Fruits are perishable items therefore their preservation is as important as their cultivation. Many of the artificial technologies used for food preservation to extend shelf life and longevity entail the addition of hazardous chemicals, which not only have harmful effects for the body but also ruin the taste of the food. Moreover, freezing and storing the fruits in a fridge can only extend its lifespan for about a week or so.
These technologically advanced inventions have become a necessity for everyday life, however there are also undiscovered ancient inventions that can do the same function more efficiently.
One such is the traditional grape storing practice of Afghanistan, which involves airtight clay pots that can keep grapes fresh for up to six months.
A lesser known technology
Grapes are a favourite staple in Afghani households, the geographical area of Afghanistan is suitable to grow a multitude of regional varieties.
Grapes are a summer crop and to keep them fresh for months after their harvesting many Afghan farmers and vendors rely on the cost free, natural technique developed centuries ago known as Kangina or Gangina.
The Kangina is a method of food preservation in which two layers of clay-rich mud are sculpted into the shape of a bowl and used as containers where the grapes are put in and stored for months.
This technique was developed centuries ago in the rural north and people who could not afford the imported produce reaped the benefits of it to enjoy fresh grapes during the off-season. People would acquire a great quantity of these luscious red and green grapes each season, half of which they would sell fresh and the other half would be preserved using kangina and sold months later for a higher profit.
How these containers from clay are made
First, mud is mixed with straw and water and then moulded in the shape of bowls. These clay bowls are then left to dry in the sun for half a day. When these bowls are completely dried,they are packed with around a kilogramme of ripe, unbruised grapes and sealed with another bowl-shaped portion of mud to create a single, airtight container.
They are then placed in a dry, cool corner, away from direct sunlight over the course of winter. Many people even prefer to have them buried underground for a more effective result.
This procedure can take anything from 20 days to a month to complete.
How it works
From the standpoint of food science, this is a passive controlled atmosphere storage.
The clay keeps the grapes alive by supplying sufficient oxygen, whereas the carbon dioxide within these containers limits their metabolism and stunts any fungal growth. Slow gas diffusion through the clay reduces the loss of water vapour that protects the moisture in the grapes from draining.
Moreover, the clay and straw combination appears to absorb any moisture that could lead to bacterial development. Because there are no added chemicals or preservatives in this method, the taste and health benefits might also remain the same.
Grapes that are not consumed fresh or preserved through kangina methods are also transformed into raisins. This is a drying procedure that can be done in direct sunshine; however it is more commonly done in ‘kishmish khanas,’ or raisin rooms, in Afghanistan. These raisins are sold at a higher price than their fresh counterparts and are even easier to preserve.
Despite the fact that this system is centuries old, there isn’t enough documentation or research on it. This method of food preservation can help people transition to a more sustainable lifestyle.
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