However, not all of them are efficient in eliminating spores due to the morphological features that provide resistance to hostile conditions. Because of their ubiquitous nature, bacterial spore-formers are widely located in all types of foods.
From the beginning of the 20th century, it has been studied the spore-forming bacteria, especially the pathogenic species, but rapidly, spoilage spore-forming bacteria were also investigated Remize, Indeed, in recent years, there has been an increasing interest in spore-forming bacteria, because they are considered a major risk in heat-treated food production plants.
Mesophilic spore-forming bacteria belong essentially to two taxonomic groups: the Bacillales order and the Clostridium genus, depending on whether they are aerobic or not.
Bacillales gathers aerobic, facultative aerobic, or facultative anaerobic bacteria. The order Bacillus , Clostridium , Sporolactobacillus , Soporosarcin , and Desulfotomaculum are capable of forming endospores. For food microbiology, the first two have a special interest because of the problems caused by some species of these orders. Of the many species of Bacillus and related genera, most do not cause disease. However, there are some species that generate important diseases in humans.
Bacillus cereus is known to be responsible for two types of foodborne diseases: the diarrheal and the emetic type. In addition, B. It has been isolated from other species such as B. Diarrheal disease is often associated with protein rich foods meat, vegetables, puddings, and milk products and is thought to be caused by vegetative cells ingested as viable cells or spores that produce enterotoxins in the small intestine Abee et al.
The emetic disease is often associated with starch-rich foods fried and cooked rice, pasta. It was identified for the first time in the United Kingdom in the early s, when microorganisms from B. The B. Within the genus Bacillus , B. Most studies related to genomic analysis have indicated that B. Clostridium are rod-shaped, Gram-positive bacteria capable of producing spores. The genus Clostridium gathers all mesophilic anaerobic spore-formers encountered in food.
According to the Health Protection Agency, the Clostridium genus consists of more than a hundred known species, including harmful pathogens such as C. The anaerobic status of these bacteria is a strong driver for niche differentiation compared to Bacillales representatives. Besides, they can be differentiated based on their biochemical activities, including saccharolysis and proteolysis.
The first four members produce powerful toxins released from vegetating growing bacteria, that is, C. Its action is the reverse of that of tetanus toxin, that is, it prevents muscle contraction, leading to flaccid paralysis of important muscles.
It inhibits the release of acetylcholine at motor nerve endings in the parasympathetic nervous system. The organism produces at least two potent toxins that are responsible for severe and occasionally fatal diarrhea.
The toxin prevents muscle relaxation, leading to persistent contraction of facial and body muscles. Formation, resistance, and germination of spores have been widely studied, essentially for Bacillus.
According to several authors Piggot and Hilbert, , Sonenshein, sporulation occurs in response to a high cellular density, nutritional limitations, or cellular communication. The resistance of spores is developed during the sporulation. These spores are metabolically dormant and resistant to heat, radiation, desiccation, pH extremes, and toxic chemicals Setlow, The transition from spore to vegetative cell involves three distinct phases: activation, germination, and growth.
In Fig. Spore wraps are multilayered, and usually are distinguished from spore core to external medium. They are composed of an internal membrane, a cortex, an external membrane, a coat, and possibly an exosporium.
Each layer presents specific structural, biochemical, and permeability properties Remize, Exosporium is a thin delicate covering made of proteins. Inner and outer spore coats are composed of layers of spore-specific proteins. The cortex is composed of loosely linked peptidoglycan and contains dipicolinic acid, which is particular to all bacterial endospores. This acid cross links with calcium ions embedded in the spore coat and contributes to the extreme resistance capabilities of the endospores because it creates a highly impenetrable barrier.
Finally, they contain the usual cell wall and, cytoplasmic membrane, nucleoid, and cytoplasm. Schematic example of spore-forming bacteria structure is depicted in Fig. Soil is considered as a major habitat of spore-forming bacteria. Besides, soil contamination can transfer to plant material silage and to feed. According to Magnusson, Christiansson, and Svensson , the major cause of contamination into foods is related to dispersion of spores by fecal material of warm-blooded animals.
