Food Microbiology

Contamination of Foods

Growing plants have a typical microbiome on their surface and can be contaminated by external sources. Animals also have a common surface...

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This article writter by MN Editors on December 30, 2021

Microbiology Notes is an educational niche blog related to microbiology (bacteriology, virology, parasitology, mycology, immunology, molecular biology, biochemistry, etc.) and different branches of biology.

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Contamination of Foods
Contamination of Foods

Contamination of Foods

Growing plants have a typical microbiome on their surface and can be contaminated by external sources. Animals also have a common surface flora, as well as an intestinal one. They also emitting organisms in secretions and excretions as well as being infected by external sources. Animals and plants suffering from parasitic diseases, naturally carry the pathogen responsible for the illness. The tissues inside, healthy of both animals and plants nevertheless, are found to be contaminated by a few microorganisms, or none at all.

Contamination of Foods From Green Plants And Fruits

The natural flora on the surface of plants is different depending on the plant, but typically comprises the species Pseudomonas, Alcaligenes, Flavobacterium as well as Micrococcus as well as coliforms and the lactic acid bacteria. Bacteria that produce lactic acid include Lactobacillus brvis and Plantarum Leuconostoc mesenteroides as well as dextranicum as well as Streptococcus Faecalis and faecium. The Bacillus species as well as yeasts and molds may also be present. The number of bacteria depend on the environment and the plant and can vary between a few hundred and thousand per square centimeter surface area to millions.

The surface of a clean tomato, for instance, might contain between 400 and 700 microorganisms for every square centimeter, while a unwashed tomato could have a number of thousand. The outer tissue of a cabbage that has not been washed could contain anywhere from 1 million to 2 million microorganisms in a gram However, washed and cut cabbage may contain as much as 200,000 to 500 000. The tissue inside the cabbage, in which the leaves’ surface is home to the most natural flora, has smaller amounts of species and less numbers, which range between a few hundred and 150,000 for a Gram.

The surfaces of plants exposed to the sun are polluted by water, soil and air pollution, as well as sewage and even animals, so that microorganisms originating from these sources are included in the natural fauna. When the conditions for the expansion of the natural flora and contaminants are present, growth in the number of specific types of microorganisms occur in particular after harvesting which will be discussed later. Certain fruits have been proven to have viable microorganisms their internal. Healthy, normal tomatoes were found to be contaminated with coliforms, Pseudomonas, Achromobacter * , Micrococcus as well as Corynebacterium and yeasts were found in healthy fruits that are not damaged. Organisms have also been discovered in the health tuber and root vegetables.

Contamination Of Foods From Animals

The sources of microorganisms that come from animals are the surface flora, the respiratory tract’s flora and the flora in the digestive tract. The natural surface flora found in meat animals is typically not as significant as the microorganisms that are contaminating their respiratory tracts and intestinal tracts. But hides, hooves and hairs contain huge amounts of microorganisms derived that originate from manure, soil water and feed but also important types that are spoilage organisms. The feet and feathers of poultry are contaminated from the same sources. The skins of many meat animals can be contaminated with staphylococci, micrococci, as well as beta-hemolytic streptococci. Staphylococci in the skin or in the respiratory tract can make their way into the carcass, and later into the final raw product. Feces and products contaminated by feces from animals may contain a variety of bacteria and fungi, including Salmonella. Salmonellosis in animals could cause contamination of with animal products and by-products, and, consequently, contaminate food products made from them with Salmonella.

The carcasses of pigs or cattle could be contaminated by salmonellae. Due to further treatment and manipulation, few of these bacteria cause human salmonellosis. In reality, the meat of slaughtered animals is usually not linked to human salmonellosis. Recent studies have found eggs and other egg products more frequently. Salmonellosis that is associated with eggs has decreased because of the pasteurization process used in egg products.

Many of the infectious diseases that affect animals can be passed on to humans through food however this is only one of the many routes for transmission. A lot of these illnesses are being eliminated or reduced through improved animal husbandry however, a list of the agents that cause animal diseases that cause infections through food could include Brucella, Mycobacterium, tuberculosis, Coxiella, Listeria, Campylobacter beta-hemolytic streptococci Salmonella Enteropathogenic Escherichia Coli as well as parasites and viruses.

The animals, from smallest to the most powerful produce waste and then their bodies to the soil and the water and the plants that grow there. The least attention has been given in the case of direct contamination to food crops by the source, except as enterococci or coliforms can be present. Birds and insects cause mechanical harm to vegetables and fruits, introduce microorganisms and open the possibility of microbial contamination.

