Location: Food Processing and Sensory Quality Research
2016 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
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 as a percent of fish weight is being determined. The major off-flavor compounds in the individual byproducts and fillets are being determined. Studies under way to add value to catfish byproducts include the evaluation of catfish bone from both frames and heads as a potential ingredient in foods and feeds and for industrial applications. Bone from frames has been cleaned using either protein degrading enzymes or high pressure cleaning with water.
Characterization of the resultant dried and milled bone samples includes evaluation of the physical properties such as color and determination of the mineral composition and amino acid composition of the bone protein component.
The flavor checkers from a catfish processing plant were visited to learn about the flavor checking process and differences in the procedures used by different processing plants. In March 2015, an ARS scientist lead a catfish processors flavor checking workshop that was attended by most of the Mississippi, Alabama, and
Louisiana catfish processors. From this workshop, many of the needs of catfish flavor checkers were identified. One project that has been initiated is to standardize the nomenclature for catfish flavor attributes. Catfish fillet samples for another project were collected from the Warm Water Aquaculture Center in
Stoneville, MS. These samples had detectable levels of the off-flavor compounds 2-methylisoborenol and geosmin and are being 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 is currently being
trained to detect different levels of off-flavors in catfish fillet and once this is completed the panel will evaluate the different cooking procedures and evaluation procedures. We plan on holding another flavor checkers workshop in the spring of 2017 and these studies will be part of the workshop.
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. A study was initiated to
evaluate the color content in four different areas of catfish fillets and correlate the color characteristics with the fat content in the different areas of the fillets. Catfish were collected, slaughtered, and filleted at the Warm Water Aquaculture Center in Stoneville, MS. Fillets were 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 is being determined. After the data is collected correlations of the color and fat content with the portion location within the fillet will be determined.
A set of experiment were initiated to evaluate the texture properties of both channel and hybrid (blue + channel) catfish. Fillets from both hybrid and channel catfish similar in age, diets and growing conditions were obtained from ARS Warm Water Aquaculture center in Stoneville, MS and after freezing were analyzed at the SRRC. 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. Analysis is under way and includes texture analysis of cooked fillets using both a texture analyzer and a trained sensory panel. In addition fat, protein, ash and moisture content of all fillets are being analyzed and the color distribution within fillets and between
channel and hybrid catfish fillets are being analyzed. Computer programs were written to calculate texture attributes and convert data to graphical form for improved data analysis.
In collaboration with a scientist at Mississippi State University, a scientist from the Food Processing and Sensory Processing Unit of the Southern Regional Research Center in New Orleans, LA initiated a study to extract proteins from catfish byproducts and to characterize the proteins chemical and physical properties for
potential utilization in surimi (fish protien gel) like gel products. Proteins in catfish waste (catfish heads and frames) were finely grounded and extracted using several procedures and the resultant protein fractions utilized to make surimi like gels. The texture of the surimi like proteins were evaluated and comparison
made to commercial surimi products. Results indicated that yield of protein extracted from the frames was higher than that from the heads. Texture analysis showed gel made from heads was similar to that made from frames. The protein composition of strength of surimi the 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 surimi making.
Louisiana State University scientist in collaboration with scientist from the Food Processing and Sensory Processing Unit of the Southern Regional Research Center in New Orleans, LA, conducted a study on catfish skin, which is a major byproduct produced from skin removal during the processing of skinless catfish fillets.
