Controlled atmosphere and modified atmosphere storage
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Controlled atmosphere (CA) and modified atmosphere (MA) storage techniques precisely control or modify the storage atmosphere gas composition to extend the shelf life of perishable foods. CA continuously controls gas levels throughout storage, while MA gas levels change dynamically depending on produce respiration and packaging permeability. Both lower oxygen and raise carbon dioxide levels compared to air, inhibiting spoilage and decay. Optimal gas concentrations vary by commodity and can benefit foods by delaying softening, toughening, browning and retaining quality attributes like flavor and chlorophyll. Deviations from optimum levels risk physiological disorders or susceptibility to decay. While effective, CA requires precise temperature control and different settings for each food, making it more expensive than MA which uses semipermeable
Controlled atmosphere and modified atmosphere storage
- 1. Controlled Atmosphere and Modified Atmosphere Storage By Nungleppam Monica Food Process Engineering Indian Institute of Technology KharagpurIndian Institute of Technology Kharagpur
- 2. CONTROL ATMOSPHERE and MODIFIED ATMOSPHERE Control atmosphere (CA): generally refers to decreased O2 and increased CO2 concentrations, by a precise control of the gas composition. Modified atmosphere (MA): is used when the control of the storage atmosphere is not closely controlled, such as in plastic film packaging.
- 3. DIFFERENCE MA: Gas composition is modified initially and it changes dynamically depending on the respiration rate of produce and permeability of film or storage structure surrounding the produce CA: Gas atmosphere is continuously controlled throughout the storage period
- 4. Scrubbers are used in controlled atmosphere storage to absorb the extra amount gases present inside the packaging material. Scrubbers
- 5. Air contains: 21% O2 0.03% CO2. Modification of the atmosphere: O2 ↓ CO2 ↑ Increased the shelf-life of perishable foods
- 6. Main crop potatoes Celery Lettuces Carrots Leeks Soft fruit Asparagus Broccoli Spinach Banana Mushroom Respiration rate HighLow Short Long Shelf Life
- 7. Minimum O2 concentration tolerated(%) Commodities 0.5 Tree nuts,dried fruits,and vegetables 1.0 Some cultivars of apples and pears,brocolli,mushroom,garlic,onion,most cutor sliced(minimally processed)fruits and vegetables 2.0 Most cultivars of apples and pears,kiwifruits,apricot,cherry,nectarine,peach,plum,strawbery,papaya,pi neapple,olive,cantaloupe,sweet corn,green bean,celery,lettuce,cabbage,cauliflower.brussels sprouts 3.0 Avocado,persimmon,tomato,pepper,cucumber,artichoke 5.0 Citrus fruits,green pea,asparagus,potato,sweet potato Table 1: Fruits and Vegetables classified according to their tolerance to low O2 concentrations Fruits and vegetables differ in their tolerance to low O2 and to high CO2 concentrations.
- 8. Table 2: Fruits and Vegetables classified according to their tolerance to elevated CO2 concentrations Maximum CO2 concentration tolerated(%) Commodities 2 Apple(Golden Delicious),Asian pear,European pear,apricot,grape,olive,tomato,pepper(sweet),lettuce,endive,Chinese cabbage,celery,artichoke,sweet potato 5 Apple(most cultivars),peach,nectarine,plum,orange,avogado,banana,mango,papaya, kiwifruit,cranberry,pea,pepper(chilli),eggplant,cauliflower,cabbage,Bru ssels sprouts,radish,carrot 10 Grapefruits,lemon,lime,persimmon,pineapple,cucumber,summer squash,snap bean,okra,asparagus,broccoli,parsley,leek,green onion,dry onion,garlic,potato 15 Strawberry,raspberry,blakberry,blueberry,cherry,fig,cantaloupe,sweet corn,mushroom,spinach,kale,Swiss chard
- 9. Table 3: Controlled atmosphere conditions for some fruit species Species Best Temp. (°C) RH(%) O2 (%) CO2 (%) Time Avocado 7 90 2-3 3-10 2 months Cherry 0 95 3-10 10-12 30 days Kiwi 0 98 2 4-5 7 months Nectarine -0.5 95 2 5 50 days Peach -0.5 95 2 4-5 40 days Plum 0 95 2 5 45 days
- 10. Table 4: Controlled atmosphere conditions for some vegetable species
- 11. BENEFICIAL EFFECTS OF PROPER CA STORAGE: delayed softening and mealiness (apples, pears, tomatoes), delayed toughening (asparagus), chlorophyll retention (apples, pears, leaf vegetables), insect control- O2(< 1%) and/or elevated CO2(40 to 60%)
- 12. BENEFICIAL EFFECTS OF PROPER CA STORAGE: inhibition of the browning of cut surface(cut fruits and vegetables), better flavour retention (pineapple, cabbage), reduction of disorders and decay (berries), Higher nutritional value after storage (vitamin C).
- 13. DETRIMENTAL EFFECTS OF CA (above or below optimum composition for the commodity): May cause irregular ripening of fruits (banana, mango, pear, and tomato, at O2 below 2%, CO2 above 5% for > 1 month). May cause certain physiological disorders. May enhance anaerobic respiration and development of off-flavors. May cause susceptibility to decay.
- 14. Table 5: Examples of CA injury
- 15. STORAGE DISORDER Low O injury₂ Internal CO injury₂ (Brown heart) Low temp. breakdown External CO injury₂
- 16. DISADVANTAGES It is quite expensive. Temp. control required. Different gas composition for each type of product. Special operation and operator training required. Once pack opens or leaks the benefits are lost.
- 17. RECENT DEVELOPMENTS IN CA STORAGE Recent improvements include maintaining CA during transport in refrigerated marine containers. CA transport of banana permits the harvest at a more fully-mature stage. In addition to CA, there is also a continuing increase in the use of plastic films and MAP.
- 18. MODIFIED ATMOSPHERE PACKAGING (MAP) Modified Atmosphere Packaging (MAP) involves the modification of the head space gas in a package in order to prolong the shelf life of the product it contains. The greatest use of MAP is for fresh-cut products (to maintain 2-5% O2 and 8-12% CO2). It is possible to improve gas control in MAP by adding absorbers of ethylene, carbon dioxide and oxygen.
- 19. O absorber:-₂ Iron powder is used commercially as the active ingredient. Ex. FeO, Fe O , Fe O₂ ₃ ₃ ₄ CO absorber:-₂ Lime(freshly hydrated high calcium lime (Ca(OH) ),activated charcoal,₂ magnesium oxide) Ethylene absorber:- Potassium permanganate, builder clay powder, hydrocarbons, silicones
- 20. TWO TYPES Active modification The atmosphere is modified by pulling a slight vacuum and replacing the packaging atmophere within the desired gas mixture. Passive modification Modification is achieved by respiration of commodity within the package and depends on the characteristics of the commodity and the packaging film.
- 21. Passive modification Product packaged with selected film Desired atmosphere develops naturally over time Takes longer to achieve desired atmosphere in package Active modification Displace or remove gases in package Replace with mix of desired gases and seal Better shelf life is achieved with Active Modification
- 22. CONCLUSIONS A strong preservation of quality and nutritional value is demonstrated by CA storage with a lowering of O2 and an enhancement of the CO2 concentrations. This results in: better quality after storage a longer storage period a longer shelf-life period after storage a higher nutritional value after storage(vitamin C) a more environmental friendly storage(no postharvest chemical treatments against scald are needed).
- 23. Thank you