Study On The Optimization Of Apple Puree Bacteria Reducing Technology & The Quality Changes During Storage

In the production process,there are some important problems of apple puree such like the residue of the cleaning agent,poor cleaning effect,low utilization of cleaning water.The traditional heating causes apple puree's nutrients lose and produce cooking odor.About the cleaning of apple,it takes different cleaning measures and study the cleaning and water-saving effect.About the problem of apple puree' s nutrients loss in traditional heating process,it starts a study of taking high density carbon dioxide to have a cold sterilization technology to apple puree.The results are as follows.This study compares tap water,sodium hypochlorite,electrolytic water,ultrasonic cleaning's effect of Escherichia coli removing rate on apple surface.The result showed that 5 times of raw materials electrolyzed water cleaned 6 times of apple,the cleaning' s effect of Escherichia coli removing rate on apple surface is 99.4%,which is high 27.5%than sodium hypochlorite.If we treat the antibacterial rate greater than 99.5%as the clean standard,tap water can' t reach this standard.The water consumption of sodium hypochlorite solution,water electrolysis and ultrasonic were 5,1 and 1.67 L/kg of apple,respectively.Electrolytic water cleaning can save water 80%compare with sodium hypochlorite cleaning.Therefor,electrolytic water' s effect to remove Escherichia coli on apple surface is better than other 3 types measures.Electrolytic water can not only reach the removal rate of E.coli on the surface of apple was as high as 99.4%after cleaning after 6 times,there is no chemical residues and it can save water 80%compare with sodium hypochlorite cleaning.The dense phase carbon dioxide treatment(DPCD)was applied to hold the quality of the fresh apple puree.The effect of DPCD pressures,time and temperature on sterilization efficiency and total color change of the fresh apple puree were investigated.And then the response surface methodology was used to optimize the DPCD parameters.The results showed that the optimal DPCD parameters were the DPCD pressure of 20 MPa at 40 ? for 45 min.Under the optimal conditions,the total colony count of the fresh apple puree was reduced by 99.4%with the total color change of 0.94.The dense phase carbon dioxide technology was used to sterilize apple puree to maintain the quality of apple puree.Study on the effect of dense phase carbon dioxide treatment pressureon on the quality of apple puree.The results show the higher treatment pressure,the greater sterilization ability towards apple puree,when the pressure was 25 MPa,the total colony counts in apple puree decreased by 89.1%,while the total phenol content was increased,ascorbic acid content was only reduced by 12.4%;According to the electronic nose analysis,5-20 MPa treatment of apple puree flavor has no significant influence.Therefore,the usage of 20 MPa dense phase carbon dioxide technology can be the most effective technology to maintain the quality of apple puree flavor.At the same time,this work investigated the effects of dense phase carbon dioxide treatment temperature and time on the quality of apple puree.The results showed that the flavor and total phenol content of apple puree did not change significantly with the temperature of dense phase carbon dioxide treatment increasing.When the temperature is high to 30 ?,the ascorbic acid content is reduced to 427.3 mg/100 g,and the pH is 3.61 close to the time when the temperature rises tyo 10?.With the processing time of dense phase carbon dioxide technology,the flavor and pH value of apple puree remained relatively stable,the total phenol content was 1.84 mg/g?1.86 mg/g,and the ascorbic acid content decreased by 25%when the treatment time was prolonged to 60 min,345.8 mg/100g.To sum up,DPCD process apple puree can not only effectively sterilize,but also maintain the original flavor,overcome cooking flavor as well as Maintain the Vc and total phenol content in apple puree.The 4? storage effect of maintaining apple puree quality is better than 25 ? storage.In the last phase,25 ? apple puree has a lower storage ascorbic acid content,titratable acid content and pH than 4 ?storage.The total colony counts of 4 ? storage was 55.6%lower than that at 25 ?.90 days apple puree flavor at 4 ? storage changed less than 25 ? storage for 25 days,and 4 ? storage of apple puree is much fresh and still has apple puree property,even 60 days later,there is no significant sensory quality changes.If we treat microorganisms as the main evaluation criteria,4 ? storage under the condition of sterilization processing for 30 mins,the group of apple puree can be stored for 60 days.when the sterilization treatment lasted for 45 mins,the apple puree group can be stored for 75 days.To extend the time of 15 min processing that can extend the shelf life of 4 ? for 15 days.25 ? storage under the condition of sterilization 30 min,this group of apple pulp can be stored for 18 days,45 min sterilization treatment group of apple pulp can be stored for 21 days,extend the processing time 15 min.the shelf life of 25 ? is extended for 3 days.