Indeed, the microorganism, C. Specifically, Svensson, Ekelund, Ogura, and Christiansson have noticed the presence of a persistent B. Overall, it is worthy to say that processed foods are increasingly a mixture of multiple ingredients and additives, each bringing its own spore-forming bacteria into the final food products. Works in the literature clearly demonstrate that the origins of B. A wide variety of methods have been developed for producing safe foods, classified in 1 physical, 2 chemicals, and 3 others, within which emerging technologies can be mentioned.
Physical methods of inactivation of microorganisms are those, based on the use of temperatures and modified pressures with the aim of altering cell structures or essential biomolecules for their metabolism as high-pressures HPP and ionizing radiations ultraviolet and infrared. Regarding the first methodology, Zhang and Mittal reported successful conditions with HPP for the inactivation of spores of various species.
However, these authors affirm that due to the complicate intrinsic and extrinsic factors, HPP conditions should be verified case by case for required sterility. These enzymes are present in the spore in an active form, but they do not act until they are activated by the mechanical damage.
Within the chemical processes, the most used are acidification and smoking. Such processes can generate added value to the product by improving sensorial characteristics of the final product. However, these treatments are not effective in spore elimination. Spores are extremely resistant to a variety of chemicals, including acids, bases, oxidant and alkylating agents, aldehydes and organic solvents.
However, treatments with strong acids can eliminate spores, probably due to the rupture of the inner membrane Setlow, On the contrary, treatment with a strong alkali is less effective because they can be reactivated with an adequate recovery by lysozymes Setlow, Within emerging technologies, we can highlight plasma and advanced process of oxidation based on radical generation. Plasma has been reported to inactivate both vegetative cells and bacterial endospores.
Three basic mechanisms have been attributed to the inactivation of spores: 1 DNA degradation by UV radiation, 2 volatilization of compounds of the spore surface by UV photons, and 3 erosion of the spore surface by the adsorption of reactive molecules as free radicals Philip et al. Finally, advanced oxidation processes are based on the generation of hydroxyl radicals using different precursors UV, hydrogen peroxide, ozone, electrons, photo catalysis with titanium dioxide, Fenton reagent, etc. In particular, the Fenton reaction has been tested for elimination of spores in water with successful results Bondala et al.
However, studies to establish whether these processes can be widely used in other foods, without a possible change in sensory characteristics must be developed.
The use of microorganisms to obtain different types of food, such as beer, wine, bread, cheeses, and fermented milk is very old. There have been reports of application of fermentation processes for the production of foods from times before Christ. In the 20th century, the industrial microbiology expanded even more, because they perceived new possibilities for obtaining large variety and quantity of products by fermentative processes. Yeasts are fungi that grow as solitary cells that reproduce by budding and can be classified either to Ascomycetes e.
Biotechnologically Important Yeast Spp. Johnson, a , Johnson, b. Yeast taxa are distinguished on the basis of the presence or absence of capsules, the size and shape of the yeast cells, the mechanism of daughter cell formation conidiogenesis , the formation of pseudohyphae and true hyphae , and the presence of sexual spores, in conjunction with physiologic data.
Morphology is employed primarily to distinguish yeasts at the genus level, whereas the ability to assimilate and ferment various carbon sources and to utilize nitrate as a source of nitrogen are used in conjunction with morphology to identify species. Of all these yeast species, only about 12 are employed at industrial scale, and around 70—80 species were used at laboratory scale to possess potential value in biotechnology Deak, , Fell et al. Traditionally, the yeast has been used for the production of alcoholic beverages, biomass, and glycerol.
In this regard, Saccharomyces cerevisiae is famously known for its role in food production. It is the critical component in the fermentation process that converts sugar into alcohol; an ingredient shared in beer, wine, and distilled beverages. It is also used in the baking process as a leavening agent; yeast-releasing gas into their environment results in the spongy-like texture of breads and cakes.
