Catfish Fillets Research Articles

Low levels of dietary methylmercury inhibit growth and gonadal development in juvenile walleye ( Stizostedion vitreum)

Mercury levels in the aquatic environment of North America have been increasing, raising the possibility that this highly toxic heavy metal might alter fish populations. Previous investigations have demonstrated toxic effects of mercury on teleost reproduction, but these findings were observed following unrealistically high exposures. In this study, we used concentrations frequently observed in North American lakes to investigate the effects of dietary methylmercury on growth, gonadal development, and plasma cortisol levels in juvenile walleye ( Stizostedion vitreum). For a period of 6 months, two groups of walleye were reared on untainted catfish fillets, while two test groups were fed fillets injected with methylmercury, one group receiving 0.1 μg Hg g −1 food (low-mercury diet) and the other receiving 1.0 μg Hg g −1 food (high-mercury diet). After the exposure period, fish fed the low- and high-mercury diets had mean body burdens of 0.254 ± 0.015 μg Hg g −1 and 2.37 ± 0.09 μg Hg g −1, respectively. Dietary mercury significantly impaired both growth and gonadal development in males, which was apparent as reduced fish length, weight, and gonadosomatic index. Testicular atrophy was observed in fish fed the mercury-tainted fillets, but was nonexistent in control animals. Mercury also suppressed plasma cortisol in juveniles (sexes combined). The findings of this study suggest that dietary methylmercury, at levels currently found in the aquatic environment, might reduce juvenile survival by impairing growth and immune function. Furthermore, these results suggest that methylmercury might also affect reproductive potential of teleosts by impairing testicular development in young.

Bacteriological evaluations of tumbled catfish with egg white

This study was conducted to determine the levels of contamination of various bacteria in a tumbled fish product and to evaluate the effect of tumbling and egg white on the bacteriological qualities of the product. The restructed product was formulated with fresh channel catfish fillets, egg white and curing ingredients and the mixture was tumbled. Total aerobic plate count (APC), psychrotrophic, Pseudomonas, Coliform, Salmonella, lipolytic and proteolytic bacterial counts were determined before and after the tumbling process. This process caused a slight decrease in the counts of APC, Pseudomonas, lipolytic and proteolytic bacteria probably due to better cure distribution and/or faster cure penetration with tumbling.

MICROBIOLOGICAL AND SENSORY ANALYSES OF REFRIGERATED CATFISH FILLETS TREATED WITH ACETIC AND LACTIC ACIDS

ABSTRACTThe influence of acetic acid (AA) and/or lactic acid (LA) dips on microbial numbers, pH, and sensory scores of catfish fillets was assessed during storage at 4C. Fillets were treated by dipping in 4C AA and/or LA solutions for 0–60s. Fillets treated with either 3–4% AA or 2% AA and 2% LA for 30–60s suppressed growth of aerobic microorganisms for 4 days and extended shelf‐life to 16 days. Treatment with either 3–4% LA or 1% AA and 1% LA for 5–60s prolonged microbiological shelf life to 12 days. AA had greater antimicrobial activity than LA. Fillets treated with AA alone or combinations of AA and LA were liked less by sensory panels than controls due to acidic odor and flesh discoloration. Thus, concentrations of AA or LA greater than 2% or exposure times greater than 30s are not recommended for catfish fillets.

Effect of monolaurin and lactic acid on Listeria monocytogenes attached to catfish fillets

The purpose of this study was to determine the effects of monolaurin and lactic acid, singly or combined, on Listeria monocytogenes attached to catfish fillets. Skinless catfish fillets were inoculated with L. monocytogenes and dip treated in monolaurin and/or lactic acid solutions for various time periods. Results showed that monolaurin up to 400 μg ml had no influence on counts. Conversely, lactic acid-treated fillets had reduced counts compared to controls. Dipping in 0.85, 1.70, or 2.55% lactic acid for 30 min reduced counts by 0.9, 1.4, or 1.3 logs, respectively. Extending the dipping time to 60 min resulted in little additional decrease in counts. Combining monolaurin with lactic acid yielded results similar to lactic acid alone. Hence, population reduction ability resides with lactic acid and not monolaurin.

