Microbiological Standards For Processed Foods

By now you know that microbiological hazards are one of the biggest threats
to food safety. With better understanding in microbiology and food safety,
safety limits have been set for a range of pathogenic microorganisms in foods.
This subunit presents the recommended microbiological guidelines for some
ready-to-eat food.

Microbiological Standards For Processed Foods

According to the Codex Alimentarius Commission of the
United Nations, an international food standard setting authority, the functions
microbiological guidelines include formulation of design requirements,
indication of required and expected microbiological status of the food
commodities, and the verification of efficacy of hygienic practice. 

guidelines stipulate the safety limits of nine major food borne pathogens such
as Salmonella species, Listeria monocytogenes, E coli O157 and Vibrio
cholerae, as well as providing a classification of microbiological quality of
ready-to-eat food for reflecting the hygienic status of the food concerned.

Purpose of Microbiological Standards

Microbiological Guidelines are criteria indicating the microbiological
condition of the food concerned so as to reflect its safety and quality. These
standard lists the maximum permissible levels of food borne microorganisms
that pose a risk to human health in nominated foods, or classes of foods. They
can be introduced to the food industry to observe voluntarily or stipulated in
legislation for compliance.


The statistical validity of a microbiological examination increases with the
number of field samples analysed. For regulatory purposes, a minimum of 5
sample units from a lot is generally specified for examination. The size of the
samples taken should also be adequate to enable appropriate microbiological
analyses to be undertaken. 
A minimum sample size of 100g or ml is
commonly required. A lot is defined as a quantity of food or food units
produced and handled under uniform conditions. This may be restricted to a
food item produced from a particular production line or piece of equipment
within a certain time period (not exceeding 24 hours).

Microbiological Assessment

There are three major components under microbiological assessment of any
Aerobic colony count is a count of viable bacteria based on counting of
colonies grown in nutrient agar plate. This is commonly employed to indicate
the sanitary quality of foods. The incubation condition of ACC used in this
guideline is 30° C for 48 hours.
Indicator organism Counts refers to the selected surrogate markers. The
main objective of using bacteria as indicators is to reflect the hygienic quality
of food. E. coli is commonly used as surrogate indicator. Its presence in food
generally indicates direct or indirect fecal contamination. 
Substantial number
of E. coli in food suggests a general lack of cleanliness in handling and
improper storage. Specific pathogens Counts refer to bacteria that may cause
food poisoning. Mechanisms involved may be toxins produced in food or
intestinal infection. 
Nine specific bacterial pathogens are included in this set
of guidelines. The symptoms of food poisoning vary from nausea and
vomiting (e.g. caused by S. aureus), through diarrhoea and dehydration
(Salmonella spp. and Campylobacter spp.) to paralysis and death in the rare
cases of botulism. The infectious doses vary from less than 10 to more than
106 organisms.

Categories of Food based on Microbial Quality

For assessment of hygienic quality, food items are grouped into five categories
taking into account the raw ingredients used, and the nature and degree of
processing before sale. The microbiological assessment of ready-to-eat food on
the above three components will lead to the classification of the food quality
into one of the following four classes:
a) Class A: the microbiological status of the food sample is satisfactory.
b) Class B: the microbiological status of the food sample is less than
satisfactory but still acceptable for consumption. 
c) Class C: the microbiological status of the food sample is unsatisfactory.
This may indicate a sub-optimal hygienic conditions and microbiological
safety levels. Licensees of food premises should be advised to investigate
and find out the causes and to adopt measures to improve the hygienic
conditions. Taking of follow-up samples to verify the improvement may be
d) Class D: the microbiological status of the food sample is unacceptable.
The food sample contains unacceptable levels of specific pathogens that is
potentially hazardous to the consumer. In addition to giving advice to
the licensee of the food premises as stated in (c) above, warning letters as
well as other enforcement actions should be considered.

Food category table for aerobic colony count assessment

Controlling microbes

Control of microbes in processed products primarily depend upon good
manufacturing practices and one of the most effective way to ensure this is by
application of HACCP. HACCP stands for Hazard Analysis of Critical
Control Point. 
HACCP is a preventive system for assuring production of safe
food. It is a process that identifies food safety hazards associated with a
product and process and strictly manages and monitors the Critical Control
Points (CCP’s) designed to control the hazard as a way of ensuring the process
is in control and that the safest product possible is being produced. 
It requires
establishment of hazard, identification of critical control points, effective
monitoring follow up and evaluation. For a food processor it is necessary to
know the microbial quality of the raw material, the processing environment,
and the packaging component. This also requires validation of all processing
stages designed to destroy both the pathogens and the spoilage agents and the
efficacy of preservative system.

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