Study On The Effect Of High Pressure Carbon Dioxide On Inactivation Of Bacteria Spores Accounted For The Spoilage Of Apple Juice In Coordination With Cofactors

The thermosensitive juices are usually disinfected by heat sterilization, suchas pasteurization, leadiing to a little loss on nutrition and flavor, but a short shelflife. And high temperature sterilization that may cause adverse impact to thenutrition and flavor of the juices, even though its excellent effect on sterilization.With the improvement on people’s living standard, food quality is required morestringently, so "Cold Sterilization" technology has certainly become the preferredalternative to instead of heat sterilization technology. As a new kind of "ColdSterilization" technology, high pressure carbon dioxide (HPCD) sterilizationtechnique can effectively kill bacterias, fungis in mild conditions to, it is muchbeneficial to keep original flavor and nutrition of food, meanwhile low cost, energyconservation, safe, non-toxic and so on.At present, how to effectively kill bacterial spores is the key difficulty onHPCD sterilization technology. Therefore, Alicyclobacillus acidoterrestris spores,which caused juices spoiled, were investigated as disinfecting object. And differentcofactors were tested on the efficacy of killing spores in the condition of HPCDtreatment, as well as the influence on the main physical and chemical indexs ofapple juice. The results showed that:1. The pressure, temperature and time of HPCD all affected the inactivationrate of Alicyclobacillus acidoterrestris spores, and the pressure was the mostsignificant impact factor. By orthogonal test, The optimized sterilization conditionwas pressure30MPa, temperature50°C, time70min, and the inactivation rate ofspores was only3.12.2. By HPCD treatments of adding four germination induction factors, theresults showed that, after the germination pretreatment at50℃for25min,L-alanine combined with HPCD treatment at60°C,30MPa,45min was the mosteffective on killing spores, the inactivation rate raised1.36compared with theblank control (only by HPCD), followed by inositol combined with HPCD, but thesynergy effect of vitamin B6is not obvious.3. By HPCD treatments of adding four natural antibacterial factors, the results show that, except chitosan, the other three antibacterial factors have synergy effectson inactivation of spores by HPCD. the synergy effect of lysozyme was the mostsignificant, followed by Nisin, the effect of cinnamyl aldehyde was inapparent.After further optimized experiments by lysozyme combined with HPCD, theinactivation rate reached to5.40orders of magnitude under the condition oflysozyme0.10g/kg, pressure25MPa, temperature45°C, time60min, increased2.30orders of magnitude compared with the blank group. In addition, by the tests of thehigh performance liquid chromatography and scanning electron microscopy, theresults showed that lysozyme combined with HPCD led to the spore core substance2,6-dipicolinic acid (DPA) leaked a lot, and some spores were totally crushed, atlast resulted in death of most spores.4. There was no significant change on the°Brix, pH, chroma, clarity of applejuices after HPCD treatment combined with lysozyme, and vitamin C of applejuices was maintained at70%-80%. And the juices still could meet therequirements of GB19297-2003Hygienic standard for fruit and vegetable juiceafter30d storage period at4℃. Compared with heat sterilization, HPCD treatmentcombined with lysozyme can better maintain the nutritional content in apple juicesand extend the shelf life.