|To Heat or Not To Heat: A Yogurt Question|
|Written by Linda Joyce Forristal, CTA, MTA|
|Wednesday, 20 July 2005 16:39|
In the Kitchen with Mother Linda
One of the most frequent questions we receive at the Foundation is the following: should you, or can you, make yogurt from raw milk? The controversy arises from the fact that the naturally occurring enzymes and bacteria in raw milk are destroyed by too much heat. Destruction of enzymes begins at 118Â°F and is complete at 180Â°F. So, if thatâ€™s true, why doesnâ€™t everybody want to make yogurt with raw milk? Itâ€™s because raw milk yogurts oftentimes have a different texture from yogurts made with heated or pasteurized milk.
Left to its own devices, fresh milk sours naturally. This is not due to the enzymes in the mix, but to naturally-occurring lacto-fermenting bacteria found in raw milk. Those bacteria produce lactic acid that sours the milk by reducing its pH., i.e., making it more acid. While the uninitiated might think this is milk to be thrown out, the wise know this acid condition actually preserves the milk against spoilage. In days gone by, the Irish housewife typically soured fresh milk overnight by the dying fireplace in preparation for making soda bread the next morning.
FERMENTED MILK HISTORY
Frank Kosikowski, a food scientist at Cornell University, classifies fermented milk in four different groups. The first group is "acid/alcohol" milk products such as kefir and koumiss. Kefir (which, by the way, does not rhyme with "reefer" but is stressed on the second syllable and pronounced "keh-FEER") is made with kefir grains, called "gift of the gods" but of unknown origin, which initiate a dual lactic acid/alcohol fermentation process. Traditional koumiss is made with mareâ€™s milk and named for the horse-herding Kumanes tribe that lived on the central Asian steppes until 1235. It is fermented by a combination of acid producing L. bulgaricus and the alcohol-producing Torula yeast. (With mareâ€™s milk in short supply most koumiss today is made with cowâ€™s milk, but since the two milks are not the same composition, making koumiss can be a complicated endeavor.)
Kosikowski identifies the second class of fermented milk as "high acid" Bulgarian sour milk cultured exclusively with Lactobacilllus bulgaricus. The third category is "medium acid" acidophilus milk and yogurt, the main type of yogurt produced in the United States. It is primarily cultured with Lactobacillus acidophilus, a slow- and low-acid producer. The fourth category is "low acid" cultured buttermilk and cultured cream.
Today, most yogurt starters, even the "Bulgarian" one I recommend, combine at least two different bacteria. The presence of two bacterial strains, one high acid and one low, moderates the acidity of the finished product. For example, Streptococcus thermophilus ferments at 110Â°F to 112Â°F and produces .9-1.1 percent acid, Lactobacillus acidophilus ferments at 100Â° to 112Â°F and produces 1.2-2 percent acid, and Lactobacillus bulgaricus grows at 110Â° to 116Â°F and produces 2-4 percent acid. My favorite yogurt starter is 50:50 L. bulgaricus/S. thermophilus.
Now letâ€™s get back to the "to heat or not to heat" raw milk controversy. What happens when you donâ€™t heat the milk is that while the enzymes are preserved, the milk also retains its own natural complement of bacteria that will naturally sour the milk. These undisturbed bacteria will also compete with any added culture resulting in a different fermented product. Controlling the conditions of fermentation, most importantly temperature, the yogurt maker can achieve varied results by adding small amounts of microorganisms from tested and tried established cultures.
Most yogurt makers heat milk sufficiently to create a tabula rasa into which the new bacteria are dumped to do their handiwork, but the temperature needed for this will be many degrees higher than 110Â°F. Whatever temperature the milk will be heated to, in my opinion it is best to begin with raw milk. It is not homogenized so you get a wonderful cream on top. It has not had milk solids added to it, so it wonâ€™t stick to the bottom of the pan. Most important, raw milk has not been pasteurized, which is a violent, rapid-heating process that has a very detrimental effect on the proteins in the milk. A slow, gentle heating on your stovetop will more effectively preserve the integrity of fragile milk proteins, especially if you remove the milk from the stove as soon as the desired temperature has been reached.
When you start with raw milk, you can decide yourself how high a temperature you want to take the milk to--a modest 110Â°F, that will preserve enzymes and some of the competing naturally occurring bacteria, or to the more traditional 180Â°F, which is hot enough to kill competing bacteria. The texture, taste and thickness of the finished yogurt will be determined by the choices you make at every stage.
