removal of microorganisms, anaerobic conditions, high and low temperature

Microbial removal is not very effective for food preservation, but it may help reduce the number of microbes under special conditions. Removal can be done by centrifugation, filtration, trimming, and washing. The main purpose of cleaning is to remove dirt, dirt particles, and contaminants on the surface and remove pesticide residues, fertilisers, and chemicals used during the manufacturing process and reduce the load of microorganisms and improve the product’s appearance. Cleaning reduces the number of microorganisms from the cleaned area.

Centrifugation can be divided into three groups: separation of immiscible liquids, clarification of liquids by removing small amounts of solids, and removal of solids. In many filtration processes, a coarse filter is used first to separate large compounds, and then ultra-filtration is used. Trimming can effectively remove rotten parts of food, which helps preserve food. The presence of pathogenic microorganisms in food leads to the development of food poisoning and other types of food poisoning. Therefore, microorganisms are kept away from food by hygienic methods at various food production or processing stages.

Microorganisms present in food are removed in various ways. The method of removing microorganisms from food depends on the type of solid food, semi-solid food, liquid food, etc. Microorganisms present in liquid foods are removed by physical separation using a filtration process. Different filters and filtration processes are used, depending on the size of the microorganisms to be removed and the thickness and consistency of the liquid food.

The growth of microorganisms in food can be stopped in various ways. Microbial growth is affected by a variety of physical factors such as temperature, water content, and aeration. The growth of microorganisms in food is prevented by altering one or more of these physical factors. Low temperature suppresses the growth of microorganisms in food by reducing enzyme activity. Most perishables are stored together in a refrigerator or refrigerated warehouse.

By storing foods and food materials at low temperatures, they are protected for a long time in terms of physical quality and nutritional value. Food is also preserved by adding an antibacterial agent as a food preservative. Various chemicals, such as organic acids and inorganic salts, are commonly used as food preservatives to directly prevent or suppress microorganisms’ growth and create food states that inhibit the growth of microorganisms.

Storage of food under anaerobic conditions suppresses the growth of aerobic microorganisms such as fungi and bacteria. Microorganisms present in food are killed by high-temperature treatment or irradiation. Cooking and pasteurising hot foods are the most commonly used processes for hot treatment of liquid foods and milk. Most packaged processed foods undergo ionising and non-ionizing radiation treatments to kill the microorganisms present there.

Principles of food preservation

Food preservation is the process of dealing and processing food to prevent or delay spoilage (deterioration of quality, edibility, nutritional value) caused or accelerated by microorganisms. In order to maintain its value as a food, it is important to maintain or create its nutritional value, texture and flavour.

1. Prevent or delay microbial degradation of food

•       While keeping  microorganisms away (asepsis)
•       By removing microorganisms (filtration)
•       By inhibiting the growth as well as activity of microorganisms (using low temperatures, implementing anaerobic conditions, by applying chemicals).
•       By killing microorganisms (by heat or radiation).

2. Prevent or delay food autolysis

•       By destroying or inactivating food enzymes (balancing or cooking)
•       By preventing or delaying pure chemical chain reactions (using antioxidants preventing oxidation).

3. Prevent damage caused by insects, different animals, or even mechanical influences (applying fumigants, fillings, packaging, etc.).

This article aims to emphasise on prevention of microbial degradation of food mainly by the removal of microorganisms.

Preventing of microbial decomposition

•  Asepsis refers to keeping microorganisms away from food by using a natural cover or by placing an artificial cover outside the food. Therefore, the natural barriers to food include nutshells (almonds, walnuts, and pecans), fruit and vegetable skins (bananas, mangoes, citrus fruits, ash gourds, etc.), eggshells or fats in meat. Packaging also prevents the invasion of microorganisms into a food. For example, peaches and mushrooms sealed in cans and clean bottles in a hygienic environment help keep microorganisms away and prevent milk spoilage during processing and collection.
•   Bacterial proof filters are widely used to transfer microorganisms from liquid food products. A variety of materials, including asbestos pads, diatomaceous earth, as well as unglazed porcelain, are used to filter fluid food products already when they enter the human body. As a result of the way liquid foods operate. Centrifugation, trimming, cleaning, etc., can also be used, but they are not good enough.
•   By inhibiting the growth or activity of microorganisms:

• Microbial growth, as well as enzyme activity in foods, are delayed by storage at a low temperature. Foods should be stored in the refrigerator underground (15 ° C) for root vegetables, potatoes, onions, etc., or at low temperatures (050 ° C) for most veggies and fruits, meat, chicken, fresh milk, dairy products, etc., below freezing. Can be stored at the temperature of. (From 18 ° C to 40 ° C).
•  Dehydrating food to levels that prevent the growth of microorganisms is an important method of preservation. Moisture can be combined by applying heat, such as sun drying or mechanical drying, or adding sugar (like jam, jelly) or salt (high salt content of raw mango) to prevent microorganisms. Examples include osmotic dehydration, raisins, apricots, onions and cauliflower.
•   Anaerobic conditions can be established by removing or expelling air or oxygen from the given package and replacing the air with an inert gas such as CO₂or nitrogen. The reduction of oxygen under these conditions impedes the growth of surviving bacteria as well as their spores. The reproduction of CO₂ at the time of fermentation as well as its accumulation on the surface area, makes the condition anaerobic to impede aerobic growth. Carbonation of beverages and storage of a controlled atmosphere of fresh food serve the exact purpose. Jam, where food is closed after the air is removed (suction), demonstrates this principle. However, anaerobic bacteria, as well as their spores, must be decapitated to prevent food spoilage. Oiling food prevents contact with the air and prevents the growth of microorganisms such as mould and yeast.

•  By adding the right amount of different chemicals to your food, you can prevent unwanted food spoilage.
• The application of heat leads to the clotting of proteins as well as the inactivation within the metabolic enzymes, leading to the destruction of microorganisms present in food. When food is exposed to high temperatures, the enzymes contained inside the food are also inactivated. Food can be further heated to temperatures below 100 ° C (pasteurised), 100 ° C (cooking), or above 1000 ° C (sterilised).
•  Irradiation consists of exposing food to either electromagnetic or ionising radiation in order to destroy the microorganisms present inside the food. Examples of irradiation include the use of UV lamps when sterilising utility knives in a bakery. Gamma (?) Radiation from Cobalt-60 or caesium-137 sources has been used to irradiate many fruits such as papaya, mango, onions, spices, and fish. It is also used to prevent the germination of onions and potatoes.

Conclusion

The process of the use of microorganism metabolism to remove pollutants is known as bioremediation. It is a technique that removes toxic chemical substances from water bodies using microorganisms such as bacteria and fungi. Bioremediation also includes plants to detoxify pollutants from the soil. The microorganisms used for bioremediation may already be present or isolated in contaminated water bodies. Since microorganisms grow and function