Late blowing is characterized by a swelling of your cheese during the aging process. It often affects hard pressed cheeses and can occur anywhere between a few weeks to months after beginning the aging stage. Traditional Swiss style cheeses, are actually meant to have late blowing. Late blowing can be caused by several different types of bacteria that feed on lactose, lactic acid, left over nutrients, and produce many different byproducts, CO2 being one of them, which causes gas bubble formation.
Though there are a few different causes of Late blowing, it is usually caused by strains of either propionic acid bacteria, or clostridia bacteria.
Propionic Acid Bacteria
Propionic Acid Bacteria is the type of bacteria that is responsible for the eyes in Swiss style cheeses. They are types of bacteria that metabolizes lactic acid and form propionic acid, acetic acid, CO2 and hydrogen. As a cheesemaker you can buy certain types of propionic acid bacteria powder to inoculate your cheese with, alongside other thermophilic type bacterias. After the lactic thermophilic bacteria has fermented the lactose into lactic acid, the propionic acid bacteria will metabolize the lactic acid and not only cause that sweet buttery flavour of Emmental cheese, but also cause eye formation from CO2 production.
Emmental and Swiss type cheeses need to be quite large to form beautiful eyes. If they are not large enough, you may end up with eyes that appear more as cracks, and they can even penetrate the surface of the cheese. There are different types of propionic acid bacteria, some may cause spoilage, but some are very useful in cheesemaking.
Clostridia
Clostridia bacteria (there are a few different strains, botulism is one of them that is more common in canned goods) is a harmful bacteria that can metabolize several different left over nutrients as cheese ages and breaks down. Their growth is inhibited at a ph of 4.5. In this, they are usually found in cheeses that have fermented down to a low ph of 4.5, but have then increased their ph during aging, due to the metabolism of the lactic acid. The main strain of clostridia that affects cheese produces butyric acid. Luckily, butyric acid smells bad! Think rotten eggs, vomit. Nobody wants to eat a vomit smelling cheese! Your nose is going to keep you safe on this one!
So why am I talking about this?
Just today, I was looking through my cheese fridge. I was looking for cheeses that were ready to be eaten, and that I could cut up into wedges and re vacuum seal for easier access. Tucked in the back of my fridge was an Asiago I had made at the beginning of April. It was about 3 months old, and I could see that it had puffed up a bit at the top. I had not noticed any signs of early blowing with this cheese, and I was intrigued to open it up and see what we going on inside.
I have never made Emmental or Swiss style cheeses, mostly because I have never bought propionic acid bacteria powder.
When I opened up the bag of this cheese, it smelled good. The first thing I was looking for was what does it smell like? If this cheese had been contaminated by Clostridia, it would have smelled bad. If it had been contaminated by an early yeast, it would have smelt fermented, and yeasty. It smelled good, so I cut it open and was so pleased to find very large eye formation.
At this point my assumption was that this cheese had been contaminated with some form of propionic acid bacteria. The thermophilic bacteria that I had added into my cheese had fermented the lactose into lactic acid, and the propionic acid bacteria had metabolized the lactic acid causing a late blowing.
I cut off a slice; sweet, buttery and delicious. I had accidentally made Swiss Cheese!
You can see in the picture that the hole formation is not perfect. This is due to the fact that 1) this cheese is small for good eye formation, and 2) I did not flip or turn this cheese at all during aging.
This cheese is a happy surprise in an unfortunate run of early blowing contamination. I won’t guarantee that this will always happen, that cheeses that have been contaminated will still turn out good, but it is a lesson in the beauty of cheese. The fact that sometimes, even when things don’t go as planned they still turn out.
I will be making fondue from this cheese, and its life will be short, because it is delicious, and yummy cheeses do not last long around here.
Happy Cheesemaking!
Robyn
Want to learn to make cheese? Check out my Homestead Cheesemaking 101 Course.
Safety Note- Contaminated cheeses can be dangerous. If I am working with pasteurized milk, I never eat a contaminated cheese. Even when working with raw milk, we still must follow clean and safe milk handling practices to ensure that unwanted bacterias or fungus do not get into our cheese. I can not endorse eating contaminated cheeses, because the fact of the matter is, you really can’t know if they are safe just by smell and taste. Do your own research, and follow your gut feeling.
Hi, how dangerous are Clostridium Tyrobutiricum for the people?
K.R
Nikos
Very dangerous.
I have attempted to make many gouda and they all look like this – late blowing. They are usually nice and formed when I wax them and place them in my cheese fridge. About 3 weeks in they start to show signs of blowing. When I cut them open they don’t smell rancid or bad, there is no mold forming however these is a different smell to it as well as taste perhaps a mild . I opened both cheeses at 6 weeks. I definitely don’t get a (store bought) gouda taste but I am wondering if I may have created a different type of cheese, I am using raw milk and meso culture. Should I avoid consuming this one as it doesn’t seem to be ‘the best’ flavor?
I’m just learn and have not made cheese yet. Good that your late blowing “Frankenstein” was yummy for your tummy and did not cause you to blow cheese instead. Too cheezy?