Value-added Products from Fisheries Resources: Smoked Catfish

APPROACH: The details for the procedures to fulfill these three sub-objectives are described as follows: Conduct shelf-life test to ensure food quality and safety of the final products (obj. 1): Three different oxygen permeability packaging materials of 100 (oxygen-impermeable), 600, and 10,000 (oxygen-permeable) will be used. Packed fillets will then be kept in refrigerator at 2 to 4 degree and at room temperatures respectively. About 10 g vacuum packaged fillet samples will be used for texture analysis each time at the fifth day and the eighth day after packaging, and thereafter every two days with the method of Volodkevich Bite Jaws. Microbiological analysis will be conducted after the texture analysis using the methods of Gonzalez-Rodriguez, et al. until products is found spoiled. The detection of viable Clostridium botulinum will be conducted at the same time of the microbiological detection following a procedure developed by the Food and Drug Administration. Both the proteolytic and nonproteolytic strains are to be detected with the tube method. Existence of C. botulinum will be confirmed by microscope examination. Statistical analyses will be performed using SAS (V 9.1, SAS Institute Inc. Cary, North Carolina). Apply for a US patent for the invention (obj. 2) In order to protect intellectual properties and facilitate promotion of hot-smoked catfish products, we will apply for a US patent for the invention with the help of the Office of Technology Transfer, Auburn University. Disclosures are currently being filed with this office in preparation for the subsequent patent application. This process will require collaboration between the investigators and the patent attorneys working with Auburn University to complete the patent application process. Establish standards and guidance for the hot-smoked catfish products(obj. 3) Unlike salmon, few reports on the study of quality and sanitary standards and regulations for smoked catfish are available and little work has been done on the quality and sanitary standards and regulations for the products. For instance, currently the U.S. Food and Drug Administration is requesting information regarding packaging materials for smoked fish to enable them to develop detailed laws or regulations on smoked fish packaging procedures. Promote and market smoked products and help to establish processing plants (obj. 4) a) Meet with representatives of large seafood buyers such as Harvest Select Inc., Inland Seafood Inc., and Poseidon Inc. etc. individually to discuss the feasibility of establishment of processing plants and a distribution and sales network for the products. b) Educate potential producers with the basic technical knowledge of smoked catfish products at conferences such as Alabama Catfish Producers Association Advisory Committee meeting. c) Get potential consumers acquainted with smoked catfish products by conducting marketing sessions at events such as AU Ag Round-up and/or exhibitions such as the International Boston Seafood Show if the budget allows. d) Help those who interested in investing in the business to license the AU processes and establish processing operations.

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PROGRESS: 2007/01 TO 2007/12<BR>
October 24, 2007 Presentations to catfish grower and processors during a workshop in west Alabama.
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IMPACT: 2007/01 TO 2007/12<BR>
During the past two years, 1) two-step optimization of extraction and physical properties of channel catfish skin gelatin (year 1) was conducted; and 2) relationships between the nano-scale structure and functional properties of gelatin (year 2) were invested. Two scientific papers based on the findings from research were published and one manuscript was submitted. Brief progress is reported below and detailed reports/papers are attached. 2-Step Optimization of the Extraction and Subsequent Physical Properties of Channel Catfish Skin Gelatin To optimize the extraction of gelatin from channel catfish (Ictalurus punctatus) skin, a 2-step response surface methodology involving a central composite design was adopted for the extraction process. After screening experiments, concentration of NaOH, alkaline pretreatment time, concentration of acetic acid, and extraction temperature were selected as the independent variables. In the 1st step of the optimization the dependent variables were protein yield (YP), gel strength (GS), and viscosity (V). Seven sets of optimized conditions were selected from the 1st step for the 2nd-step screen. Texture profile analysis and the 3 dependent variables from the 1st step were used as responses in the 2nd-step optimization. After the 2nd-step optimization, the most suitable conditions were 0.20 M NaOH pretreatment for 84 min, followed by a 0.115 M acetic acid extraction at 55 degree C. The optimal values obtained from these conditions were YP = 19.2%, GS = 252 g, and V = 3.23 cP. The gelatin obtained also showed relatively good hardness, cohesiveness, springiness, and chewiness. The yield of protein and viscosity can be predicted by a quadratic and a linear model, respectively. Nanostructural characterization of catfish skin gelatin using atomic force microscopy To determine the nanostructure of gelatin from catfish (Ictalurus punctatus) skin, atomic force microscopy (AFM) was used to study gelatin aggregates. The gelatin was extracted at an optimized acid concentration after alkaline processing. First, the AFM imaging parameters were optimized to obtain high quality images. Then height mode with a 2D plane, 3D topographical images, and error signal mode images, which removed slow variations in surface topography but highlighted the edges of sample features, were used to analyze the structure of particles. The results describe fish gelatin at a nanoscale level for the first time, and are compared with AFM images of mammalian gelatins. Both annular pores with diameters averaging 117.6 nm and spherical aggregates with an average diameter of 266.9 nm were seen in the AFM images of fish gelatin. From the AFM images, we propose that the structures formed were determined by whether the solution penetrated into the gelatin molecules evenly or not during hydrolysis. A scheme for the formation of annular pores and spherical aggregates is proposed.