Microbiology - Articles and news items
Eggs from small flocks of chickens are just as likely to be contaminated with Salmonella enteritidis as eggs sold in grocery stores, say researchers from Penn State…
Featured news • 18 November 2015 • Inlabtec
In order to create additional capacity for hygiene monitoring, the microbiology laboratory has purchased an Inlabtec Serial Diluter to simplify and accelerate serial dilutions for plate counts…
Whitepapers • 1 October 2015 • Vikan A/S
The correct selection of cleaning equipment by the food manufacturing and food service industries is essential to minimise the risk of product contamination and aid compliance…
Industry news • 16 June 2015 • Victoria White
University of Delaware researchers have discovered a soil microbe that mobilises an “iron shield” to block the uptake of toxic arsenic in rice…
Industry news • 9 February 2015 • Eurofins
As part of an investment programme in its microbiology department, Eurofins Food Testing UK has launched a new two year scheme exclusively for Microbiology Undergraduates at the University of Wolverhampton, designed to develop food scientists of the future…
Issue 5 2014 • 27 October 2014 • François Bourdichon, Corporate Food Safety, Microbiology and Hygiene Manager, Barry Callebaut
Following the food scandals of the late-1980s and early-1990s, and the increasing knowledge on foodborne and waterborne pathogen, the Agreement on the Application of Sanitary and Phytosanitary Measures (SPS) was put in place in 1995 to set the framework of all measures taken by a World Trade Organisation (WTO) member to protect human, animal or plant life or health within its territory from certain risks, and which may affect international trade…
Featuring an article on microbiology method validation which questions whether alternative methods are as good as the reference method, and an article from Barry Callebaut on defining one’s need to use the most relevant tool…
Industry news • 1 September 2014 • Campden BRI
There have been a number of food safety incidents in recent years involving pathogens such as Salmonella, which have been found on low moisture foods such as nuts and seeds…
Issue 3 2014 • 23 June 2014 • Mickaël Boyer and Jing Geng, Danone Nutricia Research
Today’s consumers have greater expectations than ever before regarding food. They expect not only safe, good quality and value-based products but also a real commitment of the food company toward social responsibility to the community, e.g. regarding nutritional education, sustainable development and adaptation to local geographical specifications. Those expectations are symbolised by a consumer needs pyramid: the basic requirement being consumer safety, the over consideration being product conformity to bring consumer satisfaction and, at the top, product superiority that brings consumer loyalty…
Issue 5 2013 • 4 November 2013 • François Bourdichon, Corporate Food Safety, Microbiology and Hygiene Manager, Barry Callebaut
Taxonomy and classification of microorganisms are based on criteria that do not always, if ever, fit with the complexity of the microbial world. Commensal, starter, probiotic, pathogen? Since the early days of Pasteur and Koch, this approach is not anymore applicable for most of the major foodborne and/or waterborne microorganisms. In the past few years, due to the evolution of regulation and need for safety demonstration, microbiologists face the new challenge of understanding and demonstrating the mechanism of action (most commonly pleiotropic) of one organism in order to assess its potential application. Among the most debated genera, one might like to see how those consequences apply to the benefit / risk assessment of Enterococcus spp., formerly Streptococcus spp. Lancefield Group D or faecal Streptococci (for microbes also, sometimes the name does not help).
Issue 5 2012 • 6 November 2012 • François Bourdichon, Nestlé Research Centre; Joerg Seifert, International Dairy Federation and Egon Bech Hansen, Technical University of Denmark
Fermentation as a chemical process was initially described in the mid-19th century by Louis Pasteur as ‘a vie sans l’air’, the metabolic process of deriving energy from organic compounds without the involvement of an exogenous oxidising agent. Fermentation, as a process for manufacturing fermented foods, is today used more broadly than the historical definition of fermentation. Fermented foods have been subjected to the action of microorganisms during which desirable biochemical changes occur, causing significant modification to the food matrix2,13.
Fermented foods are typically associated with local and traditional food consumption. The growing body of evidence with regard to microorganisms and their ecological role in the food matrix has led to industrial application of the process of fermentation starting in the early 20th century through use of specific dedicated microbiota with various levels of characterisation.
