Modified and Controlled Atmospheres for the Storage

Modified atmosphere (MA) and controlled atmosphere (CA) technologies have great potential in a wide range of applications. The increasingly global nature of food production and the increased emphasis on reducing chemical preservatives and pesticides have put the spotlight on these centuries-old technologies. Yet until now, there have been very few current resources available, and none have covered all aspects.

Modified and Controlled Atmospheres for the Storage, Transportation, and Packaging of Horticultural Commodities explores the science and application of the modified atmosphere (MA) and the controlled atmosphere (CA). It covers all technological applications, including storage, transport, and packaging for all fruits, vegetables, and ornamentals of temperate, subtropical, and tropical origin. Tracing the historical developments of these technologies, it provides information on the ideal conditions to be used for many horticultural commodities. It also outlines the effects of MA and CA on the physiology and biochemistry of these commodities as well as on their flavour and quality.

Providing the most comprehensive resource on all basic and applied aspects of these technologies, the text also reviews the vast amount of literature already written on this topic. This extensive work captures, for the first time, the entire subject of MA and CA, presenting a complete review of the technological aspects of this important development in food safety and preservation.

The controlled atmospheric storage in higher CO2 and lesser O2 are maintained is most significant contribution in storage technology. If storage done with refrigeration, it gives growth to respiratory activity and delay softening, yellowish, quality change, etc. The important factor of storage is tolerance susceptibility to injured vegetables increasing CO2 and decreasing O2.

The work on controlled atmosphere storage started in England in 1927 by kid and West. Modified atmosphere does not differ in principle from controlled atmosphere. In this the produce is held under the atmospheric condition by package, over wrap, box liner or Pallet cover. The two produce and the concentration of CO2 and O2 more benefit can be obtained by controlled atmosphere storage in apple. Among tropical fruits, the best storage of mangoes is 5% CO2 and 5% O2 at 13 0C.

Improved appearance can get by controlled atmosphere storage the O2 level was 2 % and bellows this level it is harmful slight benefit with papaya were stored in 5% CO2 and 1% O2 for 2 days at 13% C. Ripening can be delayed for months by holding banana in 1-10 % O2 and 5-10 % CO2 commercial controlled atmosphere recommendation cannot be given in case of citrus fruits.

Advantages of Controlled Atmosphere Storage:

i) Control all types of micro-organisms.

ii) Chilling injury and other physiological disorders.

iii) Black heart in potato

iv) Cost of equipment and operation

v) This is less popular in India.

Perishable food storage

Cold storages are meant to preserve the perishable commodities of food items for a longer period with retention of the original colour, flavour and taste. However, each commodity or item has certain life and they cannot be stored even in a cold storage for indefinite period. Storage beyond certain period may not be economical as well since payment of rent of cold storage increases the cost of the item. Hence, cold storages are used for high value items or when prices crash down due to bumper crop or for such items which are grown during the season but there is a demand round the year or for products like meat, fish or milk products which are quickly perishable.

PRODUCT Cold storages are being used for preservation of many food products since long. Their location has to be strategic and they should have easy access. Cold storages have demand all over the country. This note primarily looks into the prospects in Assam. Assam grows many varieties of fruits and vegetables. Consumption of meat, fish, chicken etc. is also on the higher side. Hence, a cold storage unit seems to have good scope.

MARKET POTENTIAL

Demand and Supply Location is a very critical aspect for the success of cold storage. It should be in close proximity of growing area as well as market and at the same time should be easily accessible for heavy vehicles round the year. Uninterrupted power supply is yet another pre-requisite.

Marketing Strategy Many fruits and vegetables like pineapples, apples, plums, oranges, potatoes, brinjals, cauliflowers etc. are grown in Assam. Likewise, consumption of meat, chicken, fish etc. is also Substantial. Hence, there is a good scope for a cold storage unit. A possibility of storing some milk products may also be explored. Different items are stored during different times requiring different temperatures. Hence, there is a need to divide total storage space in different temperature zones depending upon local needs.

MANUFACTURING PROCESS

A proper market analysis would throw light on storage needs and accordingly tentative plan for the whole year has to be drawn. Compressors suitable for using ammonia have to be selected as ammonia is cheap, easily available and is of high latent heat of evaporation, but it is highly toxic in nature if mixed with oil containing high carbon percentage. Hence, handling and maintenance has to be very careful. Rooms with different temperature requirements must be properly insulated and protected from moisture. On outside walls, one coating of foam with vapour proof material is advisable. Temperature and humidity is maintained according to the items stored. Use of skewed door arrangements, proper insulation and required circulation of cool air inside the storage area would make operations economical and improve profitability.

Silos

A silo (“pit for holding grain”) is a structure for storing bulk materials. Silos are used in agriculture to store grain (see grain elevators) or fermented feed known as silage. Silos are more commonly used for bulk storage of grain, coal, cement, carbon black, woodchips, food products and sawdust. Three types of silos are in widespread use today: tower silos, bunker silos, and bag silos.

Tower Silos
Storage silos are cylindrical structures, typically 10 to 90 ft (3 to 27 m) in diameter and 30 to 275 ft (10 to 90 m) in height with the slip form and Jump from concrete silos being the larger diameter and taller silos. They can be made of many materials. Wood staves, concrete staves, cast concrete, and steel panels have all been used, and have varying cost, durability, and airtightness trade-offs. Silos storing grain, cement and woodchips are typically unloaded with air slides or augers. Silos can be unloaded into rail cars, trucks or conveyors.
Tower silos containing silage are usually unloaded from the top of the pile, originally by hand using a silage fork, which has many more times than the common pitchfork, 12 vs 4, in modern times using mechanical unloaders. Bottom silo unloaders are utilized at times but have problems with difficulty of repair.

Bunker Silos

Bunker silos are trenches, usually with concrete walls, that are filled and packed with tractors and loaders. The filled trench is covered with a plastic tarp to make it airtight. These silos are usually unloaded with a tractor and loader. They are inexpensive and especially well-suited to very large operations.

Bag Silos

Bag silos are heavy plastic tubes, usually around 8 to 12 ft (2.4 to 3.6 m) in diameter, and of variable length as required for the amount of material to be stored. They are packed using a machine made for the purpose, and sealed on both ends. They are unloaded using a tractor and loader or skid-steer loader. The bag is discarded in sections as it is torn off. Bag silos require little capital investment. They can be used as a temporary measure when growth or harvest conditions require more space, though some farms use them every year.

Bins

A bin is typically much shorter than a silo, and is typically used for holding dry matter such as concrete or grain. Grain is often dried in a grain dryer before being stored in the bin. Bins may be round or square, but round bins tend to empty more easily due to a lack of corners for the stored material to become wedged and encrusted.
The stored material may be powdered, as seed kernels, or as cob corn. Due to the dry nature of the stored material, it tends to be lighter than silage and can be more easily handled by under-floor grain unloaders. To facilitate drying after harvesting, some grain bins contain a hollow perforated or screened central shaft to permit easier air infiltration into the stored grain.

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