Because of its role in fermentation, humans have known about and used S. Other yeast involved in the common fermented foods and beverages such as breads and bakery products, dairy products e. In addition to traditional industrial use, there are applications of yeasts in several food fermentations such as alcoholic beverages, sausages, cheese, bakery products, and other fermented foods.
Modern applications of yeasts involve the production of single-cell proteins, ethanol, industrial enzymes, foodstuffs and fodder, and small molecular weight metabolites see Fig.
Finally, yeasts also have important roles in agriculture as agents of biocontrol, bioremediation, and as indicators of environmental quality. On the other hand, the spoilage yeasts of drinks and foods have gained an increasing importance in food technology, being responsible for significant economic losses Thomas, In this regard, Pitt an Hocking noticed that only about 10 species of yeasts Dekkera bruxellensis, Zygosaccharomyces bisporus, Schizosaccharomyces pombe, Issatchenkia orientalis, Debaryomyces hansenii, Candida holmii, Pichia membranifaciens, Zygosaccharomyces bailii, Saccharomyces cerevisiae, Zygosaccharomyces rouxii , and Kloeckera apiculata are responsible for the spoilage of foods that have been processed and packaged.
The deterioration of food and drinks caused by yeasts is summarized in Table 3. The term mold is commonly applied to certain multicellular, filamentous fungi whose growth on foods is usually readily recognized by its fuzzy or cottony appearance.
Generally, molds are concerned in the spoilage of foods where moldy or mildewed foods are considered unfit to eat. The gross appearance of a mold growing on a food is often enough to indicate its genus. In this regard, some look dry and powdery, some look velvety on the upper surface, and others gelatinous or wet, whereas some molds are compact and others are loose and fluffy. In addition, the pigments in the mycelium black, purple red, gray, etc. Molds are characterized by the development of hyphae a mass of branching, interwined filaments , which result in the colony characteristics known as a mycelium.
In addition, molds grow on the surface of food they require free oxygen for growth and in a wide range of pH values from 2 to 8. The most important molds from the industrial point of view are as follows:. Mucor that have been used for centuries in food manufacturing for cheese ripening or Asian fermented food production. The genus Mucor contains several species.
The most common ones are Mucor amphibiorum, M. Aspergillus molds are very widespread, they are involved in the spoilage of foods, and some are useful in preparation of fermented foods. This genus grows well in high sugar and salt concentrations and hence in many foods with low moisture content.
The Aspergillus genus comprises species Samson et al. Rhizopus are involved in the spoilage of many foods such as vegetables, berries, bread, and fruits. The genus Rhizopus includes several species. The most common ones are, namely, Rhizopus arrhizus, Rhizopus azygosporus, Rhizopus microsporus, Rhizopus schipperae , and Rhizopus stolonifer.
Penicillium is well known and one of the most common fungi. It has a worldwide distribution and a large economic impact on human life. Alternaria are involved in the spoilage of many foods such as potato and tomatoes. Alternaria spp. The most common species are Alternaria citri, Alternaria tenuis , and Alternaria brassicae. Bothrytis are important pathogens of many agronomically important crops, such as grapevine, tomato, bulb flowers, and ornamental crops Jarvis, Molds also play an important role in the ripening of some dry-fermented products.
In addition, molds growth on the surface food products exerts antioxidative effects due to their obligate requirement for oxygen consumption for respiratory purposes and physical barrier effects due to the presence of their mycelial growth, which reduces the penetration of oxygen, and light into the product Bruna et al. Viruses are obligate intracellular parasites that cause a wide range of diseases in plants, animals, and humans.
As obligate parasites, viruses must continue to find new host cells and individuals, and be able to use the biochemical reactions of the cell to replicate. They can be transmitted in different ways but the infection of the cells lining the intestinal tract and dispersed by shedding into the stool or through emesis were the most important foodborne infections. Several different viruses may cause a single disease, as determined by the tissue or organ that is affected, or one virus may cause a unique disease due to the nature of its interaction with the body Rosenthal, Numerous viruses can be found in the human gut, but only few are commonly recognized as important foodborne pathogens.
