When I was growing up down south, it was unthinkable to be without buttermilk. Like a tin of Hershey's syrup, a jug of buttermilk was a constant presence in our fridge. So the more buttermilk-centric recipes I share, the more I'm surprised at how many people want to replace the irreplaceable.
Google around and it's not hard to see why buttermilk seems so frivolous—experts everywhere act like getting rid of it is no big deal. Just use milk and lemon juice! Milk and vinegar! Milk and cream of tartar! Plain yogurt! Buttermilk powder! Anything but the real deal.
These substitutions treat buttermilk as if it were simply a delivery vehicle for water, lactose, and acidity, rather than a vital means of controlling the viscosity of batters and doughs. See, cultured buttermilk is wonderfully thick,* which means you can use a fair amount of it without turning biscuit dough into pancake batter. Take my favorite drop biscuits, for example. They're made with equal parts flour and buttermilk by weight, yet the dough seems thick and dry, and as fluffy as a haystack.
*True buttermilk, sometimes called whey buttermilk, is a natural by-product of churning butter, and it's comparatively thin. Since this type is all but extinct from a commercial standpoint, I find it more expedient to focus on the sort of buttermilk most commonly found in American markets today.
That consistency helps the biscuits hold their shape in the oven, so they bake up light and tall. While buttermilk may seem super thick, it's still mostly water, which allows it to aid in gluten development for structure, provide fuel for a steamy rise, and furnish plenty of hydration to keep the biscuits moist. And that's not even taking into account its deliciously complex tang, which is so much more than a simple matter of pH.
Due to all those factors, successfully replacing buttermilk is a tall order, so how do the most frequently suggested substitutions pan out? To clearly demonstrate how these replacements affected browning in this particular drop biscuit recipe, I omitted the herbs and spices in the dough so the results wouldn't be tainted by paprika or obscured by parsley, then baked up a batch with each substitute.
Milk + Lemon Juice
It's often suggested that a shy cup of milk plus a tablespoon of lemon juice, vinegar, or cream of tartar is a reliable substitute for buttermilk, but let's be honest—when it comes to flavor, such replacements will always land in a distant second place. Instead of the mellow complexity that develops through culturing, they've got nothing but sharp, one-note acidity. That harshness is compounded by the fact that these options are often more acidic than buttermilk, a factor that can significantly inhibit browning.
While the quantity of acid could be fine-tuned, the consistency of milk-based substitutions will be unavoidably thin. Compared to cultured buttermilk, plain milk is watery, making the dough so heavy and wet that it oozes into a puddle, turning the biscuits flat and dense.
Sure, you could use less milk in order to approximate the thickness of a buttermilk-based dough, but then there'd be less water available for gluten development (making the biscuits crumbly), less water converting to steam for leavening (making the biscuits dense), and less hydration overall (making the biscuits dry). Booooo.
If you're making my Irish soda bread, drop biscuits, scones, or muffins, having a thick batter or dough is crucial to a good rise and nailing the pH that's vital to browning. So, unless you're facing some dire baking emergency that somehow precludes a change of plans, don't bother with milk and lemon juice. Grade: F-.
I initially had high hopes for powdered buttermilk, as I figured a splash of water would magically reconstitute a few spoonfuls into a glass of something thick and creamy. Unfortunately, the reconstituted buttermilk was as thin and watery as the acidified milk, and the wet dough spread out just as flat and thin.
On the plus side, buttermilk powder naturally delivered the perfect pH and flavor. My biscuits browned well, and tasted just right.
Even so, I couldn't help but feel grumpy at how they spread into veritable pancakes compared to the lofty heights of a biscuit made with real buttermilk. That loss of height and fluff will hold true for any recipe in which dough consistency matters, like Irish soda bread, muffins, and scones. Grade: C+.
Since mass-market buttermilk is thickened with active cultures, it's often said that plain yogurt makes an excellent substitute. Visually, that certainly seems to be the case—yogurt kept the dough thick and my biscuits light, with a golden-brown crust, too.
What can't be captured in a photo, however, is the way every bite squished around like a wet lump in my mouth. Due to its method of manufacture, yogurt is much higher in milk solids, including both protein and lactose (a milk sugar), than buttermilk is. That gives yogurt-based recipes a unique character: rich and moist, with a subtle sweetness. Those qualities can be amazing in the right context—I'm a huge fan of yogurt in raisin bran muffins and coffee cake—but it can feel downright gummy in baked goods that should have a more bread-like character, so use caution when reaching for yogurt in place of buttermilk. Grade: B+.
Update: Since some readers have asked, I should note that I tested both plain yogurt and yogurt thinned with milk (three parts yogurt to one part milk), and was surprised to find no significant differences in terms of spread, rise, and browning (all good!) and gumminess (bad). When I bumped up the ratio of milk beyond that, I wound up with the same textural problems of other milk-based substitutes. Since there were almost no visual differences, we opted for one photo rather than two.
I'll admit to being the sort of curmudgeonly baker who used to think kefir was part of some goofy diet craze. Happily, a reader's success with it in my Irish soda bread set me straight—thanks, DeKay! Kefir, a centuries-old tradition, is milk fermented with a combination of bacteria and yeast, which gives it a complex flavor, thick body, low pH, and a lactose content not unlike that of buttermilk.
In fact, when used as a 1:1 substitute, it's almost indistinguishable from the real thing. It kept the dough thick, so the biscuits rose up light and fluffy, with a beautifully golden crust and a light crumb. More importantly, they tasted fantastic, without any hint of gumminess or harsh acidity.
Kefir may be new enough to American markets that it's not a common grocery store item nationwide, but that also means it's likely to be found in trendy metro areas where people aren't interested in fuddy-duddy buttermilk. In cakes and soda bread and every other recipe I tried, kefir performed flawlessly as a 1:1 swap for buttermilk. Grade: A+.
Of course, for many people, access isn't the issue. From bodegas in New York to Whole Foods in Nebraska, buttermilk is readily available across most of the country. Problem is, most recipes don't call for enough buttermilk to justify the purchase of a quart.
To that, I'll offer up a bit of Kentucky-fried insight from my dad: Buttermilk doesn't spoil, it gets better. There's nothing wrong with using buttermilk well past the sell-by date; its acidic nature and complement of beneficial bacteria make buttermilk much less perishable than fresh milk. And if it gets a bit tangier over time, that's a win for most recipes.
City slickers unconvinced by country wisdom should bear in mind that buttermilk freezes extremely well, with no loss in quality when it comes to baked goods. So use what you need, then freeze the rest in heavy-duty zip-top bags to protect against freezer burn—you can even divvy it up according to the amount of buttermilk needed for your favorite recipe(s).
In the realm of baking, there are so many variables to contend with—from oven temperature to flour strength and issues of technique—that your best and safest bet in any recipe will always be to avoid major substitutions for an ingredient as multifaceted as my darling buttermilk.