In the experiment of spray drier we have discussed the general principle of drying process. It depends on mainly the relative humidity change of a product. While the processing the humidity of sample is decreasing. In the machine there are some important parameters like inlet and outlet temperatures, flow rate of liquid and the air. In order to determine the flow rate we have looked up the velocity of air with kumpas. Also cross sectional area is needed for the determination of flow rate. It was measured by anamometer. We have measured the wet bulb and dry bulb temperatures with psyhrometer.

In our experiment we have used onion liquid to make it powder.However,we have come up some diffuculties.In spray drier,nozzle is the dispersion device but onion liquid was so dense that nozzle couldn’t disperse liquid and it was stopped by dense liquid particules.If we had used atomizer instead of nozzle,we would have been able to disperse liquid through spray drier reqularly without having any problem.

Also when we got onion powder,we measured moisture content of powder by using moisture analyzer and it was nearly 65%.When we compared moisture contents of powder and liquid we saw that moisture contents were nearly the same value.This was unusual because moisture content of powder was expected to be lower than that of liquid.This might result from wet powder,waiting of powder in laboratory environment for a while and powder might absorb some moisture from environment.These could be reasons why moisture contents were nearly the same.Neverthless,moisture content of powder should be around 5-10 % in certain circumstances.

Consequently, spray driers can be used for many food products and by using spray drier,we produce powders and we can use these powders for preparation of foods easily without consuming time and taste will be nearly the same with original products.
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Tray dryers and their developed forms, tunnel dryers are equipments, which found many applications in food operation operations during dehydration of foods. All the drying characteristics of foods can be observed in these equipments.

A typical drying procedure was applied with tray dryer to investigate properties of tray dryers, its advantages or disadvantages, drying kinetics of foods that are dried in tray dryers. For these purposes, equilibrium moisture content, drying rate, mathematical and experimental drying time were calculated with some engineering formulas. Wet pepper was used as sample for this aim.

The result demonstrated that the most important parameters in drying of foods by tray dryer, which affect the time and the quality of food, are temperature and velocity of air, moisture content of food and surface area that is exposed to heated air.

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