Heat Sterilization Technology

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Heat Sterilization Technology

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1. Heat Sterilization (Technology) FDSC 3305, Principles of Food Engineering Pawan S. Takhar Animal and Food Sciences Texas Tech University

2. Retorting Types of Containers used in the retorts: Metal cans Glass jars or bottles Flexible pouches Rigid trays

3. Exhausting Removal of air from the headspace of containers

4. Reasons for Exhausting To prevent air expansion with heat. Helps to remove distortion of containers Removal of oxygen prevents internal corrosion in containers Removal of oxygen prevents oxidative changes in foods

5. Principle of Exhausting Gases occupy greater volume at a higher temperature

6. Methods Used for Exhausting Containers Hot filling the food Cold filling the food and then heating the container and contents with partially sealed lid Applying vacuum to remove air Flushing the cans with steam

7. Methods Used for Heating Containers Saturated steam Hot water Flames

8. Saturated Steam Venting: Flushing the retort with incoming steam to remove air from the retort Reason for removing air from retort: Air forms a thin boundary layer around containers, which reduces heat transfer from steam to containers

9. Steam processing It may be difficult to heat solid and highly viscous foods. Cooking for longer time to attain desirable temperature at thermal center may cause overcooking. Therefore, to increase heat transfer Containers are agitated Thinner containers are used

10. End over End Agitation of containers

11. Steam processing

12. Heating by Hot Water Used for mainly glass containers, flexible pouches and polymer trays Glass containers are thicker and have lower thermal conductivity Hot water provides lower thermal shock to containers than steam Flexible pouches and polymer trays are thinner. Therefore, they can be heated more rapidly

13. Heating by flames Used mainly for small cans

14. Three steps in retorts Pre heating Sterilization Cooling

15. Retort Equipment Batch type Horizontal or vertical

16. Continuous Retort Equipment Hydrostatic coolers

17. Continuous retorts

18. Advantages and Disadvantages of Continuous retorts Advantages: 1. Gradual changes in pressure and temperature. 2. Less strain on cans Disadvantages: 1. High capital investment 2. Breakdown will stop the process line

19. Variables Monitored in Retorts Temperature of the raw material Temperature of steam Temperature of cooling water Processing time Heating and cooling rates

20. Ultra High Temperature/Aseptic Processing

21. UHT/Aseptic Processing Processing at a very high temperature for a very short time

22. UHT is used for liquid foods

23. Manufacturers of UHT Heat Exchangers Tubular APV, Nuova Frau Plate Stork, Alfa Laval Direct Heating Alfa-Laval, APV, Stork (steam-into-product) Electric resistance APV, Elecster heating (Ohmic)

24. Examples of liquid foods processed using UHT Milk Fruit Juices and concentrates Wine Cream Yogurt Salad dressing Ice Cream Mix Cottage cheese Baby foods Tomato products Soups and rice desserts

25. Principle of UHT For a given increase in temperature, the rate of destruction of micro-organisms and many enzymes increases faster than the rate of destruction of nutrients and sensory components.

27. A disadvantage of UHT In milk some enzymes such as proteases and lipases are more heat resistant They can cause flavor changes during prolonged storage

28. UHT Process conditions are independent of container size

29. Enzymes and probiotics with low heat sensitivity can be added to the Food After Sterilization

30. Retorting (Canning) Vs. UHT (Aseptic Processing

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