Study On The Mechanism Of ?-ray Combined With Cinnamon Essential Oil On Shewanella Putrefaction

Due to high protein content and fragile tissue texture,aquatic product is more easily corrupted with the action of microorganism.Shewanella putrefaciens,one kind of specific spoilage organism?SSO?with prominent ability of corruption,can produce H₂S and reduce trimethylamine oxide?TMAO?.Seeking for effective methods of restraining the growth of SSO to keep the freshness of aquatic products are an important research field,which had a significant social and economic role.In present study,the combined effects of gamma irradiation and cinnamon oil on the microbial inhibition and quality of snakehead inoculating with S.putrefaciens stored at 4oC were investigated.Subsequently,the action mechanism of gamma irradiation and cinnamon oil on S.putrefaciens including the antimicrobial effect against S.putrefaciens,the membrane permeability,the membrane protein and fatty acid changes,and the transfer and change of the major components of cinnamon oil in S.putrefaciens was studied.The main results and conclusions are as follows:?1?The effects of cinnamon oil,?irradiation and the combination of them on the quality of snakehead incubated with S.putrefaciens during 4oC storage were investigated.Cinnamon oil and?irradiation used alone can exhibit antibacterial effect against S.putrefaciens,and with the increase of the concentration of essential oils and the dose of?irradiation the antimicrobial activity of them enhanced.During storage,the combined application of cinnamon oil and?irradiation can keep the aerobic plate count?APC?,total volatile basic nitrogen?TVB-N?,thiobarbituric acid reaction substances?TBARS?within a lower level.It can be concluded that the combination application of cinnamon oil and?irradiation can effectively inhibit the growth of S.putrefaciens,thus to maintain the freshness of the snakehead,the oxidation of fatty acid of fishes was accelerated.?2?The viability of S.putrefaciens treated with?irradiation and cinnamon oil was investigated.The minimal inhibitory concentration?MIC?of cinnamon oil was0.35?L/mL,The D₁₀ of?irradiation acted on S.putrefaciens was 0.133 kGy.The D₁₀reduced and RIS increased with the increase of the concentration of essential oils.The RIS of S.putrefaciens with 0.35?L/mL cinnamon oil is 2.38 times than irradiation used alone.The effect of the control group?CK?,0.080 kGy?irradiation?G?,0.175?L/mL cinnamon oil?C1?,0.080 kGy?irradiation and 0.175?L/mL cinnamon oil?C1+G?,0.35?L/mL cinnamon oil?C2?on the S.putrefaciens'viability were investigated.The combination of?irradiation and cinnamon oil exhibited a better effect on inhibiting the growth of S.putrefaciens than?irradiation or cinnamon oil used alone,and higher concentration of cinnamon oil displayed more effective antimicrobial activity against S.putrefaciens.?3?The effect of the combination of cinnamon oil and?irradiation on membrane of S.putrefaciens was investigated.Compared with G and C1,C1+G exhibited an obvious destruction on the cell morphology.The ATP_in reduced and ATP_outut increased more obviously than C1 and G.Meanwhile,the pH_in of S.putrefaciens reduced more significantly than C1 and G.In addition,the effect of the combination of cinnamon oil and?irradiation on the membrane protein was more obvious,resulting in reduction of40 kD and increase of 18 kD.Compared with the CK,the main membrane fatty acids of S.putrefaciens treated with C1+G reduced significantly,especially in C14:0,C16:0,C16:1,C17:1,C18:1?p<0.05?.In conclusion,the combination application of cinnamon oil and gamma irradiation can exhibit greater destruction on the morphology and membrane permeability of S.putrefaciens leading to the changes of membrane protein subunits and fatty acids,which damaged the normal physiological activities.?4?The transfer and change of the major components of cinnamon oil in S.putrefaciens treated with cinnamon oil and?irradiation was investigated.A large portion of the extracellular cinnamaldehyde of C1,C1+G,C2 was metabolized to cinnamyl alcohol?p<0.05?in nutrient broth.The intracellular cinnamaldehyde of C1,C1+G,C2 unchanged dramatically before and after the treatments,but they were less than that in 0.175?L/mL cinnamon oil without S.putrefaciens?CC1?and 0.35?L/mL cinnamon oil without S.putrefaciens?CC2?respectively.The transformation of cinnamaldehyde in C1+G was similar to C1?p?0.05?.In conclusion,there were some kind of interaction between S.putrefaciens and cinnamon oil,cinnamaldehyde was transformed into cinnamyl alcohol with the action of S.putrefaciens,while the growth of S.putrefaciens was inhibited by cinnamon oil.