Food microbiology

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Parasitic pathogens

Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food. This includes the study of microorganisms causing food spoilage; pathogens that may cause disease (especially if food is improperly cooked or stored); microbes used to produce fermented foods such as cheese, yogurt, bread, beer, and wine; and microbes with other useful roles, such as producing probiotics. [1] [2] [3] [4]

Contents

Subgroups of bacteria that affect food

In the study of bacteria in food, important groups have been subdivided based on certain characteristics. These groupings are not of taxonomic significance: [5]

Food safety

A microbiologist working in a biosafety laboratory tests for high risk pathogens in food FDA microbiologist working in a biosafety laboratory tests for high risk pathogens in food.jpg
A microbiologist working in a biosafety laboratory tests for high risk pathogens in food

Food safety is a major focus of food microbiology. Numerous agents of disease and pathogens are readily transmitted via food which includes bacteria and viruses. Microbial toxins are also possible contaminants of food; However, microorganisms and their products can also be used to combat these pathogenic microbes. Probiotic bacteria, including those that produce bacteriocins can kill and inhibit pathogens. Alternatively, purified bacteriocins such as nisin can be added directly to food products. Finally, bacteriophages, viruses that only infect bacteria can be used to kill bacterial pathogens. [6] Thorough preparation of food, including proper cooking, eliminates most bacteria and viruses. However, toxins produced by contaminants may not be liable to change to non-toxic forms by heating or cooking the contaminated food due to other safety conditions.[ citation needed ]

Fermentation

Fermentation is one of the methods to preserve food and alter its quality. Yeast, especially Saccharomyces cerevisiae , is used to leaven bread, brew beer and make wine. Certain bacteria, including lactic acid bacteria, are used to make yogurt, cheese, hot sauce, pickles, fermented sausages and dishes such as kimchi. A common effect of these fermentations is that the food product is less hospitable to other microorganisms, including pathogens and spoilage-causing microorganisms, thus extending the food's shelf-life. Some cheese varieties also require molds to ripen and develop their characteristic flavors.[ citation needed ]

Microbial biopolymers

Several microbially produced biopolymers are used in the food industry. [7]

Alginate

Alginates can be used as thickening agents. [8] Although listed here under the category 'Microbial polysaccharides', commercial alginates are currently only produced by extraction from brown seaweeds such as Laminaria hyperborea or L. japonica .

Poly-γ-glutamic acid

Poly-γ-glutamic acid (γ-PGA) produced by various strains of Bacillus has potential applications as a thickener in the food industry. [9]

Food testing

Food microbiology laboratory at the Faculty of Food Technology, Latvia University of Life Sciences and Technologies LUA, Faculty of Food Technology Food microbiology laboratory.jpg
Food microbiology laboratory at the Faculty of Food Technology, Latvia University of Life Sciences and Technologies

To ensure safety of food products, microbiological tests such as testing for pathogens and spoilage organisms are required. This way the risk of contamination under normal use conditions can be examined and food poisoning outbreaks can be prevented. Testing of food products and ingredients is important along the whole supply chain as possible flaws of products can occur at every stage of production. [10] Apart from detecting spoilage, microbiological tests can also determine germ content, identify yeasts and molds, and Salmonella . For Salmonella, scientists are also developing rapid and portable technologies capable of identifying unique variants of Salmonella. [11]

Polymerase chain reaction (PCR) is a quick and inexpensive method to generate numbers of copies of a DNA fragment at a specific band ("PCR (Polymerase Chain Reaction)," 2008). For that reason, scientists are using PCR to detect different kinds of viruses or bacteria, such as HIV and anthrax based on their unique DNA patterns. Various kits are commercially available to help in food pathogen nucleic acids extraction, [12] PCR detection, and differentiation. [13] The detection of bacterial strands in food products is very important to everyone in the world, for it helps prevent the occurrence of food borne illness. Therefore, PCR is recognized as a DNA detector in order to amplify and trace the presence of pathogenic strands in different processed food.[ citation needed ]

See also

Related Research Articles

<i>Lactobacillus</i> Genus of bacteria

Lactobacillus is a genus of gram-positive, aerotolerant anaerobes or microaerophilic, rod-shaped, non-spore-forming bacteria. Until 2020, the genus Lactobacillus comprised over 260 phylogenetically, ecologically, and metabolically diverse species; a taxonomic revision of the genus assigned lactobacilli to 25 genera.

<span class="mw-page-title-main">Food science</span> Applied science devoted to the study of food

Food science is the basic science and applied science of food; its scope starts at overlap with agricultural science and nutritional science and leads through the scientific aspects of food safety and food processing, informing the development of food technology.

<i>Clostridium</i> Genus of bacteria, which includes several human pathogens

Clostridium is a genus of anaerobic, Gram-positive bacteria. Species of Clostridium inhabit soils and the intestinal tract of animals, including humans. This genus includes several significant human pathogens, including the causative agents of botulism and tetanus. It also formerly included an important cause of diarrhea, Clostridioides difficile, which was reclassified into the Clostridioides genus in 2016.

