Clostridium botulinum

A while ago, I read the IFR document about VP and MAP food. There are some specific hurdles in there relating to the risk of C. botulinum and if one of these hurdle factors is exceeded, there isn't a risk, if not, a shelf life of 10 days or less should be considered. As far as I can see, none of the individual factors apply for cheddar (which can be matured for years). My gut feel is it's not a risk but can't afford the work to investigate it. Has anyone come across work which has been done in the past on this?

Thanks

HI GMO,

I believe, outgrowth of C. botulinum spores in cheese depends on the water activity, which is determined by the salt content (among others).

I have found this here: C. botulinum in Cheddar that might help you with your question. The abstract seems to be relevant.

Water activity of mature cheddar apparently is in the range of .85. C. botulinum needs values higher than .9 to grow, this seems to be one of the reasons, why cheddar is safe.

Hope to have been able to help

Matt

I tried to post a link in my reply, that doesn't seem to work. Another try: C. botulinum in Cheddar here: http://www.onefish.o...W50cyYzNz1pbmZv

Dear GMO,

Very interesting (general) subject.

I am only an (avidly interested) consumer of cheddar. I suspect The links below may not answer yr direct question but may prompt more input as per MKRMS.

I guess the report you mention may have been this enormous (2006) IFR / ChorleyWood item -

Final_project_report0707.pdf   1.76MB   89 downloads

Frankly, although very impressive, I found the content rather bewildering. It mainly convinced me just how complex this subject is.

However I also noticed this slightly later (2007) UK document presumably intended for the more practical consumer like myself which probably sourced the above.

safe2eat_.pdf   266.61KB   91 downloads

This contained -

The Advisory Committee on the Microbiological Safety of Food (ACMSF) who advise the Food Standards Agency, conducted a review of the scientific evidence on vacuum packed and modified atmosphere packaged foods.
Following this review they made a general recommendation that vacuum packed and modified atmosphere packed foods should have a maximum 10 day shelf-life at 8°C or less. Day one being the day the product is first vacuum packed. This must remain the first day of shelf life even if the product is subsequently opened and vacuum packed for a second time. They also emphasised the importance of temperature control, the cooler the food is kept, the lower the risk.
This applies throughout the food chain, not just once it reaches your premises. If you want to give the vacuum packed products you produce a shelf life of more than 10 days, then you must also ensure one or more of the following controls are in place.
1 The product has received a minimum heat treatment of at least 90°C for 10 minutes or equivalent.
2 The product is quite acidic i.e. has a pH of 5 or less.
3 The product has a salt level (NaCl) of at least 3.5% (aqueous) throughout the food.
4 The product has a water activity (Aw) of 0.97 or less throughout the food.
Typical pH values of some foods: red meat pH 5.4 – 6.2, poultry pH 5.6 – 6.4, cheddar cheese pH 5.9, tomatoes pH 4.0, fruit juice pH 3.5 – 3.9.
Typical Salt (NaCl) levels in some foods: bacon 3.0 – 4.8, canned ham 3.2, raw ham 2.6-3.6, smoked fish 1.9 – 4.8, raw fish 0.3, raw meat (beef, lamb, chicken and turkey) 0.2.
The typical water activity (Aw) of some foods: fresh meat, fruit and vegetables greater than 0.98, cooked sausage, cheddar and processed cheese, cured meats 0.98 – 0.93, dried beef, dry or fermented sausages 0.93 – 0.85, cakes and pastries, dried fruit, jam 0.85 – 0.60, chocolate, biscuits, crisps less than 0.60.

from the above data (typical ??) cheddar seems not hv controls 1 or 2. (the previous posted link illustrates that this pH limit may be very conservative for cheddar)
May or may not hv 4. ??
3. seems improbable to my palate. ?? (also see below)

Does this help ??

BTW, MKRMS, Welcome to the forum ! and many thks yr input.

added - another link I found suggested cheddar typically has a composition with pH 4.95 - 5.25 (ie on borderline or > so maybe not routinely hv control 1.) and salt of 1-6 - 1.8pct (ie not hv control2)

Rgds / Charles.C

Dear Charles

Thanks for posting the project report on Cl. botulinum in VP & MAP chilled foods. It is a very detailed and good reference. I will go through it in detail.

Dear GMO,

I have found the something regarding incidence of Cl. Botulinum on the link below (page 62):
http://books.google....C85yHk#PPA62,M1

Generally in cheese production the rate at which the pH decreases due to the presence of LAB is a factor that can control the development of other microorganisms and within these there is Cl. Botulinum.
But this is not the only inhibition mechanism as these bacteria also produces a number of bacteriocins.
These can be looked at as obstacles during the ripening prcess and at a later stage during ageing there is also the Aw reduction that inhibits Cl. Botulinum.

On the link below there are some other info (page 149):
http://books.google....QfTtE#PPA149,M1

Does the above answer your questions?

Regards,
Marco