The food storage

Preservation techniques

As previously mentioned, the food substances are subject to alterations that modify the organoleptic and nutritional properties, making them harmful to the body.

The food preservation is based on methods and techniques that are intended to slow or block their natural process of alteration, taking under control or completely destroying the microbial load.

The microbial load, also called bacterial load, is represented by the number of micro-organisms present in 1 cubic centimeter, or 1 gram of food substance. The hygiene rules for each food substance indicate the tolerance limit of the dangerous bacteria charges for human life.

 

 The conservation benefits of the foods are obvious. For consumers increases the time interval between the time when foods are available and the time they are consumed, with the consequence of having a greater availability of choice, and greater ability to implement a correct and diversified diet. In industrial and macroeconomic level, even for the high-speed means of transport, agricultural and food products are distributed everywhere, resulting in well-being of populations, and significant cost savings nationwide.

Before proceeding, there should be two key points.

First point. The food preservation techniques have, albeit with different modes of actions, the common goal of creating an environment unfavorable to life, to the development and activity of the microorganisms. With the progress of knowledge in microbiology, namely the science of bacteria, yeasts and molds and their optimum conditions of existence and development, it is very effectively can now attack them by intervening with temperature factors action, air, water. The effects are of bacteriostatic, but prevents the activity and the growth of microorganisms, or bactericidal type, if you have the complete destruction of microbial forms and spores in food.

Second point. It has been carefully studied the influence of technological treatment, especially the use of relatively high temperatures, such as sterilization, on the organoleptic and nutritional properties of the foods themselves For each conservation technique. It would be a Pyrrhic victory destroy bacteria significantly degrading foods also (we can make life difficult or impossible for the bacteria, but what we certainly can not do is take away their food!).

That said, as we see from the following list, conservation techniques may belong to physical methods, chemical or biological:
• fisici1.Pastorizzazione Methods
2.Sterilizzazione
3.Congelamento
4.Surgelazione
5.Essiccamento
6.Concentrazione
7.Liofilizzazione
8.Sotto vacuum or with inert gases

• chemical methods conservazione1.Aggiunta of additives
2.Affumicatura

• biologici1.Fermentazioni Methods


 

 physical methods

In order to clarify and deepen the above key point, the following is reported, for each method, a short list of definition and description of each technique:
Pastorizzazione.La Pasteurization is a heat treatment that destroys the pathogenic forms, and most of those vegetative, deactivates enzymes, but does not destroy the thermophilic bacteria, the development of which can be limited with the "cold chain", with l ' addition of chemical additives and with the packaging under vuoto.Un classic example of modern pasteurization: pasteurization or rapid HTST (High Temperature Short Time) at 75-85 degrees for 15-20 seconds, conducted on liquid food flowing in a thin layer between two heated metal walls. Followed by a rapid cooling of the product, in order to limit the development of microorganisms residui.Altri types of pasteurization: - low pasteurization: 60-65 degrees for 30 seconds, used for wine and beer, milk for cheese production; - high pasteurization: 75-85 degrees for 2 or 3 minutes, a time used method for the milk and now replaced dall'HTST, which has the least impact on the organoleptic properties and nutrizionali.SterilizzazioneLa Sterilization is a thermal treatment that uses higher temperatures and times greater than those of pasteurization. With sterilization are destroyed almost all microbial forms, including spores and is therefore a much more drastic treatment of pasteurization. The product, however, is not completely sterile and can not be maintained indefinitely. Compared to pasteurization, the impact on the organoleptic and nutritional properties is maggiore.Tipi sterilization: - classical or apertizzazione sterilization: 100-120 degrees for longer than 20 minutes, made of boxed foods; - UHT (Ultra High T for a few seconds, it carried out in bulk on the food immersed in water or in an autoclave; - direct UHT or uperizzazione: 140-150 degrees for a few seconds, carried out with superheated steam injection into the product sfuso.CongelamentoIl freezing consists in a gradual cooling of the food product, generally down to -20 ° C, unfortunately with formation of ice crystals relatively large in the cell membranes, and therefore the possibility of perforation of the same, and consequent loss of nutrients for the escape of intracellular liquids being scongelamento.SurgelazionePer freezing means the cooling to very low temperatures and in a short time of food products. You do not have the drawbacks of freezing, because the ice crystals that form in the food cell membranes are more numerous - effect of rapid cooling - and therefore necessarily smaller. You get the total inhibition of microbial activity is that of those biochemical and enzimaticheLa temperature of the product, after thermal stabilization, it must be maintained in all its points continuously to values ​​equal to or lower than - 18 ° C. The law only admits 3/2 for the cryogenic freezing of food products: air, nitrogen dioxide and carbonica.Essiccamento and concentrazioneL 'essiccamentoessiccamento is a preservation technique of the foods that is achieved by exposing the food to a source of natural or artificial heat, or to a ventilation system with hot air (pasta) Concentration is a preservation technique of the foods that is obtained by subtraction of the food water; the water content in the food may be reduced or for administration of heat, or under vacuum, or with the combination of the two factors of action (concentrators multiple effect vacuum - see on GOOGLE - NB difficult topic.) LiofilizzazioneLa lyophilization is a preservation process used both for food and for medicines. It consists in the total elimination of water, which is necessary for their survival microorganisms. The principle of freeze-drying is as follows: freezing of the product, and subsequent removal of water by sublimation under vacuum accompanied by a sudden controlled heating (within a predefined temperature range) .With the lyophilization, the volumes of the substances are reduced greatly, with the advantage of lower costs for shipping and storage. At the time, the foods are reconstituted by adding the amount of water prescribed on the label of the prodotto.Sotto vuotoSi apply the vacuum to the container that contains the food, so as to neutralize the aerobic bacteria. Alternatively, you can use inert gas atmospheres permitted by law. -------------------------------------------------- ------------------------------ the conservation, continuation Methods chimiciAggiunta additiviLa of choice, for the 'addition of additives falls on natural additives or artificial that for dehydrating or antienzimatica action, have antimicrobico.◦L'argomento effect, because of its importance, will be developed separately in the next paragrafo.◦AffumicaturaL 'smoking is use of this possibility especially for meat, fish, sausages, and some types of dairy products (milk cheese smoked). The chemical action is due to some substances - in particular the phenol - which develop wet combustion of particular types of wood (oak, chestnut, beech, alder, juniper) biologiciFermentazioniLa Methods fermentazioneè a food processing process, from product ' action of microorganisms that, in the absence of oxygen, to transform the sugars in conservative action compounds. Examples: cheese, yogurt, butter, sauerkraut, sausages and hams, wine, beer, vinegar, and, in the phase of initial preparation, even bread. The duration of storage depends on the type of food. • The ancient people already knew the practice of fermentation: yoghurt, for camel caravans crossing the desert; beer, from the Celts (the Roman legions appreciated the use of beer when they realized that their wine, great at home, but went "sour" with the passage of time and the action of the forced marches sballottolamenti not up to par with the most stable beer!)
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