Conservation of food
According to food and means placed at the disposal, several techniques can be used for to preserve food . The conservation of the food is the process which consists in treating and to handle the Nourriture in a manner such as deterioration of the latter is stopped or strongly slowed down in order to avoid possible a Food poisoning all while maintaining the value nelle Nutrition, texture and the Goût.
The Conservation usually implies to prevent the development of the Bactérie S, Champignon S and others Micro-organisme S, to delay the oxidation grease S which causes the Rancissement and the Autolyse by clean the Enzyme S of the cells of food.
The current methods of conservation of food include the Séchage or Dessiccation, the Congélation, the vacuum setting, the Pasteurization, the Appertisation, the irradiation and the preserving addition of . Other methods not only help to maintain food but to also add taste him, like salting, the Confiture and the manuring.
The drying, which reduces the action of water, is the oldest process with the manuring which introduces chemical compounds which inhibit the micro-organisms.
The vacuum setting reduced the quantity of air thus the action of oxygen.
The Brine or the addition of Vinaigre can be used.
To add Hydroxyde of sodium makes the medium too alkaline for the bacterial growth. It also will saponify greases what changes its taste and its texture. The Lutefisk and certain olive receipts use this soda.
Conservation of food
- Certains prehistoric men preserved already their grain in holes dug in the ground, holes whose walls were coated lime, or in silos in height inaccessible to the rodents; they consumed dry fruits which they carried with them.
- Certain fruits and seeds can be stored in a dry and fresh place (a barn, an attic, a garage…) without suffering damage and being thus preserved for approximately a year, even much more (on the condition of being protected from the rodents, birds, insects,…) These fruits are for example: the Apple S, the Nut, the Hazel nut S… Old corn grains two thousand years, found in Egyptian pyramids, could be put in culture.
- Jam S : very easy technique, it is enough to mix fruits with their equivalent in weight of Sucre and to carry a few minutes to boiling. To scald the bottles before filling them to the maximum what avoids the formation of Moisissure. Fruit pastes, or the candied fruits also use the preserving virtues of sugar (candied fruits losing the essence of its components which in fact is replaced by sugar)
- Réfrigération : the fall in the temperature decreases the action of the bacteria and the enzymes present in food.
- Pasteurization : technique which consists in subjecting food to a temperature lower than 100° and to cool them brutally.
- Canning (put out of preserve): the conservation of food in tight packing allows for one long period without particular conditions (in particular of temperature). Nevertheless the Procédé requires conditions of temperature at the time of the preserve setting which are relatively constraining.
- Congelation : technique which consists in lowering the temperature of food and to maintain it in lower part Melting point of the Glace (0 °C). It makes it possible to consume food several years after the beginning of their congelation if this one is uninterrupted.
- Freeze-drying : technique of drying by brutal congelation (between - 40 °C and -80 °C surroundings) with sublimation vacuum. The food preserves all their savors like their nutrients, once réhydratés they find almost the same texture of origin. This method is employed for food of the astronauts in space.
- Conservation in the alcohol . Original organoleptic qualities and the vitamins are lost, as for the candied fruits.
- the meat and the fish can be salted, dried, boucanés (smoked)…
- the fruits can be crossed in plates and dried or dried in the state (prunes, apricots, figs, dates.) possibly treated with an edible oil to limit oxidation.
- Conservation in Acid medium like the Vinegar . Acidity modifies appearance, texture, decreases the taste as well as the number of vitamins (examples: (Cornichon S, onions) which one adds dyes and salt to record savor and appearance of it.
- Conservation in basic medium like the Oil (dried tomatos)
Conservation of the bread
The bread is preserved at dryness and can, when it is hard, be made roast with a toaster.Certain types of bread, the large bread and especially the bread of sea, are manufactured according to methods allowing its conservation, rolled up in a cloth, during two to three weeks. There in addition exist dry breads with long conservation as the Pane carasau in Sardinia.
One can also use the dry bread to make Chapelure or Pain lost.
Conservation of the meat
- Desiccation , which leads to the dried Viande
- Fumage
- Salaison : friction of the pieces of meat with salt (salt 2kg for meat 10kg) in order to make it return, then provision of the meat in a salting tub by intercalating a layer of meat with a layer of salt for six months during which lactic Ferments will develop.
- Refrigeration
- Congelation
Methods of conservation of milk
- Refrigeration with 4°: the fresh milk not heated less cooled than 1 a.m. after the treaty is preserved very well during 4 to 5 days.
- Heating : less few hours after the draft, to carry milk to boiling during five to ten minutes allows to preserve milk during a few days. With this process milk will lose much vitamins, its taste is deteriorated and there will be a fine layer of skin on the surface and at the bottom of the pan, in fact proteins (albumins) were precipitated by heat.
- Congelation : after the operation of heating, it is possible to freeze milk.
- Pasteurization: milk is heated with more 65° during at least 15 seconds: the conservation cooled during ~4 days
- Chauffage allows ultra high temperature (UHT): principle which consists in heating milk during a few seconds at a temperature of 135-155°c and to put it in sterile packing . Thanks to this treatment all the micro-organisms are destroyed but there remain enzymes. Modern technologies (UHT) of sterilization of milk and fruit juices in particular allowed a better conservation of the taste and vitamins.
- Dehydration : dried milk is a milk which one removed all water by Dessiccation
Principal methods of conservation of food
External bonds
- Lacto fermentation