raw milk cheese: what causes 'blow'?
This from a friend:
I’ve had great success with mozzarella, and I have cheddar aging, so I’m hoping I have success there. I tried Gouda and while my cheese was drying (day 3) it balloon’d up. According to the cheese forum I’m a part of they said it is ‘late blow.’ My chickens were delighted to have some of it, but sadly it got tossed due to the contamination. I am curious, however, if you have advice on what cheeses may be a good place to start.
Congratulations on success with your cheeses! Having a cheese blow isn't as big a deal as people think. There can be multiple causes, air- or surface-borne yeasts being at the top of my list. Sure, it could be some kind of coliform bacteria, but your kitchen is full of yeasts, and is much less likely to be full of coliform bacteria. Moreover, most coliforms are benign to humans (if you want more information, check out this link). Only some coliforms are fecal, only some fecal coliforms are escherichia-type, and only a few escherichias are pathogenic. When folks say 'E. coli', they assume they've said something scary, but the bad guy who is usually responsible is E. coli 0157:H7, just one strain among a great many.
Either way, a blown cheese does not have to be scrapped! It will end up with a slightly different texture because of the small pockets left behind after the gas escapes, but that isn't a negative thing, just a fact. The one problem I have had with a blown cheese was when it got so big it cracked; after that it was hard to manage the surface molds, and when it matured I had to do a lot of trimming. I have two blown cheeses aging right now, and expect to enjoy them both thoroughly.
So, why would some cheeses blow and not others? Well, spring and fall can have a lot of airborne yeasts via pollen-dispersal; older milk (more than a couple of days) may have a higher yeast load just because whatever yeast landed in it has had time to reproduce. And winter cheeses in a house with forced air may be picking up more yeast just because the furnace blower is on. One thing our experience has taught us is that raw milk has a life of its own, and the maker of raw milk cheese will have greatest success if she works with, and not at cross-purposes to, her milk biota. Mostly that just means knowing that cheese is a living food, and like other living things it will behave unpredictably at times. If we accept the variations what we find is that, instead of learning to control cheese so we can get a single, desirable, consistent product (something that only happens under lab conditions), we have learned to work with milk and milk solids to produce a wide range of delicious, nutritious cheeses of varying character.
A further note: even the USDA confirms that raw milk cheese that is aged 60 days can be trusted to be pathogen-free, regardless of possible contamination in the milk's fresh state. In other words, after 60 days of hanging out with raw milk probiots, pathogens have given up the ghost.
The best cheese making book out there that I know of is The Art of Natural Cheese Making, by David Asher. Read the whole thing; it will change the way you understand milk and cheese making, and it's beautiful. One caveat: David uses kefir as a starter, and I do not: kefir has yeasts in it, and I prefer not to add them if I can help it. Raw milk is its own starter, so you don't have to add any other; if I do want to add one, yogurt or buttermilk work great.
I'd love to hear how your next cheese turns out. Cheers!