The number of foodborne viruses is relatively small, but the Norovirus and Hepatitis A are currently recognized as the most important human foodborne pathogens with regard to the number of outbreaks and people affected in the world Cliver, Both viruses are highly infectious and may lead to outbreaks.
There are other viruses involved in the transmission of food or waterborne but they occur occasionally: Hepatitis E, Aichivirus, Astrovirus, Coronavirus, Rotavirus, and Saporavirus. Norovirus is a very contagious virus that can infect anyone, from an infected person, contaminated food or water, or by touching contaminated surfaces. The virus causes inflammation of stomach or intestines or both. This leads to have stomach pain, nausea, and diarrhea and to throw up. These symptoms can be serious for some people, especially young children and older adults CDC, a , and many people are infected in a very short time.
Most outbreaks of norovirus illness happen when infected people spread the virus to others. However, norovirus can also be spread by consuming contaminated foods or water. Food can be contaminated with norovirus at any point when it is being grown, shipped, handled, or prepared.
Foods that are commonly involved in outbreaks of norovirus illness are: leafy greens such as lettuce , fresh fruits, and shellfish such as oysters. Hepatitis A virus HAV is classified as a picornavirus. Primates are the only natural host Balayan, After ingestion, uptake in the gastrointestinal tract, and subsequent replication in the liver, HAV is excreted in bile, and high concentrations are found in stool specimens. Hepatitis A is an increasing problem because of the decrease in immunity of populations in countries with high standards of hygiene.
HAV contamination of a food product can occur at any point during cultivation, harvesting, processing, distribution, or preparation. HAV can be spread either by eating or drinking food or water contaminated with the virus, including frozen or undercooked food. The food and drinks most likely to be contaminated are fruits, vegetables, shellfish, ice, and water CDC, b.
Recognizing foodborne transmission using routine surveillance data may be difficult because: 1 case patients may have difficulty recalling food histories during the 2—6 weeks before illness, 2 cases may accrue gradually or not be reported, 3 a food item may be focally contaminated, 4 some exposed persons have unrecognized HAV infection, 5 some exposed persons have preexisting immunity from a previous infection or previous vaccination , 6 persons who acquire infection through contaminated food are not recognized amid an ongoing high incidence in the community, and 7 cases are geographically dispersed over several public health jurisdictions Fiore, Hepatitis E is common in many parts of the world, especially in oriental and meridional Asia, and it is transmitted from ingestion of fecal matter, even in microscopic amounts, and is usually associated with contaminated water supply in countries with poor sanitation CDC, b.
There are at least four different genotypes: 1 and 2 have only been found in humans, while 3 and 4 circulate in several animals including pigs, wild boars, and deer without causing disease, and occasionally infect the human being WHO, In developing countries, HEV genotypes 1 and 2 are spread by fecally contaminated drinking water. Consumption of shellfish was a risk factor in a recently described outbreak in a cruise ship. HEV genotype 4, detected in China, Taiwan, and Japan, has also been associated with foodborne transmission.
The picornaviruses isolated from human were termed Aichivirus. Transmission occurs by the fecal-oral route, by direct contact either with a HAV-infected person or by ingestion of HAV-contaminated food or water. Astrovirus AstV is a type of viruses classified as Astroviridae family genus Mammoastrovirus that cause gastroenteritis. Food plays an important role in its transmission.
AstV is stable in drinking water, fresh surface water, and seawater, indicating another means of transmission. Coronaviruses are an extensive family of viruses, some of which may be the cause of various human diseases, ranging from the common cold to severe acute respiratory syndrome. Coronaviruses are enveloped viruses with a positive-sense RNA genome.
