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The cleanliness of products to consume and especially poor conservation, especially in summer, are the main causes of increased food poisoning
"One of the most common public health problems in the contemporary world ", explains Barbara Paolini Assistant Secretary Adi ( Italian Association of Dietetics and Clinical Nutrition ), stating that each year" it is estimated that in industrialized countries only 30% of the population is affected by food-borne diseases, with around 360 000 cases of complaints and 30 000 interventions of infections and food poisoning. – he remembers – there are more than 250 food poisoning in the world that manifest themselves with different symptoms and caused by various pathogens that increase with age. "
The Listeria Case
A very controversial case on the web a few days ago, frozen products recalled in Europe because of contamination by Listeria a bacterium that grows mostly in soil excrement and animals and multiplies especially in fresh foods such as cold cuts or undercooked, cheeses based on unpasteurized milk, vegetables and various ready-to-eat or frozen foods, precisely because, unlike many other food bacteria, it tolerates salty environments and low temperatures (between 2 and 4 degrees). "The subjects most at risk for Listeria infections are the elderly, people with weakened immune systems, pregnant women and newborns," says Paolini. Eriosi are often badociated with ready-to-eat and refrigerated foods such as dried meats, soft cheeses, milk or other dairy products. For soft cheeses, the risk of listeriosis per dose is estimated to be between 50 and 160 times higher for those produced with unpasteurized milk than pasteurized milk. However, care must be taken – he warns – because despite pasteurization killing the bacteria, there is often a risk of contamination of milk and products due to inadequate hygiene practices after pasteurization. "
The transformations they encounter in fresh foods make them inedible, which is why, over the centuries, different techniques have been found to preserve them for as long as possible, by fighting the causes of biological alterations.
Alterations of biological origin are caused directly by the enzymes present in the food cells, or indirectly, if they belong to the microorganisms that contaminate and develop in the food. [19659007] They may alter the organoleptic characteristics and nutritional value of foods that cause rot (on protein and amino acids), bitterness and rancidity of fats, fermentation
of carbohydrates
● compromise the safety of the food in the case of pathogenic germs and / or their toxins, if they are poorly preserved, food can be invaded by mold, parasites or consumed by rodents. Among the physico-chemical causes of food spoilage are: oxygen, light and UV rays (they promote rancidity and browning), heat (dehydrates food, accelerates chemical reactions). and reproduction of microorganisms), changes in water content (decrease causing wilting while increase favors the development of mold and bacteria, hydrolysis of fats and enzymatic reactions)
● preserves, long-life products at low or room temperature (sterilized, frozen, freeze-dried, dried, concentrated and / or chemically added);
● semi-preserved, of limited duration in time as pasteurized, refrigerated, stored in modified atmospheres,
● processed products, with substantial modifications of the original structure (fermented, salted, hardened) . [19659002] Depending on the method used to extend edibility, preservation methods can be clbadified in
● physical methods: low and high temperatures, dehydration, radiation, modification
of the atmosphere; ] ● chemical methods: natural or artificial preservatives,
● chemico-physical methods: smoking,
● biological methods: fermentations
High temperatures inactivate enzymes and destroy microorganisms; The techniques used for food preservation are pasteurization and sterilization. In pasteurization, foods are brought to temperatures above 60-65 ° C for a few seconds and cooled rapidly. The pathogenic micro-organisms and the germs responsible for the alterations are thus destroyed, but not the thermophiles or the spores. Food should therefore be stored under conditions that prevent its development, refrigerated or added with preservatives or must be vacuum packed. Based on the temperature reached
and the time of exposure we have
● low pasteurization (60-65 ° C for 30 ") for wine, beer, egg products
● fast pasteurization or HTST (70-85 ° C for 15-20 ") used for fresh milk
● High pasteurization (at temperatures above 85 ° C) for pasteurized milk with a longer service life than freshness.
With the sterilization of food they are brought to temperatures above 100 ° C; in this way all microorganisms, including spores, are destroyed. In sterilization or conventional preparation, the food, already prepared and packaged, is brought to temperatures of about 120 ° C in autoclaves, apparatus in which the pressure and the temperature are regulated. The food (meat, fish, vegetables, fruits) treated in this way is maintained until five years. The UHT method allows sterilization up to 140 ° C of bulk product, cooling and subsequent aseptic packaging in glbad, plastic or multilayer containers. It is used for long-life milk, soups, sauces, etc.
Store at Low Temperature
Low temperatures block enzymatic and microbial activity, which can resume when food returns to room temperature. The cold therefore has no sterilizing action and the processed food must be hygienic irreproachable. The use of low temperatures includes refrigeration and freezing.
Refrigeration involves lowering the food storage temperature to values (from -1 to + 8 ° C) to maintain water in this state. liquid; the temperature varies with the food and with the required storage time.
Refrigeration can be
● simple, in the refrigerator or refrigerated warehouse
● in a controlled atmosphere, in cold rooms where the air is almost completely deprived of Oxygen
● under modified atmosphere, in containers filled with inert gases, the composition of the atmosphere changes in contact with food;
● Vacuum, with removal of air
By freezing the food is brought to temperatures such that the water contained solidifies. For most foods, the freezing point is -0.5 to -4 ° C. Freezing can be slow or fast:
● slow freezing is unusable because large ice crystals form break up the cell walls and thaw the liquid, [●ultra-fastistobringthefoodto-40°temperaturesthissamebelowMicrocrystalsarestillformedandthefoodstuffsremainincontactwiththeirnutritionalvalue
Frozen foods are foods subjected to ultra-rapid freezing, conditioned and maintained at -18 ° C until On their sale. The quality of frozen food depends on the authenticity of the starting product and the maintenance of the cold chain. The changes caused by the low temperatures are limited: the proteins are denatured, therefore more digestible, the fats can become rancid, the mineral salts and the vitamins can be lost with a possible previous scalding.
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