You may have seen something called ultra-filtered milk popping up in the dairy aisle. According to the manufacturers, ultra-filtered milk is a milk product that contains nearly twice the protein of ordinary milk with only half the sugar. It's also completely lactose-free. This makes ultra-filtered milk appealing to a wide range of folks, including fitness types who like the extra protein, people who are lactose intolerant, and those that need to limit their sugar intake, such as diabetics.
But what is ultra-filtered milk and how exactly is it made? First, let's take a look at how ordinary milk is made, and then we'll discuss what makes ultra-filtered milk different.
What Is Milk?
Milk is an emulsion of water, butterfat, and protein. Back in the old days, a bottle of milk would separate with the cream rising to the top. You'd either shake it up to combine it or simply enjoy the rich creamy goodness that accompanied that first sip or pour.
Now milk goes through a number of processes before it reaches the supermarket shelves, both to increase safety, shelf-life, and to create a variety of products, including skim, 2 percent, lactose-free, and so on.
First, milk is pasteurized, which involves heating it to 167 F for 10 to 15 seconds. This is done to kill bacteria that could cause food poisoning and spoilage. Ultra-high temperature pasteurization is an alternate technique involving heating the milk to 280 F for just 2 seconds. It increases shelf-life significantly, although the flavor is diminished somewhat.
Next, the milk goes through a fat separator, which is a large centrifuge that spins the milk at a rapid speed and captures the fat which rises to the top, leaving pure skim milk at the bottom. The fat is then added back in the desired proportions to produce whole milk (3.5 percent fat), 2 percent, 1 percent, and skim. Some of this pure butterfat is also used to make butter, cheese, and half and half.
After this the milk is homogenized, which involves heating, agitating, and pumping the milk through a narrow valve, thereby breaking up the fat globules into smaller bits which are then able to stay evenly dispersed throughout the milk, instead of rising to the top. In most cases, that's it. Vitamins A and D are added and the product is bottled and shipped off to stores. But with ultra-filtered milk, there's yet another step added to the process.
What Is Ultra-Filtered Milk?
To make ultra-filtered milk, the skim milk that comes out of the fat separator is passed through one or more membranes to filter out about half of the milk's water content along with about half of the lactose, or milk sugar, while letting the milk protein molecules through. What you're left with is essentially concentrated milk—all the protein, plus half the water and half the lactose.
This high-protein concentrate is then re-diluted with water, but at a higher protein concentration so that it ends up with around 13 grams of protein per cup as opposed to around 8 grams per cup for ordinary milk. Fat is added back to the desired levels (such as 1 or 2 percent) followed by the addition of an enzyme called lactase which breaks down the remaining lactose into its component sugars, glucose, and galactose, which are easier to digest than lactose. The addition of lactase is also how most lactose-free milk is produced.)
Finally, the ultra-filtered milk undergoes the usual homogenization process, as well as the addition of vitamins, before being bottled and shipped to the stores. As advertised, the resulting product boasts half the sugars (around 6 grams instead of the usual 13) and nearly twice the protein (13 grams versus 8). Calorie-wise, the numbers balance out, with the added protein making up for the fewer sugars, so that a cup of ultra-filtered 2 percent milk has the same number of calories as its 2 percent counterpart.
Using Ultra-Filtered Milk
Ultra-filtered milk also has a slightly thicker consistency that might be described as "creamier," although the thickness is achieved not through additional cream but rather additional protein.
Flavorwise, ultra-filtered milk might taste slightly sweeter than ordinary milk, which might surprise you given that it's supposed to be lower in sugar. But that has to do with the way the lactose is broken down into glucose and galactose. Glucose and galactose are perceived as sweeter by your taste receptors than lactose is. If you're used to drinking lactose-free milk, you might not notice a difference in sweetness.
It's worth noting that if you're baking with ultra-filtered milk, because of this thickness, you might find that you need to add either more milk than the recipe calls for or a bit of water to thin out the batter.
Where to Buy Ultra-Filtered Milk
You can find ultra-filtered milk in the dairy aisle of most supermarkets. Fairlife is a popular brand that is sold at most Wal-marts, Targets, and other big grocery chains. Horizon and Organic Valley also make ultra-filtered milk and are sold in many healthfood stores.