Food Preservation Methods - Food Poisoning

Food preservation is the procedure by which food is treated and handled to stop or slow down food spoilage, loss of quality, edibility, or nutritional value and thus allow for longer food storage.

Preservation usually involves preventing bacteria, fungi (such as yeasts), and other microorganisms from developing, as well as retarding the oxidation of rancid-causing fats.

Importance of Food Preservation

Food preservation stops the growth of microorganisms (such as yeasts) or other microorganisms (although some methods work by presenting benign bacteria or fungi into the food), and slows the oxidation of rancid-causing fats.

1. Food preservation gives the food more variety. For example, if fresh peas are unavailable during the hot summer months, canned or dehydrated peas might be substituted.

2. Food preservation extends food's shelf-life. Pineapples, cherries, and other fruits and vegetables can be preserved for lengthy periods of time using various ways.

3. Food preservation expands the supply of food.

4. Food preservation cuts down on food waste. Excess foods that would have been wasted otherwise are processed and preserved, adding to existing supply and reducing food waste.

5. Food preservation helps to reduce dietary deficiencies. Preserved foods help to add variety to the diet. For example, due to arid soil conditions in several Middle Eastern nations, no vegetables are grown. This shortfall is compensated for by importing fresh and preserved fruits and vegetables.

Methods of Preservation 

A number of food preservation techniques can be used which can either prevent, delay, or otherwise reduce food spoilage altogether. Preservatives can extend the shelf life of food and can last as long as it can be grown, stored, marketed, and kept in the home of the customer for a reasonable period of time.

Preserving or producing nutritional value, texture and flavour is an important aspect of food storage methods, although some methods have drastically altered the character of the preserved foods. These changes have now been seen in many cases as desirable qualities, such as cheese, yogurt, and pickled onions.

Any change that renders food unfit for human consumption is considered food spoilage. Contamination by microbes, insect infestation, or breakdown by endogenous enzymes is all possible causes of these alterations (those present naturally in the food). Food spoilage can also be accelerated by physical and chemical changes, such as the tearing of plant or animal tissues or the oxidation of certain food constituents. Foods derived from plants or animals deteriorate quickly once they are harvested or slaughtered. Any mechanical injury induced during postharvest processing may cause the enzymes stored in the cells of plant and animal tissues to be released. The cellular substance is broken down by these enzymes. Food quality is degraded as a result of the chemical processes catalysed by enzymes, such as the production of off-flavours, texture deterioration, and nutrient loss.

Food preservation is a term that refers to a variety of techniques for keeping food from spoiling after it has been harvested or slaughtered. Such customs can be traced back to primordial times. Food preservation is the procedure by which food is treated and handled to stop or slow down food spoilage, loss of quality, edibility, or nutritional value and thus allow for longer food storage.

Preservation usually involves preventing bacteria, fungi (such as yeasts), and other microorganisms from developing, as well as retarding the oxidation of rancid-causing fats.

Drying, refrigeration, and fermentation are some of the oldest methods of preservation. Canning, pasteurisation, freezing, irradiation, and chemical addition are all examples of modern processes. Modern food preservation has benefited greatly from advancements in packaging materials.

Drying

Drying is one of the most ancient techniques of food preservation which reduces water activity enough to prevent bacterial growth.

Refrigeration

Refrigeration preserves food by slowing down microorganism growth and reproduction and the action of enzymes that cause food to rot.

Freezing

It is also one of the most frequently used processes for preserving a wide range of foods, including prepared foods that in their unprepared state would not require freezing.

Salting

The salting or curing process removes moisture from the meat through an osmosis process. Meat is salted or cured with sugar, or a combination of the two. Nitrates and nitrites are also widely used to treat meat, leading to the distinctive pink colour and inhibiting Clostridium botulinum.

Crystallisation

Sugar is used to maintain fruits, either in fruit syrup such as apples, peaches, apricots, or in a crystallised form where the preserved material is cooked in sugar to the point of crystallisation and the resulting product is then stored in a dry place.

This method is used for citrus (candied peel), angelica, and ginger skins. An alteration of this process creates glacé fruit, such as glacé cherries, in which the fruit is preserved in sugar but then extracted from the syrup and sold, preserving the fruit sugar content and superficial syrup coating.

