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| <u>Room cooling: </u>produce is put into a cold (refrigerated) room<ref>FAO (2009) Horticultural Chain Management for Countries of Asia and the Pacific Region. [Online] Available from: http://www.fao.org/3/a-i0782e/</ref><br/> | | <u>Room cooling: </u>produce is put into a cold (refrigerated) room<ref>FAO (2009) Horticultural Chain Management for Countries of Asia and the Pacific Region. [Online] Available from: http://www.fao.org/3/a-i0782e/</ref><br/> |
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| <u>Forced-air cooling:</u> a fan is used to drive air through packed produce within a refrigerated room. The usage of the fan increases the cooling rate compared to basic room cooling. Produce should be packed and stacked in a way that allows air to flow through fast<ref>FAO (2009) Horticultural Chain Management for Countries of Asia and the Pacific Region. [Online] Available from: http://www.fao.org/3/a-i0782e/</ref> | | <u>Forced-air cooling:</u> a fan is used to drive air through packed produce within a refrigerated room. The usage of the fan increases the cooling rate compared to basic room cooling. Produce should be packed and stacked in a way that allows air to flow through fast<ref>FAO (2009) Horticultural Chain Management for Countries of Asia and the Pacific Region. [Online] Available from: http://www.fao.org/3/a-i0782e/</ref> |
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| '''Water cooling''' | | '''Water cooling''' |
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− | Uses water to take up the heat from harvested produce<ref>FAO (2009) Horticultural Chain Management for Countries of Asia and the Pacific Region. [Online] Available from: http://www.fao.org/3/a-i0782e/</ref>. | + | Uses water to take up the heat from harvested produce<ref>FAO (2009) Horticultural Chain Management for Countries of Asia and the Pacific Region. [Online] Available from: http://www.fao.org/3/a-i0782e/</ref>. Cold or chilled water is sprayed on produce or the produce is dipped into it. Water should be able to flow through the produce rather than around it<ref>FAO (2009) Horticultural Chain Management for Countries of Asia and the Pacific Region. [Online] Available from: http://www.fao.org/3/a-i0782e/</ref><span style="line-height: 1.5em; font-size: 0.85em;">.</span> |
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− | <u>Hydro cooling: </u>cold or chilled water is sprayed on produce or the produce is dipped into it. Water should be able to flow through the produce rather than around it<ref>FAO (2009) Horticultural Chain Management for Countries of Asia and the Pacific Region. [Online] Available from: http://www.fao.org/3/a-i0782e/</ref>. | + | <br/> |
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| + | '''Ice cooling''' <br/> |
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| + | Ice is used to remove heat from fresh produce. |
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| + | |
| + | {| border="1" cellspacing="1" cellpadding="1" style="width: 100%;" |
| + | |- |
| + | | style="width: 129px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Advantages</span> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Advantageous if packages are too dense to be cooled with air (FAO, 2009)</span> |
| + | |- |
| + | | style="width: 129px;" | <br/> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Removes heat rapidly (FAO, 2009)</span> |
| + | |- |
| + | | style="width: 129px;" | <br/> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Continues to remove heat through absorption while melting</span> |
| + | |- |
| + | | style="width: 129px;" | <br/> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Usable during transport, distribution and storage (FAO, 2009)</span> |
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| + | | style="width: 129px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Challenges</span> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Ice used must not contain any chemical, physical or biological hazards (FAO, 2009)</span> |
| + | |- |
| + | | style="width: 129px;" | <br/> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Inefficient since about half of the cooling effect is lost to heat exchange with the environment instead of actually contributing to cooling the produce (USAID, 2009)</span> |
| + | |- |
| + | | style="width: 129px;" | <br/> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Depending on the proximity of the ice-making facility and the availability of insulating packaging, losses during the transport to the cooling facility will occur (USAID, 2009)</span> |
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| + | | style="width: 129px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Adequate for</span> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Produce with high respiration rates (FAO, 2009)</span> |
| + | |- |
| + | | style="width: 129px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Equipment required</span> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Ice</span> |
| + | |- |
| + | | style="width: 129px;" | <br/> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Storage and package containers which are suited for icing applications has to remain stable if being wet, such as waxed fibreboard cartons, wooden wire-bound creates, baskets, hampers and perforated plastic liners (FAO, 2009)</span> |
| + | |} |
| <br/> | | <br/> |
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| + | <u>Top icing:</u> crushed ice is applied on the produce either manually or mechanically (FAO, 2009) |
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| + | |
| + | {| border="1" cellspacing="1" cellpadding="1" style="width: 100%;" |
| + | |- |
