Concerns about botulism etc.

[Zoey]

I've made my peace with listeria. It seems like a minor risk to me since I talked to my milk supplier and he says that in their farm history they have never had a positive test result on listeria (in 40 years) and it seems that the milk industry demands regular testing.  I'll have to rethink this if I ever get pregnant, but no luck on that yet, so no worries.

Anyways, the thing I'm more concerned about is botulism. Deadly if you catch it, present everywhere, every country and impossible to kill without 120C warming, which obviously is no option in cheese (even with UHT milk, it could get contaminated post-pasteurization).

So, do you guys worry about this at all? If not, what makes you so confident, or are you just willingly taking a risk?

I've given some thought on how to fight it though.


• Acid: it seems to not like acid; I've read aroung 4.4 might be to low a pH. But cheese doesn't get that low, does it?
• anaerobic conditions: it needs those, right? Does a waxed or natural rind cheese breathe enough to keep the insides aerobic? Enough to prevent gowth?
• Hygiene; well, of course. But I believe it is impossible to keep something a hundred per cent out, so I'm more worried about not to let it thrive when it does...


Any thoughts? Or am I just being paranoid, again?

[Sailor Con Queso]

You're right. It is not possible to keep everything out. Everything we eat is loaded with all sorts of bacteria in small doses. But those bacteria are generally at sub-clinical levels and do not cause any problems.

The acidity from starter bacteria pretty much prevents botulism bacteria and most pathogens from growing beyond those really small quantities. The addition of salt makes it even less likely. So, unless you are starting off with REALLY bad milk or unsanitary conditions, it's not going to happen.

If you do get a bad cheese from Clostridium or coliforms, you'll know it. Can you say stinky cheese?

The interior of a cheese does have some oxygen so it is not actually anaerobic. Although the botulinum TOXIN is destroyed by thorough cooking the SPORE itself is not killed by temperatures reached with normal boiling, leaving it free to grow and produce the toxin when conditions are right. FYI - Since you mentioned pregnancy. the only known prevention measure for infant botulism is to avoid feeding honey to infants less than 12 months of age.

[Zoey]

Thanks Sailor, your reply is pretty much what I was hoping for.

I really want to believe those three things: 1) acidity is enough to slow pathogen growth, 2) salt also reduces it and 3) you would notice in smell/flavor if the cheese was bad.

Anyone happen to know what to look for in part 3, in other words, what are the signs of clostridium in cheese? Or would it mean that the cheese would smell/taste so completely different that it would be obvious that it's not edible?

Also, I wonder, are there differences between used starter bacteria? I believe that some of them may leave more room for pathogens than others? I'm only using buttermilk starters and the like, since I find commercial starter cultures be too far from the original artisan cheese making process. If I weren't concerned about pathogens, I'd probably make my own buttermilk to start with. Anyway, that's why I don't know exactly what bacteria my starter cultures contain, and can't be sure if it contains the most effective starter bacteria (effective in the sense of taking over the growth space of pathogens) or not...

About infant botulism; where I live (in Finland) all honey products must have that warning on the label, so it's pretty straightforward. I'm really more worried about the adult form (which would have to include much more bacteria in the consumed food, I suppose). With listeria, it's another thing...

[susanky]

There is a report in the medical literature showing that botulism does not freely cross the blood milk barrier.  They infected cows and measured blood levels and milk levels.  All tests in blood were positive.  All in milk were negative.  Having said that, first, they only looked at one Type of botulinim (C).  Also, there are certainly reports of milk contamination.  So, as Sailor also seems to be saying, there is a risk, but it is probably fairly low.  We don't live in a sterile world. 

Somehow I feel the need to defend this villianized (is that a word?) bacterium.  My face is full of it .  My biggest fear is that I would develop antibodies to it and become resistant (kidding!).  It has numerous benefits in the medical world from controlling debilitating sweating to releasing contractured limbs in children with cerebral palsy.  Ok, but yes. I still don't want it in my milk or cheese. 
Susan

[Sailor Con Queso]

Clostridium botulinum is a gram-positive, rod shaped bacterium that produces neurotoxins which can cause muscular paralysis. Ironically, it is also the paralytic agent in botox. It is an anaerobic spore-former commonly found in soil. As I said previously, heating destroys the neurotoxin but not the spores. Paradoxically, you can eat handfuls of the spores and it will have little or no effect. Acid in the digestive tract prevents the bacteria from multiplying. So Botulism is NOT a disease, it's a reaction to neurotoxins that are produced outside of your body. This is very different from E. coli where relatively few bacteria from contaminated food can rapidly multiply and become an internal infection.

Because botulism is not an actual disease process, it is not transferred from an infected animal. That does not mean that spores aren't passed along by the milk handler. The problem comes when Clostridium spores find a nice low oxygen, high pH (low acidity), nutritional environment.

Clostridium tyrobutyricum is of more concern to cheese makers. This is the one that generally causes “late-blowing” defects in high-pH cheeses such as Emmental or Gouda. Even low spore counts can bring about this phenomenon, if the growth conditions are suitable. So, what are the symptoms of late-blowing? Well, Clostridium produces butyric acid, acetic acid and hydrogen gas as the major fermentation products. So, irregular eyes, slits, and cracks caused by the production of the gas bubbles as well as an abnormal flavor from the Butyric acid and hydrogen compounds are a good clue that the cheese was contaminated. Unlike botulism, there is no lethal neurotoxin so it really won't make you sick. It will just taste disgusting.

Clostridium contamination happens on a regular basis with home canned foods even if you do everything right. If you open a "bad" jar of home canned beans, you will know it immediately from the gas bubbles and a strong hydrogen sulfide (rotten) smell. Same with a bad cheese. There will be no doubt.

I have had late-blowing happen twice. In both instances my wife let our dogs into the kitchen while I was making cheese.