Design Of Cool Storage Device With Nature Cold Resource And The Quality Change Of Paddy

As one of the staple grain crops,paddy sustains one-thrid population of the world at present,which is also an important source of carbohydrates.However,high quality paddy is rarely found in the market,and domestic consumers purchase is mostly broken rice.In addition to paddy varieties and processing factors,paddy drying methods and storage mode which currently used in our country are the main cause of the high rate of broken rice.Paddy can easily generate stress cracks during the high temperature drying process,which affects eating quality and selling price of paddy.During storage process,paddy can easily aging,infested with mould or insects,which will reduce paddy storage quality.In order to enable consumers to buy good edible quality rice,this study plans to research a low temperature storage paddy method to store high moisture paddy which can reduce paddy quality loss in storage process,and to improve the paddy storage quality and decrease paddy losses caused by drying.Based on these aspects,this paper proposes to adapt nature cold resource to store high water moisture content,based on analysising the advanced technology within domestic and foreign.In this paper,we independently developed a low temperature storage warehouse for paddy by using nature cold resource,with the aim to keep high edible quality of paddy.The change moisture regulation and storage quality of paddy during storage process are studied.To validate the feasibility of nature cold resource warehouse which can keep the high-moisture paddy,and the optimal storage process parameters are determined.In this paper,the main research issues and conclusions are obtained as follows.?1?Experimental study on paddy moisture and quality change law under different storage environmentsIn order to study the feasibility of storing high-moisture paddy by using nature cold resource and realize the transformation from traditional paddy drying and regular paddy storage method to storage paddy with nature cold resource.Static weighing method was used to study the effect of different ambient humidity and temperatures on the moisture rate of paddy,and the effect of different storage temperature on the quality of high-moisture paddy was also tested.The regression equations between storage conditions,including ambient temperature and relative humidity to the changing pattern with time on the moisture content of paddy under absorption and desorption conditions is established.5 models that describe the equilibrium moisture of paddy in absorption and desorption process are selected to fit the equilibrium moisture data of paddy.On the basis of the above,MCPE equation wad determined as the optimal model that will be used as the theoretical basis for judging paddy moisture content during storage period.The result of high-moisture paddy storage test indicates that:Storage temperature can affect the storage quality of high-moisture paddy significantly;the higher moisture content paddy,the quicker paddy quality will decrease.The result showed that 20%moisture content of paddy was stored in 0?and outdoor with average temperature was-9.6?,which had better quality than those stored in other temperature conditions.After 150 days storage,the mold amount were3.9×10³ CFU/g and 1.0×10⁴ CFU/g,respectively;their final fat acid value were 10.9 KOH mg/100g and 15.9 KOH mg/100 g,and their germination percentage were 92.25%and 90.5%,respectively.In order to ensure paddy storage quality and reduce the power consumed during paddy storage,the initial paddy moisture for storage should be reduced and storage temperature should be increasing in the following tests.?2?Design and testing of nature cold resource paddy storage warehouseAccording to paddy storage characteristics,nature cold resource paddy storage warehouse which used the nature ice for providing cold energy to stored high moisture paddy was designed,which including storeroom,ice storing room,heat exchange system,ventilation system and control system.Analysis regarding the influence on cooling capacity by face velocity,cold water flow,water inlet temperature was conducted,based on CCD approach in Design-expert 8.0.Then regression model would be established,leading to the best set of parameters with the optimum operation parameter of nature cold resource warehouse heat exchange system is:face velocity 2.5m/s,cold water flow 0.8 m3/h and water inlet temperature 4?.?3?Optimization paddy storage experiment of natural cold resources paddy warehouseIn order to determine the optimal paddy storage conditions for natural cold resources paddy warehouse and achieve the requirement for low power consumption,the optimization experiment was designed in 2 factors with 3 levels,i.e.3 storage temperature levels?5?,10?and 15??and3 paddy moisture content levels?15.0%,16.5%and 18.0%,?.A suitable combination of storage temperature and rice storage moisture content was obtained by cluster analysis.The regression equation of the mold count,fat acid value,germination percentage,?-amylase activity and catalase activity were established by SPSS software.In consideration of paddy storage quality and ice consumption,the optimal storage conditions for natural cold resources paddy warehouse are determined by cluster analysis method as below:initial paddy moisture content was 16.5%and the paddy storage temperature was 10?.After 150 d storage experiment under this condition,total mold count was 5.9×10⁴ CFU/g,fat acid value was 19.89 KOH mg/100 g,germination percentage was 86%,?-amylase activity was 0.682 U and catalase activity was 7.28 U.?4?Optimization paddy storage experiment of natural cold resources paddy warehouseIn order to verify that the natural cold resources paddy warehouse can ensure paddy storage quality,according to the early optimization result,verification test was chosen paddy with 16.5%moisture content,storage temperature was 10?,and the paddy was packaged and set up as cross-flow well type ventilation stacks in natural cold resources paddy warehouse.The test result indicates that the average temperature of natural cold resources paddy warehouse and the average paddy temperature were both reached 9.8?.After 153 days storage,The total mold count was5.1×10⁴ CFU/g,fat acid content was 18.3 KOH mg/100 g,germination percentage was 86.75%,?-amylase activity was 0.533 U and catalase activity was 6.27 U,paddy moisture decreased slowly from 16.5%to 15.1%which achieved the optimal moisture for rice milling.Compared with paddy which stored,the rate of husked rise and head rice yield of paddy stored in natural cold resources paddy warehouse were 5.41%and 9.57%higher,the crack rate was 13.88%lower,and yellow rice was not detected.?5?Economic analysis of natural cold resources paddy warehouseTaking large warehouse as the example,it was reconstructed by putting polyurethane panels to become a low-temperature large warehouse which can use nature cold resource to refrigerate the high moisture content paddy,the coefficient of thermal conductivity of warewhous wall was 0.239W/?m²·K?.After calculation,the total cost of large warehouse reconstruction and equipment was CNY 230,400.Compared with the refrigeration of grain chiller,using nature cold resource to store paddy can save power consumption 5,737.7 kW·h,power rates of CNY 4,972 and coal of 2.3 t.The newly natural cold resources paddy warehouse was able to reduce CO₂ emission by 5.72 t.Compared with traditional drying and regular storage methods,using nature cold resource to store paddy increase income from paddy by RMB 170 per ton.Therefore,the nature cold resource warehouse to store paddy possessed broad space for development.