My own preference is for heated yogurt, which results in a smooth, thick product. I begin with raw milk which I slowly and gently heat to 180Â°F and then let it cool until I can stick in my finger for 10 seconds, which is around 110Â°F. When it has cooled, I add a rounded teaspoon of "Bulgarian" culture, which is really only 50 percent true Bulgarian, as explained previously. The finished yogurt comes out sharp, smooth and wonderful.
I want to pass on something I learned while researching the article. I have always made a gallon of yogurt at a time in four quart jars, and kept them up to two months. It does not spoil easily, so my family and I would happily scoop away at it until it was gone--adding our own preserves, maple sugar or honey. My favorite yogurt concoction is a couple scoops of yogurt, sprinkled with a tablespoon of freshly ground flax seed and topped with a quarter or half of a grated apple--applesauce is good, too.
But if master yogurt maker Max Alth is correct, milk begins to exhibit "antibiotic" powers as soon as the lactic acid bacteria start to curdle the milk--either naturally or in the process of making yogurt--and a peak is reached about seven days later. And according to Alth, the antibiotic effect disappears about a week later. At its most effective, the antibiotic strength of yogurt is equal to about .06 penicillin units per cubic centimeter, or about nine units of penicillin in every 8 ounces of yogurt. I have not confirmed this information, but if thatâ€™s true, in the future I plan to make smaller batches of yogurt more often.
Annaâ€™s Bulgarian Yogurt
I have had the great fortune of living close enough to a Bulgarian friend, Anna Pavlova, to get a container of yogurt every so often from her as a starter. If you donâ€™t have a Bulgarian friend, a company in California sells a Bulgarian-style Yogurt StarterÂ®. (See www.natren.com and look in their specialty items.) This wonderful product is a combination of 50 percent Streptococcus thermophilus and 50 percent Lactobacillus bulgaricus. Each bottle is decorated with the picture of a Bulgarian woman.
Over low heat, slowly bring the milk to at least 180Â°F, or until a ring of bubbles forms around the edge of the pan, but donâ€™t boil. Let cool until you can keep your finger in the milk while you count to 10. Divide yogurt starter or reserved yogurt between two wide-mouth quart-size sterilized glass jars. Pour in about 1/4 cup milk and stir to incorporate the starter. Fill the jars with the rest of the milk and screw on the lids.Wrap the jars in a warm blanket and let sit overnight in a warm place or for at least eight hours. Unwrap and place in the refrigerator. I know you will enjoy this creamy, healthy yogurt.
FOR MORE INFORMATION
Max Alth, Making Your Own Cheese & Yogurt, Funk & Wagnalls, New York, 1977
QUICK RAW MILK YOGURT
In the Middle East, yogurt is a thick drink, not something you eat with a spoon. To make raw milk drinkable yogurt, place 1 quart raw milk in a glass container and add 1/4 cup yogurt. Place in a warm place (such as a warm oven) overnight. The milk will sour and become slightly thick and perhaps lumpy.
You can drink this as is, or whisk it to make it smoother. In Iran, the traditional yogurt drink is quite salty, so you may wish to add some unrefined salt. The addition of salt makes drinkable yogurt the perfect beverage for a hot climate. Of course, you may also use your drinkable yogurt to make smoothies by blending with fruit and a natural sweetener.
Another method, suggested by raw-foodist Aajonus Vonderplanitz, is to warm milk to about 80 degrees and add a small amount of good quality commercial yogurt or yogurt from a previous batch and put in a yogurt maker. Leave in the yogurt maker much longer than called for in the instructions, that is about 8 hours or overnight. Results may not be consistent and the product tends to be thinner than heated yogurt.
MARIAâ€™S RAW MILK YOGURT
We are grateful to Maria Garcia for coming up with this wonderful raw milk yogurt, and to Kristina Boudrezux for working out the details. This recipe makes a smooth, thick yogurt loaded with beneficial stuff for your body. It requires no electricity, and ensures a high quality product using glass, versus plastic, for yogurt culture growth. It is easiest to start at night, after dinner, and let it set overnight. You will wake up to yummy yogurt for breakfast.
This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly magazine of the Weston A. Price Foundation, Spring 2005.
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|Last Updated on Tuesday, 09 June 2009 16:56|