Contamination Of Foods From Sewage

When untreated domestic wastewater is used to fertilize plants There is a chance that the raw food products are contaminated by bacteria that are harmful to humans, specifically those that cause gastrointestinal disorders. The usage of “night soil” as a fertilizer is still used in certain regions of the world, but is uncommon within the United States. In addition to disease-causing bacteria, the coliforms enterococci, anaerobes and other intestinal bacteria and viruses could contaminate food items that are derived that come from the source. The natural waters that are contaminated by sewage can contribute microorganisms that are found in shellfish and fish as well as other seafood. The sewage that is treated before it goes into the soil or into the water provides microorganisms. However, it is likely to contain fewer and less pathogens than raw wastewater.

Contamination Of Foods From Soil

The soil has the most diversity of microorganisms found in any contamination source. If microbiologists seek out new microorganisms, or strains that are suitable for specific reasons, they typically look first to the soil. Not just a wide variety of microorganisms, but also huge number of them are found in soils that are fertile, and which are able to infect the surface of plants that grow within them or on the surface of animals that roam all over the land. Soil dust is whipped by air currents, and the particles are carried away by the flow of water to move into or onto food sources. Soil is an important source of spore-forming bacteria that are heat-resistant. It is not possible to identify the microorganisms that are important in food microbiology which could be derived from soil, however it can be established without doubt that virtually every microorganism important can be found from soil.

Particularly important are the various species of yeasts and molds of the bacteria genera Bacillus, Clostridium, Enterobacter, Escherichia, Micrococcus, Alcaligenes, Flavobacterium, Chromobacterium, Pseudomonas, Proteus, Streptococcus, Leuconostoc, and Acetobacter and certain of the more powerful bacteria, such as the actinomycetes and iron bacteria. Modern methods for handling food generally involve washing the food’s surfaces and removing large amounts of soil from these surfaces. Also, care is taken to prevent contamination with soil particles.

Contamination Of Foods From Water

Natural water contains not only their natural flora, but also microorganisms that come from soil and, possibly, from animals or the sewage. Surface water in streams, storage pools and the water that is stored in large ponds and lakes differ in their microbial count and range from thousands of microorganisms per milliliter after a storm to the much lower numbers that result from the self-purification of calm lakes and ponds, or from flowing water. The ground water from springs or wells have been filtered through layers of soil and rock to a certain level, therefore, the majority in the bacteria along with the majority of the other suspended matter has been eliminated. The numbers of bacteria present in these waters could vary from a few to hundreds of microliters of bacteria.

The types of bacteria found in natural waters are mostly varieties of Pseudomonas, Chromobacterium, Proteus, Micrococcus, Bacillus, Streptococcus (enterococci), Enterobacter, and Escherichia. Bacteria belonging to the three genera are likely to be pollutants rather than a an element of the natural biota. The bacteria found in the waters around the fish and other marine life appear on the surface of the water and inside their intestinal tracts in marine fauna.

Food microbiologists are attracted by 2 aspects related to water bacteria: (1) public health aspects and (2) economic aspects. From a health-related viewpoint, the water that is consumed in connection with food must be sage for drinking, i.e. completely free of pathogens. Tests for indicators bacteria can be verified and completed using the methods that are described by the American Public Health Association (1985). Escherichia Coli which is believed to be to be more frequently of a digestive origin, is distinct from Enterobacter aerogenes, which are often found on plant surfaces as well as in soils more frequently than in the contents of the intestines. Certain laboratories for control run complete plate count and tests for coliforms on water on a regular basis and also increase the concentration of chlorination whenever they suspect something is not right. A lot of non-fermenting bacteria like Pseudomonas species can be found in the water lines, and cannot be identified by conventional coliform analysis and therefore the count of total plates is crucial. Chlorination of drinking waters is a common practice whenever there is doubt as to the cleanliness of the water, with the amount of chlorine that is found in the water ranges between 0.025 and up to 2 parts or greater of chlorine for every million cubic feet of water according to the water’s composition and the level of contamination.

From an economic standpoint an aqueous water with acceptable chemical and bacteriological properties is required when food is that is being processed or handled. The water should possess acceptable taste, odor and color, as well as clarity chemical composition, and bacteria content. It should be readily available at the desired temperature as well as being consistent in composition. Chemical composition of the water is affected by alkalinity and hardness and also by the organic matter content such as manganese, iron and fluorine.

According to the guidelines that the water used to prepare food products should be in compliance with the bacteriological requirements for drinking water. It must be safe from a sanitation perspective and also from an economic point of view. In general however, water is more significant in terms of the kind of microorganisms that it can introduce into or onto food rather than from the perspective of the overall numbers. The contamination could be caused by the use of water for the purpose of a food ingredient. To wash food items as well as cooling food that has been heated and also for manufacturing frozen ice to preserve food items. For each food item, there will be microorganisms that should be avoided, particularly. The coliform bacteria that produce gas could enter milk from cooling tank water, and cause problems in cheeses made of the milk.

