The activities of spoilage agents are dependent upon many factors which a change in any of those results in their decreased performance.
The principles of the food preservation based exactly on this information and on the understanding of however chemical reactions, physical changes and pest attack collectively cut back the standard of foods.
These Principles of food preservation could also be expressed as follows:
1) Principles of food preservation
Autolysis in food could also be prevented or delayed by the destruction or inactivation of enzymes and by the treatment and handling of food preservation in such a way so on inhibit the reactivity of with chemicals active molecules.
2) Principles of food preservation
Spoilage in foods as a results of microbe activity could also be prevented or delayed by either prohibiting the entry of microorganisms into the food.
physically removing them from the food, preventive their growth and activity or perhaps destroying them, if they’re already present within the food.
3) Principles of food preservation
Quality defects and losses in food caused by insects, rodents and birds could also be controlled by adequate packaging and by instituting a sustained social control programme of such pests.
4) Principles of food preservation
The deterioration in food caused by the natural phenomenon occurring throughout process, handling and storage could also be reduced by the event of best handling, process and storage conditions.
1) Prevention or delay of autolysis
Enzymes need specific pH scale vary to catalyse the life reactions. The enzymes are terribly sensitive to changes in pH scale of the atmosphere.
This data is used to preserve many foods by simply fixing their pH scale. for instance, in biological preservation of vegetables (pickling).
pH scale of raw materials is reduced through the activities of carboxylic acid) bacterium that turn out drinkable acid.
Some meat and milk products are likewise preserved or made as a results of amendment within the pH scale. generally preformed organic acids, like carboxylic acid (vinegar), area unit additional to foods for the aim.
Enzymes thrive best in a very specific temperature range. Any deviation from this to the upper or lower aspect has associate adverse impact on
enzyme activity. The food are often subjected to a selected warm temperature which will either destroy or inactivate the enzymes.
within the food trade, some fruits associated most vegetables are commonly subjected to around 100°C for some seconds to couple of minutes in an operation known as blanching or scalding.
As a results of this exposure, some damaging enzymes, e.g., the enzyme system, are destroyed. Blanching is sometimes a pre-treatment in many food preservation ways like canning. dehydration and freezing:
Another procedure used to delay autolysis is that the use of low temperature. The accelerator reactions are stupid at low temperatures that prevail within the icebox or cold storages.
Thus, refrigeration delays ripening method in fruits freeze inactivates the enzymes and generally destroy them; thus frozen a much longer we have a tendency to than the contemporary ones or those unbroken at higher than 0°C.
Enzymes need wetness for the organic chemistry reactions that they catalyze in foodstuffs. Absence of water would mean that these reactions cannot surface within the medium.
This property of enzymes is used, partly, within the preservation of foods by removal or binding of moisture.
The wetness in foods is removed by sun drying, dehydration, concentration and evaporation. accessible wetness may be certain by the employment of chemicals as seen within the production of intermediate moisture foods.
2) Prevention or delay of microorganism activity
While enzymes are half and parcel of recent foods, microorganisms are invaders and wherever undesirable, they must be treated like every alternative invader. Firstly, precautions is also taken to prevent their entry into the food.
However wherever they need already gained access, these is also thrown out. part such a method isn’t possible.
The microorganism activities is also controlled by making conditions that don’t favour their traditional existence. As a final resort, they may be destroyed by any appropriate means that
a) Keeping Microorganisms out
Nature creates all foods free from microorganisms and provides a protecting covering to prevent their entry within the tissues. Orange, banana, mango, wheat, maize, rice and groundnuts area unit all free from microorganisms once created.
The skin, peel, husk and shell give these commodities protection against infection from external sources.
Similarly, tissues of healthy animals are free from microorganisms. The skin and fatty tissues provide the animal protection from offensive microorganisms.
As before long because the outer covering of plant materials or animals is injured, microorganisms invade the tissues and begin growing, therefore inflicting infection or spoilage.
To guard against the entry of microorganisms from an outside supply, protecting covering is supplier for the food within the trade. whereas fruits, vegetables, meat and alternative foods is also packed and protected.
In tin cans or glass containers, some foods area unit given a coating of wax or alternative inert material to guard them from the attack of microorganisms. Examples are coating of some cheese varieties and eggs with wax or similar substances.
Removal of Microorganisms food process, it’s difficult to stay microorganisms away since these are present. Even without obvious signs of microorganism attack, microorganisms gain entry into food throughout harvest, storage and resulting process operations.
Since microorganisms are terribly tiny, it’s dangerous to select and throw them out. Fruits and vegetables carry microflora on their surface or in their bruised, broken and decaying tissues.
The food processor washes the staple completely so abundant of the contaminants, as well as microorganisms, are far from the surface.
The contused, broken and decayed parts are cut off within the operation selected as trimming. These operations facilitate to cut back the microorganism load within the foodstuff and aid in its preservation.
b) Creation of unfavourable conditions
Most food spoilage and infective microorganisms are aerobic in nature. The spores of a number of these organisms should have gas to germinate. This info provides the food technologist with yet one more tool to control their activities.
Creation of anaerobic atmosphere can stop growth of vegetative cells and germination of spores. this is often typically accomplished in canning by the utilization of mechanical vacuuming or in an operation called exhausting.
The air from the product is removed and therefore the will sealed airtight. Thus, though these microorganisms have gained entry, below the prevailing anaerobic conditions, they’re going to not. grow.
