Detection And Study Of Alicyclobacillus Spp And Heat Resistant Mould From The Concentrated Fruit Juice

Alicyclobacillus spp,also called as thermophic acidophlic bacteria(TAB),can survive heat treatments in the juice processing,causing unfavorable odds and spoilage of juices.Alicyclobacillus is therefore an important target micro-organism in the juice processing.In the international trade,strictly require the content of Alicyclobacillus is smaller than 1 per 10 mL concentrate fruit juice.But in our country,the research on isolation and detection for Alicyclobacillus are few,and only focus on the apple juice.Therefore,it's necessary to reaearch the isolation,and identification of Alicyclobacllus in production line it's also great significance to or juice production of our country and the import-export trade.The research studies the finished juice products of different batches from the production line,the raw materials for concentrated juice,as well as sugar and water,the results of the study are shown in the following:(1)Citric-acid-adjusted YSG nutrient medium was chosen and has been cultivated for 2-5 days under 45? to serve as the nutrient medium for the separation of Alicyclobacllus in the juice.(2)The research adopts the optimized routine detection method and MPN method to detect 24 batches of concentrated juice raw materials,and the detection rate by MPN was as high as 87.5%,and 43 strains of suspected Alicyclobacllus were obtained through separation.With the use of 16 S rRNA gene sequencing,those strains were proved to be Alicyclobacllus,among which there was 1 strain of A.acidiphilus,4 strains of A.mali,9 strains of A.vulcanalis,3 strains of A.acidoterrestris,and the rest of them were all A.acidocaldarius and its subspecies.(3)During the research,we found out that heat-resistant moulds also survived the high temperature short time(HTST)sterilization in the juice processing.The detection rate was as high as 53.3% with the detection and identification of the heat-resistant moulds in 15 batches of concentrated juice.Then,28 S rDNA gene sequencing was adopted to identify the species of moulds,and as a result,most of them were eupenicillium and talaromyces,as well as a few IrPex Cacteus,Trametessp and Capnodiales sp.(4)The characteristic research on the regular strain A.acidoterrestris ATCC49025 and the typical separated strains showed that: The growth of A.mali COJI3-2 is similar to the growth of A.acidocaldarius subsp ROJD1-1,both of them barely grow under pH1.73 and pH6.20,and they grow vigorously under pH5.05,and entered the logarithmic phase of rapid growth after 7-37 h,however the growth of A.vulcanalis T4-2 is similar to the growth of A.acidoterrestris ATCC49025,barely grow under pH1.73 and pH6.20,and they grow vigorously under pH2.91,and entered the logarithmic phase of rapid growth after 7-19 h;the guaiacol of the separated strains of A.acidoterrestris and A.vulcanalis generated guaiacol,while the separated strains of A.mali didn't.The result of A.acidocaldarius subsp still remains unsure;the taste of the juice that has been inoculated with the regular strains didn't change much with only an increase of sourness.