Research On The Processing Technologies Of Two Dried Fruits

Persimmon and pitaya are belong to the cold natures of fruits,rich in vitamins,minerals and dietary fiber.Pitaya has biological activities such as anti-oxidation,anti-aging,and free radical scavenging effect.Persimmon has the functions of tonifying spleen,relieving diarrhea,relieveing acough and stop bleeding.As an important raw materials of food processing,Persimmon and pitaya has great advantages in resources and development.After harvested,the fruits are still breathing intensity and easily perishable.Therefore,it is difficult to reserve them.However,these problems can be solve defficiently by drying the fruits.Intermittent microwave heating has the unique characteristics such as short drying time,high efficiency energy saving,high product quality and so on,therefore persimmon and pitaya could dry through intermittent microwave drying.Drying characteristics,kinetics model,drying process of persimmon and pitaya were studied.The main conclusions included the following gaspects:?1?The intermittent microwave drying characteristics and kinetic model tests of Pitaya slices showed that:Pitaya slices intermittent microwave drying process showed the acceleration,constant speed and speed down the three stag.The kinetics model of the intermittent microwave drying of pitaya slices satisfies the Page equation,and the predicted values agree well with the test results.?2?On the basis of single factor experiment,the optimum conditions of microwave intermittent drying of pitaya slices were determined by orthogonal test.There sults showed that the primary and second aryorder is:slice thickness,total drying time,intermittent ratio,microwave power.It was determined that microwave power was 280 W,intermittent ratio is 2,slice thickness of 3 mm and total drying time is 34 min was the optimum intermittent microwavedrying condition.?3?The shelf life tests of dried pitaya showed that:the water content,anthocyanin content,sensory evaluation of dried pitaya were gradually decreased under different temperature storage conditions.The total number of colonies and mould and total acidty increased gradually,and the higher the temperature,the faster the rise.The shelf life of the dried pitaya is 96 days at 25?,412 days at 4?.?4?Magnetic analysis and nuclear magnetic resonance imaging were used to analyze the water migration rule of persimmon slices in the intermittent microwave drying process.The experimental results showed that:In the persimmon slices,there are mainly three types of water,that is,free water,semi-combined water,the most closely bound water in persimmon slices.CPMG attenuation curve is closely related to microwave power.The water loss rate was gradually decreased under different microwave power conditions,and the higher the microwave power was,the faster the decline was.With the prolongation of drying time,the relaxation time of T₂ shifted to the left,and the total peak area continued to decrease.As the drying progresses,the moisture content of the persimmon slices is gradually lost from the outside to the inside,and the interior is finally dehydrated.The greater the microwave power,the faster the disappearance of H protons;In the late drying period,the water is concentrated in the inner layer of the persimmon slices.Due to the low water content,the imaging is blurry and the background color is basically close.?5?On the basis of single factor experiment,the optimum conditions of microwave intermittent drying of persimmon slices were determined by or thogonal test.There sults showed that the primary and secondary order is:total drying time,microwave power,intermittent ratio,loading capacity.It was determined that microwave intermittent drying parameters were microwave power was 560 W,intermittent ratio is 7,loading capacity is 1.8kg/m² and total drying time is 177 min was the optimum intermittent microwave drying condition.?6?The shelf life tests of dried persimmon showed that:the water content,sensory evaluation of dried persimmon were gradually decreased under different temperature storage conditions.The total number of colonies and total acidty increased gradually,and the higher the temperature,the faster the rise.The shelf life of the dried persimmon is 81 days at 25?,253 days at 4?.