Anaerobic gas formers can infiltrate food items through soil-laden water. Cooling water from canneries often includes coliform and other spoilage-related bacteria that get into canned food during cooling by small holes in the seals or seams in the seals of cans. The water is usually chlorinated, however there are reports that a flora that is resistant to chlorine could develop in the course of time. The bacteria that cause ropiness in milk e.g., Alcaligenes viscolactis* and Enterobacter aerogenes, are usually derived from water, just like slime-forming species like Achromobacter * Alcaligenes and Pseudomonas that cause problems within cottage cheese. The bacterium that causes the taint that appears on the surface that is found in butter Pseudomonas putrefaciens originates primarily from water. Iron bacteria, which’s sheaths are laced with ferric hydroxide can cause a blockage to the entire water supply, and can be difficult to remove. The bacterial community of crushed ice that is used to treat fish and any other food item comprises mainly comprised of Corynebacterium, Alcaligenes, Flavobacterium, Pseudomonas, and cocci.

It’s clear from the discussion above that it is essential to select a place that has an adequate supply of water when setting up a facility to process or handle food items and food items. It is often essential to purify the water in order to ensure it is of a satisfactory chemical and bacteriological purity. The water supply should be secured against the contaminant sewage. They can be cleansed through sedimentation in lakes or reservoirs as well as through filtration using finer filters or sand or through the process of chlorination, ultraviolet irradiation or boiling. The purification process is only likely to be the result of sedimentation. Filtration that is efficient greatly reduces amount of microbial matter, however filters may be the source of contamination of water by harmful bacteria. So, filters used for water used in soft drink have been observed to contain massive amounts of coliforms. Treatment of water using ultraviolet rays is a common method used on soft drinks’ water.

Contamination Of Foods From Air

Food contamination from the air could be vital both for health and economic reasons. In particular, the pathogens that cause disease, particularly those that cause respiratory illnesses can be transmitted to employees via air or food item could be affected. The number of microorganisms found in food items could increase from air, especially when air is being used to aerate the food, for instance, in bread yeast that is growing, but the amount of bacteria introduced through air sludge are not significant. Spoilage bacteria can come from air, and so could those that interfere with fermentation of food. Airborne mold spores can cause problems in the meat, cheese sweetened condensed milk and bacon and bread slices.

Sources of Microorganisms in Air

Air is not the natural microorganisms that live there and all present are a result of accident , and typically are found in suspended solid materials or in droplets of moisture. The microorganisms that are present in air come from dust or lint, dry soil; sprays from lakes, streams, or oceans, droplets of water from coughing, sneezing or talking. They also grow on the surface of the sporulating molds found on ceilings, walls flooring, floors, food items, and even the ingredients. Therefore, the air around a facility manufacturing yeast typically is rich in yeast, and the air in the dairy plant could be contaminated with bacteria, or at the very least the starter bacteria employed in the plant.

Kinds of Microorganisms in Air

The microorganisms living in the air do not have the chance for expansion, but simply remain there and the ones that are the most resistant to desiccation are the ones that will last for the longest. Mold spores, due to their small size, their resistance to drying, and their large quantities per mold plant are typically found in the air. Most mold spores do not easily water-wet and tend to be less likely be able to swell in humid conditions than particles that are easily wet. There is a possibility for every type of bacterium in the air, particularly when dust is present or droplets of water, but certain species are more common in air that is not disturbed. Cocci generally are more prevalent than rod-shaped bacteria. Likewise, bacteria spores are not common in clean air. The spores of yeasts, particularly asporogenous chromogenic ones, can be found in the majority of air samples. Naturally, when the dusts and sprays from a variety of materials are released to the atmosphere, microorganisms associated with those suspended substances are present: soil organisms from soil as well as dust as well as water organisms from water sprays and plant species from feed or fodder dusts, etc.

Contamination Of Foods During Handling And Processing

The contamination of food products by the natural sources mentioned could occur prior to the time that food is harvested or collected or when processing and handling or processing. The contamination can also come from equipment that is in contact with food as well as packaging materials and also from employees. The processor tries cleaning as well as “sanitize” equipment to reduce the risk of contamination, and also to use packaging materials that reduce contamination.

The word “sanitize” is used here in place of “sterilize” because although an attempt to sterilize the machine, i.e., free it from all life-forms and organisms is rarely achieved. The possibility of contamination during handling and processing of different types of food items will be covered in the subsequent sections on the specific food items. Food processing workers may infect food products through handling and processing. Different researchers suggest that human beings shed anywhere from 103 to 104 viable microbes every minute.

The amount and type of organisms that are shed are closely connected to the subject’s working environments. Since the importance of food handlers in outbreaks of foodborne diseases is well-established from a health perspective the source of contamination garnered much attention. The table below illustrates the risk of contamination of food items through the hands of various employees.

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Microbiology Notes is an educational niche blog related to microbiology (bacteriology, virology, parasitology, mycology, immunology, molecular biology, biochemistry, etc.) and different branches of biology.

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