Abstract
Practical applications Herring fillets were inoculated with Photobacterium phosphoreum and Morganella psychrotolerans, vacuum packed and subjected to high-pressure processing (HPP) treatment (100, 200, 300, and 500 MPa for 5 min) or left untreated as controls. The samples were stored at 4 +/- 1 degrees C up to 21 days, and subjected to microbial quality evaluation. The results revealed that 500 MPa pressure treatment significantly (p < .05) delayed the growth of P. phosphoreum and M. psychrotolerans until 12th and 7th days of the storage, respectively, as compared to the controls. Total psychrophilic bacterial growth was not observed until 19th day of the storage in 500 MPa pressure treated herring fillets inoculated with both P. phosphoreum and M. psychrotolerans. In the samples inoculated with P. phosphoreum and treated with 500 MPa pressure, H2S-producing bacteria were not observed during 14 days for M. psychrotolerans, while for entire storage period for P. phosphoreum. High-pressure processing (HPP) is a nonthermal preservation technique that depends on the magnitude of the pressure, processing time/temperature, and product characteristics that allows microbial inactivation at low temperatures with mild changes in texture, color, and flavor of the product as compared to the conventional technologies. Targeted inhibition of specific spoilage bacteria rather than more drastic means inhibiting the total microflora may therefore be a useful approach to achieving lower rates of spoilage and may thereby extend shelf life. In this study, HPP treatment up to 200 MPa did not significantly (p > .05) affect the microbial growth of vacuum-packed herring fillets, but further higher pressure levels (300-500 MPa) were effective to inhibit the growth of microorganisms. Overall, the findings of this study suggested that HPP application of 300 MPa and above could help to industry for commercial production of microbiologically free fish and fish products.