<span class="mw-page-title-main">Nisin</span> Chemical compound

Nisin is a polycyclic antibacterial peptide produced by the bacterium Lactococcus lactis that is used as a food preservative. It has 34 amino acid residues, including the uncommon amino acids lanthionine (Lan), methyllanthionine (MeLan), didehydroalanine (Dha), and didehydroaminobutyric acid (Dhb). These unusual amino acids are introduced by posttranslational modification of the precursor peptide. In these reactions a ribosomally synthesized 57-mer is converted to the final peptide. The unsaturated amino acids originate from serine and threonine, and the enzyme-catalysed addition of cysteine residues to the didehydro amino acids result in the multiple (5) thioether bridges.

<span class="mw-page-title-main">Probiotic</span> Microorganisms said to provide health benefits when consumed

Probiotics are live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut microbiota. Probiotics are considered generally safe to consume, but may cause bacteria-host interactions and unwanted side effects in rare cases. There is some evidence that probiotics are beneficial for some conditions, but there is little evidence for many of the health benefits claimed for them.

<i>Lactobacillus acidophilus</i> Species of bacterium

Lactobacillus acidophilus is a rod-shaped, Gram-positive, homofermentative, anaerobic microbe first isolated from infant feces in the year 1900. The species is commonly found in humans, specifically the gastrointestinal tract and oral cavity as well as various fermented foods such as fermented milk or yogurt. The species most readily grows at low pH levels, and has an optimum growth temperature of 37 °C. Certain strains of L. acidophilus show strong probiotic effects, and are commercially used in dairy production. The genome of L. acidophilus has been sequenced.

<i>Heyndrickxia coagulans</i> Species of bacterium

Heyndrickxia coagulans is a lactic acid–forming bacterial species. This species was transferred to Weizmannia in 2020, then to Heyndrickxia in 2023.

<span class="mw-page-title-main">Lactic acid bacteria</span> Order of bacteria

Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical (cocci) bacteria that share common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and milk products, produce lactic acid as the major metabolic end product of carbohydrate fermentation, giving them the common name lactic acid bacteria (LAB).

Natural growth promoters (NGPs) are feed additives for farm animals.

Levilactobacillus brevis is a gram-positive, rod shaped species of lactic acid bacteria which is heterofermentative, creating CO2, lactic acid and acetic acid or ethanol during fermentation. L. brevis is the type species of the genus Levilactobacillus (previously L. brevis group), which comprises 24 species. It can be found in many different environments, such as fermented foods, and as normal microbiota. L. brevis is found in food such as sauerkraut and pickles. It is also one of the most common causes of beer spoilage. Ingestion has been shown to improve human immune function, and it has been patented several times. Normal gut microbiota L. brevis is found in human intestines, vagina, and feces.

<span class="mw-page-title-main">Extracellular polymeric substance</span> Gluey polymers secreted by microorganisms to form biofilms

Extracellular polymeric substances (EPSs) are natural polymers of high molecular weight secreted by microorganisms into their environment. EPSs establish the functional and structural integrity of biofilms, and are considered the fundamental component that determines the physicochemical properties of a biofilm. EPS in the matrix of biofilms provides compositional support and protection of microbial communities from the harsh environments. Components of EPS can be of different classes of polysaccharides, lipids, nucleic acids, proteins, lipopolysaccharides, and minerals. This chemical formula is (C135H217N15Na2O74P10).

Limosilactobacillus fermentum is a Gram-positive species in the heterofermentative genus Limosilactobacillus. It is associated with active dental caries lesions. It is also commonly found in fermenting animal and plant material including sourdough and cocoa fermentation. A few strains are considered probiotic or "friendly" bacteria in animals and at least one strain has been applied to treat urogenital infections in women. Some strains of lactobacilli formerly mistakenly classified as L. fermentum have since been reclassified as Limosilactobacillus reuteri. Commercialized strains of L. fermentum used as probiotics include PCC, ME-3 and CECT5716

<span class="mw-page-title-main">Microbiology</span> Study of microscopic organisms

Microbiology is the scientific study of microorganisms, those being of unicellular (single-celled), multicellular, or acellular. Microbiology encompasses numerous sub-disciplines including virology, bacteriology, protistology, mycology, immunology, and parasitology.

<i>Pediococcus acidilactici</i> Species of bacterium

Pediococcus acidilactici is a species of Gram-positive cocci that is often found in pairs or tetrads. P. acidilactici is a homofermentative bacterium that can grow in a wide range of pH, temperature, and osmotic pressure, therefore being able to colonize the digestive tract. It has emerged as a potential probiotic that has shown promising results in animal and human experiments, though some of the results are limited. They are commonly found in fermented vegetables, fermented dairy products, and meat.

