‘Blowing’ Defect / ‘Blown Cheeses’ Fault – what is it and how do I fix it?

This fault is commonly associated with Continental-style cheeses (Gouda, Gruyère, Comté, and Parmesan-style recipes). The low acidity of this type of cheese in the make means they are particularly susceptible to it.
It is caused by butyric spores producing butyric acid and gas as the cheese ages, and is usually evident from two weeks of maturation. It cannot be solved by pasteurisation of milk because the spores survive heat treatment.

The French have a great phrase for it “C’est Gonflé” (roughly “it’s swollen”).

Ultimately, the fault is harmless, but causes wet-silage, farmy, rancid off-flavours (my favourite tasting note is ‘baby’s breath’) and a cheese that has big fissures and cracks, which can then be liable to browning and later blueing.

There are only two guaranteed ways of stopping it:

• Stop using fermented and wet feed-stuffs to feed cows. Feeding cows just on hay, grass or dry fodder should eliminate the prevalence of ‘blowing’. (There is a reason it is illegal to make Comté, Gruyère and Parmesan with silage-fed cows’ milk. Sometimes you just can’t change the science.)
• Higher/faster acidification in the make. Look at culture type and usage. Though ultimately, this may change the character of your cheese. This is why the ‘blowing’ defect rarely affects ‘British-style’ cheeses even though there is high silage usage in the UK – the higher acidity in making eliminates the germination.

If the butyric spore population is medium-to-low, there are other mitigating controls that can work, to limited success, to help reduce or stop the effects:

• Adding Lysozyme. This is an antimicrobial enzyme that can stop butyric germinating. It is added to the milk prior to cheese-making. The enzyme is usually selected from egg whites, so needs listing as an allergen. (Interesting note: Lysozyme is also found in human tears). You will find it listed as an ingredient on many British made ‘Continental-style’ cheeses.
• Increasing salt (and/or brining time). Higher salt can help reduce germination.
  (increase time in brine, increase temp of brining (may bring other issues), increase salt in brine or additional salt pre-brine; to inhibit salt needs to be >1.8% – be sure to test your final cheese to verify).
• Lower maturation temperatures. Keeping maturation <8C can stop the butyric spores germinating. However this leads to longer maturation times for flavour development and slight differences in profile. The spore can then also ferment much later on in the final stages of transport, maturing and sale if it gets >8C again.
• Using cultures (NSLAB – non-start lactic acid bacteria). Some culture houses supply bacteria which can ‘outcompete’ with the butyric bacteria and should have no or only negligible impact on the final cheese.
• Turbulence – if the spores have been present in the past they can remain in pipework/equipment even after cleaning as they are not destroyed by chemicals/heat. The best way to remove them is to make sure cleaning schedules have plenty of ‘turbulence’ in them to make sure they are cleared out.

PS This blowing defect is more commonly called late blowing defect, and usually occurs after 2 weeks.  If your cheese is blowing before that and blows in a different way (more eye holes / spongy look / gassy); that is a different cause – yeast or coliform contamination.  This is usually associated with starter issues and or/milk hygiene.

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