So you decide to go into your cheese cave and select a couple of interesting loaves, cause no one else is bring home made cheese! How clever, how thoughtful, how unique. How smug you feel for being this inventive.
Only problem is, when you crack open the gift, there is a distinctive bitter aftertaste. Not excessive, but certainly there. Enough of an aftertaste that it doesn't really blend in taste wise with all the other delicious food. Why is this one bitter, when the other one that was made *the same day* and with *the same recipe* tastes great with no bitterness at all? How did this happen, and how can it be stopped?
Well, predicting and troubleshooting flavors in food that takes a long time to mature is maddening. Home made cheese is a living organism, and it's almost impossible to control every aspect the affects flavor. However, there are some important defects that I think should always be avoided--corky texture, limited flavor development, and bitterness. This post is about preventing bitterness, since once it is there it isn't leaving.
According to the University of Guelph, "Some off flavours associated with undesirable or excessive protein breakdown in cheese are bitter, stringent, putrid and brothy. " They go on to say, "Proteases break proteins into smaller peptides, some of which are flavour compounds. For example, bitter and brothy flavoured peptides are well known to occur in cheese." The breakdown of protein and fats would occur naturally without any work from us, but the introduction of cultures and bacteria significantly speed the process up. The problem is, these compounds can break down into lots of different things. Some of peptides impart a positive flavor and texture, while others do not and make your cheese taste like Sierra Nevada Pale Ale.
Investigating further, I found an intriguing snippet that I didn't quite understand: "Culture adjuncts such as Lactobacillus helveticus in Cheddar cheese hold much promise to replace the normal diverse microflora of raw milk."
Hmm, very curious. So we know that during Pastuerization the microflora, or naturally occuring bacteria, are mostly destroyed. However, when you make a cheese out of raw milk they are still present. But what does this have to do with bitterness in cheddar or jack type cheese? Well, after doing a bit of research on this bacterium I found an eye opening post on Wikipedia:
Lactobacillus helveticus is a lactic-acid producing rod shaped bacterium of the genus Lactobacillus. It is most commonly used in the production of Swiss cheese and Emmental cheese but is also sometimes used in making other styles of cheese, such as Cheddar, Parmesan, romano, provolone, and mozzarella. The primary function of L. helveticus culture is to prevent bitterness and produce nutty flavors in the final cheese. In Swiss and Emmental cheese production, L. helveticus is used in conjunction with a Propionibacter culture, which is responsible for developing the holes (known as "eyes") through production of carbon dioxide gas.
This is it! This is why when I use store bought, Pasteurized milk many of them end up with bitter notes, but when I use raw milk or milk inoculated with the cultures to make Swiss I have never tasted any bitterness! The only problem is the possibility of 'eyes' growing in cheddar or other styles that aren't supposed to have them, but there is an easy solution to that--those bacteria love warmer temperatures, so moving the cheese into a 50F cave more quickly and aging it a bit longer should do the trick. At least it did for me, even though it was unintentional.
So, lessons learned here? It's probably a good idea to start using specific, controlled cultures, as well as documenting the specific strains I'm using so it will be possible to troubleshoot flavor defects in the future. This one turned out to be pretty easy to figure out, but I suspect the next problem that comes up may be more difficult.
Cheers, and happy Cheese a Day!