<span class="mw-page-title-main">Biopreservation</span>

Biopreservation is the use of natural or controlled microbiota or antimicrobials as a way of preserving food and extending its shelf life. The biopreservation of food, especially utilizing lactic acid bacteria (LAB) that are inhibitory to food spoilage microbes, has been practiced since early ages, at first unconsciously but eventually with an increasingly robust scientific foundation. Beneficial bacteria or the fermentation products produced by these bacteria are used in biopreservation to control spoilage and render pathogens inactive in food. There are a various modes of action through which microorganisms can interfere with the growth of others such as organic acid production, resulting in a reduction of pH and the antimicrobial activity of the un-dissociated acid molecules, a wide variety of small inhibitory molecules including hydrogen peroxide, etc. It is a benign ecological approach which is gaining increasing attention.

Hurdle technology is a method of ensuring that pathogens in food products can be eliminated or controlled. This means the food products will be safe for consumption, and their shelf life will be extended. Hurdle technology usually works by combining more than one approach. These approaches can be thought of as "hurdles" the pathogen has to overcome if it is to remain active in the food. The right combination of hurdles can ensure all pathogens are eliminated or rendered harmless in the final product.

<span class="mw-page-title-main">Food spoilage</span> Often due to bacteria and fungi

Food spoilage is the process where a food product becomes unsuitable to ingest by the consumer. The cause of such a process is due to many outside factors as a side-effect of the type of product it is, as well as how the product is packaged and stored. Due to food spoilage, one-third of the world's food produced for the consumption of humans is lost every year. Bacteria and various fungi are the cause of spoilage and can create serious consequences for the consumers, but there are preventive measures that can be taken.

<i>Lactobacillus bulgaricus</i> GLB44 Subspecies of bacterium

Lactobacillus delbrueckii subsp. bulgaricus is a bacterial subspecies traditionally isolated from European yogurts. Lactobacillus bulgaricusGLB44 differs from other L. bulgaricus strains because it was isolated from the leaves of Galanthus nivalis in Bulgaria.

Proteobiotics are natural metabolites which are produced by fermentation process of specific probiotic strains. These small oligopeptides were originally discovered in and isolated from culture media used to grow probiotic bacteria and may account for some of the health benefits of probiotics.

Ramesh Chandra Ray is an agriculture and food microbiologist, author, and editor. He is the former Principal Scientist (Microbiology), and Head of the Regional Centre at Indian Council of Agricultural Research ICAR - Central Tuber Crops Research Institute in Bhubaneswar, India.

References

  1. ↑ Fratamico PM (2005). Bayles DO (ed.). Foodborne Pathogens: Microbiology and Molecular Biology. Caister Academic Press. ISBN   978-1-904455-00-4.
  2. ↑ Tannock GW, ed. (2005). Probiotics and Prebiotics: Scientific Aspects. Caister Academic Press. ISBN   978-1-904455-01-1.
  3. ↑ Ljungh A, Wadstrom T, eds. (2009). Lactobacillus Molecular Biology: From Genomics to Probiotics. Caister Academic Press. ISBN   978-1-904455-41-7.
  4. ↑ Mayo, B (2010). van Sinderen, D (ed.). Bifidobacteria: Genomics and Molecular Aspects. Caister Academic Press. ISBN   978-1-904455-68-4.
  5. ↑ Ray, B. Fundamental Food Microbiology, 3rd Ed. (2005), pp 29-32
  6. ↑ Sillankorva, Sanna M.; Oliveira, Hugo; Azeredo, Joana (2012). "Bacteriophages and Their Role in Food Safety". International Journal of Microbiology. 2012: 863945. doi: 10.1155/2012/863945 . PMC   3536431 . PMID   23316235.
  7. ↑ Rehm BHA, ed. (2009). Microbial Production of Biopolymers and Polymer Precursors: Applications and Perspectives. Caister Academic Press. ISBN   978-1-904455-36-3.
  8. ↑ Remminghorst & Rehm (2009). "Microbial Production of Alginate: Biosynthesis and Applications". Microbial Production of Biopolymers and Polymer Precursors. Caister Academic Press. ISBN   978-1-904455-36-3.
  9. ↑ Shih & Wu (2009). "Biosynthesis and Application of Poly(gamma-glutamic acid)". Microbial Production of Biopolymers and Polymer Precursors. Caister Academic Press. ISBN   978-1-904455-36-3.
  10. ↑ "Food Testing Laboratories". Archived from the original on 2011-10-20. Retrieved 2012-04-18.
  11. ↑ "Rapid Testing and Identification of Salmonella in Foods". Archived from the original on 2022-03-27. Retrieved 2012-04-18.
  12. ↑ "FOOD PATHOGEN DNA EXTRACTION filter paper card". Archived from the original on 2021-11-27. Retrieved 2014-07-11.
  13. ↑ "Microbial Detection Identification Kits". Archived from the original on 2014-07-15. Retrieved 2014-07-11.
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