Protective Effect Of D-fructose On The Structure And Key Substances Of Bacillus Subtilis Spores Treated With PATS

In the past decade,pressure-assisted thermal sterilization(PATS)has gradually become a commonly used sterilization technology in industrial production.However,recent studies have found that food ingredients can affect the effect of physical sterilization,and food ingredients(protein,fat,salt,and minerals)have a greater impact on pressure-assisted thermal sterilization,resulting in less effective sterilization than expected.D-fructose is also a common ingredient in food,but the effect of D-fructose on the killing of spores by PATS is not clear.Therefore,this paper takes Bacillus subtilis spores as the research object.In the joint physical field of PATS treatment of Bacillus subtilis spores under pressure and temperature,different concentrations of D-fructose are added for research,and the effect of D-fructose on Bacillus subtilis spores under PATS treatment is comprehensively analyzed..The main research content and results are as follows:(1)Effects of different concentrations of D-fructose on spores treated with PATSThis chapter studied the changes of Bacillus subtilis spore survival,OD600 value,leakage of intraspore,conductivity of supernatant and DPA leakage rate under the treatment of PATS combined with D-fructose.The results showed that PATS treatment alone had obvious inactivation effect on Bacillus subtilis spores,and the inactivation effect of different concentrations of Dfructose on PATS treatment significantly decreased.D-fructose weakened the bactericidal effect of PATS treatment on Bacillus spores in a certain sense.The detection results of OD600 value,leakage of intraspore substance and conductivity of supernatant showed that D-fructose could protect Bacillus subtilis spores under PATS treatment,and the higher the concentration of D-fructose,the better the protective effect.(2)Effects of different concentrations of D-fructose on the morphology and structure of spores treated with PATSThis chapter studied the changes of spore microscopic morphology,inner membrane permeability,particle size,fatty acid content and other indicators before and after PATS treatment with different concentrations of D-fructose.The results showed that the multilayer structure of spores was damaged after PATS treatment,and the damage of Bacillus subtilis spores under PATS treatment was significantly weakened after adding D-fructose.D-fructose had obvious protective effects on the permeability of spore inner membrane and spore size.After 200 MPa and 600 MPa treatment,the contents of C13:0,C14:1,and C15:0 three fatty acids decreased to varying degrees compared with the untreated group.After adding D-fructose,the fatty acid content of Bacillus subtilis spores treated with PATS increased significantly compared with PATS alone,and Dfructose had an obvious protective effect.(3)Effects of different concentrations of D-fructose on the key substances of spores under PATS treatmentThis chapter studies the changes of Na+/K+-ATPase,Ca2+/Mg2+-ATPase,SDH enzyme,nucleic acid,protein and membrane phospholipid in spores after PATS treatment.The results showed that the enzyme activities were all reduced to varying degrees.However,D-fructose could protect the activity of spore enzymes under PATS treatment.The results of infrared spectroscopy showed that the membrane phospholipids,proteins and nucleic acids of the spores treated with PATS changed significantly.PATS treatment led to the decrease of the α-helical structure of the spore protein and the increase of the random coil structure.When D-fructose was added,PATS had no effect on the This effect of protein secondary structure gradually weakens.At the same time,D-fructose also has the same protective effect on spore membrane phospholipids and nucleic acids.The detection results of the fluorescence spectrum showed that the positions of the fluorescence peaks of the spores after PATS treatment had blue shifts in different degrees.After adding D-fructose,the shift of the fluorescence peaks of the Bacillus subtilis spores under the PATS treatment decreased,and the fluorescence intensity was lower than that of the PATS treatment alone.Enhanced,closer to unprocessed state.It indicated that D-fructose effectively protected the protein structure of Bacillus subtilis.(4)Effect of D-fructose on the kinetics of PATS killing sporesThis chapter studies the bactericidal kinetics of D-fructose combined with 600 MPa-65℃/75℃treatment on spores under different holding times.From the perspective of fitting parameters,the Weibull model has a higher coefficient of determination(R2),so the Weibull model has a relatively better fitting effect.Compared with the first-order kinetic model,Weibull model can better describe the inactivation of Bacillus subtilis spores under different concentrations of D-fructose under PATS treatment.