Organic Acid Dipping of Catfish Fillets: Effect on Color, Microbial Load, and Listeria monocytogenes

Abstract

Microbiological and color changes of catfish fillets were determined following dip treatment in solutions at 4 degrees C of 2% acetic, citric, hydrochloric, lactic, malic, or tartaric acid. Fillets were inoculated with an eight-strain mixture of Listeria monocytogenes prior to dipping. L. monocytogenes, coliform, and aerobic plate counts and surface pH and Hunter color were measured at 0, 2, 5, and 8 days of storage at 4 degrees C. Acid dipping reduced surface pH and L. monocytogenes, coliform, and aerobic microbial loads. Little microbial proliferation was observed on acid-treated fillets, however, controls had a distinct foul odor and microbial loads in excess of 10(6) CFU/g by day 8. On untreated fillets, L. monocytogenes counts did not increase during storage, perhaps due to competitive inhibition by normal catfish microflora. Hunter color analysis revealed lighter and yellower acid-treated fillets than untreated controls, with malic acid producing the least bleaching. The shelf life of refrigerated fillets increased when fillets were acid dipped. It remains to be established if this enhanced microbial quality also parallels sensory acceptability.

Antimicrobial Activity of Vinegar on Bacterial Species Isolated from Retail and Local Channel Catfish (Ictalurus punctatus)

“…There was a large reduction in bacterial growth for vinegar 0.5% and then remained constant in bacteria growth with little variation. These results were similar to a study by Bal'a and Marshall who evaluated the microbiological changes of catfish fillets following treatment of dipping 2% acetic acid [32]. He concluded that little microbial proliferation was observed.…”

Recent Advances in Citric Acid Bio-production and Recovery

“…The environmentally friendly nature of sodium citrate is a major factor in the use of citrates in the detergent industry. CA exhibits bacteriocidal and bactiostatic effects against Listeria monocytogenes, a food-borne pathogen capable of growth at refrigerated temperatures and in high-salt environments (Buchanan and Golden 1998;Bal'A and Marshall 1998). L. monocytogenes frequently contaminates post-process ready-to-eat meat products, including frankfurters (Nickelson and Schmidt 1999).…”

“…Different applications of citric acidAs an acidulant, used in carbonated and non-carbonated beverages for flavoring and buffering, used in dry powder beverages for flavor and pH control ModerateBal'A and Marshall (1998) Antioxidant, increase effectiveness of antimicrobial preservatives, control sugar inversion, provides tartness and enhance flavor, control the product pH for optimum gelationModerateDairy products Sodium citrate is used in creamers to stabilize the casein, prevents feathering of the creamers when added to hot beverages, sodium citrate functions as an emulsifying salt to stabilize the water and oil phases of the cheese and improves body and textureModerateCanning industry Acts as chelating agent, helps preserve the natural color and prevent discoloration in canned mushrooms, kidney beans and canned corn, acts as an antioxidant synergist antimicrobial agent that can be applied to the surfaces of cured meat products prior to packagingAlong with ascorbic acid, inhibits enzymatic and trace metalcatalyzed oxidation reactions which can cause color and flavor deterioration Moderate Oils Used in canola oil degumming in the deodorization and hydrogenation steps in oil processing to chelate trace metals which can catalyze rancidity reactions Moderate Seafood Prevents discoloration and the development of off-odors and flavors by chelating trace metals Moderate Meat industry Sodium citrate is used in slaughter houses to prevent the coagulation or clotting of fresh blood Used as an anticoagulant, as effervescent combined with bicarbonates or carbonates in antacids and dentrifices, as a flavoring and stabilizing agent in liquid suspensions and solutions, imparts a desirable tart taste that helps mask medicinal flavors, calcium citrate is used as a dietary calcium supplement Added to hair care formulations, cosmetics, detergents to adjust the pH, as buffering agent and chelate metal ions to prevent discoloration and stabilizes the formulation Moderate 3. Agriculture Animal feed CA increases solubility, easily digestible chelates of essential metal nutrients, enhance response to antibiotics, enhance flavor, to control gastric pH, and improve the efficiency of the feed, used in pet food as flavor enhancer Moderate Fertilizers Chelates Fe, Cu, Mg and Zn, is used to correct soil deficiencies, enhance phosphorous availability in plants.Used to chelate copper in formulations used to kill algae in reservoirs and natural waters.…”

Low-Dose X-Ray Treatment of Fresh Channel Catfish Fillets Does Not Affect Color, Texture, or Oxidation

“…Because the color of raw catfish fillets can vary (Marshall, 2004), consumers may be accustomed to this variation and may not make purchase decisions based on this attribute. In addition, catfish fillets are regularly marketed for batter/breading/frying purposes, where raw fillet color may be relatively insignificant to final consumers (Bal'a and Marshall, 1998).…”