumer sensory panel evaluated their appearance, taste, and texture, as well as undergo an experimental auction to determine the price they would be willing to pay for each product. The results showed the baked, breaded Delacata fillet was the most preferred, but varied with socio-economic factors. Consumer preferences of certain visual and taste attributes in addition to their effect on an acceptable price will give guidance to those launching these and similar products in the market.