Study On Antibacterial Mechanism Of Plantaricin BM-1 And Control Of Listeria Monocytogenes In Cooked Ham

Because of its biodegradation security,bacteriocin has been used as a kind of natural safe food preservatives and got great attention.This research focused on antibacterial mechanism of plantaricin BM-1 and studied the control effect of different methods including alone and combined with physico-chemical treatments based on plantaricin on the control of L.monocytogenes in cooked ham.The main contents are as follows:(1)Antibacterial mechanism of plantaridn BM-1:For L.monocytogenes of 104CFU/mL and107 CFU/mL,the minimal inhibitory concentration(MIC)of plantaricin BM-1 were respectively 1.6AU/mL and 25.6AU/mL,and the minimal bactericidal concentration(MBC)of plantaricin BM-1 were respectively 204.8AU/mL and 2457.6AU/mL.Compared to control group,the MIC of plantaricin BM-1 could significantly increase change rate of electrical conductivity in bacterium suspension of L.monocytogenes,and the time needed to stabilize could be reduced 0.5 h.It could be intuitively observed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM)that cell membrane was damaged by plantaricin BM-1.Therefore,plantaricin BM-1 has bactericidal effect by destroying cell membrane.(2)Effects of two application methods of plantaricn on control of L.monocytogenes in cooked ham:Plantaricin BM-1 treatment(320,640,1280AU/g)significantly reduced the survival of L.monocytogenes compared with the control.The inhibitory effect of the plantaricin BM-1 at the same concentration on Z.Monocytogenes depended significantly on the application method.The inhibition effect of the same amount of plantaricin applied onto the surface of the ham on L.monocytogenes was significantly better than it incorporated into the meat batter.Even 320AU/g plantaricin applied onto the surface exhibited a gjreater inhibition of Z.monocytogenes than 1280AU/g plantaricin incorporated into the cooked ham at day 1,14,and 28.1280AU/g plantaricin applied onto the surface of the ham was the most effective,inhibiting the L.monocytogenes counts below the detection limit from the first day to the 21st day of storage.A conflicting result was obtained in which the inhibitory effect on the total bacteria counts of the plantaricin BM-1 incorporated into the meat batter was better than that of the surface application as measured by the inhibition of Z.monocytogenes,1280AU/g plantaricin incorporated into the meat batter was the most effective because it reduced the total bacteria counts from an initial bacterial counts to 2.76log CFU/g at the end of the storage period(lower 2.851og CFU/g than control).(3)Effect combined physico-chemical treatments(temperature,sodtiun nitrite,beat treatment,high a)hydrostatic pressure)based on plantaricin on the control of L.monocytogenes in cooked ham:a)1280AU/g plantaricin combined with refrigeration storage at 4? produced greater inhibition of Z.monocytogenes than the 5120AU/g plantaricin combined with refrigeration storage at 9?.b)The combined application of 5120AU/g plantaricin and 0.075mg/g sodium nitrite caused a reduction of 1.97log CFU/g compared to samples treated with 5120AU/g plantaricin alone.Therefore,the combination of plantaricin and sodium nitrite could not only reduce the concentration of nitrite,also enhance the inhibitory effect of plantaricin.c)5120AU/g plantaricin containing 0.075mg/g sodium nitrite and heating(60 ? or 2min)made counts of?L.monocytogenes below the detection line at 50 days of storage.Therefore,they had synergistic inhibitory effect on L.monocytogenes in the ham.d)Counts of L.monocytogenes in the samples treated with 5120AU/g plantaricin containing 0.075mg/g sodium nitrite and high hydrostatic pressure(600MPa for 5min)were reduced 5.79log CFU/g compared to untreated samples at the end of storage.Therefore,they had synergistic inhibitory effect on L.monocytogenes in the ham.