This month's post is the second of a two-part series on milk in which we explore the processing of milk, pasteurization and homogenization.
From the time dairy cows were first brought to New England by the earliest settlers in the first half of the 1600’s until the American Revolution, dairy products were consumed, by in large, on the farms on which they were produced.
In the late 1700’s, establishment of major urban centers such as Boston, New York, and Philadelphia opened up markets for large-scale milk production and distribution. Initially when the cities were small, pasture was set aside in town so that families could keep a family cow--Boston Common was one such place. But as the cities grew, these urban oases for the dairy cows got squeezed out while demand for milk increased.
Meanwhile, the whiskey industry was growing. George Washington himself owned the largest distillery in the nation at the time, and in 1810 there were more than 3600 distilleries in the state of Virginia alone. As a result, enormous amounts of swill, or distilled grains, the byproduct of whiskey and other alcohol distillery, were produced. Distilleries opened dairy farms adjacent to them in order to capitalize on the waste, which was fed to the cows. Unfortunately, these grains are depleted of many important nutrients: starch content is dramatically reduced, fat composition is compromised, and protein quality is diminished, while other nutrients, such as phosphorous and sulfur are increased to a point that is detrimental to the cow. But this swill actually increased milk production, which was what mattered. What ensued was growing industrialization of milk production wrought with sick cows producing milk of such poor quality that butter, cheese, and cream could not be made from it. This came to be known as the swill milk system—sickly cows were confined to small pens surrounded by their own manure with high rates of mortality. In 1852, 75% of milk sold in New York was swill milk. The milk was so thin and bluish in color that it was often augmented with starch, flour, and/or chalk. But it didn’t matter because it was cheap.
Until it did. What resulted was a public health crisis and the spread of milk-borne illnesses, such as typhoid fever, diphtheria, and tuberculosis which caused a spike in infant mortality. Substandard dairy production practices along with lack of refrigeration created milk that teemed with deadly pathogens--people were dying by the thousands.
Enter: Louis Pasteur. In 1862, this renowned French chemist and microbiologist who is credited with dramatically decreasing mortality from milk-borne illnesses, developed the process of pasteurization, originally developed to preserve beer. Milk is heated to a high enough temperature to kill bacteria, including those that are potentially pathogenic. This made it so that the milk, while still unfit for human consumption, no longer spread infectious diseases.
Pasteur’s discoveries of microorganisms being responsible for widespread infectious disease understandably created a microbe-phobic milieu that persists today.
Fast forward to 2014. Over 99% of milk produced in the United States is pasteurized with more or less the same process that was developed by Pasteur over 150 years ago, and while swill milk production is gone, intensive industrialized milk production and the resulting low-quality product remains very much a reality and continues to hide behind the glory of the mostly eradicated infectious disease epidemic at the beginning of the 20th century. As consumers, we can do better than to choose milk that’s merely not going to kill us.
Interestingly, as of 2012, 40% of corn production in the United States is used to make ethanol for fuel, and there has been renewed interest in recent years in using the abundant corn byproduct as a supplement to feed dairy cows (sound familiar?). There are a number of studies investigating the effects of using these so-called distillers grains on animal health only in regards to quantity of milk production but none on the resulting quality of milk from a consumer standpoint. The studies have one thing in common, however, which is to warn against the potential nutritional pitfalls of a dairy cow’s diet significantly based on distillers grains.
Pasteurization of milk is regulated on state, county, and municipal levels. In 1924, the United States Public Health Service issued the Standard Milk Ordinance, now the Grade "A" Pasteurized Milk Ordinance, for voluntary adoption by local governances. Current regulations on milk pasteurization vary from state to state and are constantly in flux. In California, only licensed retail sale of raw milk and raw milk products is legal. But as of spring of this year the Home Dairy Farm Raw Milk Safety Act was introduced in the California General Assembly. The bill would allow unlicensed on-farm sales direct to the consumer only on very small farms.
Often government regulated standards for the sale of raw milk is much more stringent than that of other milk, which is one way to distinguish milk producers of a higher quality. Usually retail raw milk producers raise their cattle on pasture in much less intensive settings compared to their factory-farmed counterparts since they can’t rely on the pasteurization process to conceal substandard husbandry practices. Healthy cows make for healthy milk.
While choosing pasteurized or unpasteurized milk is quite a personal decision, the following is some information on the process of pasteurization:
- Pasteurization is effective in killing potentially pathogenic bacteria, but heat is not selective. Despite the FDA’s claims to the contrary, numerous studies (here is one and another) have shown raw milk to contain beneficial probiotic bacterial species, such as those in Lactobacillus, and these are eliminated in the process as well.
- High heat denatures (unravels and renders useless) potentially beneficial proteins and enzymes. To name a few:
Lysozyme, an antimicrobial enzyme
Lactoperoxidase, another antimicrobial enzyme
Lipases, involved in fat digestion
Proteases, involved in protein digestion
- As you can see, raw milk potentially has antimicrobial properties and can be easier to digest, as is indicated by much anecdotal evidence by people who are milk-sensitive being able to tolerate raw milk.
