Dear wallabies,
I certainly agree that there is no clear consensus on this subject.
I found the topic rather interesting so I hv done a bit more searching and put together the data I prev. posted with some more I found to facilitate comparison.
A lot of this material is fairly old however I saw one recent detailed official survey in UK (operational swabbing of chopping boards / worktop surfaces) so I extracted 2 sections (opening / closing) which seemed interesting -
The effectiveness of cleaning practices can be monitored and/or verified by environmental sampling. Under Commission Regulation (EC) No 2073/2005 on Microbiological Criteria for Foodstuffs (6) environmental sampling must be undertaken in:
i) premises producing RTE foods which may pose a risk of L. monocytogenes and
ii) premises producing dried infant formula or dried foods for special medical purposes intended for infants below 6 months which pose a risk of Enterobacter saklazakii (in these premises the processing environment and equipment should be sampled for Enterobacteriaceae).
In other premises, environmental sampling should be carried out as necessary. The Regulation does not specify criteria for the acceptable level of microorganisms on surfaces. Rather, environmental sampling should be used as a tool by FBOs (= food business operators) to ensure the foodstuffs under their control meet the relevant process hygiene and food safety criteria.
Very few guidelines have been published on the acceptable level of microorganisms on surfaces. The US Public Health Service recommends that cleaned and disinfected food service equipment should not exceed 10 viable microorganisms per cm2 (7). The Public Health Laboratory Service (PHLS) in the UK recommended guidelines for cleaned surfaces ready for use: less than 80cfu/cm2 is satisfactory, 80-1000 cfu/cm2 is borderline and over 1000 cfu/cm2 is unsatisfactory (8). In addition, a Local Authorities Co-ordinating Body on Food and Trading Standards (LACOTS)/PHLS study of cleaning standards and practices in food premises correlated samples (surface samples and cleaning cloths) having aerobic colony counts > 1000cfu/cm2 with premises that did not have adequate food hygiene training, hazard analysis, cleaning schedules or cleaning records in place (9).
……..
Few standards have been published on the acceptable level of microorganisms on food preparation surfaces. This is because many factors (including the level of microorganisms on food, the availability of nutrients, the presence of preservatives and the environmental temperature) influence the microbial surface population prior to cleaning and the design and performance of the sanitation programme will determine the levels after cleaning. As these factors differ for every establishment, a common standard is hard to set (5). However, as a guideline ACC counts _ 1000 cfu/cm2 appear to be a suitable cut-off point between acceptable and unacceptable surface hygiene for the food preparation surfaces examined in this survey (the applicability of this guideline to other types of food preparation surfaces cannot be assumed). Where appropriate, swabbing can be used in conjunction with other inspection activities to draw a complete picture of the hygiene of a food premises.
food_prep_surfaces__2006_.pdf 282.21KB
2373 downloads I hv tabulated the data seen with a few personal language adjustments / interpretations, please consult original references for accuracy -
Obviously substantial variations. Similar differences can also be seen if one compares micro. guidelines so perhaps it's not so surprising but I hv to say the data surprised me. As noted in the text above, the specific product application is relevant but even so ….?
What values are you using at the moment wallabies ???
It is quite possible there are calculative errors in above so I hv added the raw data below, any amendments etc are welcome to be pointed out.
added -
The central question here is, (as per thread title
), what is the criterion for setting the limits? Interestingly, none of the links above seems to quantitatively explain the basis for their proposed values
. Several make the comment that the nature of the production imposes a restriction on the achievable degree of cleanliness, eg this extract –
In addition, processors may wonder about standards for acceptable counts in their environmental testing program. Adequate cleaning and sanitizing should be sufficient to keep counts low. The Compendium of Methods references the U.S. Public Health Service recommendation that “adequately cleaned and sanitized food service equipment
have not more than 100 colonies per utensil”1 and also states, “Generally, the level of microorganisms should not exceed more than a few colonies per sampling site.”
Because counts may vary depending on the operation or type of product being processed, it is difficult to give a one-size-fits-all standard. What may be "normal" for one product or process may not be "normal" for another. For instance, an incoming area for food which comes directly from a farm field may have higher counts than an area containing a highly processed frozen food. Both count levels may be acceptable based on the expected microbial load of the food being processed.
http://www.3m.com/in...q_swab/use1.pdfI can see that there may inevitably be a practical relationship as referred above but how to define any tolerable variation has not been discussed in the refs I have seen. The ATP methods seem more determined to analyse such variables but I hv little knowledge this route. (One link suggested that there is now a 60+% penetration in the US market for ATP technique with the possibility of it becoming a specific standard.)
I have also seen an opinion that “too” clean a production area may be a bad thing in a food factory since it faces the law of diminishing returns plus may promote the occurrence of pathogenic species.
Rgds / Charles.C
(link 1)
The U.S. Public Health Service suggests that a sanitized surface must have less than 100 total aerobic organisms per 8 square inches of surface (e.g., cutting board, dish, tabletop, etc.) or 100 organisms per utensil (e.g., spoon) (190). This is an adequate standard that is used as a sanitation guideline in the Grade A Pasteurized Milk Ordinance (54).
http://www.hi-tm.com...t-5A.html#clean
(link 2)
Food Processors Surface Hygiene
A major component of the hygiene of a kitchen, processing line or food production plant is the control of the cleaning of equipment, storage tray, utensils and preparative benches. A simple inexpensive test provides a quantitative test with has a sensitivity down to 0.4 CFU/square centimetre. The Australian standard (AS 2997-1987) states that an acceptable limit to indicate satisfactory cleaning operations by this method is less than 6 CFU/square centimetre.
http://www.biotechla...u/services2.htm
(Link 3)
- 5.3.10.2 Performance Standards
a. Pre-operational:
For raw meat processing, microbiological loading of commercially clean food contact surfaces has been found over time to normally be <102cfu/cm2. One-off counts could be in the 102 to 103 cfu/cm2 range but would not be the norm.
b. During operations:
The microbiological condition of any food contact surface during operations, as measured by the mean log10 count of the indicator organism(s), should not exceed the expected mean log10 count of similar indicator organism(s) on product.
The numbers of micro-organisms on food surfaces throughout a processing day will be influenced by cleaning programmes, incoming microbial loads on the food and the opportunities for growth during production. The objective of this standard is to minimise contamination of foods through redistribution of micro-organisms from food surfaces.
http://www.nzfsa.gov...h-3/page-04.htm
(link 4) ( you will hv to google the book), extracted from a review of “yoghourt science and technology” / tamime and robinson (1999)
some suggested standards for plant in contact with foods prior to pasteurisation/heat treatment have been suggested by Harrigan and McCance(1976)
cfu / 100cm2 conclusion
500(coliforms <10) satisfactory
500 – 2500 dubious
>2500 (coliforms > 100) unsatisfactory
With improved cleaning regimes a total colony count of 200cfu/100cm2 would be expected nowadays and below 50cfu/100cm2 for any plant containing pasteurised products (Luck and Gavron 1990)
