I recently toured the Straus Family Creamery dairy farm in Tomales Bay, an area in northern California most famous for unparalleled farmed oysters (the Hog Island Oyster Company) and the San Andreas fault. Straus is also a happy anomaly and attraction in the area, garnering attention for its pioneering (literally, they were one of the first) organic dairy farming practices as well as its truly amazing milk, cream, yogurt, butter, and ice cream.
I'm not going to do another "atta boy" article about how Straus is doing things right by stewarding the land and making a profit (although after you hear their pitch, you get this feeling that doing elsewise is just loco as well as irresponsible). Instead, I learned a great deal about cows and making yogurt, and that's what this post is about.
What Is Milk? Why do we care?
Let's not forget, milk is what cows feed their young. For this reason, it contains a mix of nutrients, sugars, and fats balanced for nurturing calves that's also (and very fortunately) a versatile raw material for making a huge range of wonderful foods. After years of careful selection, cows have been transformed from efficient grazers into extreme lactators. If lactating were a sport, Holsteins would win for their productivity, and Jerseys for their higher butterfat content. Straus uses a mix of both breeds to balance their herd.
A Quick Bit About Organic
Unlike conventional industrial farms, Straus feeds their cows exclusively on organically fertilized pasture grass, organic silage (carb-rich green plants), and some extras like corn, peas and soybeans. Since this blog has been obsessed with all kinds of fermentation processes, I'll just take a moment to say that silage is fermented green grassy plants and legumes often including grass, sorghum, oats, vetch, and alfalfa.
To make silage, fresh plant material gets chopped, packed tightly into a pile, and covered. The moist, anaerobic environment incubates acetobacter and lactobacter perfectly, which digests the complex carbs and sugars. As the digestion progresses, the pH lowers (acidity rises) to a point where unwanted rot can't get started. At Straus I had the opportunity to smell the fermenting silage. It was unmistakably vinegary. Cows find it appetizing, and why not?
Yogurt is Spoiled Milk
Not everyone likes milk--on cereal or otherwise. I happen to be one of these people. Ice cream, yogurt, cream, and butter on the other hand, are entirely different stories. Yogurt has great advantages, however, because it lacks lactose (which can cause distress if you're unable to bust it up in your gut), tastes great, and it comes in fat-free varieties.
To make yogurt, you have to start with pasteurization. Everybody knows milk gets pasteurized to kill unwanted bacteria, but what you may not know (I didn't) is that there's more than one method--and the method impacts the flavor. At Straus they heat their milk to around 161 degrees for 15 seconds, then quickly chill it; it's the second slowest method that's considered safe. In most commercial milk production operations, by contrast, milk is heated to 191 degrees or hotter for as little as a second. According to Straus and many other experts, the higher heat deadens not only the dangerous flora, but the delicate flavors, so slower is better.
After pasteurization, the milk gets inoculated with helpful lactobacter and other friendly microbes--there's a "weeding the garden and replanting" metaphor in there somewhere, and the happy outcomes are many: digestion of the lactose in the milk, flavor development, and texture changes.
Yogurt and Silage Have a Lot In Common
In the same way that the lactic acid prevents unwanted spoilage of silage, the low pH of yogurt protects it from unwelcome bacteria getting a foothold. This doesn't mean yogurt is bullet proof. In the words of our Straus tour guide, and I paraphrase, "You can't technically spoil yogurt, because it's already spoiled, but you can spoil it more if yeasts and molds get in."
In addition to controlled spoiling, the acidity denatures (basically cooks) the milk proteins in a consistent and orderly fashion, causing them to tangle and thicken the texture uniformly. In another recent post I talked about denaturing proteins in relationship to tenderizing meat, so if you're interested check it out.
Thickening via acid, however, only takes the texture so far. To get that creamy mouth feel that separates yogurt from kefir, especially in non- and low-fat varieties, additional steps are required. In commercial manufacturing processes, milk solids in the form of dried or evaporated milk, gums and pectins are added. There are even laws governing total milk solid percentages.
The upshot? If your yogurt is bouncy, super shiny, or sticky you're most likely eating tree sap or pectin along with powdered milk. Most commercial yogurts are fermented right in the little cup that you buy, so everything has to be in the mix when the cup's filled. It's easy to see why they might want to use thickeners to ensure a consistent--if not totally desirable--end product.
At Straus, rather than making the yogurt in the cup, they make it in a vat. Instead of adding non-dairy thickeners or powdered milk solids (which are scarce if you're looking for organic sources), they reduce the water content through a process called reverse osmosis. Aside from being an interesting tidbit that won me a free quart of yogurt in a friendly "pop quiz" at the end of our tour, you care about that fact for one good reason: it's one of the best ways to extract excess water without changing the flavors because there's no heat involved. And heat, as we discussed in the pasteurization part, deadens the flavor of milk.
Reverse osmosis is really just superfine filtering--mainly water passes through a semi-permeable membrane, but most everything else doesn't. This concentrates the milk solids, increases the thickness, and does no harm to the taste of the milk.
If you want to try Straus product, look for it at Whole Foods or other uppity and/or swishy food sellers. Straus costs almost double it's conventional counterpart so get ready for sticker shock. In my mind, though, the care they take of their herd, their land and nearby Tomales Bay, added to the truly remarkable quality of their products, makes it more than worthwhile.