THE EFFECTS OF STORAGE TEMPERATURE ON BIO-PRESERVATION OF LAB ON ATLANTIC SALMON

• Main Author: Winta Gebreyohanis
• Other Authors: Professor Turid Rustad
• Format: Master Thesis
• Language: English
• Published: NTNU 2019
• Subjects: Atlantic salmon
• Online Access: http://hdl.handle.net/11250/2623987

Abstract Fish is a nutritious, protein-rich food which is highly perishable and has a short shelf-life unless preservation methods are used. The common spoilage bacterial in fish are Pseudomonas putida, P. fluorescens P. perolens, P. fragi , Shewanella putrefaciens, Brochothrix thermosphacta , Alteromonas nigrifaciens, Aeromonas salmonicida, A. hydrophila and Photobacterium phosphorous. The most common pathogens associate to fish are Listeria monocytogenes, Aeromonas spp., Salmonella spp., Staphylococcus aureus, Cl. perfringens, Escherichia coli, V. cholera and Vibrio parahaemolyticus. In addition to microorganisms, enzyme activities in the food are also responsible for fish muscle softening. It is very important to develop methods that can help ensure safety and extend the shelf life of seafood. Bio-preservation by using lactic acid bacteria is a natural and powerful method used to extend the shelf life and improve the safety of foods. The efficiency using LAB bio-preservation is affected by physicochemical factors such as temperature, pH. The objective of this study is to investigate the effect of temperature on Bio-preservation of LAB on Atlantic salmon by including both effect on microbial growth and effect on enzymatic activity. To conduct this study, Carnobacterium ssp (SF1994) Lactic Acid Bacterial strains were used. The salmon fillets were dipped into the LAB strain solutions and the control was dipped in sterile distilled water. These samples were packed in plastic bags and stored at three different storage temperatures (0 °C, 4 °C, 8 °C). For analysis of effect on microbial growth, the growth rate of spoilage microorganisms and the LAB growth rates were measured for the three different storage temperatures during 7 storage days. Furthermore, for enzyme activity analysis, the activity of cathepsin B was measured during the storage days for the three temperatures. The result indicated that storage temperature significantly affected the efficiency of LAB to inhibit spoilage microorganisms. The LAB strain showed the highest inhibition efficiency at lowest storage temperature (0 °C) and the lowest inhibition efficiency at highest storage temperature (8 °C). The lower storage temperature increased the susceptibility of spoilage microbes to carnobacterium bacteriocin. Furthermore, the enzyme activity study revealed 8°C storage temperature measured the highest cathepsin B activity, the highest protein degradation, high amount of free amino acid and acid soluble peptides. Key words: Bio-preservation, LAB, carnobacterium, temperature, spoilage microorganisms, cathepsin B activities, Atlantic salmon.