Effects Of Ultra High Pressure Treatment On Microbial Inactivation And Quality Of Koumiss

The study uses ultra high pressure treatment of different pressure modes,different holding time and different temperature of sample,by analyzing and evaluating the effect of sensory,microorganisms,quality changes and taste of koumiss.The best conditions of ultra high pressure koumiss sample was selected refrigerate stored at 4?.Periodically detect microorganisms,acidity,viscosity and color of koumiss.Meanwhile analyzed the change of tendency.The results were showed as follows:(1)After 400 MPa for 10 min by ultra high pressure treatment koumiss,the total number of bacterial colonies decreased significantly.The lethally rate of microorganisms reached above 99.82%,the indexes of sourness,astringency was decreased,Sweetness,saltiness and umami increased,so ultra high pressure treatment has the function of improving taste.Moreover,the ACE inhibitory activity of koumiss significantly increased after the ultra high pressure treatment.(2)Single pressure(400?600 MPa)and alternate pressure(400+600 MPa?500 +600 MPa)treatment the results show that,single pressure was obviously better than alternate pressure.Then the best conditions of single pressure was 600 MPa.(3)Under 600 MPa pressure for different time(5?10?15 min).The research showed that sourness,activity of ACE and reducing activity of koumiss was decreased gradually with the increased of holding time.But the extent of color change was increased.Microorganisms,viscosity,taste had no significantly change.The best processing sample was at 600 MPa for 5 min.(4)Koumiss was treated by ultra high pressure(600 MPa 5 min)refrigerate storage the results show that microorganisms were slowly growth.It can be see ultra high pressure can extended shelf-life.Its acidity was gradually increased during storage.At the same time,the color of koumiss had no obviously change.(5)After koumiss of different temperature(20?40?60?)was treated by ultra high pressure(600 MPa 5 min).The total bacterial colonies were slowly increased with the storage time expand during 4? storage.It is said that combine sample temperature with ultra high pressure treatment still have pressure-proof bacterial.