The Effect Of Different Heat Treatment On Milk Sterilization Based On PCR-TGGE Technology

There are a large number of microorganisms in fresh milk,sterilization by heating is an important means of modern dairy processing,however,especially the excessive heating heating sterilization sterilization will cause damage to the milk protein,vitamins and other nutrients,and cause dairy nutrition loss.Heat sterilization process and technical parameters of the current dairy processing process,are the traditional microbial pure culture technique for obtaining and evaluating based on,as in recent years the metagenomics technology and the rapid development of the people on the microbial awareness has been raised to a new level and stage.Studies have shown that the traditional pure culture technology can only observe less than 1%of the actual micro-organisms,and more than 99%of the microorganisms in fact we have ignored in the past.In the formulation of the sterilization intensity and process parameters of dairy products,the existence of the vast majority of microorganisms was ignored.Therefore,how to use modern methods of metagenomic technology,based on milk technology and parameters of different heating sterilization modified heating sterilization process and parameters to obtain more objective and accurate,to minimize the thermal loss of nutrients in milk,energy saving and emission reduction,has important significance in practical production.In this study,a large dairy enterprises acquisition standard fresh milk as raw material in the laboratory,respectively,dairy production line,using microwave pasteurization,high-temperature short-time different heating sterilization were determined by the total number of bacteria,microbial genome macro in the samples of traditional pure culture technology and PCR-TGGE technology,comparative analysis of the bactericidal effect.At the same time the milk samples of dairy enterprises inspection indexes were determined.The result shows:1.Different sterilization sterilization conditions of 33 groups of milk bacteria showed different degrees of decline,the total number of bacteria decreased obviously,the same total number of bacteria and higher intensity of sterilization groups,selected 9 microwave sterilization,9 laboratory pasteurized long low temperature sterilization,7 dairy production's short-time high temperature sterilization conditions of chin,a total of 25 treatments were extracted before and after sterilization conditions in microbial metagenomics,PCR-DGGE by denaturing gradient gel electrophoresis and 16S rDNA sequencing and homology comparison,analysis,to further determine the bactericidal effect of each treatment group.2.Different microwave sterilization research shows that with the increase of temperature and intensity of microwave sterilization of milk at the end of pure culture microbial quantity decreased gradually,in order to achieve the requirements of drinking milk,TGGE results showed that the main microbes present seven strains can be found,although the total number of colonies that sterilization conditions meet the requirements,but by TGGE the detection can be found,including E.coli.Under the conditions of 700W,the best sterilization conditions were obtained when 38S was heated2.Different microwave sterilization research shows that with the increase of temperature and intensity of microwave sterilization of milk at the end of pure culture microbial quantity decreased gradually,in order to achieve the requirements of drinking milk,the final temperature of sterilization at 27 ?,while the microwave intensity and treatment time is not the same,but the detection of microorganisms in samples for milk seven,and included Escherichia coli;and in the final sterilization temperature is three degrees Celsius in a sample of 100,with other bands are different,but on behalf of Escherichia coli bands disappeared.From the point of view of environmental protection and practical application,the conditions of sterilization are best when heating 38S under the condition of 700w.3.Under the condition of low temperature and long laboratory pasteurization studies showed that with increasing time and temperature,pure culture microbial quantity in general is reduced,but there is too long resulting in waste of energy and nutrient loss.Analysis of TGGE fingerprints showed that when the degree of sterilization was insufficient,there were Pseudomonas harmful microorganisms in milk,and the number of microorganisms in pure culture was too high.The best conditions in the premise of economic and environmental protection under the laboratory conditions for pasteurized milk is heated 45min at 62 DEG C,if the milk quality have higher requirements,can use 65 degrees Celsius,68 degrees is 45min or 30min.4.Under the condition of low temperature and long laboratory pasteurization studies showed that with increasing time and temperature,pure culture microbial quantity in general is reduced,but there is too long resulting in waste of energy and nutrient loss.With the combination of the physical and chemical indicators of the determination results can know,in ensure some sterilization effect on sterilization can select lower intensity,select 72 ? for15s or 95 ? for 5 s can reach the traditional sterilization purposes,but also can reduce the milk nutrition,energy saving and emission reduction.Therefore,the proposed laboratory small scale sterilization of milk,can be used under 62 ? for 45min heating by microwave sterilization,if you can choose 38S heating under the condition of 700W,the sterilization temperature reaches 100 ?.Short-term high temperature sterilization treatment,treated at 72 ? for 15s or 95 for 5s.