- Levels of vitamins B1, B2, B12, C, E, and folate are decreased in pasteurized milk
- Heat oxidizes and damages unsaturated fats. About 35% of milk fat is unsaturated (30% monounsaturated and 5% polyunsaturated). This may partially explain changes in flavor in pasteurized and especially ultra-pasteurized milk.
- Very high heat, as in ultra-pasteurization can also damage heat sensitive amino acids, further decreasing nutritional value.
- Although not well studied, there is much anecdotal evidence that those who are lactose intolerant can consume raw milk. So much, in fact, that there is a study underway at Stanford Medical Center elucidating the matter.
- The allergy-mitigating effects of raw milk are well documented. Studies have shown that the incidence of allergies is dramatically lower in children who consume raw milk on farms compared to those who drink pasteurized milk on farms.
Active enzyme activity also means that raw milk is a much more dynamic product, making it sour more easily. But that’s ok! Soured raw milk turns into clabbered milk, which is a salubrious, gut-healing, traditional food similar to yogurt. By comparison, soured pasteurized milk becomes rancid and inedible and needs to be discarded. The difference is that beneficial lactic acid bacteria take over in the raw milk while potentially harmful bacteria take over in pasteurized milk.
A number of traditional European cheeses that we all know and love are made with unpasteurized milk. Many cheese producers believe that depth and complexity of flavor cannot be achieved using pasteurized milk because so many of the flavor compounds in cheese (and all fermented foods) are metabolic byproducts of the ambient bacteria. Recent reviews by the FDA are putting their availability in the United States in question.
A very abbreviated list of raw milk cheeses:
- Brie (many types)
- Camembert (some)
- Feta (many types)
- Grana Padano
- Gouda (many types)
- Cave-Aged Gruyère
- Manchego (some)
- Parmigiano Reggiano (has been made in pretty much the same fashion since the 13th-14th centuries)
- sPecorino Romano (some)
- Raclette (some)
Many of our own Northern California artisanal cheese producers are following suit using raw milk:
- Bellwether Farms
- Cowgirl Creamery
- Matos Cheese Factory
- Point Reyes Farmstead Cheese Company
- Redwood Hill Goat Dairy
- Sierra Nevada Cheese Company
- Organic Pastures
Milk is naturally an emulsion in which small fat droplets, 2 to 10 µm in diameter, are suspended in liquid amongst proteins, vitamins, and minerals. Over time, as fat does not mix well with water, the fat (or cream), being less dense than water, rises to the top. Casein proteins come in clumps called micelles and are held together by calcium phosphate. It is these casein micelles that make calcium in milk so bioavailable. The micelles act as a sort of escort service for the calcium.
Homogenization is the process by which milk is forced through very small holes with very high pressure, typically 2000-3000 psi, and sometimes upwards of 15,000 psi! The small fat droplets in the milk are torn apart by the shear force into minuscule fat droplets, now 0.2-2 µm. The casein micelles are also shredded and the calcium left without its escort. You guessed what that means—lower calcium bioavailability in homogenized milk. Parts of the casein, now somewhat homeless, start binding to milk sugars in a process called glycation, and form products implicated in increased inflammation and their associated diseases.
Casein gloms on to the increased surface area of the fat, which weighs down the fat to keep it suspended so that it doesn’t rise to the top. The increased surface area of the fat droplets means more exposure to degrading enzymes that will make the milk spoil. Pasteurization disables enzymes, so is therefore usually done prior to homogenization. The new aggregates that are made can be hard on the GI tract, another contributing factor to dairy intolerance.
This article shows microscope pictures of changes in the microscopic structures of the milk in raw, pasteurized, and homogenized milk.
Homogenized milk looks whiter and feels creamier because the fat is dispersed throughout the milk.
Pasteurization and homogenization resulted from the commodification of milk, which disconnected and distanced people from their food source. These processes became necessary for public health when considering the bottom line. Many of us are lucky enough to live in a place where there is a trend towards reconnection with our food, fostering our health and the health of our environment.
Here's a guide to some of our local dairies:
Here is an illuminating video about the milk renaissance and its response to industrialized milk from the PBS program, Food Forward.
Crème fraîche is a fermented cream not too different from sour cream. Besides being delicious, it's teeming with probiotic bacteria. For savory preparations, you can add it to sauces and dressings, or to finish a soup, stew, or even mashed potatoes. Or for desserts, whip it and use it in place of whipped cream, or try it in ice cream or cheesecake. Real crème fraîche is made by allowing raw cream to sour at room temperature. If you can get your hands on some raw cream, try it--it's a treat! Otherwise, just take pasteurized heavy cream and introduce some buttermilk cultures. It's a great way to preserve leftover cream that you only used a small amount of for a recipe. Making your own is a cinch!
Give It a Try!
Crème Fraiche (2 ways)
raw heavy cream
Leave cream out at room temperature until thickened and reached desired taste and consistency, about 24 hours.
1 cup pasteurized heavy cream
2 T buttermilk
Stir buttermilk to cream, heat gently until just warm, about 85 degrees. Leave in a warm spot for about 8-24 hours, or until it has reached desired taste and consistency.