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    Inhibitory effects of high pressure processing on Photobacterium phosphoreum and Morganella psychrotolerans in vacuum packed herring (Clupea harengus)
    (Blackwell Publishing Ltd, 2018) Ucak I.; Gokoglu N.; Toepfl S.; Galanakis C.M.
    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 °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. Practical applications: 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. © 2018 Wiley Periodicals, Inc
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    Inhibitory effects of high pressure treatment on microbial growth and biogenic amine formation in marinated herring (Clupea harengus) inoculated with Morganella psychrotolerans
    (Academic Press, 2019) Ucak I.; Gokoglu N.; Kiessling M.; Toepfl S.; Galanakis C.M.
    Inhibitory effects of high pressure processing (HPP) on the biogenic amine formation (histamine, tyramine, putrescine and cadaverine) in marinated herring fillets (2% acetic acid+8% NaCl; or 4% acetic acid+8% NaCl solutions) were investigated. Marinated fillets were inoculated with M. psychrotolerans followed by vacuum-packaging and HPP treatment at 100, 300 and 500 MPa for 5 and 10 min. One batch was left untreated for each marination group and the batches were stored at 4 °C for 3 months. HPP in combination with 4% acetic acid had a strong inhibitory effect on the growth of M. psychrotolerans, since there was no growth in samples treated with 300 MPa for 10 min and 500 MPa for 5, 10 min. Psychrophilic bacteria growth was not detected in samples marinated with 4% acetic acid and treated with 500 MPa H2S-producing bacteria were not observed in marinated herring during the storage period. Histamine and cadaverine formation were not observed in the samples marinated with 4% acetic acid along the storage. Taken together, the findings of this research might be helpful to enhance the safety of consumption of marinated herring. © 2018 Elsevier Ltd