Experiment And Study On Air Conditioning Storage And Fresh-keeping Of Iron Persimmon

As a large agricultural country,China has a wide variety of agricultural products,and its output ranks first in the world all the year round.However,due to improper preservation technology of fruits and vegetables in the storage and transportation process,a large number of fruits and vegetables are rotted and wasted,resulting in serious losses.Iron-sheet persimmon,a traditional tomato type in Northeast China,is considered as the aristocrat among fruits with green shoulder,sweet and sour taste,and high nutritional value.However,its storage system after harvest is not perfect,and it is easy to soften and age.Air-controlled storage is an advanced method for storing fruits and vegetables at present,but it is seldom used in postharvest storage of persimmon fruits,and the appropriate gas ratio of persimmon fruits is unknown.Therefore,it is of great significance to carry out the experiment and research on air controlled storage of iron persimmon.In order to effectively inhibit post-harvest metabolism of fruits and vegetables,it is necessary to precool them after harvest.Storage quality of fruits and vegetables also depends on the rapid or not precooling and the appropriate temperature.In order to avoid Browning caused by low temperature,persimmon fruit should be precooled to 5?.In order to improve the air-conditioned storage efficiency of persimmon fruits,based on the thermal physical properties of each layer of persimmon fruits,the internal heat transfer characteristics of persimmon fruits in the pre-cooling process were simulated and verified by experiments with FLUENT software,which provided a theoretical basis for accurately predicting the pre-cooling time and temperature field changes.At the same time,the suitable conditions of persimmon fruit gas storage were thoroughly studied.Therefore,this paper carries out research from the following aspects:(1)A mathematical physical model of stratified heat transfer in persimmon precooling process was established,and the stratified thermal physical parameters and convective surface heat transfer coefficient of persimmon were determined,which provided theoretical and data support for the simulation of persimmon precooling temperature field;(2)On the basis of the above,the FLUENT simulation of persimmon pre-cooling process was carried out to study the temperature field changes in the pre-cooling process,and the experimental verification was carried out.Through experiments and simulations,it was found that the skin of persimmon fruit was responsive to the external temperature faster,while the temperature of the inner layers of persimmon fruit showed different degrees of lag.At the same time,it was found that increasing the air flow rate could shorten the precooling time,and for fruits and vegetables with obvious internal structure differences,the stratified heat transfer model could reduce the error to the maximum extent;(3)In order to explore the optimum temperature and gas volume ratio for persimmon fruit storage,the experiment of air-controlled storage was carried out on persimmon fruit after pre-cooling.Compared with the persimmon fruits of other storage methods,the respiration intensity of persimmon fruits was significantly inhibited by the air-conditioned storage,and there was no persimmon fruit rotted during the storage period.Different storage conditions were set through the experiment,sensory degree,respiration intensity,weight loss rate and other indicators were analyzed,the temperature was single-controlled,and the optimal air-controlled storage temperature of iron persimmon was 0?.It was found that the optimal storage environment for persimmon fruit was 3%O2+5%CO2.