Semester of Graduation

Fall 2021

Degree

Master of Science (MS)

Department

Nutrition and Food Science

Document Type

Thesis

Abstract

Seafood has a short shelf-life because of its unstable nature. Shrimp has a shelf-life of only eight days. Edible coatings, like those made from gelatin, have been used to apply antimicrobial agents to food product surfaces. Organic acids are naturally occurring, low-cost options that have been proven to effectively reduce bacterial loads on food products and extend their shelf-life. Gelatin can be extracted from catfish skin, helping to reduce product waste. The purpose of this study was to determine the potential effectiveness of fish skin gelatin as an antimicrobial coating alone and in combination with lactic acid, and then compare its effectiveness between fresh shrimp and frozen then thawed shrimp (Litopenaeus setiferus), followed by the extraction and characterization of channel catfish (Ictalurus punctatus) skin gelatin. For the shelf-life studies, fresh, never frozen shrimp was collected from Louisiana to be analyzed. Four treatment groups were analyzed: 1) untreated (control); 2) coated with fish skin gelatin; 3) coated with lactic acid then gelatin; and 4) coated with gelatin infused with lactic acid. Analyses included microbiology, physical, and chemical changes to the shrimp over time for both fresh, and frozen then thawed shrimp samples. Gelatin was extracted from catfish skin to undergo characterization, including gel strength, melting point, setting point, setting time, and amino acid profiling. Lactic acid lowered microbial counts and extended the shelf-life by six days, compared to the 12-day shelf-life of the control shrimp, while the addition of just a gelatin coating was able to increase shelf-life by three days. Lactic acid and gelatin treatments showed significant reduction in bacterial counts and lipid oxidation. Samples showed a delay in reaching the spoilage threshold for psychrophilic bacteria. Characteristics present in extracted catfish skin gelatin make it a viable option as a protective coating on food products. The extracted gel showed a gel strength of 376.20 ± 12.17g, setting temperature of 17.63 ± 0.60oC, a setting time of 285.6 ± 10.2s, and a melting point of 31.46 ± 0.35oC. These characteristics are consistent with the amino acid composition determined by HPLC analyses and when compared to other warm water fish species.

Committee Chair

Evelyn Watts

DOI

10.31390/gradschool_theses.5459

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