Investigation And Control Of Pathogens In Dariy Products

Pollution levels of Salmonella and Enterobacter sakazakii in raw milk samples were investigated;the effect on sterilization using ultra-high pressure technology(UHP)combined with bactericidal substances was further studied.The results supplies the technical foundation for sterilization of raw milk by ultra-high pressure cold sterilization technique.423 raw milk samples were collected to investigate the pollution status of Salmonella and Enterobacter sakazakii.The results showed that there was no sample polluted by Salmonella and Enterobacter sakazakii.The minimum inhibitory concentration of two kind of antibacterial substances:?-polylysine and potassium sorbate to Salmonella and Listeria monocytogenes is 0.5 mg/mL;however,2 mg/mL ?-polylysine and 4 mg/mL potassium sorbate to the growth condition of Salmonella and Listeria monocytogenes are both no inhibition effert.Processing Salmonella in milk by 500 MPa UHP combined with 2 mg/mL?-polylysine,Salmonella was detected as 0 CFU/mL after 0 h cultivation,0 log CFU/mL after 6 h cultivation and 2.2 log CFU/mL after 12 h cultivation;Processing Salmonella in milk by 500 MPa UHP combined with 4 mg/mL potassium sorbate,Salmonella was detected as 0 CFU/mL after 0 h cultivation,0 log CFU/mL after 6 h cultivation and 2.6 log CFU/mL after 12 h cultivation;Processing Listeria monocytogenes in milk by 500 MPa UHP combined with 2 mg/mL ?-polylysine,Listeria monocytogenes was detected as 0 CFU/mL after 12 h cultivation;Processing Listeria monocytogenes in milk by 500 MPa UHP combined with 4 mg/mL potassium sorbate,Listeria monocytogenes was detected as 0 CFU/mL after 12 h cultivation.The cells after coprocessing were compared with the cells unprocessed and the cells after processing UHP.The results showed that the high pressure alone treatment portion of the cellular integrity of the cells sustained minor damage;integrity of cells after coprocessing was severely damaged and parts of cells were fragmented.The content of free thiol groups of protein in coprocessing milk was compared with which in unprocessing milk.The results showed no obvious difference between them.Digestive experiment in vitro showed that no significant difference was noted in protein digestibility of coprocessing milk as compared from unprocessing milk.