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 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 project is related to NP 306 Project No: 6054-44000-078-00D, titled “Postharvest Sensory, Processing and Packaging of Catfish” and annual reports share some progress and accomplishments.
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 in fillets 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 between hybrid and channel species with channel having a larger amount of yellow color. Other comparisons are still being evaluated. This may have implications on the management of the feeding regimen of channel species to control the amount of yellow content. 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.
The yellow off-color problem associated with some catfish fillets is caused by colored fat-soluble pigments that are deposited in the fish fat. Previous studies improved the method used to identify the colored fat-soluble pigments responsible for the yellow color found in some catfish fillets. In this study catfish were collected, slaughtered, fillets tagged, frozen and then each fillet was cut vertically and horizontally into 4 portions. The color characteristics of each fillet portion has been collected and the fat content of the fillet portions has been determined. Ongoing data analysis includes correlations of the color and fat content with location within the fillet.
New methodologies were examined to evaluate catfish quality attributes and included evaluation of near infrared spectroscopy as a method for obtaining rapid proximate analysis (protein, fat, and moisture) of catfish fillets. Also, a vacuum-assisted solid phase microextraction methodology was evaluated for quantification of off-flavors of catfish fillets. A fat and moisture analyzer was evaluated for rapid quantification of moisture and fat in catfish samples. The technology for quantification of the yellow colored xanthophylls in catfish fillets was transferred to the ARS salmon research group at the National Cold Water Marine Aquaculture Center in Franklin, Maine, for use in evaluating salmon fillet color.
Progress has been made on Objective 2. The major byproducts from farmed male and female catfish including heads, inner organs, frames and skin were collected along with fillet and the yield of the individual byproducts is being analyzed. Other studies have been completed to add value to catfish bone from frames as a potential ingredient in foods and feeds and for industrial applications. Bone from catfish frames (backbone) was cleaned using proteolytic enzymes or high pressure water cleaning. Characterization of the resultant dried and milled bone samples included evaluation of color, proximate composition, composition of major elements and amino acid composition have been completed. Catfish heads are another underutilized byproduct and studies are under way to make bone and protein hydrolysates from catfish heads. Catfish skin is a major byproduct produced during the processing of boneless skinless fillets and ARS scientist from the Southern Regional Research Center in New Orleans, Louisiana, are conducting a study on the adhesive properties of catfish skin protein and gelatin extracted from catfish skin.
ARS and Louisiana State University scientists collaborated to evaluate the potential to increase shelf life of catfish fillets with a coating of chitosan. Chitosan is a biopolymer produced from chitin and is a major constituent of shrimp, crawfish and crab shell. Chitosan can be used as a food preservative due to its antimicrobial and antioxidant properties. The goal of this study was to evaluate the effect of coatings containing chitosan on the storage quality of refrigerated catfish fillets. Chitosan solutions were applied to the fillets using three techniques: (1) spraying, (2) dipping, and (3) vacuum tumbling. After application of chitosan, the fresh catfish fillets were kept under refrigerated storage for 16 days. 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 increases 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.
Channel catfish farming is the most important warm water aquaculture species in the United States. The by-product from catfish processing includes heads and frames, which can be excellent sources of high quality protein. ARS scientist worked with Mississippi State University Scientists to evaluate the use of different proteolytic enzymes to digest protein from catfish heads and frames for potential used as food, feed and industrial ingredients. Catfish heads and frames obtained from commercial processors were ground and proteolytic enzymes including papain, ficin, bromelain, neutrase, alcalase, and thermolysin were used for hydrolysis of byproduct protein. Hydrolysis was initiated for 10, 20, 40, 60 and 120 min and the hydrolysis kinetics for each enzyme analyzed. Results indicated that enzyme activity varied significantly among different enzymes and ficin was the most efficient in hydrolyzing the ground catfish by-product. This study provides important engineering information for choosing enzymes and processing conditions for optimizing efficiency, yield and economy. The information from this project is useful for further scale-up production and product quality enhancement.
Accomplishments
1. Evaluation of catfish texture. Methods for determining textural differences between catfish fillet samples were needed in order to evaluate variation resulting from differences in gender, geographical location, harvest season, and processing. ARS scientists at New Orleans, Louisiana, developed methods to analyze the texture of cooked catfish fillets using both a trained sensory panel (7 attributes) and a mechanical texture analyzer (6 attributes). Catfish fillets from processors in Mississippi and Alabama were collected and differences in several texture attributes were found with a greater difference seen for the male gender than for female. Frozen fillets containing phosphate had lower hardness values than fillets without phosphate. Correlations were found between several sensory and mechanical texture attributes; which is of importance in providing further validation of the much faster and cheaper mechanical texture measurements. This information will be used by the catfish industry to improve the quality of U.S. grown catfish.
2. Comparisons of commonly used method to evaluate the catfish flavor. 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”. ARS scientists at New Orleans, Louisiana, collected catfish fillet samples that had detectable levels of the off-flavor compounds 2-methylisoborenol and geosmin. A sensory panel was trained to detect different levels of off-flavors in 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 frying. The cooking methods may have had a slight effect on off-flavor perception, and may have contributed flavor to the cooked catfish. After further analysis of this information will be made available to the flavor checkers for their use during a Fall 2017 catfish flavor checkers workshop.
Review Publications
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.
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.
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.
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.
