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Microbiological Testing – Food Safety, Bacteria, and Salmonella
The role that microbiology plays in our food cannot be underestimated. Bacteria and microorganisms multiply on everything we eat. Many types of bacteria can be ingested in small amounts without causing any harm. However, they may still cause food to spoil. Other bacterium, such as salmonella and E. coli (and even some ‘friendly’ bacteria) can cause food poisoning. Food manufacturers have a responsibility to their consumers to ensure that their food is regularly and rigorously tested. Otherwise, their products could have possibly lethal or fatal effects on their customers.
In order to test food, a sample is needed. For liquid food products, such as milk or juice, it is easy to ensure a homogenous sample, as liquids are easily mixed. Any micro-organisms present in the sample will exist throughout the entire product. However, it is more difficult to determine the homogeneity of solid food samples. This is due to the differences between the surface and inner core of solid food. Therefore, a cross-section of the food is taken and ‘digested’ to assure relative homogeneity. Samples taken are cultivated on a plate, complete with a growth medium, and placed in a state of aerobic incubation (at temperatures close to human body temperature). Following a period of growth that lasts approximately 48 hours, the bacterial colonies are observed, and a total bacterial count can be made. This count provides the manufacturer with the microbiological makeup of the product. It can also determine whether or not further testing is required for certain bacteria whose presence violates the set safety standards.
Food manufacturers are particularly concerned about the presence of salmonella in their products. Many countries have a no-tolerance policy towards salmonella in food. The Hong Kong Centre for Food Safety’s standard is set at absence per 25 grams of food. Salmonella causes gastrointestinal problems, the most serious of these being typhoid fever. It can be detected by the toxin that causes the secretion of hydrogen sulphide. Food manufacturers need to be aware of food safety at all times and test their products regularly. This will help ensure that neither their business operations, nor their customers, are affected by harmful bacteria.
In Hong Kong, Centre for Food Safety provide ready- to- eat food guidelines (May 2007, revise) to the public to ensure the food safety. With reference to the guideline, food items are grouped into five categories and have its own classification of microbiological quality (Satisfactory, Acceptable, Unacceptable and Unsatisfactory) on TVC and Salmonella spp. should not be found in any of 25g food sample.
Aerobic Plate Count/Total Viable Count (TVC)
Common and Conventional Methods:
• FDA-BAM Ch 3 , Aerobic plate count
• Australian Standard AS 50 13.1, Standard plate count
• ISO 4833, Microbiology of food and animal feeding stuffs -- Horizontal method for the enumeration of microorganisms -- Colony-count technique at 30 °C
Rapid Methods
• AOAC 990.12 ,TVC Petrifilm™
• AOAC 2008.10 ,TEMPO TVC Method: Automated Enumeration of Total Viable Count in Food
• AOAC 010404, Compact Dry TC
Salmonella spp.
Common and Conventional Methods:
• FDA-BAM Ch 5, Salmonella spp.
• Australian Standard AS 5013.10 ,Salmonella
• ISO 6579,Microbiology of food and animal feeding stuffs -- Horizontal method for the detection of Salmonella .spp
Rapid Methods
• AOAC 999.08 BioControl Assurance Gold
• AOAC 2009.03 Assurance GDS™ Salmonella method for foods
• AOAC 996.08 VIDAS Salmonella (SLM) Assay
• AOAC 071101 VIDAS UP Salmonella method (VIDAS SPT)
• AOAC 2001.09 VIDAS Immuno Concentration Salmonella (ICS)
• AOAC 031001 MicroSEQ(R) Real-Time PCR System for Detection of Salmonella in food
• AFNOR BIO 12/16 ¡V 09/05 VIDAS EASY Salmonella method
Chemlab (HK) can provide TVC by 3M petrilfim and detection of Salmonella spp. by conventional FDA-BAM method. Welcome to contact us for more information.
Reference:
http://www.ils-limited.co.uk/food-division/microbiology/microbiological-quality-determination
http://www.foodauthority.nsw.gov.au/_documents/science/microbiological_quality_guide_for_rte_food.pdf
http://www.fao.org/docrep/003/t1768e/t1768e04.htm
http://faculty.weber.edu/coberg/class/3853/3853%20Microbial%20Testing%20Procedures.htm
http://multimedia.food.gov.uk/multimedia/pdfs/microbial.pdf
http://cms.walsall.gov.uk/index/business/food_safety/sampling_food_for_microbiological_examination.htm
http://www.bccdc.ca/NR/rdonlyres/5E3CE5A9-EF67-41DC-9644-81E8E814B931/0/FoodQualityMicroRecommendationsnoschedule.pdf
http://www.microbac.com/testing-services/food-microbiology/
http://www.accugenlabs.com/brochure.html
http://www.ijstr.org/final-print/june2013/Analysis-Total-Microbial-And-Detection-Of-Salmonella-On-Smoked-Fish.pdf
http://www.eolss.net/Sample-Chapters/C10/E5-08-06-06.pdf
http://cdn.intechopen.com/pdfs-wm/26437.pdf
http://www.daff.gov.au/biosecurity/export/meat/elmer-3/approved-methods-for-microbiological-testing-of-meat-and-meat-products
http://www.candyusa.com/files/LauriePostPresentation.pdf
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