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FOOD PRESERVATION METHODS - Coggle Diagram
FOOD PRESERVATION METHODS
High temperatures
-Degree of heat processing required to produce a product of acceptable stability will depend on the nature of the food, its associated enzymes, the numbers and types of microorganisms, the conditions under which the processed food is stored and other preservation hurdles used.
Blanching
-Blanching stops enzyme actions which otherwise cause loss of flavor, color and texture.
-Blanching not to reduce the microbial population on the surface of foods but it will still reduce the numbers of organisms of lower heat resistance.
-Without blanching step, the shelf life of, e.g. frozen vegetables would be substantially reduced as a result of chemical breakdown during storage.
Batch thermal processing
-Food heated within it is package and a commercially sterile food.
-Various packaging materials for canning (metal, glass, plastic (pots, trays, bottles and pouches) and aluminium cans.
-The most heat-resistant pathogen that might survive the canning process of low-acid canned foods is C. botulinum
Continuous thermal processing (aseptic and hot fill)
-UHT (ultra high temperature or ultra heat treatment).
-Typical temperatures and holding times in a UHT process are of the order 140◦C for a few seconds.
-In aseptic filling, UHT treatment is followed by filling into sterilised packages within a sterile environment
Pasteurisation
-Pasteurisation is a process in which packaged and non-packaged foods (such as milk and fruit juice) are treated with mild heat, usually to less than 100 °C (212 °F), to eliminate pathogens and extend shelf life.Spoilage enzymes are also inactivated during pasteurization.
-Sterilised packaged foods for ambient storage have shelf lives of 18–24 months
Low temperatures
Freezing
-Freezing can reduce the levels of some susceptible microorganisms
-At commercial freezing temperatures (−18 to −24◦C):
-Storage life of frozen foods tends to be dictated more by consumer handling than the effectiveness of the freezing processes
Chilling and cooling
-Chilling: lowers food temperature to between a safe storage temperature of 0–5◦C
-Cooling: general term to the lowering of a food temperature.
Chilled food pack needs to be clean but not sterile.
Drying and water activity control
-Reducing the water in a food is one way of slowing or preventing microbial growth.
-Selection of suitable packaging materials is therefore critical in extending the shelf life of dried foods.
Chemical preservation
-Addition of specific chemicals to foods to inhibit microbial growth and chemical reactions food
-Two types of preservatives most widely used:
sorbic and benzoic acids and their salts
sulphur dioxide and its derivatives.
Curing
Pickling
Smoking
Fermentation
-fermentation, chemical process by which molecules such as glucose are broken down anaerobically.
-Three main types of fermentation in the food industry:
Bacterial fermentation of carbohydrates, as occurs in yoghurt manufacture,
Bacterial fermentation of ethanol to acetic acid (as in vinegar production)
Yeast fermentation of carbohydrates to ethanol (as in beers, wines and spirits).
Modifying the atmosphere
-Modified atmosphere is the practice of modifying the composition of the internal atmosphere of a package in order to improve the shelf life.
-Process times and temperatures have evolved from original sous-vide concept of pasteurising at 70◦C for 40 min.
Other techniques and developments
. High pressure processing(HHP)
-allows gentle preservation of food by high pressure without additives or heat.
-Chilled storage or high acidity are essential hurdles in preventing microbial growth.
Ohmic heating
-A process of heating the food by passing electric current.
-Ohmic heating results in faster heating of food along with maintenance of color and nutritional value of food.
Irradiation
-Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources.
-Effective in killing Salmonella on poultry
Membrane processing
-Used in the food industry for filtration and separation processes
-The product can be either permeate or concentrate
Microwave processing
-use of electromagnetic waves of certain frequencies to generate heat in a material.
-Frequencies of 950 and 2450 Hz are used to excite polar molecules, which produces thermal energy and increases temperature
Pulsed light
-Potential for packaging surface decontamination
-Uses very high intensity light in the visible spectrum, of the order of 20,000 times the intensity of the sun at the earth surface.