Dehydro Freezing .pptx

Dehydrofreezing

1. DEHYDRO FREEZING SUBMITTED TO Dr. Anil Kumar Chauhan DSFT, BHU.

2. INTRODUCTION Dehydro freezing is also known as the freeze-drying it is a method of preserving perishable materials such as food, pharmaceuticals, and biological samples by removing water from the material through the process sublimation. The process involves freezing the material to a very low temperature and then subjecting it to a vacuum. Under vacuum conditions, the frozen water in the material is converted directly from a solid to a gas (sublimation) without passing through a liquid phase. This leaves the material dehydrated and in a stable, freeze-dried state.

3. TRIPLE POINT OF WATER

4. FREEZE DRYERS Freeze dryers are large-scale dehydro freezing instruments that are commonly used in industrial settings. They work by removing water from food products through a process called sublimation, where ice is directly converted to vapour without going through a liquid phase.

5. INSTRUMENTATION OF FREEZE DRYER Freeze dryer chamber : This is the main component of a freeze dryer. It is a vacuum-sealed container where the product to be freeze-dried is placed. The chamber is equipped with shelves or trays that hold the product during the drying process. Vacuum pump: A vacuum pump is used to create and maintain a low-pressure environment in the freeze dryer chamber. This is essential for the sublimation process to occur. Condenser: A condenser is used to trap the water vapor that is removed from the product during the freeze-drying process. The water vapor is frozen onto the condenser coils and removed from the chamber, preventing it from re-entering the product

6. Temperature sensors: Temperature sensors are used to monitor the temperature of the product and the freeze dryer chamber during the drying process. This helps to ensure that the temperature is maintained within a safe range and that the product is not overheated. Pressure sensors: Pressure sensors are used to monitor the pressure within the freeze dryer chamber. This helps to ensure that the vacuum level is maintained at the appropriate level for the sublimation process to occur.

7. Control system: A control system is used to monitor and control various aspects of the freeze-drying process, such as temperature, pressure, and vacuum level. This helps to ensure that the process is carried out accurately and consistently. Heating source: A heating source, such as a heating coil, is used to provide heat to the product during the drying process. This helps to speed up the sublimation process and reduce the overall drying time. Overall, the freeze dryer instrumentation is a complex and precise system that requires careful monitoring and control to ensure the quality of the final product.

8. WORKING Pretreatment pre concentrate your product in normal dryer. Prefreezing -18°C TO -50°C Primary drying Application of vacuum reduce the boiling point of water. 30°C/24hrs. Secondary drying At 20°C Packaging Vaccum or inert gas .

9. TYPES OF FREEZE DRYER Different types of dryer are used depending on the materials to be dried. The dryers are c lassified as :- 1. Pilot freeze drying. 2. Industrial freeze drying a. Multi batch freeze dryers b. Continuous freeze dryers c. Tunnel freeze dryers d. Vacuum spray freeze dryers

10. PILOT FREEZE DRYERS Pilot freeze dryers mainly used for food laboratories and pharmaceutical industries. Since they are used to explore possibilities for the preservation of biological materials.

11. INDUSTRIAL FREEZE DRYERS Multi batch freeze dryers:- Utilization of resources is minimum in batch type dryers. So as to increase the utilization of available resources the multi batch freeze dryers are introduced with number of batch cabinets .

12. Continous freeze dryers The continuous type of dryers is economic in terms of labours, large capacity and to get uniform drying. Two types of continuous freeze dryers are available: 1. Static or tray in which the freeze dried products is stationary on trays. 2. Dynamic or trayless dryer, in which product is moved with belt conveyors.

13. Tunnel freeze dryer A tunnel type freeze dryer consists of large vacuum cabinet in which tray carrying trolleys are loaded at one end. The end is discharging end where the dried products are unloaded. Vacuum locks are fixed in each end of the dryer. Low pressure steam is used to heat the plates. In this type of dryers it is impossible to dry different type of food materials at the same time. Cottage cheese and coffee are the best examples for this method of drying.

14. Vacuum spray freeze dryers The product is sprayed from a single jet upward or downward in a cylindrical tower of 3.7m diameter by 5.5m height. The liquids solidify into small particles by evaporative freezing. The whole plant operates under a vacuum of about 67 Pa. Frozen particles obtained by spraying into a vacuum are about 150mm in diameterand loose about 15% of moisture in the initial evaporation. There is no sticking of the particles.

15. APPLICATIONS OF FREEZE DRYER IN FOOD INDUSTRY Coffee products The brewed coffee from ground beans is pre concentrated by evaporation and freeze dried immediately to prevent the large ice crystal. Then heat is applied for sublimation process and further drying. The entrapped vapour is remixed into the freeze dried coffee to enhance the flavor .

16. Fruits and vegetables Most of the fruits and vegetable are suitable for freeze drying process. For example strawberries should be sliced then loaded directly into trays, and dried with a temperature of 50 ° C. A drying time of 2hours is possible.

17. Mushrooms Wide varieties of mushrooms are preferred for freeze drying, pigmented varieties tending to shrink more. They should be peeled, sliced and blanched before being loaded into trays. With a platen temperature of 82 ° C, a drying time of 3 hours is possible.

18. Shrimp The pink varieties of shrimp are preferred to the brown for freeze drying. After cooking for 3 min, the shrimp is placed in the drying chamber in trays between platens. Best results are obtained with the platens at 52 ° C, which gives a drying time of 10h. Higher drying temperatures give a product which dries in 8 hours but rehydrates less well. The product quality is much lower at the higher temperature. Precooked salmon steaks 13 mm thick dry in about 9 hours with a temperature of 100 ° C.

19. Egg Liquid egg is mixed with stabilizers to a thick cream. The mix is then filled into trays to a depth of 10 mm and the product temperature reduced to -25 ° C. The complete drying stage is of the order of 9-10 hours and egg is left in the trays in the form of a crystalline porous cake. The egg is broken up and then sieved to a powder and packed in sacks.

20. WHY TO CHOOSE FREEZE DRIED FOODS?

21. ADVANTAGES OF FREEZE DRYING Retain taste, smell and texture Fewer loss of nutrients Reduce weight Fewer preservative Extended shelf life Rapid rehydration advantage.

22. DISADVANTAGES OF FREEZE DRYING Expenses Storing Select food

23. DEHYDRATED Vs FREEZE DRIED STRAWBERRY TOMATO MEAT

24. CONCLUSION The freeze drying process is expensive, which restricts its applicationon wide range in the food industry. New technical solutions are applied to modify the freeze drying process and make it time and cost effective. It is suitable for high value products with specific biological and phytochemical properties.

25. THANK YOU… REFERENCE Akers MJ, Fites AL, Robinson RL. Journal of freeze drying science and technology. Rambhatla S, Pikal MJ. Heat and mass transfer scale up issues during freeze drying. Roy ML, Shah S. Importance of freeze dried pharmaceuticals. SUBMITTED BY Shivansh Suman MSc. Food Technology DSFT, BHU.