For someone who really likes food, but doesn’t easily understand the science of making food, cheese making can be kind of frustrating. The reason for this is that if you ever want to get a consistent product from one batch to another, there are certain principles you have to master or at least understand.
Cheese is essentially a series of chemical processes applied to milk. The first step involves “culturing” the milk, or adding bacteria so you can develop acid (lactic acid is a by-product of the bacteria eating the milk sugars) and therefore flavor. The next step is “curd formation”, which is what I’ll be talking about here. And then there’s “forming the wheel”, followed by “aging”. Oh yeah, then there’s “eating.”
Curd formation involves a chemical process called flocculation. Never heard of it? Neither has spell-check. Also it is fun to say out loud. Go ahead and do it…See? I told you. Anyhow, flocculation is the process where colloids (in this case butterfat) come out of suspension (in this case suspended in water) and form a floc (in this case a cheese curd). Here’s what’s happening: Milk is basically butterfat and protein suspended in water. When you add rennet, it causes a reaction where the fats gel together and trap the moisture. The milk becomes the consistency of Jello. The progression from adding the rennet to achieving the jello-like consistency is flocculation.
So why is this important? The amount of liquid trapped in the jello-like curd is a major factor in the final moisture content of the final cheese. Think Parmigiano-Reggiano vs. Brie. The longer you let the curd form, the more moisture is trapped in the curd. Okay, sounds straightforward enough. Here’s the problem…you can make the same cheese one day and the time it takes to achieve a specific curd consistency can be different on the next day. And there is a scientific reason for that, but I don’t understand it…I just understand the timing varies and that variation matters a whole lot. So following a recipe that says “let the curd form for 30 minutes” won’t give you a consistent product from batch to batch and that is super annoying.
BUT, there is a trick amongst cheese makers to achieve flocculation consistency and it is also fun to do. It is called the “spinning bowl” method.
It is very simple. Once you add the rennet, you start a stop watch, then float a light weight bowl on the surface of the milk and start to spin it. Since the milk is still in liquid form, the bowl will spin. At some point, the bowl will stop spinning because the curd has started to form and become Jello-like. Once that happens, you note the time on your stop watch and multiply that time using a factor specific to that type of cheese. Hard cheeses like Swiss have a low floc multiplier…like 2.5. A soft and moist cheese has a high floc multiplier like 6 or 6.5. So for instance if you were making a brie…let’s say the time it took for the bowl to stop spinning was 9 minutes and 30 seconds. Using a flocculation multiplier of 6, you would have a total flocculation time of 57 minutes. If you made brie the next day and it took 13 minutes for the bowl to stop spinning, using the same multiplier would give you a total flocculation time of 1 hour and 18 minutes. However, the final moisture content will be roughly the same. Whereas if you had simply used a recipe that told you to wait 50 minutes, you would have a very different cheese. Voila! Food science. It’s confusing, but when you spend an entire day making a cheese and then spend the next six months carefully aging that cheese, aiming for consistency is worth it. For me it is the difference between having people say, “that’s delicious” vs. them politely spitting out the cheese when I’m not looking. And a positive reaction is really why I make this stuff anyway. Truth be told, I don’t really love cheese. I love making it, but eating it? Did I mention I’m lactose intolerant? Seriously, I am.
Okay, the whole point of this post is below. I made two quick videos of the spinning bowl method so you could see what it looks like
desired flocculation is achieved, bowl is removed and you can see the Jello-like consistency