Antimicrobial kinetics of nisin and grape seed extract against inoculated Listeria monocytogenes on cooked shrimps: Survival and residual effects

The antimicrobial effects of nisin (2000 IU/mL) and grape seed extract (GSE, 1%) against Listeria monocytogenes (SSA184, SSA97 and LM10) inoculated on cooked shrimps (Litopenaeus vannamei) were investigated. Notable reductions (1.7-1.9 log CFU/g reduction) of L. monocytogenes were observed after 15-min treatment of combined nisin and GSE while SSA184 showed the highest susceptibility to the activity of nisin and GSE as compared to other strains. The atomic force microscopy results indicated that greater morphological changes were found in combination treated cells of SSA184, whose width (0.47 mu m) and height (0.25 mu m) were decreased while the surface roughness (10.12 nm) was increased significantly (P < 0.05). Residual nisin and GSE further inhibited the listerial growth during storage (0.4-0.8 log CFU/g increment). Based on the fitting goodness, Weibull and Baranyi models were verified as the best ones to describe inactivation kinetics of L. monocytogenes and growth dynamics during storage, respectively. Additionally, the colour of cooked shrimpsafter combined treatment were not negatively affected and even protected during storage. In conclusion, the antimicrobial treatment of combined nisin and GSE could be a potential antilisterial strategy for shrimps.