Cheesemaking for hypochondriacs

[lota]

Hi!

I'm a bit hypochondriac and I worry about provoking some illnesses in my friends-family when they eat my aged cheeses.
I've read some posts regarding the molds and bacterias that I should be rid of depending on their look. But I wanted to know if there are any invisible contaminations I should worry about when aging cheese.
For example, I'm aware of the risks of brucellosis and tuberculosis when aging raw milk cheeses. Is there anything like that for pasteurized milk cheeses?

Thanks!

[mikekchar]

I always hate replying to these kinds of questions, but somehow I always reply to them 

Food safety is a very complicated and deep topic.  You can be poisoned by a frozen dinner.  What should you look for in the supermarket when you buy frozen dinners?  Well, of course, people don't look for anything.  They trust that "they" have made the food safe.  But how do "they" know that it is safe?  These are the kinds of questions that pop up when "we" become "they".

In reality safety is a statistical thing.  You are very, very unlikely to get ill, but the chance still exists.  It's not zero.  This is why I hate the question.  What can I say that reflects the actual probability of getting ill?  What if I say to someone, "You are almost certainly safe" and that person is the one that "wins" the lottery and becomes ill?  What can I say in a post on a forum that is both understandable and also complete enough to be representative of reality.  Well... nothing.  If one was smart, they would look at these kinds of questions and run a hundred miles from it.

Well, I'm not that smart, so I'll tell you the very little that I know.  It's a problem because I don't actually know that much.  In terms of "knowing", I know nothing, really.  I've only been led to believe things by things that I've read.  They could be wrong.  But I reckon it's better to tell you what I've read rather than running away.

With that said: My understanding is that virtually all food bourne illness from cheese originates with the milk.  Raw milk is a risk.  It's a relatively small risk, but on average some people get very seriously ill each year.  Every few years a few people die.  Sometimes more than one person dies in a year.  Millions of people consume raw milk products and only a very small handful get seriously ill, but the more that consume the products, the more that will get ill.  It doesn't appear that you can avoid it by choosing a "good" supplier.  Even suppliers with spotless records sometimes have outbreaks.  It just seems to be something that can't easily be controlled.  So the most important thing to do for safety is to start with pasteurised milk.  Pasteurised milk also has risks, but it's about 1000 times less likely to make you ill than raw milk.

The next most important thing is to avoid using milk that has gone off.  Never use soured milk.  This is actually considerably more important for pasteurised milk than raw milk.  Raw milk contains mostly bacteria that we *want* in cheesemaking.  Because it contains a large supply of "good" bacteria, it can out-compete the "bad" bacteria that can make you ill.  Pateurised milk has *no* bacteria.  That means that if the milk has gone sour, it's gotten bacteria from somewhere else.  We have no idea what it is like.  Also, most bacteria that makes you ill are cold loving bacteria.  So if you have milk sitting in the fridge and going sour, then you have a much higher chance of it making you ill than raw milk sitting around at room temperature.  If you think your milk is going off, throw it away.  As a matter of practicality, if you buy milk in containers, only use milk from a fresh, brand new container.  Never use milk that comes from a container that you opened.  Again, the risk is very small, but if the goal is to reduce the risk, this is one of the best ways to do it.

Some people realise that they need lactic acid bacteria in their cheese.  They reason that their sour dough starter also has lactic acid bacteria.  Their pickles and sauerkraut and kimchi has lactic acid bacteria.  Why not add these things to milk and cultivate wild bacteria just like people in the old days must have?  This is naive.  Recent research suggests that lactic acid bacteria in milk is already in the milk when it comes out of the cow.  In other words, it seems that the cows ingest things that contain the bacteria and that the cow acts like a filter to let some of it come through.  Starter cultures come from raw milk.  Do not try to make your own starter culture from anything other than raw milk.  You can buy isolated cultures from big companies that sell them.  You can use live buttermilk from the store.  You can use live yogurt from the store.  You can use kefir grains that you get off the internet or from your friends.  All of these cultures originated from milk and are likely very safe.

Next, you need to make sure that your equipment does not contain rogue bacteria.  It's not necessary to sterilise your equipment, but you should sanitise it.  The way I do it is by boiling or steaming anything that will come in contact with the milk.  You can also buy a product called "Star San" which is very acidic and kills bacteria, but is also very convenient to use.  Those are the two methods I recommend.  There are other ways, but they are more complicated.  "House" bacteria and yeast will get into your milk if you omit this step.  Well... it probably will anyway, but our goal is to overwhelm it with the starter cultures, so the less that make it through the better.

After that it gets pretty interesting.  You may be aware that cheese is often aged with a variety of yeast, bacteria and mold on it.  Cheese is basically pickled milk.  It is acidic.  It is salty.  Very few things can grow on it.  For whatever reason (just like other pickles) the things that can grow on cheese are by and large safe to eat.  In fact, as far as I can tell there has never been a reported case of anyone being poisoned from eating something growing on the outside of a hard cheese.  It's hard to believe.  In fact, most of the molds that grow on aged cheeses *can* produce toxins.  However, for reasons that nobody seems to understand (and nobody seems to study) those molds basically never produce toxins while growing on cheese.

However, it is a mistake to think that you are completely safe.  First, some people are very allergic to some molds.  A good example is aspergillus niger (the dreaded "black mold" that you are often told to fear).  This is the same black mold that I'm sure you've seen growing on onions.  It's harmless, generally, but some people are allergic to it and can get very ill when exposed to it.  Likely if you are one of those people, you have already been exposed to it and already know.  But you should still be careful.