Quality Changes During Refrigerated Storage of Packaged Shrimp and Catfish Fillets Treated with Sodium Acetate, Sodium Lactate or Propyl Gallate

ABSTRACTThe effects of sodium acetate, sodium lactate, and propyl gallate were determined on microbial populations, pH, ammonia content and color of film‐overwrapped or vacuum‐skin packaged fresh shrimp and catfish fillets. Products were stored at 4°C up to 12 days. Vacuum‐skin packaged shrimp or catfish fillets contained lower (P < 0.05) ammonia compared to film‐overwrapped products. Catfish fillets treated with 2% sodium acetate had lower populations of psychrotrophic and anaerobic bacteria compared with untreated catfish, regardless of packaging. Treatment with 2% NaAc has potential for extending shelf life of refrigerated catfish fillets.

Quantification of Antioxidants in Channel Catfish during Frozen Storage

Levels of ascorbic acid, α- and γ-tocopherol, glutathione, and volatile aldehydes were monitored over 6 months in frozen minced and intact fillets of channel catfish. For both samples, decline of g...

Determination of Geosmin and Methylisoborneol in Catfish Tissue (Ictalurus punctatus) by Microwave-Assisted Distillation−Solid Phase Adsorbent Trapping

Methylisoborneol (MIB) and geosmin (GEO) are algal off-flavor compounds, which when present in catfish tissue create undesirable taste and odors in the prepared products. These undesirable taste and odor problems are not limited to catfish aquaculture. A procedure was developed for the determination of off-flavor compounds in channel catfish tissue that involves microwave radiation distillation with solid phase trapping. This is a modification of a microwave distillation−cold trapping procedure but without the need of a cryogen or a liquid−liquid extraction step. A channel catfish fillet sample is placed in a container located within a microwave oven. This container, which is directly connected to a thermostated condenser containing a solid phase adsorbent, is continually purged with argon gas. The trapped distillate components are eluted with ethyl acetate and then injected into a gas chromatograph−ion trap mass spectrometer for analysis. This technique offers a rapid and sensitive means of off-flavor an...

Determination of leucogentian violet and gentian violet in catfish tissue by high-performance liquid chromatography with visible detection

A sensitive analytical procedure for the determination of residues of leucogentian violet (LGV) and gentian violet (GV) in catfish tissue is presented. Frozen (−20°C) catfish fillets were cut into chunks and then blended in a Waring blendor. A 10-g amount of catfish muscle tissue was homogenized and extracted with acetonitrile-buffer, partitioned against methylene chloride, and cleaned up on tandem neutral alumina and propylsulfonic acid cation-exchange solid-phase extraction cartridges. Samples of 100 μl (0.5 g equiv.) were chromatographed isocratically in 15 min using an acetonitrile-buffer mobile phase on a cyano phase column in-line with a post-column PbO 2 oxidation reactor. The PbO 2 post-column reactor efficiently oxidized the LGV to the chromatic GV permitting visible detection at 588 nm for both LGV and GV. Linearity was demonstrated with standards over the range 0.5–50 ng per injection. Recoveries of LGV and GV from catfish tissues fortified at 20, 10, and 1 ng/g were 83.1 ± 1.2, 78.4 ± 4.0, 84 ± 8 and 92.7 ± 1.8, 95.0 ± 2.2, 93 ± 2 (mean ± S.D., n = 4), respectively.

Fish Oil Dietary Effects on Fatty Acid Composition and Flavor of Channel Catfish

ABSTRACTA typical channel catfish diet was supplemented with 0, 1.5, and 3% menhaden oil. Fillets were subjected to lipid, fatty acid, and TBA analyses. After 6 mo storage at −18°C, fillets were again analyzed for TBA value and flavor panel profile. Fillets from catfish fed diets with 1.5 and 3% supplemental fish oil had elevated levels of n‐3 fatty acids (P<0.05). TBA number and off‐flavor attributes were not affected by treatments. Menhaden oil supplementation up to 3% enhanced the content of n‐3 fatty acids in channel catfish fillets without adversely affecting flavor attributes or storage quality.