The use of sugar in brandy or other spirits is often combined with alcohol for preserving luxury products such as fruit. These should not be confused with spirits that are aromatised with fruit such as cherry brandy.

Smoking

Smoking is used to prolong the shelf-life of perishable food. This effect is achieved through the exposure of the food from burning plant materials such as wood to smoke. The meats and fish that have undergone curing are most commonly subjected to this method of food preservation.

Also smoked are fruits and vegetables such as paprika, cheeses, spices, and ingredients for making drinks such as malt and tea leaves, but mostly for cooking or flavouring. It is one of the oldest methods of food preservation which probably emerged after cooking with fire evolved.

Additives

Additives to the preservative foods can be antimicrobial. These inhibit bacterial or fungal growth, including mould or antioxidants, such as oxygen absorbers, which inhibit the oxidation of food components. 

Preservatives

Adding preservatives is the chemical method of food preservation. Conventional antimicrobial preservatives include calcium propionate, sodium nitrite, sodium nitrate, sulphites (sulphur dioxide potassium hydrogen sulfite, sodium bisulfite, etc.), and disodium EDTA. BHA and BHT are antioxidants. 

Pickling

Pickling is a food preservation method used in an edible antimicrobial liquid. Pickling can be broadly divided into two categories: chemical pickling and pickling by fermentation.

Canning

Canning includes cooking food, sealing it in sterile canisters or pots, and boiling the containers as a method of sterilisation to destroy or weaken any remaining bacteria. Foods have varying degrees of natural spoilage protection and may require the final step in a pressure cooker. 

No preservatives are added to High-acid fruits like strawberries and only a short boiling period, while marginal fruits such as tomatoes require longer boiling and the addition of other acidic components. Feeding stuffs with low acidity, such as vegetables and meats, require canning pressure.

Food preserved through canning or bottling is at immediate risk of spoilage after opening the can or bottle.

1. Pasteurisation

It is defined as heat treatment of food material at 72°C for 15 seconds, 63°C for 30 minutes, or 90°C for 0.5 seconds, followed by quick cooling to 7°C. High-temperature-short-time (HTST) treatments are favoured over low-temperature-long-time (LTLT) treatments because they cause less damage to the nutrient composition and sensory properties of meals.

2. Sterilisation

Microbes are completely eliminated during sterilisation. Fruits and acidic vegetables, such as tomatoes, can be sterilised at 100°C for 30 minutes; however, non-acidic veggies must be sterilised at 116°C for 30 minutes.

3. Freezing

Many food products can have their shelf-life extended by storing them at 4°C or below. Fresh fruits and vegetables, eggs, dairy products, and meats are all commonly refrigerated foods. However, some items, such as tropical fruits (bananas, for example), are destroyed by low temperatures. Freezing is an excellent way to preserve the nutritional value of foods. It's done at a temperature of –18°C to –4°C. The majority of juices are kept by freezing.

4. Chemicals used

Sulphur dioxide is a bleaching and antioxidant agent. Sulphite, bi-sulphite, and metabisulphite are some of the salts that are employed. The permissible level in fruit juices, including RTS and nectar, is 100 parts per million; however, it is 350 parts per million in squash, crush, and cordial. Sulphur dioxide keeps beverages' original colour for a longer time than benzoic acid.

Benzoic acid, in the form of sodium benzoate, is allowed up to 100 parts per million in RT5 and nectar, and 600 parts per million in squash, crush, and cordial.

5. Dehydration

Dehydration is the process of removing moisture from food materials in order to preserve them. The temperature of dehydration starts at 43°C and gradually rises to 60–66°C (for vegetables) and 66–71°C (for meat) (for fruits).

1. For vegetables, the moisture content in dried products should not exceed 6–8 percent, and for fruits, 10–20 percent.

2. Sweating is a process that is used to equalise the moisture content of preserved materials by storing them in bins or boxes.

3. Sulphuring is a method of preventing discoloration by fuming food materials (especially potato slices) with sulphur dioxide.

4. Freeze-drying is accomplished by using high vacuum conditions that allow for precise temperature and pressure.

Other types of preservation may Include irradiation, jellying, jugging, processing of pulsed electric fields, modified atmosphere, ground burial, biopreservation, and high pressure.