This structure also protects the virion from harsh conditions and allows this enveloped virus to be transmitted by the fecal-oral route in addition to the respiratory route Rosenthal, RV is a contagious virus that can cause gastroenteritis inflammation of the stomach and intestines by the fecal-oral route CDC, c. Symptoms include severe watery diarrhea, often with vomiting, fever, and abdominal pain. Infants and young children are most likely to get rotavirus disease. RV can be spread by contaminated water and food, especially shellfish Bishop, Sapovirus SaV is an important pathogen causing acute gastroenteritis in humans globally, especially in infants and young children.
SaV are widespread and its outbreaks have become more frequent recently Oka et al. This point describes a limited number of parasitic diseases as representative of the major groups of foodborne parasitic organisms. Numerous parasites can be transmitted by food including many helminths and protozoa. In developing countries, the most common way that parasites are transmitted in foods occur by consumption of undercooked fish, crabs, mollusks, meat, raw aquatic plants such as watercress and raw vegetables that have been contaminated by human or animal feces.
Symptoms of foodborne parasitic infections vary greatly depending on the type of parasite. Helminthic infections can cause abdominal pain, diarrhea, muscle pain, cough, skin lesions, malnutrition, weight loss, neurological, and many other symptoms depending on the particular organism and burden of infection. Protozoa such as Cryptosporidium spp.
Therefore, the foodborne parasites could be classified as described later. A variety of human helminthic infections could be acquired through the consumption of food products from infected animals and plants, through the accidental ingestion of infected invertebrates in foodstuffs or drinking water, or through inadvertent fecal contamination by humans or animals. People acquire trichinosis by consuming raw or undercooked meat infected with the Trichinella parasite, particularly wild game meat or pork.
Even tasting very small amounts of undercooked meat during preparation or cooking puts you at risk for infection. Several different species of Trichinella can cause human disease; the most common species is Trichinella spiralis , which has a global distribution and is the species most commonly found in pigs.
However, there is an increasing number of reports of Trichinella britovi as a cause of human infection caused by meat from domestic pigs Gamble et al.
Trichinosis is considered a zoonosis because infection occurs after ingestion of raw or poorly cooked meat from infected animals. One to two days after the ingestion of heavily encysted meat, trichinae penetrates the intestinal mucosa, producing nausea, abdominal pain, diarrhea and sometimes, vomiting.
The larvae begin to invade striated muscles about 7—9 days after the initial symptoms. About 6 weeks after the initial infection, encystment occurs, accompanied by tissue pain, swelling, and fever Jay et al. Taeniasis is the result of ingesting tissue cyst of either T. Flatworm and roundworm parasites in humans are their definitive hosts Jay et al. People with taeniasis may not know they have a tapeworm infection because symptoms are usually mild or nonexistent.
Although most cases of taeniasis are asymptomatic, up to one-third of patients complain of nausea or abdominal pain that is often relieved by eating. Generally, epigastric pain may be accompanied by weight loss, increased appetite, headache, constipation, dizziness and diarrhea.
Allergic reactions, such as urticarial and pruritus may also be due to the worm and its metabolites Gamble et al. Anisakiasis is a parasitic disease caused by anisakid nematodes that can invade the stomach or intestine of humans. This roundworm infection is caused by two closely related genera and species: Anisakis simplex and Pseudoterranova decipiens.
Both of these organisms have several intermediate hosts and generally more than one definitive host Jay et al. The transmission of this disease occurs when infective larvae are ingested from fish or squid that humans eat raw or undercooked Sakanari et al. In the invasive form, worms typically penetrate the mucosa of the stomach or small intestine, resulting in epigastric pain, nausea, vomiting, and diarrhea, usually 12 h after consumption of the infected seafood Hayunga, In some chronic cases, the only treatment is the removal of the larvae via endoscopy or surgery.
Diphyllobothrium latum are the largest tapeworms that can infect people and can grow up to 9 m long. The definitive hosts of D. While most infections are asymptomatic, complications include intestinal obstruction, nausea, abdominal pain, diarrhea, and weakness. Diagnosis is made by identification of eggs or segments of the tapeworm in a stool sample with a microscope.
Safe and effective medications are available to treat Diphyllobothrium. Infections, as in the case of anisakiasis, are acquired by eating raw or undercooked fish, usually from the Northern Hemisphere Europe, North America, and Asia , but cases have also been reported in Uganda and Chile.
