Microbial changes and growth of Listeria monocytogenes during chilled storage of brined shrimp ( Pandalus borealis )

• Published in: International Journal of Food Microbiology
• Main Authors: Mejlholm, Ole, Kjeldgaard, J., Modberg, A., Vest, M.B., Bøknæs, Niels, Koort, J., Bjorkroth, J., Dalgaard, Paw
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2008
• Subjects: Fiskeprodukter; Pandalus borealis
• Online Access: https://orbit.dtu.dk/en/publications/44230c25-64b7-464e-a7e7-2dcf554a271f; https://doi.org/10.1016/j.ijfoodmicro.2008.03.022

Thirteen storage trials and ten challenge tests were carried out to examine microbial changes, spoilage and the potential growth of Listeria monocytogenes in brined shrimp (Pandalus borealis). Shrimp in brine as well as brined and drained shrimp in modified atmosphere packaging (MAP) were produced and studied. Different recipes were used to study the effect of preserving parameters (organic acids, pH and NaCl) on growth of microorganisms and shelf life at 7-8 degrees C or 12 degrees C. Particularly, brines with different concentrations of (i) benzoic, citric and sorbic acids or (ii) acetic, citric and lactic acids were studied. Furthermore, the effect of adding diacetate to brined shrimp was evaluated. A single batch of cooked and peeled shrimp was used to study both industrially and manually processed brined shrimp with respect to the effect of process hygiene on microbial changes and the shelf life of products. Concentrations of microorganisms on newly produced brined shrimp from an industrial scale processing line were 1.0-2.3 log (CFU g(-1)) higher than comparable concentrations in manually processed samples. This resulted in a substantially shorter shelf life and a more diverse spoilage microflora of the industrially processed brined shrimp. In addition, shelf life of brined shrimp was affected by the types and concentrations of organic acids and by the storage temperature as expected. The effect of MAP was less pronounced. Eighty-two isolates from the spoilage microflora of brined shrimp were identified and they included 53 lactic acid bacteria, 6 coagulase negative Staphylococcus spp., 18 Pseudomonas fluorescens and 5 yeast isolates. After storage at 7 degrees C, P. fluorescens, Enterococcus-like isolates, E. malodoratus, Carnobacterium maltaromaticum, coagulase negative Staphylococcus spp. and Lactobacillus sakei constituted the dominating microflora of shrimp in brines that contained benzoic, citric and sorbic acids as preservatives. L sakei dominated the spoilage microflora of brined and drained MAP ...