Optimization And Experimental Study On Vacuum Cooler For Cooked Food

China is the largest country in meat production.With the increase of per capita meat consumption in China,meat products are favored by more and more consumers.However,the backwardness of processing technology and equipment of cooked meat products has brought serious food safety problems.Among them,temperature is an important index affecting the processing and storage of cooked meat products.In order to make cooked meat products pass through the dangerous temperature band of bacteria and meet the storage requirements,vacuum cooling has developed rapidly in the food cold chain because of its rapid cooling and low energy consumption.Vacuum cooling is based on the principle of boiling evaporation of moisture in materials at low pressure to remove heat,which is generally suitable for materials with high moisture content.However,the inevitable mass loss caused by water evaporation has not been widely accepted by the commercial community.In order to further promote the development of vacuum cooling technology,scholars at home and abroad have studied a lot of optimization processes,such as mixed cooling.In the process of vacuum cooling,water supply,control of pressure reduction rate and cooling final pressure,immersion vacuum cooling and so on.However,there is a lack of vacuum cooler which can realize a variety of cooling processes at the same time.Therefore,on the basis of summarizing the experimental and theoretical research status of scholars at home and abroad in the field of vacuum cooling,this paper optimizes the design of a new type of cooked food composite vacuum cooler,and through different operation technology,The cooling process of boiled pork was studied experimentally.The main conclusions are as follows:(1)Air temperatures have great influence on the cooling time of cooked meat.When the cold air temperature is-10℃,the cooling time is 3725 s,and the weight loss rate is only 3.23%.The lower cold air temperature brings greater system energy consumption,is 1.11kW·h.(2)Different cold trap temperatures have significant effects on the final pressure of cooked meat during cooling.When the cold trap temperature is-15 ℃,-25 ℃ and-35 ℃,the final pressure in the vacuum chamber can reach 200 ±30 Pa,150 ±30Pa and 80 ±30 Pa,respectively.Therefore,different cold trap temperatures have different effects on the cooling rate of cooked meat,and it is not that the lower the cold trap temperature is,the better the cooling effect is.The vacuum cooling processes at-15 ℃,-25 ℃ and-35 ℃ are compared.The results show that the optimum temperature of the cold trap is-25 ℃,the cooling time is 320 s,the weight loss rate is 11.11%,and the energy consumption is 0.26 kW·h.(3)The cooling rate of vacuum cooling is obviously faster than that of cold air cooling.The cooling time of vacuum cooling with cold trap temperature of-25 ℃ is 320 s,which is more than 10 times faster than that of cold air cooling with cold air temperature of-10 ℃.The advantage of this time brings about energy saving,the former is about four times more energy-saving than the latter.(4)Mixed cooling can make up for the slow cooling rate of cold air cooling and the high quality loss of vacuum cooling at the same time.after comparing the experimental results of mixed cooling at 70 ℃,65 ℃ and 60 ℃,respectively,it is found that the mixed cooling can make up for the slow cooling rate and high quality loss of vacuum cooling at 70 ℃,65 ℃ and 60 ℃,respectively.When the air cooling temperature is 65 ℃,the cooling time is 1285 s,the weight loss rate is 5.88%,and the energy consumption is 0.38 kW·h.(5)The ultrasonic water-replenishing in the vacuum cooling process can reduce the quality loss of the cooked meat,and the negative effect generated is the extension of the cooling time and the increase of the energy consumption.The experimental results show that the cooling time of the water in the vacuum cooling process is 970 s,the weight loss rate is 5.35%,and the energy consumption is 0.54kW·h.