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Published Nov 26, 2016
New preservation technologies are not just working to increase longevity; they are also functioning to sustain the same qualities of the food that make it desirable in the first place...
Increasing demands of consumers for high quality fresh food products have increased the interest in the development of new food processing technologies over the past decade. Food preservation is processing designed to protect food from spoilage caused by microbes, enzymes, and autooxidation. It is one of the oldest technologies used by human beings to prevent from food-borne disease hazards. The basic idea behind food preservation is either to slow down the activity of disease-causing bacteria or to kill the bacteria altogether. Nowadays different preservation techniques commonly used worldwide like Refrigeration and freezing, Canning, Dehydration, Freeze-drying, Salting, Pickling, Pasteurizing, Fermentation, Carbonation, Cheese-making and Chemical preservation.
Refrigeration and freezing are the most popular forms of food preservation in use today. In the case of refrigeration, the idea is to slow bacterial action or stunt microbial growth to a crawl so that it takes food much longer (perhaps a week or two, rather than half a day) to spoil. In the case of freezing, the idea is to stop bacterial action altogether. In freezing bacteria become completely inactive. Refrigeration and freezing are used on almost all foods like meats, fruits, vegetables, beverages, etc. In general, refrigeration has no effect on a food's taste or texture. Freezing has no effect on the taste or texture of most meats, has minimal effects on vegetables, but often completely changes fruits (which become mushy).
Canning and bottling remains a very common technique of food preservation. The process is very efficient and it can leave the food edible for many years. It has provided a way to store foods for extremely long periods of time. In canning, food is boiled in the can to kill all the bacteria and sealed (either before or while the food is boiling) to prevent any new bacteria from getting in. Since the food in the can is completely sterile, it does not spoil. Once the can is opened, bacteria enter and begin attacking the food, hence it is necessary to "refrigerate the contents after opening". Major drawback of canning is that canned food remains susceptible to anaerobic microbial growth, most notably that of Clostridium botulinum.
Boiling of food can kill all bacteria and make the food sterile, but it significantly affect the taste and nutritional value of the food. Pasteurization a food (almost always a liquid), is heating it to a high enough temperature to kill certain (but not all) bacteria and to disable certain enzymes, with minimizing the effects on taste as much as possible. Commonly pasteurized foods include milk, ice cream, fruit juices, beer and non-carbonated beverages. Milk, for example, can be pasteurized by heating to 145 degrees F (62.8 degrees C) for half an hour or 163 degrees F (72.8 degrees C) for 15 seconds. Ultra high temperature (UHT) pasteurization completely sterilizes the product. It is used to created "boxes of milk" that you see on the shelf at the grocery store. In UHT pasteurization, the temperature of the milk is raised to about 285 degrees F (141 degrees C) for one or two seconds, sterilizing the milk.
Many foods like powdered milk, dried fruits and vegetables, pasta and instant rice etc. are dehydrated to preserve them. Since most bacteria die or become completely inactive when dried, dried foods kept in air-tight containers can last quite a long time.
In freeze-drying, food is frozen and placed in a strong vacuum to removes all moisture and tends to have less of an effect on a food's taste than normal dehydration does. The water in the food then sublimates - that is, it turns straight from ice into vapor. Freeze-drying is most commonly used to make instant coffee, but also works extremely well on fruits such as apples.
Salting is an ancient preservation technique. The salt draws out moisture and creates an environment inhospitable to bacteria. If salted in cold weather (so that the meat does not spoil while the salt has time to take effect), product can last for years. Pickling was widely used to preserve meats, fruits and vegetables in the past. Pickling uses the preservative qualities of salt (see above) combined with the preservative qualities of acid, such as acetic acid (vinegar). Acid environments inhibit bacteria.
Drying is for the purpose of moderating the amount of water activity to prevent the growth of bacteria by aerobically respiring. Clearly, drying food does not fully prevent contamination, but in addition, the process changes the physical properties of the food. The acidic products that result from fermentation help to kill off contaminating microbes, Fermentation uses yeast to produce alcohol. Alcohol is a good preservative because it kills bacteria. But similarly to drying, fermentation changes the chemical properties of the food.
Carbonated water is water in which carbon dioxide gas has been dissolved under pressure. By eliminating oxygen, carbonated water inhibits bacterial growth. Carbonated beverages (soft drinks) therefore contain a natural preservative.
Cheese is way of preserving milk for long periods of time. Cheese-making is a long and involved process that makes use of bacteria, enzymes and naturally formed acids to solidify milk proteins and fat and preserve them. Once turned into cheese, milk can be stored for months or years.The main preservatives that give cheese its longevity are salt and acids. Cheese-making is complicated. It produces a product that preserves milk proteins and sugars with acids and salt.