Fish infected with Diphyllobothrium larvae may be transported to and consumed in any area of the world. Adequately freezing or cooking fish will kill the parasite. Although the four helminths discussed earlier are the most important, there are many of them that can be transmitted by other sources of food Hayunga, such as Clonorchis sinensis, Paragonimus westermani, capillaria philippinensis, Gnathostoma roundworms, Heterophyles heterophyles, Metagonimus yokagawai, Echinostomum, Nanophyetus salmincola, Eustrongylides, Phylometra , and Nybelinia surmenicola from fish or marine source, Faciola hepatica, Fasciolopsis buski, Dicrocoelium, Angiostrongylus costaricensis, Trichostrongylus , and Echinococcus granulosus acquire from vegetation or Dracunculus medinensis and Gnathostoma spinigerum acquire from drinking water.
Protozoan parasites have long been associated with foodborne and waterborne outbreaks of disease in humans. Difficulties arise with the inactivation of these organisms because of their resistance to environmental stresses Ortega, Cryptosporidium is a microscopic parasite that causes the diarrheal disease cryptosporidiosis. There are many species of Cryptosporidium that infect animals, some of which also infect humans such as C. The parasite is protected by an outer shell that allows it to survive outside the body for long periods and makes it very tolerant to chlorine disinfection.
While this parasite can be spread in several different ways as food contaminated with Cryptosporidium oocytes , water drinking water and recreational water is the most common way to spread the parasite. Generally, C. Immunocompetent patients develop a profuse diarrhea accompanied by epigastric cramping, nausea, and anorexia Ortega, Cyclospora cayetanensis is a coccidian that is closely related to the cryptosporidia, and some human infections by the latter it has been misdiagnosed as cyclosporiasis Jay et al.
People become infected with Cyclospora by ingesting sporulated oocysts, which are the infective form of the parasite. This most commonly occurs when food or water contaminated with feces is consumed. An infected person sheds immature and noninfective Cyclospora oocysts in the feces. The oocysts are thought to require days to weeks in favorable environmental conditions to become infective. Therefore, direct person-to-person transmission is unlikely, as is transmission via ingestion of newly contaminated food or water.
Cyclospsoriasis is characterized by mild-to-severe nausea, anorexia, abdominal cramping, mild fever, and watery diarrhea Ortega, Cats are the definitive hosts, while other warm-blooded animals serve as intermediate hosts.
The oocytes are environmentally resistant and can survive several years. The unsporulated oocysts require 24 h outside the host to differentiate and become infectious.
When the oocysts are ingested, the sporozoites are released and they invade epithelial cells and rapidly multiply asexually, producing tachyzoites. Choriorentinitis is frequently observed in adults who acquire the infection. Other symptoms as fever with rash, headache, muscle aches, and pain and swelling of the lymph nodes were described Jay et al. In immunosuppressed patients, toxoplasmosis could be reactivated from latent infections Reiter-Owona et al.
Toxoplasmosis can also be acquired by transplacental transmission when a pregnant woman becomes infected. Most infected children do not show any signs of the disease until later in life, when they may present with choriorentinitis and mental retardation Ades, , Brady-McCreery et al. Giardia is a protozoan flagellate that belongs to the phylum Sacomastigophora.
The prothozoites have eight flagella that arise on the ventral surface near the paired nuclei and give rise to falling-leaf motility Jay et al. Most human infections result from the ingestion of contaminated water or food or direct fecal-oral transmission. Giardia is protected by an outer shell that allows it to survive outside the body for long periods. Five different species of Giardia have been described G. Giardia can be observed in the form of trophozoite and the cyst.
The cyst is the infectious form and is relatively inert. After cysts are ingested, excystation occurs in duodenum after exposure to the acidic gastric pH and the pancreatic enzymes. The majority of Giardia infections are asymptomatic, but they can present a chronic diarrhea. Symptomatic patients present with loose, foul-smelling stools, and increased levels of fat and mucus in fecal samples. Flatulence, abdominal cramps, bloating, nausea, anorexia, and weight loss are common.
