Changes in the microbiological quality of shellfish, brought about by treatment with high hydrostatic pressure

Abstract

Summary Four types of shellfish, mussels, prawns, scallops and oysters, were pressure treated at 300, 400, 500 and 600 MPa for 2 min at 20 °C and stored for up to 28 days at 2 °C. The shellfish were sampled before and after pressure treatment and at 7‐day intervals for total aerobic counts, psychrotrophic counts, pseudomonads and coliforms. Pressure treatment readily inactivated psychrotrophic bacteria, coliforms and pseudomonads. Randomly selected isolates were identified from the shellfish before and after pressure treatment and after storage at 2 °C. The range of bacteria present in the shellfish decreased after pressure treatment. This was predominantly because of inactivation of Gram‐negative bacteria leading to an increase in the proportion of Gram‐positive species isolated. The main types of bacteria isolated from pressure‐treated shellfish, after storage, were Bacillus, Acinetobacter/Moraxella and lactic acid bacteria. Together these made up 96% of the bacteria isolated from all the pressure‐treated shellfish.

Effect of high pressure processing on the quality of herring (Clupea harengus) and haddock (Melanogrammus aeglefinus) stored on ice

“…Bacterial counts were determined using the spread plate method with Maximum Recovery Diluent (Oxoid CM733) as diluent, as described by Linton, McClements, and Patterson (2003). The incubation conditions used for total aerobe counts were 30 C for 48 h; for psychrotrophic counts 7 C for 10 days, and for anaerobe counts the plates were incubated at 35 C for 48 h in an anaerobic cabinet (Electrotek Scientific, Shipley, U.K.).…”

“…If necessary, the isolates were stained for spore production using Schaeffer and Fulton's modification of the Wirtz method (Schaeffer & Fulton, 1933). Bacteria were then placed in taxonomic groups according to the identification keys as described by Linton et al (2003). The Acinetobacter/Moraxella group also included Moraxella-like bacteria, as described by Juni and Heym (1986).…”

Microbial shelf-life extension of chilled Coho salmon (Oncorhynchus kisutch) and abalone (Haliotis rufescens) by high hydrostatic pressure treatment

“…However, the conditions during storage determine which bacteria are responsible for spoilage (Linton, Mc Clements, & Patterson, 2003). Seafood's microflora from temperate-waters is dominated by psychrotrophic, aerobic, or facultative anaerobic Gram-negative, rod-shaped bacteria, and, in particular, by Pseudomonas, Moraxella, Acinetobacter, Shewanella putrefaciens, Flavobacterium, Cytophaga, Vibrio, Photobacterium, and Aeromonas (Hubbs, 1991;Lalitha & Surendran, 2006;Pantazi, Papavergou, Pournis, Kontominas, & Savvaidis, 2008).…”

Effect of high‐pressure treatments on mechanical and functional properties of restructured products from arrowtooth flounder (Atheresthes stomias)

“…HPP profitability improves for shorter processing times even when it requires a higher pressure. 6 Dong et al 7 found that the larvae of the nematode 10 found that 500 MPa for 2 min at 20 • C is a feasible treatment to inactivate psychrotrophic bacteria present in shellfish (mussels, prawns, scallops and oysters) reducing considerably the microbial count of vacuum packaged products stored at 7 • C for up to 28 days. These studies suggest the feasibility of using pressure levels higher than 400 MPa for less than 5 min to reduce microbial loads and thus expand the shelf life of restructured arrowtooth flounder products.…”