Hence won’t be ready to spoil the food. but anaerobic organisms could cause a problem in such processes if their activities aren’t checked or these are not later destroyed.
Another technique wont to produce unfavourable conditions and stop the activities of microorganisms in foods, even once they need Temperature is yet another terribly effective tool within the hands of individuals engaged in food preservation to form unfavourable conditions.
Use of cold (chilling or chilling) inhibits the expansion of microorganisms-their activities are bogged down at chilling and utterly stopped at freezing temperature. Holding foods at chilling temperature or in frozen state additionally helps to destroy or kill some microorganisms.
c) Destruction of Microorganisms
Spoilage in foods may additionally be prevented by destroying microorganisms. High temperatures (above the utmost growth temperature) have adverse effects on microorganisms.
Blanching is used within the food business primarily to destroy or inactivate enzymes: Some chemicals also are terribly effective in dominant microorganism activity in foods.
Use of dioxide and carboxylic acid is common in fruit and vegetable preservation business. In baking, wherever mould growth is feared, propionates are employed: Microorganisms in foods may be destroyed by the utilization of radiations of varied frequencies.
The ultraviolet waves from the spectrum have antiseptic properties. Gamma rays, emitted from by-products of atomic fission also are antiseptic and once applied to food, facilitate preserve them.
3) Control of pest activities
Insects, rodents and birds have attained pest standing in most countries. However, solely those are therefore selected that exhibit prolific procreative capabilities and compete, typically menacingly, with humans for food and house and should be related to transfer of diseases to man.
These are a constant threat to man’s survival. The apparently. harmless species ar, in fact, a necessary a part of the balanced. ecological system within which we tend to live.
Co Insects alone account for the destruction and waste of just about fifty percent of the annual cereal grain crops in some developing countries.
These little enemies of man attack food within the field, process plants, warehouses, supermarkets, additionally as within the home.
The most desirable management measures are those that demonstrate effective management over long periods while not making defiant adverse effects on man and therefore the surroundings.
Experiences with the control of insects like alternative animal pests, have shown that management measures that momentarily and indiscriminately reduce insect populations could introduce serious health hazards and environmental issues within the long-term.
Gross rodent infestation is quickly discovered by the presence of burrows, dark oil and dirty stains on rodent runaways, odour of mice, filth deposited on food, still as broken food and different materials.
Dry urine appears as darkened stain on food and containers. These stains can fluoresce under ultraviolet radiation. The presence of rodent filth in food process and storage premises necessitate prompt management live.
Complete destruction of rodents has, however, established associate nearly not possible task. The case is worse in developing countries wherever rodent populations are best-known to overwhelm on the market management facilities because of poor environmental sanitation.
Systematic management of mice and rats is practiced with a reasonable degree of success in most industrialised countries. A typical systematic management includes the employment of poison baits, cat-traps and biological ways to kill.
Mice and rats. rodent harbourages after typically either destroyed or sealed after treatment with a long rodenticide. Foods are prepacked and keep in environments that create gnawer invasion tough.
A sustained management effort will yield positive results provided that backed by an affordable live of sanitation around food handling and storage sites.
Birds consume substantial quantities of grains within the field prior to harvest. In some tropical countries, birds, like the weaverbird, are best-known to devastate entire corn crop within the field.
This loss by bird invasion has historically been checked by putting in noise-making dummies (shaped like humans or animals) at strategic points on the farm to scare birds away.
Aside from the consumption of grains, birds will contaminate food and water. to forestall this, bird screens will be erected over necessary facility sources and food handling areas.
4) Reduction physical defects
Added to the defects caused by lysis, microorganisms and biological pests, further quality deterioration in food will be caused by physical and physio-chemical interactions. These interactions are induced by series of treatments that accompany food manufacture, handling and storage.
There’s no easy rule of thumb that predicts the most effective process conditions for all sorts of foods.
However, experimentation, expertise and current exchange of scientific and technical info on the results of assorted process variables on food quality have helped within the development of optimized processes geared toward keeping physical defects in foods to minimum.
a) Surface Drying
The desiccation or drying out discovered on the surface of sure foods throughout frozen storage is a very important physical defect that may be controlled by adequate packaging and therefore the maintenance of a gradual storage temperature.
In cold storage of flesh foods, wet loss and surface drying will be decreased by maintaining beyond standard average ratio within the storage chamber.
The rise in microorganism activity evoked by such high relative humidity is unbroken under check by the employment of source of illumination as storage atmosphere sterilant.
Another common physical defect involves crystallization of from syrups and different sugar-based products.
Such defective products develop a distasteful sandy texture. Unwanted-sugar crystallization in foods will be prevented by employing a mixture rather than single sugar.
An answer containing on top of sixty percent plant product at close temperature can develop crystals, whereas an answer containing seventy five percent total sugars created.
That plant product, aldohexose and ketohexose can show no visible signs of crystals. this data is applied within the production of high sugar products like jams and sugar-based jellies.
c) other Defects
Attempts at reducing physical and textural-defects in foods throughout process and storage are seen in method handling and storage controls applied by the trade.
The ratio and drying rates are controlled in dehydrators to reduce the incidence of case hardening; stabilizers area unit wont to stop the collapse of emulsions throughout handing and storage.
Freeze removes moisture from heat sensitive foods and enhances the retention of natural biological process and textural properties on rehydration.
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