The use of preservatives in food has expanded a great deal in recent years. There are two forms of chemical food preservatives: antimicrobial preservatives and antioxidants.
a)Antimicrobial preservativeswork to break down, and prevent the growth of bacteria and fungi.Chemical preservatives are added to food to either inhibit the activity of bacteria or kill the bacteria. Commonly used preservatives in foods are Benzoates (such as sodium benzoate), Nitrites (such as sodium nitrite) and Sulphites (such as sulphur dioxide) and sorbic acid.
b)Antioxidantsare used to avert the oxidation of the food. Antioxidants generally include Butylatedhydroxyanisole (BHA), Butylatedhydroxytoluene (BHT), and tert-Butyl hydroquinone (TBHQ).
Latest Preservation Technology
Preventing the growth of microbes for the sake of storing food can be achieved through many diverse methods. Continuous innovation to food preservation techniques has been necessary for subsistence across the globe. Over the years, improved techniques for processing foods have resulted in the expansion of our food supply by prolonging keeping times, preventing spoilage and increasing the variety of food products available. More modern techniques have been evolved such as irradiation and high pressure food preservation. Some of the latest methods of food preservation are irradiation, e-beam irradiation, high pressure processing, Pulsed electric field treatment, extrusion, natural preservative, Ozone, and nanotechnology. Although these methods are currently in use, they are expected to expand and develop further.
Nuclear radiation is able to kill bacteria without significantly changing the food containing the bacteria. So if food is sealed in plastic and then radiated, it will become sterile and can be stored on a shelf without refrigeration. Irradiation of food is the process of exposing food to ionizing radiation (x-rays or gamma radiation) to kill bacteria and mold. It may be combined with vacuum packing to seal out microbes. Irradiation to a dose of between 1 kGy and 10 kGy is an effective method of reducing the microbial load of food. Low dose irradiation (less than 1 kGy) is also used to inhibit sprouting (e.g. onion, garlic, potato), delay ripening (e.g. of mango, papaya and other fruits) and is also used for the purpose of insect disinfestations and inactivation. Food irradiation is effective against a wide variety of pathogens including bacteria, fungi, viruses and parasites without harming the food. Irradiation is attractive because of its selective targeting. It will extend the shelf life of food because spoilage organisms are also reduced in number, and as with heat treatment, irradiation may also inactivate enzymes that would otherwise assist food spoilage. The Food and Agriculture Organization (FAO), the International Atomic Energy Agency (IAEA), and World Health Organization (WHO) concluded in their report, that any food irradiated up to a maximum dose of 10 kGy is considered safe and wholesome. Essentially three things were concluded in their report:
1) It won’t lead to toxicological changes in the food that will negatively affect our health,
2) The technology won’t increase the microbial risk of the consumer, and
3) Irradiation won’t lead to nutritional losses.
But due to the words "nuclear radiation", irradiated food is not very common in this country.
E-beam irradiation, though it uses the same term as gamma ray irradiation, is a completely different kind of treatment. High-energy electron beams are produced in an electron gun, a larger version of the cathode ray gun found in devices such as televisions and monitors. The electrons can be directed by a magnetic field to a target food. The term "irradiation" is really a misnomer, since the food not exposed to electromagnetic radiation or beta rays (electrons produced by a radioactive source). Nevertheless, the process has a similar effect to that of gamma ray irradiation. E-beam irradiation requires shielding as well, but nothing like the concrete bunkers used in gamma ray irradiation.
• They can be turned on only as needed
• They do not require replenishment of the source as does cobalt-60
• There is no radioactive waste
• Shallow depth of penetration (about an inch), preventing its application to many foods and limiting the amount of food that can be processed in bulk.
• e-beams must be converted to x-rays to penetrate large items such as carcasses
• High electric power consumption
• Complexity, and potentially high maintenance
High Pressure Processing (HPP)
High Pressure Processing (HPP) is a way to process foods without using heat. It has the potential to produce high-quality, fresh, nutritious, safe-to-eat foods without using chemical preservatives. HPP involves subjecting food to 300 to 700 MPa of pressure. For comparison, atmospheric pressure is normally around 0.1 MPa and the pressure at deepest point in the ocean is around 110 MPa. The high pressure used in HPP kills most micro-organisms, by damaging cell components such as cell membranes. The main applications of high pressure processing are preservation and preparation. For preservation applications, enzymes and micro-organisms are inactivated under high pressure. This results in a preserved product while remaining fresh taste, flavour and colour. Examples are pasteurization of fruit juices, fruit desserts and guacamole. In Japan, for example, several rice-based foods are available with novel textures induced by high-pressure treatment. Other examples are gelatinization of starches and proteins, preparation of pectin gels (jams) and tenderization of meat. Commercial products have now been appearing in the US and Europe.
• Retention of taste, texture and nutrients
• combined with heat or antibacterial agents (spores inactivation)
• Food poisoning organisms can be destroyed leading to safer products
• Discontinuous or semi Discontinuous or semi continuous process
• Impact on texture, structure, appearance, functionality
• Expensive. High-pressure machines typically cost $3 million.