Using enzymes that degrade the catfish skin proteins can be reduced in size to smaller protein fragments (hydrolysates), which have antioxidant properties. Shrimp and many other seafoods contain an abundance of unsaturated fatty acids containing 1 or more double bonds, which make them susceptible to lipid oxidation during frozen storage. A study was conducted to evaluate the effects of a coating material containing hydrolyzed catfish skin on improving the quality of blast frozen shrimp. Shrimp were immersed in coating solutions for 1 min before the air-blast freezing process. The shrimp were placed into Ziploc freezer bags for storage at -20 °C. Distilled-water-coating shrimp and non-coating shrimp were used as controls. Catfish skin hydrolysates were evaluated for degree of hydrolysis and for their ability to reduce fat oxidation. Shrimp samples were analyzed during 60 days of frozen storage for oxidation, color, texture, aerobic plate counts, and
moisture content. After 60 days frozen storage, shrimp coated with water and the hydrolyzed skin treatment had slightly lower lipid oxidation than shrimp coated with distilled water. However, no differences were found between treatments at 60 days of frozen storage for texture, moisture, and color. Other frozen storage time points are being evaluated.
In a similar study, a Louisiana State University scientist in collaboration with scientist from the Food Processing and Sensory Processing Unit of the Southern Regional Research Center in New Orleans, LA, evaluated a water soluble chitosan (carbohyrdrate from shrimp shells) product with antioxidant and antimicrobial properties on improving the shelf life of refrigerated catfish fillets. Three treatments were prepared for this study: 1% acetic acid (weak acid) solution, (2) 0.5% chitosan solution in the 1% acetic acid solution, and (3) 0.5% water soluble chitosan in distilled water. Water was used as a control solution. Fresh catfish fillets were separately tumbled with the different treatment solutions for 10 min in a vacuum tumbler and then the catfish fillets were stored in a refrigerator (4 °C) for 20 days. The fillets were analyzed for texture, color, pH, oxidation, yeast and molds counts, and aerobic plate counts on days 0, 5, 10, 15, and 20 days. Catfish fillets treated with water soluble chitosan had the lowest lipid oxidation and inhibited yeast and mold counts more than the other treatments during the 20 days in refrigerated conditions. This study demonstrated that water soluble chitosan product, combined with vacuum tumbling, can be effective at reducing yeast and mold and lipid oxidation in catfish fillets during refrigerated storage.
Accomplishments
1. Where best to check for off-flavor in catfish fillets. The project goal was to provide a set of standards for catfish flavor checkers to reduce the number of off-flavor fish from reaching the market. The object was to evaluate what part of the catfish fillet should be used to determine where best to check for off-flavor. ARS scientists from the Food Processing and Sensory Quality Unit of the Southern Regional Research Center in New Orleans, Louisiana processed catfish in to fillets and then each fillet was cut vertically and horizontally into 4 portions and analyzed for the off-flavor compounds 2-methylisoborenol (2-MIB) and geosmin, and fat content. Results indicated no trend was observed to support the hypothesis that portions of the fillet had higher concentrations of off-flavor compounds than other portions. There was little difference in the concentration of 2-MIB and geosmin within the fillet with current analytical techniques; therefore, no specific site within the fillet can be recommended for evaluation of off-flavors.
2. Improving the shelf life of fresh catfish fillets. Improving the shelf life of fresh catfish fillets is of great economic importance to catfish, retail food, and food service industries. Louisiana State University scientists collaborated with ARS scientists from the Food Processing and Sensory Processing Unit of the Southern Regional Research Center in New Orleans, Louisiana to evaluate the use of water soluble chitosan to improve the shelf life of refrigerated catfish fillets. Three treatments were prepared for this study: (1) 1% weak organic acid, (2) 0.5% chitosan (carbohyrdrate from shrimp shells) solution in 1% weak organic acid, and (3) 0.5% water soluble chitosan in water and water was used as a control solution. Fresh catfish fillets were tumbled with different solutions for 10 min in a vacuum tumbler and then the catfish fillets were refrigerated at 4 °C for 20 days. Results indicated catfish fillets treated with water soluble chitosan had the lowest lipid oxidation and inhibited yeast and mold counts more than the other treatments during the 20 days in refrigerated conditions. This study demonstrated that water soluble chitosan product, combined with vacuum tumbling, can be effective at reducing yeast and mold and lipid oxidation in catfish fillets during refrigerated storage.
None.
