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Food Processing and Preservation

In the 19th century, major breakthroughs in food preservation had begun. During Napoleonic times, food was preserved with salt. This method was not very dependable. Later, Nicolas Appert observed that food heated in sealed containers could be preserved for a longer period, and Louis Pasteur noted the relationship between microorganisms and food spoilage. These breakthroughs increased the dependability of the food processing. Raw food is usually preserved by cold storage or refrigeration, because the low temperature can stop microorganisms from growing. There are many different ways of preservation such as heating and freezing.


Canning is also called sterilization because the heat treatment eliminate all spoiling microorganisms and pathogenic bacteria. Its principle is that bacteria destruction increases as temperature increases. After the exposition to high temperature, food still retains its natural flavor.

The freezing process was used commercially for the first time in 1842, in large scale only in the late 19th century. This process prevents microorganisms from multiplying and reduces enzymes' activity. In preparation for freezing different methods are applied depending on the type of the food(i.e. vegetables are blanched before being frozen). Frozen food resembles the fresh food,but its quality depends on the rapidity with which the food is prepared and the rate at which it is frozen.
Drying and Dehydration
Both these terms mean the removal of water from food. The protection of food is achieved because bacterial growth and enzyme activity are absent in water-free environment. Dehydrated food must be packaged in moisture-proof containers to avoid absorbing water from the air.
This process is a combination of freezing and dehydration. At first food is frozen then is is dehydrated under vacuum conditions with application of heat. Freeze-dried foods must be reconstituted with water before being consumed.
Miscellaneous Methods
Salting: Salt can binds with water in the food, thus inhibiting the bacterial activity.
Smoking: It is used to preserve fish, ham and sausage. Its preservative action is provided by chemicals present in the smoke. It can also enhance the flavor of the product.
Sugar: It's the major ingredient of jams and jellies. It acts in the same way as salt.
Vinegar: Acetic acid, the preservative function is due to its high acidity.
What are food additives?
Additives are added to food to enhance safety (by preventing microbial spoilage), nutritional value( by avoiding degradation of components) and appeal (by maintaining the consistence, texture and sensory properties). Codox Alimentarius Commission operates for food additives .
Origins of additives:
•products extracted from vegetables (thickening agents, colors, acidulants)
•nature-identical products produced by synthesis (acidulants)
•modified natural substances ( emulsifiers, thickening agents, bulk sweetners)
•artificial antioxidants (butylated hydroxyanisole)
Microbes in food
Part One
Food usually contains harmless microbes, but occasionally, it may contain pathogenic microbes which have various origins. Food spoilage is due to microbes' multiplication and atmospheric oxygen which change the composition of the food . Conversely ,some microbes are useful to manufacture food through their biochemical activity. WHO( World Health Organization) reports that food safety and foodborne diseases remain a major public health concern. There are two types of foodborne illness :
•Infections (pathogenic bacteria)
•Intoxication (toxins)
Part Two
Foods which pose risk of food borne illness include:
Foods of animal origin which pose the greatest risk.
Eggs and meat which can carry bacteria.
Red meats which can be easily contaminated.
Dairy products which can contain pathogens from dairy animals or its environment. Pasteurization and sterilization are applied to ensure products' safety.
Shellfish which can concentrate pathogens in their body and cause infections.
Herbs and spices.
Avoiding food contamination
Food safety crosses through the entire production chain. At farm level, there are critical control points in animal rearing and crop agriculture where contamination can be controlled by good practices. At food manufacturing level, in-house quality system is applied to ensure the food safety and some measures are used to help prevent contamination. These measures regard raw materials, equipments, process and the staff.
HACCP is the abbreviation of hazard analysis critical control points. The concept of HACCP consists on the control of particular processes which may endanger consumers' health. The principles that must be considered are : analysis of hazard, identification of hazard points and the critical ones, determination of measures and realization of control, and final verification.

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