Targeting shrimp spoiler Shewanella putrefaciens: Application of ε-polylysine and oregano essential oil in Pacific white shrimp preservation

To inhibit the activity of Shewanella putrefaciens, which is an important psychrotrophic spoilage bacterium in Pacific white shrimp, the effectiveness of ε-polylysine (PL) and oregano essential oil (OEO) against S. putrefaciens QY38 in broth and shrimp were evaluated. Under in-vitro conditions, the minimal inhibitory concentrations of PL and OEO against S. putrefaciens QY38 were 75 mg/L and 0.12% (v/v), respectively. At these concentrations, they could not only inhibit the proliferation of the strain and affect the microstructure, but also inhibit its proteolytic activity and the production of total volatile basic nitrogen (TVB-N). In-situ experiment, the combined treatment of PL + OEO inhibited the growth of the total viable counts in shrimp inoculated by S. putrefaciens QY38 from 9.11 log cfu/g (CK) to 6.35 log cfu/g. The TVB-N contents also maintained as low as 20 mg N/100 g during the whole storage period. The proton magnetic resonance images displayed that the preservatives could retard the water migration and moisture loss in shrimp muscle.