Fever is occasionally present at the beginning of the infection Ortega, There are thousands of different types of microorganisms everywhere in air, soil, and water, and consequently on foods, and in the digestive tract of animals and human.
Microbes such as bacteria, molds, and yeasts are employed for the production of foods wine, beer, bakery products, dairy, etc. On the other hand, microbial contamination of food can occur at any point in the food production process: growth, harvesting, transport, storage, or final preparation.
In this regard, the microbial growth in foods can also cause visible changes such as change in color, deposition of powdery growth, making it lose its organoleptic characteristics, and effervescences on food surface. National Center for Biotechnology Information , U. Innovative Technologies for Food Preservation.
Published online Sep Jose M. Lorenzo , 1 Paulo E. Saraiva , 3 and Daniel Franco 1. Paulo E. Jorge A. Guest Editor s : Francisco J. Barba University of Valencia, Valencia, Spain. Guest Editor s : Anderson S. Author information Copyright and License information Disclaimer.
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Abstract Microbiology is important to food safety, production, processing, preservation, and storage. Keywords: Spoilage, molds and yeast, industrial application, gastroenteritis, foodborne outbreak, parasites and viruses, spore-forming bacteria, food contamination. Related Articles How can I tell if chicken is spoiled? Do spoilage bacteria make people sick? Can bacteria grow in the refrigerator? Is if safe to consume perishable food such as meat or poultry that has been left out at room temperature?
What are the signs of food spoilage? Trending Articles How long is meat or poultry safe to use after the sell-by date? How long can you store eggs in the refrigerator? This effect is achieved by exposing the food to smoke from burning plant materials such as wood.
Most commonly subjected to this method of food preservation are meats and fish that have undergone curing. Fruits and vegetables like paprika, cheeses, spices, and ingredients for making drinks such as malt and tea leaves are also smoked, but mainly for cooking or flavoring them.
It is one of the oldest food preservation methods, which probably arose after the development of cooking with fire. Preservative food additives can be antimicrobial. These inhibit the growth of bacteria or fungi, including mold, or antioxidant, such as oxygen absorbers, which inhibit the oxidation of food constituents. Common antimicrobial preservatives include calcium propionate, sodium nitrate, sodium nitrite, sulfites sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, etc.
Other preservatives include formaldehyde usually in solution , glutaraldehyde kills insects , ethanol, and methylchloroisothiazolinone. Pickling is a method of preserving food in an edible anti-microbial liquid. Pickling can be broadly categorized into two categories: chemical pickling and fermentation pickling. Canning involves cooking food, sealing it in sterile cans or jars, and boiling the containers to kill or weaken any remaining bacteria as a form of sterilization.
Foods have varying degrees of natural protection against spoilage and may require that the final step occur in a pressure cooker. High-acid fruits like strawberries require no preservatives to can and only a short boiling cycle, whereas marginal fruits such as tomatoes require longer boiling and addition of other acidic elements.
Low acid foods, such as vegetables and meats require pressure canning. Food preserved by canning or bottling is at immediate risk of spoilage once the can or bottle has been opened. Preserved Food : Canning food is one method of food preservation. Other forms of preservation can include: jellying, jugging, irradiation, pulsed electric field processing, modified atmosphere, high pressure, burial in the ground, and biopreservation.
Privacy Policy. Skip to main content. Industrial Microbiology. Sadly, it is not a recommened method to decide whether or not to eat an egg. If an egg is spoiled it will smell bad, like Sulphur, when you crack it. This does not mean it has pathogens, it is just rotten and undesirable as food. All eggs can potentially have pathogens, and should be cooked to the proper internal temperature.
For best quality, eggs should be consumed within weeks after purchase. For more information about food spoilage or food pathogens contact your local Michigan State University Extension office, or visit us online. This article was published by Michigan State University Extension. Did you find this article useful?
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