The Study Of The Influence Of Dense Phase CO₂ On The E. Coli Protein

Dense phase CO₂ is a non-thermal method which has received considerable attention for potential applications in a number of food processing fields because of the advantage of low tempreture, non-residual, no contamination and nutritional. But there was few investgation about the mechanism of bactericidal especially the study about dense phase CO₂ on the cell protein which can cause the death of microorganisms.This article investigated the change of total protein and soluble protein of E. coli in order to exploring the mechanism of the bactericidal.The influences of dense phase CO₂ on the total protein and alkali-soluble protein of E. coli was studied by SDS-PAGE analysis and the inactivation curve of E. coli. The results showed that the solubility of E.coli alkali-soluble protein(pH8.0) was significantly decreased when E. coli was inactivated by dense phase CO₂.But there was no change of the species and content of total protein of E.coli after dense phase CO₂ treatment. The content of alkali-soluble protein was decreased when the survival rate of E. coli was 2.8% after 30min treatment at 37℃and 10MPa, and the survival rate of E. coli and the content of alkali-soluble protein was not more decreased when the pressure was increased up to 50MPa.The survival trend of E. coli was consistent with the change of the solubility of alkali-soluble protein under the different temperature and treating time of dense phase CO₂. The survival rate of E. coli and the content of alkali-soluble protein dropped off with the increase of treating time or temperature,but there was no change of the species and content of total protein of E. coli. The increasing temperature could strengthen the denaturalization and insolubility of E. coli alkali-soluble protein more obviously than increasing pressure.This article sdudied the influences of dense phase CO₂ on the molecular weight distribution of E. coli acid-soluble protein, soluble protein and alkali-soluble protein by gel-filtration chromatography. The result showed that the percentage of each molecular weight range changed significantly after dense phase CO₂ treatment with different pressure at 37℃,the alkali-soluble protein of 89.8-53.1KDa dropped to 50.2% from 63.6%, the alkali-soluble protein increased to 27.2% from 24.5%, the alkali-soluble protein of 28.7-13.1KDa increased to 22.6% from 11.8%.We studied the influence of dense phase CO₂ on the protein secondary structure by fourier transform infrared spectroscopy and CD,the results showed that theα-helix and the corner could change toβ-pleated after different pressures (10-50MPa,37℃,30min) dense phase CO₂ processing, when the pressure was 50MPa, the content ofβ-pleated was 75.63% which increased 26.7% more than control.