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 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
This project is related to NP 106 Project No: 6054-44000-077-00D, titled “Postharvest Sensory, Processing and Packaging of Catfish” and annual reports share some progress and accomplishments.
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 if there is a higher concentration of the off-flavor compounds geosmin
and/or 2-methylisoborneol in different parts of the fillet in order to determine
where best to check for off-flavor. Although our previous work has shown that
there is little difference in concentrations in the fillet when cut into vertical
portions there was a need to evaluate fillets cut into horizontal portions and
correlate concentrations with the fat content of the potions. Catfish were
collected, slaughtered, and processed at the USDA/ARS Warm Water Aquaculture Center
in Stoneville, MS. Fillets were tagged, frozen and then each fillet was cut
vertically and horizontally into 4 portions and analyzed for the off-flavor
compounds 2-methylisoborenol and geosmin 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. Other studies are
being conducted at the USDA/ARS Southern Regional Research Center in New Orleans, LA to improve the detection of 2-methylisoborneol and geosmin in catfish products by direct placement of the fish tissue in the sample vial with subsequent heat treatment.
The flavor checkers from 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 led 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 USDA/ARS 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.
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 the USDA/
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 the U.S. market place there are few U.S. catfish products designed to be microwave cooked or reheated. The goal of this study was to examine the properties of raw frozen catfish fillets microwave cooked or precooked fillets reheated by microwave cooking. A second goal was to evaluate the effect of fillets containing adding phosphate on properties of microwave cooked or precooked frozen catfish fillets. Both fresh and individually quick frozen fillets containing added(contain added phosphate were purchased from a commercial Mississippi catfish processor. Precooked pieces of fish were cooked to an internal temperature of 60°C, followed by storing frozen until cooked to 93-99°C in a microwave. 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. After microwave cooking, the precooked
fillets containing phosphate had an overall harder texture than non-precooked
fillets. This study will be used to develop precooked catfish products that can be
reheated in a microwave.
There are very few examples of vacuum sealed bags designed for cooking or reheating catfish fillets. The goal of the present study was to examine the
properties of raw frozen and precooked frozen catfish fillets that were cooked in
vacuum sealed pouch in boiling water. The effect phosphate added to the fillets on
the properties of boiled raw frozen and precooked frozen catfish fillets was also
evaluated. Both fresh and individually quick frozen (containing added phosphate)
fillets were purchased from a commercial catfish processor. Precooked pieces of
fish were cooked to an internal temperature of 60°C, and then stored frozen until
the precooked pieces of fish were cooked to 93-98°C in a pouch in boiling water.
After cooking, sample analysis included weight loss, moisture content, color, pH,
mechanical texture (hardness) and fat oxidation. Pilot studies indicated boiling
in water for 15 minutes was the best for frozen catfish fillet pieces to reach a
uniform temperature of ~95°C. Both raw frozen and precooked frozen fillets
containing phosphate showed significantly lower moisture loss after cooking
relative to the fillets without phosphate. Color analysis showed an increase in
yellow color after cooking for fillets without phosphate. An overall harder texture was determined 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.
Other similar studies were completed in which the precooked catfish fillet pieces
were cooked or reheated to 71°C in an oven and then analyzed. Both raw frozen and
precooked frozen fillets with added phosphate showed significant higher moisture
contents relative to the fillets without phosphate. There were differences in
texture properties and an overall harder texture was determined for fillets without
phosphate.
Accomplishments
1. Precooked catfish product for microwave reheating. In the U.S. market place there are few U.S. catfish products designed to be microwave cooked or reheated. The goal of this study was to develop a process for precooking catfish fillets that would be warmed by cooking microwave precooking and characterize the process. An ARS scientist from the Food Processing and Sensory Quality Unit of the Southern Regional Research Center in New Orleans, Louisiana, purchased both fresh and individual quick frozen fillets, which contained added phosphate to improve quality during freezing and thawing, from a commercial processor. Precooked fillet sections were cooked in an oven to an internal temperature of 60°C, followed by storing the precooked samples frozen until cooked to 93-99°C in a microwave. After microwave cooking, sample analysis included weight loss, moisture content, color, pH, mechanical texture (hardness) and fat oxidation. Results indicated after microwave cooking the precooked samples had less moisture loss and lower levels of fat oxidation when they contained phosphate. Precooked fillets containing phosphate had an overall harder texture than non-precooked fillets after microwave cooking. This study will be used to develop precooked catfish products that can be reheated in a microwave.
2. 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, from the Southern Regional Research Center processed catfish in to fillets and then each fillet was cut vertically and horizontally into 4 portions and analyzed for the off-flavor compound 2-methylisoborenol (2-MIB) and geosmin and fat content. Results indicated no trend was observed to support the hypothesis specific site within the fillet can be recommended for evaluation of off flavors.
None.