The other problem is that when yeasts and molds grow on cheese, they make the cheese less acidic.  Over time, this allows other things to grow on the cheese that can produce toxins.  Certain bacteria hitch a ride on the "roots" of the molds that penetrate the rind and can poison cheese.  However, like I said, it doesn't seem to ever happen on hard cheeses.  It may be due to the low moisture levels of those cheeses.  Soft cheeses, though, are still at risk.  Generally, if the rind (outer skin) is intact, then the cheese is generally safe.  But if the cheese is cut or the rind is broken, then these soft cheeses can be at risk -- especially cheeses that soften over time (bloomy rinds -- white fluffy rinds like Camembert or Brie, washed rinds -- red "smeared" rind cheeses that smell like sweat socks, and blue cheeses).  If you see things growing on those cheeses that you don't recognise, you should throw out the cheese.

But apart from these caveats, cheese is remarkably safe.  Odds are when you first make a cheese and start to age it the things that grow on it are from a collection of only 4-5 organisms that can tolerate the salt level, can tolerate the acidity level and can thrive at the cool temperatures that we age cheese at.  It really doesn't take that many cheeses before you start to recognise them.  For me they are like old friends.  OK, blue mold is like the annoying old friend that always comes by at awkward times, but...

If you decide to do natural rind cheeses, you will get used to the look and especially the smell of some of these things (some of them smell pretty odd -- shimeji mushrooms, broccoli, sweat socks, farts, etc)  But once you know what things look and smell like, you can proceed pretty fearlessly.  As a cheese ages, it goes from being a bit of a battlefield for those initial 4-5 things to a slow progress of other molds -- some of which are pretty exotic.  In my cave I've seen bright yellows and orange molds, pink yeasts and lots of different browns.  But as long as the milk is sound and your initial aging is good, then these are all safe.  Or so I am led to believe.  With a little work, I've been able to identify (to my own statisfaction, though I could be completely wrong) everything that has grown on my cheeses.  There really isn't anything to fear.

But I have also thrown out some cheeses that went bad.  These were also easy to identify.  They smell weird.  They look weird.  They get softer than they should.  It's happened *very* rarely, but it's important not to be reckless and eat things that are obviously off.

I hope that helps.  Like I said, it's a very hard question to answer.  A thorough answer would not be understandable by a normal person.  Neither would I be able to muster up a thorough answer as I'm simply not knowledgable enough.  But I hope this sets your fears mostly at rest.

[lota]

Well, what can I say...? That was very generous of you. Reading it felt like listening to *your* realist wise uncle: a mix of common sense and experience. Thank you!

Some years ago I learned about botulism. Who would have thought that making your own pesto and happily canning it to eat it in the winter would be able to punctually cause invisible contamination which can lead to severe health issues? I wouldn't, certainly. I had been doing it for years. That made me grow the fear of "invisible" contaminations.
With in-good-condition pasteurized milk cheesemaking, I guess I'll need to be familiar with what looks good and what doesn't, as you said. I always boil everything and clean with ethanol and peroxide hydrogen.

Now I will ask something hoping I don't abuse your energy. It's about something visible that I can't find answers about. Look what some of my cheeses are growing sometimes (I throw them away). Have you ever seen something like this, a really bright pink spot?

https://postimg.cc/1VcGNsVj
https://postimg.cc/3WCfGThh

[Bantams]

A lot of good info in the previous post but I'll add some more.

I don't know where you live, but if it's in the US (or a country with similar regulations), all Grade A dairy cattle are either annually tested or reside in a TB free state. All Grade A dairy cattle are vaccinated for Brucellosis. So those worries are non-existent these days. And if you are in a region where Brucellosis or TB status is questionable, pasteurize the milk.

Most undesirable bacteria/molds/yeasts/etc that happen to survive the salty/acidic environment of cheese and affect the appearance, smell or taste would maybe cause an upset stomach, but usually they just make the cheese look/smell/taste bad and you would likely toss it before eating.

However, there are some potentionally serious pathogens worth consideration.
Salmonella, E coli, and Campylobacter contamination typically originate in raw milk  (vs pasteurized) but they don't usually survive for long (hence the 60 day aging rule for raw milk cheeses).  Choose a farm that keeps clean healthy animals and has good sanitation and chilling practices.

Listeria is the most worrisome pathogen. It does not necessarily originate in the milk, as it is often a post-processing contaminant. It resides in fridge fans, floor drains, etc, and is spread to cheese through water drops via hosing floors, condensation, etc. Unfortunately Listeria does not affect the appearance or taste of cheese, so there's no way to know aside from testing. 
It is of little concern in salty or amply aged cheeses like feta, Cheddar, grating cheeses, etc.  It is most often a problem in surface ripened cheeses (bloomy rinds and washed rinds) due to the neutral surface pH. 
Unlike other aged cheeses that become lower risk with longer aging, surface ripened cheeses become riskier the longer they are urged.  I believe France actually limits raw milk Camembert to be sold only before 59 days as the chance of Listeria contamination become too high with longer aging and over ripe cheese.  Unfortunately the US 60 day rule is not nuanced enough to distinguish between surface ripened cheeses and other aged varieties and so producers strive to produce raw milk versions that hold up for aging over 60 days.
Anyway, fresh acidic cheeses made from high quality milk are quite safe, as are nicely aged firm cheeses.  Use more caution when making surface ripened cheeses (and I'd add in soft blues here as well).
Also avoid using raw milk produced from herds eating silage or haylage as this is the #1 risk factor for Listeria contamination.

[lota]

Hi,
Thanks for the detailed list! Very helpful, these are the things I needed to know. Informed means more active and less worried