Preervation by Low Temperature
2 likes617 views
This document discusses preservation of food by refrigeration. It describes how refrigeration slows spoilage processes by autolysis and microbes. There are two main refrigeration methods - cool storage and frozen storage. Cool storage preserves food by controlling humidity, ethylene levels, and chilling injury through temperature control between 0-13 degrees Celsius depending on the food. Frozen storage fully preserves food by storing it at temperatures below freezing. The document also notes that about 30% of fruits and vegetables in India are wasted due to gaps in the cold chain, insufficient storage, lack of refrigeration near farms, poor transportation, and limited processing infrastructure.
Preervation by Low Temperature
- 1. PRESERVATION BY LOW TEMPERATURE REFRIGERATION MUNNA IYPE JOY BTF-11-222 IICPT
- 2. REFRIGERATION ● One of the first application of mechanical refri. Was to preserve food Refrigerated storage Cool Storage Frozen storage
- 3. COOL STORAGE Sources of spoilage in a harvested product – ●autolysis ● microbes ● rodents, ● worms, ● mechanical damage. ● Refri. Doesnt make any irreversible changes. ● Slows down all kind of spoilage processes.
- 4. REFRIGERATED GAS STORAGE ● In addition to low temp., Gas composition control (CO2 and O2). ● It increases shelf life. ● If CO2 level goes beyond critical limit, internal physiological breakdown leading to rotting. ● Soln is wrapping the fruits with tissue paper impregnated with colourless odouless mineral oil.
- 5. Factors considered I.Control of humidity II.Control of ethylene III.Control of chilling injury IV.Temperature
- 6. I. Control of humidity ● Uses direct expansion system ● Refrigerand inside coils expands by absorbing temperature from product. ● Temp. Gradient causes water loss. ● Indirect expansion is preferred. ● Control of RH is important for long term storage of commodities.
- 7. II. Control of ethylene ● Ethylene is a plant hormone which induces ripening and senescence. ● Ripended fruit emits more ethylene. ● Hence it should not be stored with unripen fruits which are sensitive to ethylene. ● Usually ventillation is provided in order to remove ethylene. ● If ventillation is not feasible, ethylene can be destroyed by oxidation.
- 8. II. Control of ethylene contd.. ● Potassium permanganate held on an inert substrate is generally used for this pupose. ● UV light is also an industrially used alternative. ● The intermediate compounds formed during ozone formation destroys ethylene. ● Research about catalytic converters is being done( Platinum).
- 9. III. Control of chilling Injury ● Chilling injury dependent on temperature and time of exposure to that temp. ● Early stages of chilling injury are reversible. ● Some products tolerate chilling injury without symptoms if the time of exposure is short. ● There are a number of methods available to limit chilling injury.
- 10. III. Control of chilling Injury contd.. These include ● Stepwise reduction in storage temp. ● Intermittent warming during storage.
- 11. IV. Temperature ● Temperature control helps to prevent chilling injury ● Storage temperature varies from product to product. ● Each 10 deg rise results in doubling of rate of enzymatic reactions and microbial spoilage.
- 12. Temp & RH for some produces PRODUCE TEMPERATURE( deg c) RELATIVE HUMIDITY Apple -1-4 90-95 Avocado 7 85-90 Black berries -0.5-0 90-95 Grapes(American) -0.5-0 85 Jackfruit 13 85-90 Beans,dry 4-10 40-50 Broccoli 0 95-100 Carrots, mature 0 98-100 Cucumber 10-13 95 Okra 7-10 90-95
- 14. PART II REASON FOR POST HARVEST LOSSES IN INDIA
- 15. LOSSES ... ● About 30% of f&v grown in India gets wasted ● 40 million tonnes ● 13 million US $
- 16. Losses due to.. ● Gap in cold chain ● Insufficient storage capacity ● Unavailability of cold storages near farms ● Poor transportation facility ● Lack of processing technology and facility
- 17. Sites of losses Harvest Preperation Preservation Processing Storage Transportation
- 18. REFERENCES Wisemax & Lockhart, Fruits and vegetable preservation, p 138-139 Lisa kitinoja& A. Kader, 2003, Small scale post harvest hhandling practices: A manual for horticultural crops, 4th edition, p 133-138 Chilukuri Maheswar, Post harvest losses due to gaps in cold chain in India- A solution, 2006
- 19. Thank You