In recent decades, the use of microbial food cultures (MFC) has come under various regulatory frameworks in many countries, directly or indirectly. Several of these regulatory frameworks put emphasis on ‘the history of use’, ‘traditional food’, or ‘general recognition of safety’ without clear guidelines for the expected level of evidence.
Issue 3 2012 • 4 July 2012 • Hilton Deeth, Emeritus Professor, University of Queensland
Milk is a highly perishable food so to enable it to be stored and distributed for consumption without spoilage, and without being a health risk through growth of pathogenic bacteria, it is heat treated. The most common type of heat treatment in many parts of the world is pasteurisation, which is performed at a minimum of 72°C for 15 seconds. This is the least heat treatment needed to destroy most pathogenic microorganisms and it also destroys most spoilage organisms. However, a small number of bacteria remain after pasteurisation and packaging, and can grow during storage. Such growth is slow at low temperature and consequently pasteurised milk is always kept refrigerated. Even under refrigeration, pasteurised milk only keeps for about two weeks1.
One way of extending the shelf-life of milk is to heat it at temperatures high enough to destroy almost all microorganisms, and then store it in sealed containers without contamination by bacteria. There are two ways in which this can be carried out: in-container sterilisation and ultrahigh- temperature (UHT) processing. Both produce a ‘commercially sterile’ product which means the milk does not contain micro – organisms which can grow under the normal conditions of storage which, in this case, is room temperature2,3.
In-container sterilisation, which uses canning technology, is a batch operation which involves heating the final containers of milk in an autoclave at 110-120°C for 10-20 minutes. By contrast, UHT processing involves heating the milk in a continuous flow system at about 140°C for a very short time – around five seconds.
Issue 3 2012 • 3 July 2012 • François Bourdichon and Katia Rouzeau, Food Safety Microbiology, Quality and Safety Department, Nestlé Research Centre
‘Something is fishy’ is a widely used expression over a doubtful, suspicious situation, a good example of how mankind has taken advantage of microbial spoilage to assess the wholesomeness of a food product. The reduction of trimethylamine oxide to trimethylamine by bacteria associated primarily with the marine environment (e.g. Alteromonas and Vibrio) and animal intestines (Enterobacteriaceae) constitutes this major spoilage reaction during the storage of marine fish and typically identified ‘fishy’ as off note. The microbial alteration of fish can be therefore organoleptically identified by consumers, considering the food as suspicious for consumption1.
Spoilage of food involves any change which renders food unacceptable for human consumption and may result from a variety of causes, which include: Insect damage; Physical injury due to freezing, drying, burning, pressure, radiation; Activity of indigenous enzymes in plant and animal tissues; Chemical changes not induced by microbial or naturally occurring enzymes (These changes usually involve O2 and light and other than microbial spoilage are the most common cause of spoilage e.g. oxidative rancidity of fats and oils and the discolouration of cured meats); and growth and activity of microorganisms: bacteria, yeasts and moulds.
Issue 3 2012 • 3 July 2012 • Dr Evangelia Komitopoulou, Head of Food Safety, Leatherhead Food Research
Many bacteria are able to attach to and colonise environmental surfaces by producing a biofilm, which allows the organisms to persist in the environment and resist desiccation, UV light and treatment with antimicrobials and sanitising agents. Biofilms are formed when microbes attach to a solid support and to each other by extracellular polymeric substances (EPS), and on a wide variety of surfaces, including metal, plastic, rock and living or dead tissue. Once in a biofilm, bacteria can be several orders of magnitude more resistant to antimicrobials than their planktonic counterparts1.
Biofilms are of particular concern in the process and food industries as well as in potable and wastewater distribution systems. Biofilms formed on the inside of pipes can reduce flow rates while increased fouling can lead to decreases in heat transmission and thus ineffective processing, product contamination and pipe corrosion due to acid production in the biofilm. Biofilm formation in drinking water distribution systems can lead to a decrease in water velocity and carrying capacity, clogging and pipe corrosion, increase in energy utilisation and decreased operational efficiency. In marine and other aquatic environments, submerged surfaces attract organisms such as algae, diatoms and bacteria that are able to attach and form biofilms on ships’ hulls and become resistant to the different antifouling paints that have been developed to prevent the initial colonisation.
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