Gram-Negative Bacteria in Refrigerated Catfish Fillets Treated with Lactic Culture and Lactic Acid

Catfish fillets were treated with combinations of lactic culture (Lactococcus lactis spp. cremoris ATCC 19257) and lactic acid using a meat tumbler. Fillets were placed individually in Ziploc bags and stored at 4 or 10°C. Counts of gram-negative bacteria on crystal violet tetrazolium chloride agar (CVT), the pH, and the sensory quality of fillets were evaluated after 0, 3, 6, and 9 days of storage time. The combination of 2.5% lactic culture and either 2% lactic acid dip (5 min) or 3% lactic acid dip (1 or 5 min) effectively (P < 0.05) inhibited counts for 9 days. The most effective treatment combination was 2.5% lactic culture incubated for 48 h and 3% lactic acid dip. The pH of samples treated with lactic culture and lactic acid ranged from 5.6 to 6.1 for 9 days at 4 or 10°C Lactic culture and lactic acid combinations extended the refrigerated shelf life of catfish for an additional 3 days at 4 and 10°C and reduced CVT counts by two log cycles over untreated fish. The combination of lactic culture and lactic acid were generally preferred for flavor and odor compared to controls after 6 and 9 days of storage, respectively.

Extending Shelf Life of Refrigerated Catfish Fillets Using Sodium Acetate and Monopotassium Phosphate

The effects of sodium acetate (SA) and monopotassium phosphate (MKP) on total aerobic plate counts (APC), pH, odor, and appearance of catfish fillets during storage at 4°C were determined. Use of 0.75% and 1.0% SA lowered (P < 0.05) initial APC by 0.6 to 0.7 log units compared to the control. Microbial counts of SA-treated fillets remained lower than the control during storage, resulting in a 6-day shelf-life increase. MKP alone had no effect on APC values, but it did influence the activity of SA. The results indicate that a combination of SA and MKP could prolong the microbiological shelf life of catfish to 12 days at 4°C. Fillets treated with 1% SA alone or SA-MKP combinations had pH values and odor scores that were similar to fresh controls for up to 9 days; however, appearance scores were lower after 3 days, probably due to a brownish and watery appearance. MKP alone is not recommended for shelf-life extension of catfish fillets. Conversely, SA alone or combined with MKP is recommended to extend the microbiological shelf life of refrigerated catfish fillets.

Sodium Acetate and Bifidobacteria Increase Shelf‐Life of Refrigerated Catfish Fillets

ABSTRACTMicrobiological and sensory evaluations of catfish fillets treated with sodium acetate (SA) and bifidobacteria were studied at 4°C. Cultures of Bifidobacterium adolescentis, B. infantis, or B. longum (2.5% V/W) extended lag phase, but not generation time of aerobic bacteria. One‐half percent (W/W) SA increased lag phase and generation time. SA and bifidobacteria reduced counts more than either alone, extending shelf‐life by 3 days. Amount of culture (1.5–4.5%) or culture age (24–72 hr) had no effect on inhibition. Treated fillets odor and appearance resembled fresh fillets for up to 6 days, while untreated fillets were unacceptable aher 3 days. SA, either alone or combined with bifidobacteria, extended refrigerated shelf‐life of catfish fillets.

Effects of Dietary Vitamin E Enrichment on Frozen Channel Catfish,(Ictalurus punctatus)Fillets

The storage quality of channel catfish (Ictalurus punctatus), following long term frozen storage, fed diets containing 5 and 10 times the normal level of vitamin E for 45 or 60 days prior to harvest, was evaluated. There were no unusual effects of treatment on fish weight, survival or feed conversion ratios. Muscle vitamin E content was higher (P < 0.05) from fed diets containing supplemental vitamin E than in the control. Oxidation as measured by TBARS and sensory analysis values did not differ (P > 0.05) in response to vitamin E supplementation. Lipid oxidation increased as storage time increased. Lack of change in phospholipid and neutral lipid fractions during storage indicated that autoxidations was the major cause of oxidation in catfish. Vitamin E levels up to 10 times the normal amount did not improve the overall quality of catfish fillets.

