CONSERVING FOOD – ZEER POT STORAGE OF VEGETABLES AND FRUITS
For most fruits and vegetables the shelf life varies from only a few days to several weeks. So it is a challenge to store these products.
One of the challenge is to retain the water of vegetables and fruits during storage since they consist to a large extent of water. Fruits and vegetables are not only an important source of food for the family, they can also bring a good price if sold on the market. Good quality of products means more profit. Consumers like products that look fresh.
Other challenge is to recognize the fruits and vegetables that are sensitive to ethylene. Ethylene is a gas that we cannot see or smell, but it causes the fruits to ripen. Fruits that are sensitive to ethylene, for instance tomatoes, can be harvested before they reach their full ripeness. Then they are less vulnerable and can be stored longer. The second group of fruits is not sensitive to ethylene. They ripen only while attached to the plant. Among them are pepper and citrus. They must be harvested when they are ripe. Some fruits are sensitive to ethylene, but do not produce it themselves. They can ripen off the plant when stored in the presence of fruits that produce ethylene.
Many vegetables are also sensitive to ethylene. In vegetables ethylene causes aging, which is unfavorable in most cases. Therefore, if you want to store these vegetables for a week or more, you should not store them in the presence of ethylene-producing fruits
COOLING
Controlling temperature is one of the main tools to extend post-harvest life: low temperatures slow product respiration and the activity of micro-organisms responsible for deterioration. As a result, ripening is retarded and water loss is reduced. These factors contribute towards maintaining freshness, and the nutritional value of the product is preserved.
The basic principle is that the products are cooled through evaporation. When water evaporates it draws energy from its surroundings, producing a considerable cooling effect like in the same way that sweating cools you down. The sweat takes the heat from your body as it evaporates and turns to a gas.
The faster the rate of evaporation the greater the cooling. The efficiency of an evaporative cooler depends on the humidity of the surrounding air.
Very dry air can absorb a lot of moisture, causing greater cooling. On the other hand, if the air is totally satured with water, no evaporation can take place and no cooling occurs.
ZEER POT
Zeer pot model was invented in rural areas in Nigeria in the 1990s, it is also called “pot-in pot� system because it is made of two different sized clay pots with a layer of wet sand in between. The pot cools as the water evaporates, which gives you non-electric refrigeration in hot, dry climates.
Common tropical fruits. Storage duration for fruits that are harvested
Common Vegetables, approximate storage duration and sensitive to ethylene
Source: Agrodok-series No.31 – Storage of Agricultural Products Manual low Input FNS Manual 2015