Effect Of Ultra High Pressure Treatment On ACE Inhibitory Activity And Quality Of Lactobacillus Delbrueckii QS306 Fermented Milk

In this paper,ultra-high pressure technology is used to optimize the optimal process parameters of ultra-high pressure treatment of Lactobacillus delbrueckii QS306 fermented milk by using treatment pressure and treatment time as variables and ACE inhibitory activity of fermented milk as the detection index.Using untreated fermented milk and pasteurized milk(75?,15 s)as controls,the effects of ultra-high pressure treatment on the physicochemical,sensory,microbial,and antioxidant properties of fermented milk were detected and analyzed,and the fermented milk was observed at Changes in various indicators during storage.The main findings are as follows:(1)By treating the Lactobacillus delbrueckii QS306 fermented milk's ultra-high pressure treatment pressure and treatment time level as variables,the ACE inhibition rate was used as the detection index.The optimal process parameters for ultra-high pressure treatment were:pressure 400 MPa,holding time 10 min,At this time,the ACE inhibition rate of the fermented milk reached 86.79±0.17%.(2)After ultra-high pressure treatment,the free amino acid content of strain QS306 fermented milk was significantly increased,with 7 more species and 0.71±0.35mg/g.(3)The total number of lactic acid bacteria in the untreated fermented milk of strain QS306 was 1.1×107 CFU/mL.The number of lactic acid bacteria in the untreated fermented milk of strain QS306 was reduced to 7.0×104CFU/mL after the ultra-high pressure treatment,but its ACE inhibitory activity increased from 79.83 ±0.06%to 91.63 ±0.02%.Moreover,during the storage period,the increased number of lactic acid bacteria was positively correlated with the ACE inhibition rate.(4)Strain QS306 fermented milk after ultra-high pressure treatment of fermented milk during the period of storage,the apparent viscosity ultra-high pressure treatment group increased by 1.6 Pa.S,and with the extension of shear time presents the downward trend,finally remained stable,and the water holdup dropped to 39.63 from 41.70±0.25%plus or minus 0.22%,no whey separation pHenomenon,storage period of the treatment group was no significant loss in protein.(5)During the storage of fermented milk in each treatment group,the reddness and yellowness of fermented milk in the ultra-high pressure treatment group increased,while the brightness decreased.During the storage period,the brightness of fermented milk increased,and there was no reddening and yellowing.After ultra-high pressure treatment,umami taste and abundance increased significantly,while bitter taste and astringency decreased significantly,but there was no significant change during storage.Acidity and saltiness also declined in comparison with untreated groups.Ultra-high pressure treatment can increase the volatile aromatic substances.(6)During the storage period of each treatment group of strain QS306 fermented milk,the ACE inhibition rate of all the treated groups was significantly increased by 11.81±0.02%,while that of the pasteurization group was decreased by 2.01 ± 0.20%.During the storage period,the proteolysis ability of fermented milk increased from 1.208±0.03%to 1.392±0.01%.