Isolation, Identification And Ultrasonic Sterilization Of Thermo-Acidiphic Bacteria (TAB) In The Processing Of Apple Juice Concetrate (AJC) Production

Nine thermo-acidiphilic bacteria which polluted AJC were isolated from major sections and environments of the native AJC production. Compared with the standard strain A. acidoterrestris 3922T and the already known isolated strain, three of them were systematically identified in terms of cell morphology, colony morphology, cultural characteristics and physiological characteristics. And their genetic status were confirmed by 16s rDNA sequencing and phylogenetic tree construction. The growth curves and the hazards of each strain to the quality of AJC were also confirmed. The utilization feasibility of ultrasonic sterilization in controlling the TAB were comprehensively evaluated by studying and discussing the effect of ultrasonic sterilization on each strain and the effect of ultrasonic treatment on the quality of AJC.The results showed,1. Nine thermo-acidiphic bacteria were successfully isolated from the major sections and environments of the native AJC production.2. Three thermo-acidiphic bacteria were systematically identified. They had great similarity with the standard strain A. acidoterrestris 3922T and the already known isolated strain in terms of cell and colony morphology, cultural and physiological characteristics. The comparison result of 16s rDNA sequence of each bacteria and their phylogenetic tree showed that the three strains belonged to the genus of Alicyclobacillus.3. The hazards of standard strain, isolated strain, H25, H30 and H33 on the quality of AJC were analyzed. Great depositions and odoriferous metabolites were formed in the AJC. Moreover, the soluble solid concentration and the total sugar concentration declined, the total acid concentration increased, the transmittance and the color value greatly reduced, which destroyed the quality of AJC badly.4. The ultrasonic sterilization was proved to have good effect on killing the TAB. And sterilizing dynamic models of each bacterium were also built in the thesis. The standard strain and the isolated strain were easier to be killed under lower power, while they were harder to be killed under higher power than H25, H30 and H33. And the latter strains were easier to be killed than the standard strain and the isolated strain under the same sterilizing time. 5. The ultrasonic treatment could make the total acid concentration reduced, and the total sugar concentration, the transmittance and the color value of AJC increased. The indexes could still be in accordance with the requirements of national standards for AJC except the transmittance. Furthermore, the effect of ultrasonic treatment on AJC quality was generally lower than the effect of TAB on AJC quality, which proved that the ultrasonic would be a choice for controlling TAB.