Amplified Immunoassay ELISA-ELCA for Measuring Clostridium botulinum Type E Neurotoxin in Fish Fillets

The measurement of Clostridium botulinum type E toxin in fish was accomplished using an amplified immunoassay (enzyme-linked immunosorbent assay-enzyme-linked coagulation assay [ELISA-ELCA]) based on the coagulation cascade. Fresh catfish fillets inoculated with a mixture of spores from five strains of C. botulinum type E were packaged in high barrier film with air, vacuum and modified atmosphere and stored at 4, 8 or 16°C for up to 75 days. Toxin production was monitored during storage by both mouse bioassay (trypsin and non-trypsin treated) and ELISA-ELCA on the non-trypsinized samples. All 26 inoculated products that were positive by the mouse bioassay were also positive by ELISA-ELCA. Of 35 uninoculated samples which were not toxic in mouse bioassay, none were positive by ELISA-ELCA; of 73 inoculated samples which were not toxic by mouse bioassay, 14 had toxin measurable by the ELISA-ELCA. The position of these immunoassay-positives in the sampling sequence indicated that the toxin was identified by the immunoassay before it was found in the mouse bioassay. These results suggest that the ELISA-ELCA technique is a usable alternative to the mouse bioassay for monitoring C. botulinum type E toxin production in fish challenge studies.

Bacteriological and Color Changes in Modified Atmosphere-Packaged Refrigerated Channel Catfish

Channel catfish (Ictalurus punctatus) fillet strips were packaged under aerobic (AIR), 25% carbon dioxide (CO2) (LC) and 80% CO2 (HC) environments with the remainder being air; and stored at 2 and 8°C for 4 weeks. Aerobic plate counts (APC) for HC fish at 2°C declined from 6 log CFU/g to 1.4 log CFU/g after 2 weeks but increased to 5 log CFU/g by the third week. The HC-stored strips at 8°C had an initial increase in APC followed by a decline to 1.4 log CFU/g on the third week, and a rise to 9 log CFU/g by the fourth week. Aerobic plate counts in AIR- and LC-packed fish at either temperature increased steadily throughout storage. Fish surface pH declined in HC-packed product from 6.2 to 5.6 by the fourth week, but did not change in LC and AIR packs. Hunter L-values increased in CO2-packed products, while Hunter a-values decreased. Listeria monocytogenes was isolated from fish under LC and AIR at 8°C in the second and third weeks. Salmonella spp. was present in fish stored in all storage atmospheres at 8°C, but only in AIR-packed fish at 2°C. Clostridium botulinum was not found in product at any of the storage atmospheres at either temperature at any time. The best treatment was fish packed in HC and stored at 2°C.

Determination of Sulfadimethoxine and Ormetoprim Residues in Channel Catfish Fillets After Treatment with Romet and Evaluation of a Commercially Available Rapid Diagnostic Test for Drug Residues in Fish Fillets

Abstract Sulfadimethoxine (SDM) and ormetoprim (OMP) residues were determined in catfish fillets after treatment with Romet. A liquid chromatographic (LC) method capable of simultaneously detecting SDM and OMP at 0.05–40 ppm was used. The recoveries were 92% for SDM and 108% for OMP. The intra- assay variabilities were determined for SDM and OMP at fortification levels of 0.05–40 ppm, and a coefficient of variation (CV) of less than 10% was achieved at all levels. The interassay variations were determined at fortification levels of 0.1 ppm (CVs: SDM, 6.4%; OMP, 4.9%) and 1.0 ppm (CVs: SDM, 2.8%; OMP, 3.5%). SDM and OMP residues in catfish fillets were rapidly depleted after treatment with Romet. By day 2 posttreatment, SDM and OMP were essentially nondetectable. The use of an enzyme-linked immunoassay (ELISA)-based rapid diagnostic test to determine SDM and OMP in catfish fillets was evaluated. An assay procedure to adapt the test for residues in tissue samples was developed. SDM and OMP were extracted from ground catfish fillet with methanol–water (80 + 20, v/v); the extract was diluted with buffer and filtered, and the filtrate was then tested with an EZ Screen test card. The effectiveness of the rapid test assay to detect SDM residues at levels above the U.S. Food and Drug Administration tolerance (0.1 ppm) was verified with fillets from Romet-treated catfish. All samples with residues at &amp;gt;0.1 ppm were identified correctly by the test. The results indicate that the diagnostic test could be used as a rapid method for monitoring Romet residues in catfish.

