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Understanding the Standard Plate Count Procedure

A basic standard plate count definition is estimating to what degree of contamination is present in a food sample. After an incubation period, the number of living cells within the petri-dish or plate will be determined. The cells or microbes form colonies, and if the colonies merge, it means that the concentration of bacteria is too great, and it makes the sample become uncountable. There are a couple of standard plate count method choices that are more standard across the scientific communities around the world. There is the pour method in which the sample is poured into the plate and a spread method in which the sample is spread across the plate. These different methods produce different results, but still, the bacteria will grow within colonies and the test results will give a volume of bacteria colonies, present within the sample on a scale. Usually, the sample scale runs from 25-250 or 30-300 depending on the preferences of any given lab and what type of food product being sampled and the end-use of it. The standard plate count is used to make sure that any given food product meets the microbiological specifications within any given country which are set forth by governing bodies and public health agencies.

The Pour Method
When preparing a standard plate count method which will be poured into the plate, the sample is melted and poured into the centre of a petri-dish and will be swirled to mix and spread evenly over the plate. The pour method allows for the bacteria to develop into colonies both on the surface of the plate but also within the medium of the plate as well. Most of the colonies will form in the medium and will be very small and will be tightly merged. There will be very few colonies on the surface of the plate but will be of comparable size and shape as that of the spread method.

The Spread Plate Method
When using the standard plate count method that will spread the sample onto the plate; the sample is properly diluted and spread onto the plate and must be dispersed evenly across the entire plate to get proper distribution of the bacteria present, and the correct formation of colonies is possible. Unlike the pour method, the colonies only form on the surface of the plate but are in much greater numbers. The number of bacteria present is counted to make sure there are not too many presents and surpass the samples' allowable limits.

Each method of standard plate count is used to measure the number of bacteria within a food product sample. The need to meet the microbiological specifications for any given raw food product is of great importance to the health of public consumers. Governing agencies and public health officials continuously monitor and develop guidelines and standards that need to be adhered to so the consumers of these food products are kept free of food-borne bacteria’s that cause illnesses and disease throughout all countries of the world. 
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