Identifier

etd-0710102-143553

Degree

Master of Science (MS)

Department

School of Nutrition and Food Sciences

Document Type

Thesis

Abstract

Quality deterioration of smoked catfish is caused by lipid oxidation and microbial spoilage. Smoked catfish can be cross-contaminated during processing and may harbor several pathogens, e.g., Listeria monocytogenes, and Salmonella spp. Lipid oxidation causes unpleasant flavor, thus making smoked fish unacceptable. Hydroperoxides and free radicals, formed during oxidation, may directly react with fish tissues to promote complex reactions. Through such complex reactions, physicochemical properties of smoked catfish may be adversely affected. A combination of smoking and treatments with antimicrobial agents and antioxidants would retard microbial spoilage, extend shelf life, and enhance safety of smoked catfish. The objective of this study was to assess microbial and physicochemical quality of smoked catfish (Ictalurus furcatus) treated with antimicrobial agents and antioxidants during 6-week storage at room temperature. Raw catfish steaks were subjected to the following treatments for 30 minutes prior to smoking: 25% NaCl and 1% ascorbic acid; 3% sodium lactate; 3% sodium lactate and 5% rosemary extract; and/ or 5% sorbic acid. The non-treated catfish served as control. Smoked catfish samples were drawn after 0, 2, 4, and 6 weeks for microbial, pH, water activity, proximate, color, thiobarbituric acid reactive substances (TBARS), and peroxide value (PV) analysis. All treated smoked catfish had a water activity (aw) less than 0.85 compared with 0.94 for the control. Total plate count (TPC) for all dried samples was 1.2- 2.2 log CFU/g at day zero and increased to 1.48-3.0 log CFU/g after 4-week storage. The control was moldy after 6-week storage. No mold was observed on samples treated with sodium lactate, or sorbic acid even after 4-week storage. No Salmonella and Listeria monocytogenes were isolated from any smoked samples. Samples treated with 3% sodium lactate had the lowest microbial loads and were shelf-stable up to 6 weeks without refrigeration. The sample treated with rosemary extract was more stable to oxidation than all other treatments. Protein content of smoked sample ranged from 54 to 87%, 2.82 to 5.80% for ash, 13.11 to 22% for fat, and 11 to 22% for moisture. No significant change in color of smoked catfish was observed during storage. Sodium lactate treatment was most efficient in controlling microbial quality and extending shelf life of smoked catfish.

Date

2002

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Witoon Prinyawiwatkul

Included in

Life Sciences Commons

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