Liquid Chromatographic Determination of Sarafloxacin Residues in Channel Catfish Muscle Tissue

Abstract A liquid chromatographic method is described for the determination of sarafloxacin hydrochloride residues in channel catfish (Ictalurus punctatus) fillets. Sarafloxacin was extracted from fillet tissue with acetonitrile–water (1+1). The extract was centrifuged and the supernatant was partitioned with hexane. The aqueous fraction was filtered through a 0.45 μm filter and evaporated to dryness. The sample was redissolved with 20% acetonitrile–methanol (3 + 2) and 80% trifluoroacetic acid (0.1%), centrifuged, and filtered to remove proteins. Samples were analyzed by chromatography with gradient elution on a C18 column and with fluorescence detection (excitation at 280 nm and emission above 389 nm). Mean recoveries ranged from 85.4 to 104%, and relative standard deviations ranged from 1.06 to 5.58% in samples spiked at concentrations of 10.0–863.8 ng/g. The method detection limit for sarafloxacin was 1.4 ng/g.

Rancidity in Frozen Catfish Fillets as Influenced by Antioxidant Injection and Storage

The effects of antioxidant injection and frozen storage on volatile aldehyde concentrations and TBA values of three external fillet sites and an internal site were compared with sensory evaluations of whole, frozen stored fillets. Fillets were IQF processed, ice glazed and stored at -20°C for up to 6 months. The fillet site tissues were excised bimonthly from whole, frozen stored fillets for chemical and instrumental analysis of rancidity. The lateral line and skin-side of fillets were two sites most susceptible to rancidity as reflected by increasing volatile aldehyde concentrations and TBA values over storage time. Injection of a polyphosphate and lemon juice antioxidant significantly reduced rancidity-related aldehydes in all external fillet sites. Antioxidant injection significantly improved flavor of frozen fillets stored beyond 2 months. TBA analysis of only the dark muscle was a good indicator of rancidity, while volatile aldehyde content of either the lateral line or skin-side site was a good ranc...

Evaluation of Impedance Microbiology for Rapid Assessment of Shelf-Life and Quality of Processed Channel Catfish,Ictalurus punctatus

Total bacterial numbers on freshly processed channel catfish, "Ictalurus punctatus," fillets were determined and correlated with shelf-life. In addition, the Bactometer Microbial Monitoring System (bioMérieux-Vitek, Hazelwood, Missouri), an automated instrument using the principles of impedance microbiology, was evaluated as a rapid method to determine microorganism numbers on fillets. Freshly processed channel catfish fillets were collected from two commercial farms from May, 1991 to January, 1992. After using the rinse bag method to isolate bacteria from samples, the microorganisms in the rinsate were enumerated on plates by means of serial dilutions and the spread plate method. The total number of colony-forming units per gram (cfu/g) of channel catfish fillet was then correlated with the capacitence detection time in the bactometer. Fillets collected in May and June typically contained 2.0 to 2.5 x 104 cfu/g, and the bactometer detection time varied from 4.3 to 5.1 hours. The microbial quality of freshly processed fillets decreased in July and August, and 1.3 to 2.4 x 105 cfu/g were isolated with a bactometer detection time that varied from 3.4 to 4.4 hours. Shelf-life was examined in July and August and again for December and January samples and ranged from 6-8 days for the different lots. Fillets that exceeded shelf-life contained over 107 cfu/g. The Bactometer Microbial Monitorial System provided a rapid estimation of microorganism numbers on processed channel catfish fillets. Product with a detect time of 3.8 hours or less (i.e., more than 2.5 x 105 cfu/g) did not have a shelf-life greater than 6 days when maintained at a refrigeration temperature of 1.7°C.

Gram Negative Bacteria Inhibition by Lactic Acid Culture and Food Preservatives on Catfish Fillets during Refrigerated Storage

ABSTRACTTreating catfish fillets with sodium acetate (SA) and/or potassium sorbate (PS), with or without lactic culture (Lactococcus lactic spp. cremoris ATCC 19257 grown in 20% milk solids) was studied at 4°C. Gram negative bacterial (CVT) counts on crystal violet tetrazolium chloride agar, pH, and sensory evaluation of fillets were assessed over time. Treatment with the combination of 0.50% SA, 0.25% PS with 2.50% lactic acid culture (LC) and, also, 0.50 to 1.00% SA alone completely inhibited growth for 6 days at 4°C. After 12 days, counts with this treatment and the 1.00% SA increased ∼1.3 and 1.2 log cycles, respectively. The antimicrobial effects did not appear to be due to pH values. The combination of 0.50% SA and 0.25% PS with 2.50% LC, or 1.00% SA, alone, improved catfish odor and appearance during 13 days storage.