Pulsed Electric Field Treatment (PEF)
Pulsed electric field (PEF) processing is a non-thermal method of food preservation that uses short bursts of electricity for microbial inactivation and causes minimal or no detrimental effect on food quality attributes. PEF can be used for processing liquid and semi-liquid food products. PEF processing offers high quality fresh-like liquid foods with excellent flavor, nutritional value, and shelf-life. Since it preserves foods without using heat, foods treated this way retain their fresh aroma, taste, and appearance. PEF has been mainly applied to preserve the quality of foods, such as to improve the shelf-life of bread, milk, yogurt, soups, orange juice, liquid eggs, and apple juice, and the fermentation properties of brewer's yeast.
PEF processing involves treating foods placed between electrodes by high voltage pulses in the order of 20–80 kV (usually for a couple of microseconds). The applied high voltage results in an electric field that causes microbial inactivation. The electric field may be applied in the form of exponentially decaying, square wave, bipolar, or oscillatory pulses and at ambient, sub-ambient, or slightly above-ambient temperature. After the treatment, the food is packaged aseptically and stored under refrigeration.
• Low acid food: combined process for spore inactivation = under investigation
• Dependence of el. Dependence of el. conductivity of food
• Ohmic heating occurs during the PEF discharge, which cause the temperature of the sample to rise, and hence a cooling system has to be in place in order to maintain a low temperature of the liquids.
• Potential health risk (electrolytic reaction) since the electrodes have to be immersed in the liquid, they are regarded as major contamination sources to the liquid due to the erosion of electrodes during discharge.
• PEF technology is not being used to preserve foods commercially at present.
Extrusiona process by which a set of mixed ingredients (compressed into a semi-solid mass) are forced through an opening in a perforated plate ordiewith a design specific to the food, and is then cut to a specified size by blades . The machine which forces the mix through the die is anextruder, and the mix is known as theextrudate. The extruder consists of a large, rotating screw tightly fitting within a stationary barrel, at the end of which is the die. Extrusion can take place under high temperatures and pressures or can be simply a non-cooking, forming process. Extrusion enables mass production of food via a continuous, efficient system that ensures uniformity of the final product. Food products manufactured using extrusion usually has high starch content. Extrusion processing has become an important food process in the manufacture of pasta, breads(croutons,bread sticks, andflat breads), manybreakfast cerealsand confectionery, pre-madecookie dough, somebaby foods,full-fat soy,textured vegetable protein (TVP), somebeverages, and dry and semi-moistpet foods.
Some of the natural compounds are being used as safe alternatives to chemical preservatives. One of the examples of natural preservative is bacteriocin. These are produced by some good bacteria to kill competing organisms such as Listeria monocytogenes. The whole bacteria that produce the bacteriocin, or the purified bacteriocin itself, can be added to foods such as soft cheeses to reduce the risk of pathogen growth.
Ozone is a safe and powerful disinfectant. It can be used to control biological growth of unwanted organisms in products and equipment used in the food processing industries. In aqueous solutions, ozone can be used to disinfect equipment, process water, and some foodstuff. In gaseous form, ozone can act as a preservative for certain foods products and can also sanitize food packaging materials. Some products currently being preserved with ozone include eggs during cold storage, fresh fruits and vegetables, and fresh fish.
· Most powerful oxidizer available
· Does not affect product taste
· Can be used in air and water
Nanotechnology in Food Industry
Nanofood can be considered a term to define a food product which is produced using any application of nanotechnology. It promises improved food processing, preservation, packaging, quality and safety, enhanced flavour and nutrition, functional foods, as well as increased production, cost-effectiveness and sustainability.Nanotechnology can help to preserve food in at least two different ways: The first way that nanotechnology can improve food is by sealing the bags that the food is in. nanotechnology can help this is by forming a criss-cross net over the container that takes air a very long time to get through. The other way that nanotechnology can help preserve food is mostly limited to bread, specifically. When you first buy (or bake bread) it’s loaded with many proteins and fat cells that are sturdy and fight each other for space. Over time, however, the stronger fat cells eventually win out and the bread begins to get stiff and moldy. Nanotechnology can help this by reinforcing the proteins to make them stronger which means that the fat cells take much longer to take over.
In conclusion, food preservation has been essential to our society since the beginning. Preservation has come from simple processes such as salting, to more complex preserving methods such as irradiation, HPP and PEF etc. New preservation technologies are not just working to increase longevity; they are also functioning to sustain the same qualities of the food that make it desirable in the first place. The physical characteristics and chemical composition of the food will no longer be compromised during the preservation process. With new techniques and innovations to packaging materials, meals maintain their same fresh qualities over the course of their storage.
very nice article
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