Mechnism Of Moisture Loss Of Apple In Hyo-on Storage Under The Weak Differential Pressure

Hyo-on storage is a new generation of fresh-keeping technology in fruits andvegetables, which has the advantages of maintaining the structural integrity of fruit andvegetable cells, effectively restraining respiration of fruit and vegetable, applying to widescopes and pollution-free. In this paper, the Hyo-on storage experiments and numericalsimulations carried out under different conditions, using Fuji apple as experimental material,the Hyo-on storage experiments was carried out under four experimental conditions inwhich the humidity is85,85,65and65, corresponding with the wind speed of3m/s,2m/s,1m/s and0m/s, respectively. Meanwhile, another experiment was conducted underlaboratory conditions. Measuring parameters include freezing point, water loss rate,respiration intensity, hardness, relative electric conductivity.Hyo-on storage is a new generation of fresh-keeping technology in fruits andvegetables, which has the advantages of maintaining the structural integrity of fruit andvegetable cells, effectively restraining respiration of fruit and vegetable, applying to widescopes and pollution-free. In this paper, using Fuji apple which is porous plant material asthe research object by the Hyo-on storage experiments and numerical simulations twomethods to study the freezing point, the rate of loss water, respiration rate, hardness,relative conductivity and other parameters mainly. Clarify the mechanism of water flow inthe macro and the micro under the weak differential pressure, focus on the water flowphenomena and rules of fruits and vegetables and other porous media, to realize the Hyo-onstorage optimization and control.Experimental studies include four Hyo-on storage experiments which are the humidityare85%and65%, respectively, corresponding to the wind speed are3m/s,2m/s and1m/s,0m/s; Meanwhile, another experiment was conducted under laboratory conditions.Numerical simulation （COMSOL4.5）studies include photomicrograph of different appleparts (0.25R,0.5R,0.75R,0.95R and skin) cell tissue structure which using microscopeto get, porosity, fractal dimension calculation. Using Adobe Photoshop7.0software, Matlaband AlgoLab Photo Vector software make the flesh sliced of apples in0.25R,0.5R,0.75R,0.95R and skin locations into apple internal porous structure graphwhich COMSOL4.5can cognitive, to establish physical model and mathematical model ofFuji apple, to simulate the apple in the pressure field and velocity field in the process ofwater loss using COMSOL4.5software.Experimental studies indicate that:1, Freezing temperature: Fuji apple’s freezing temperature is1.5℃, freezingtemperate(T) range is form0℃to-1.4℃.2, Rate of loss water: With increasing Hyo-on storage time of Fuji apple, the rate of loss water of the apple showed a trend of gradual increase; the minimal rate of loss waterappears on the experimental group with the humidity of85%, the wind speed of3m/s,which is3.205%.3, Respiration intensity: With increasing Hyo-on storage time of Fuji apple, therespiration intensity of the apple showed a trend of first decrease and then increase, thereare twice respiratory peak appeared during storage. The experimental group of85%humidity,3m/s the wind speed has the minimum respiration intensity values. Compare withthe control group, the respiration intensity in the experimental groups of apple reduced by15%.4, Hardness: With the increase of Hyo-on storage time of Fuji apple, the hardness ofthe apple showed a trend of gradual decrease. Apple hardness in Four groups of Hyo-onstorage experiments change slightly, the maximum hardness is2500g, the minimum is1234g, compared with the control group, it increased by about45%.5, Relative conductivity: With increasing Hyo-on storage time of Fuji apple, therelative conductivity of the apple showed a trend of gradual increase; the experimentalgroup of85%humidity,3m/s the wind speed has the minimum relative conductivity changeand the minimal tissue damage of apple; while the experimental group of65%humidity,1m/s wind speed has the maximum relative conductivity change and the maximum tissuedamage of apple. Compare with the control group, the relative conductivity in theexperimental groups of apple reduced by12%~20%.Numerical simulation studies indicate that:1, Fuji apple is porous media and has fractal characteristics.2, With the increase of apple radius, porosity first decrease and then increase, skinparts of porosity is the largest.3, The fractal dimension increases as porosity increases and decreases as porositydecreases. Capillary pressure increases as porosity decreases and decreases as porosityincreases. Permeability increases as porosity increases and decreases as porosity decreases.4, Apple’s internal capillary differential pressure and water flow rate in theexperimental group of85%humidity,3m/s wind speed is less than that of85%humidity,3m/s wind speed experimental group; The greater the capillary pressure difference, thegreater the flow velocity.5, Apple’s internal water flow velocity in the central is the maximum, the part near thefruit pits water flow velocity take the second place, and the part of peel is the minimum.In summary, Fruits and vegetables are porous media with fractal structure, internalorganizational structure of the fruit and vegetable plays an important role in the dehydrationprocess. Fuji apple in Hyo-on storage, the rate of loss water greatly affected by humidity, the greater the humidity, the less water loss rate; respiration rate affected by humidity andwind speed is not very obvious; hardness affected by humidity and wind speed is not veryobvious; relative conductivity greater affected by humidity, the greater the humidity, thesmaller the relative conductivity changes. It is feasible to simulate the water flow process inirregular micro porous structure using COMSOL4.5software, the flux of loss water and thevelocity of water flow calculated by numerical simulation is close to that of theexperimental value. In conclusion, this study provides a certain universality theoreticalbasis for technology of Hyo-on storage which applied to fresh fruits and vegetables andprocess optimization.