| + | | style="width: 129px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Adequate for</span> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Brokkoli, green onions, leafy greens, brussel sprouts, leeks, cantalpupes, parsley, carrots, peas, chinese cabbage (FAO, 2009)</span> |
| + | |} |
| + | <br/> |
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| + | <u>Liquid icing:</u> ice and water mix is injected through vents or handholds into packages. This is done without opening packages and without removing them from pallets (FAO, 2009) |
| + | |
| + | |
| + | {| border="1" cellspacing="1" cellpadding="1" style="width: 100%;" |
| + | |- |
| + | | style="width: 129px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Advantages:</span> |
| + | | style="width: 636px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Can be used for small and large operations alike (FAO, 2009)</span> |
| + | |- |
| + | | style="width: 129px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Challenges:</span> |
| + | | style="width: 636px;" | <div><span style="line-height: 20.400001525878906px;">Produce gets in contact with water increasing the threat of microbial development. Sanitation is crucial. (FAO, 2009)</span><br/></div> |
| + | |} |
| + | <br/> |
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| + | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);"><u>Individual package icing:</u> <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">crushed ice is added manually on top of the packaged produce (FAO, 2009)</span></span><br/> |
| + | |
| + | |
| + | {| border="1" cellspacing="1" cellpadding="1" style="width: 100%;" |
| + | |- |
| + | | style="width: 130px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Advantages</span> |
| + | | style="width: 635px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Very simple (FAO, 2009)</span> |
| + | |- |
| + | | style="width: 130px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Challenges</span> |
| + | | style="width: 635px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">There is the danger of produce being cooled unevenly since ice is simply put on top of packages/cartons (FAO, 2009)</span><br/><span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Application of ice on every single package is labor intensive and slow and is therefore mainly applied to small operations (FAO, 2009)</span> |
| + | |} |
| + | <span style="font-size: 0.85em; line-height: 1.5em;"></span> |
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| + | <u>Ice bottles:</u> ice bottles wrapped in paper are placed in between produce (FAO, 2009) |
| + | |
| + | <br/> |
| + | |
| + | |
| + | {| border="1" cellspacing="1" cellpadding="1" style="width: 100%;" |
| + | |- |
| + | | style="width: 130px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Advantages</span> |
| + | | style="width: 635px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Produce has no direct contact with ice (FAO, 2009)</span> |
| + | |- |
| + | | style="width: 130px;" | <br/> |
| + | | style="width: 635px;" | <span style="line-height: 20.400001525878906px; background-color: rgb(255, 255, 255);">Can be used during transport (FAO, 2009)</span> |
| + | |} |
| + | <br/> |
| + | |
| + | <br/><br/> |
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| <br/><br/> | | <br/><br/> |
Precooling refers to the rapid removal of field heat shortly after the harvest of a crop. Field heat can be defined as the difference in temperature between the temperature of the crop harvested and the optimal storage temperature of that produce. In general the temperature should be cooled down till it reaches 88% of the existing difference in temperature and its optimal storage temperature. Field heat should be removed as fast as possible since, for most produce, an hour delay at field conditions of about 35°C will lead to a loss in shelf-life of about 1 day – even at optimal storage conditions[1] [2]. Nevertheless, due to biological factors, the importance of rapid pre-cooling varies. According to the Indian Board of Horticulture[3], especially grapes, mandarins, berries, cherries, leeches, melons, stone fruits, sapotas, okra, tomatoes, capsicum, chilli peppers, eggplant, cucumbers, green beans, peas, and spinach should be rapidly pre-cooled, whereas other, less perishable produce is made up of mangoes, papaya, guava, green bananas, pomegranates, radish, cabbage, cauliflower and carrots.
More detailed information about adequate pre-cooling methods for various fresh produce items can be found here.
According to the FAO, precooling is “amongst the most efficient quality enhancements available” and is regarded “as one of the most value-adding activities in the horticultural chain”. Precooling benefits include:
There are several methods that can be chosen to precool produce. Which method is the most suitable choice depends on various factors of which some are listed below:
Regardless of which method is used, the process should always be monitored in order to ensure that precooling is achieved in the most efficient way. Depending on method and product at hand, produce will cool at different rates.
In general, there are three different methods to precool produce, using either air, water or the creation of a vacuum. Below each method and possible variations are shortly explained:
The simplest, most low cost and low technology option to reduce field heat is to move produce to a deeply shaded area directly after harvest. The temperature in packing houses, with roofs that are light colored or reflective, can reduce temperatures as much as 20°C[10].
Use of refrigerated air in a conventional cold storage room, a special pre-cooling room, a funnel cooler, or a forced air cooler. Air cooling can be subdivided in the methods of room cooling and forced-air cooling:
Ice is used to remove heat from fresh produce.