Buttermilk Radish Protein Shake with the Thermomix®

When we think of a diet shake, the first things that come to mind are berries, banana or vanilla protein powder. This one turns that idea on its head: it is savoury, sharp and almost like a cold soup in a glass. Buttermilk, radishes, cress, a pinch of salt, a little mixed pepper. Any sweetness comes only from the lactic acid in the buttermilk; the rest is spice and fresh herbs.

We have been drinking this shake for years, always in the afternoon when the craving for something sweet hits and we do not want to feed it. With 500 g buttermilk and 100 g radishes, the whole double portion comes to around 163 calories, which works out at roughly 80 calories per glass. For something that genuinely fills you up and actually tastes like food, that is an honest number. Our daughter used to call it the ‘green farm shake’, and the name has stuck.

Why savoury actually keeps you fuller than sweet

The trick in this shake is not what is in it but what is not: no banana, no honey, no apple, no date sweetener. Buttermilk naturally contains around 4 g of lactose per 100 g but very little fat (around 1%), and with 8 g of protein in a double portion it delivers exactly what keeps you full: protein and volume, without a big glucose spike.

Fruit shakes work differently. A banana alone is 90 calories, an apple 70, add 200 g of berries for another 100 calories and you are quickly at 350 calories for a single glass. This one sits at around 80 calories per glass and still tastes like a proper meal, because salt and pepper engage the palate differently from fruit. Sweetness quickly creates a craving for more sweetness. Savoury makes you feel satisfied.

What the radishes do to the buttermilk

Radishes contain a mustard oil called allyl isothiocyanate. That is exactly what creates the mild sharpness in the mouth that rises towards the back of the nose. Buttermilk has a pH of around 4.6, making it noticeably more acidic than regular milk. When we chop the radishes first and then add the buttermilk, the lactic acid and mustard oils meet and the sharpness is softened. The shake becomes tingly rather than biting.

The cress plays a second role. It adds bitterness and a slightly nutty aroma that lifts the shake out of the plain yoghurt category. A whole punnet of garden cress sounds like a lot, but once blended the stalks almost completely disappear visually, and the flavour stays largely in the background. If you do not have cress to hand, you can replace it with a small handful of flat-leaf parsley or a few sprigs of dill; the effect is similar.

The blending sequence: why radishes first, then buttermilk

We do not add the 100 g radishes to the mixing bowl together with the buttermilk; instead we chop them dry for 5 seconds at speed 4.5 first. The reason is simple: if the radishes are already floating in liquid, they spin around during blending instead of being cut. The result is large chunks alongside almost pureed buttermilk. Chopped dry, they break into fine splinters that you can actually chew when drinking.

The cress goes in second, snipped from the punnet with scissors and dropped on top. Then come the 500 g buttermilk, the half teaspoon of salt and the quarter teaspoon of mixed pepper. 20 seconds on reverse direction, speed 4 is enough. Reverse direction matters here because we do not want to chop further, only stir. On normal direction at speed 4 the shake would be blended completely smooth, and that is exactly the texture we want to avoid. A little bite, a little texture, that is part of the shake.

Mixed peppercorns make a difference

The recipe calls for mixed peppercorns, and that is a deliberate choice. Mixed peppercorns are a blend of black, white, green and red berries. The red ones are harvested ripe and taste almost fruity, the green are mild and herby, the white are sharp and earthy, the black are rounded. Ground fresh from the mill, the shake carries all four notes at once. If you only have black pepper, you get a more straightforward, slightly one-dimensional shake. It works fine for drinking, but the full flavour complexity is missing.

For the salt, a standard fine table salt is all you need. We have made the shake with fleur de sel as well; that was pleasant but made no real difference, because the Thermomix® distributes the salt crystals evenly regardless. The money is better spent on the pepper.

Pitfalls we have come across ourselves

One issue we used to run into: buttermilk straight from the fridge can curdle slightly in combination with the fast-spinning mixer. This happens when 4 degrees Celsius buttermilk meets a mixing bowl that has been warmed to around 35 degrees by chopping. Solution: rinse the mixing bowl briefly under cold water after chopping the radishes, or take the buttermilk out of the fridge ten minutes before you start. That keeps the shake smooth.

Second point: if you increase the 20 seconds to 30 or 40 because you think more is better, you end up with a foamy, over-processed buttermilk. It becomes a little thick and loses the cool, fresh quality. Better to stick to 20 seconds and, if needed, give it one push with the spatula. The cress stalks tend to gather at the edge of the bowl; a quick nudge with the spatula is enough.

Third point: the amount of salt. Half a teaspoon sounds modest, but for 600 g total volume it is exactly right. If at the start you think ‘that is a lot of salt for a shake’ and add just a pinch, you get a flat, somehow unfinished drink. The half teaspoon is what lifts the buttermilk and radishes to the point where they become a flavour in their own right rather than a vaguely healthy mixture.

When we drink it and when we do not

The classic slot for this shake is our afternoon meal, somewhere between 3 and 5 pm, when the day has already been long and dinner is still two hours away. It also works well before exercise, because it sits lightly in the stomach and the 8 g of protein make a solid starting point. What we do not do is drink it at breakfast, when we want to begin the day with porridge or bread. Straight after cereal, the acidity of the buttermilk feels a bit heavy.

On hot summer days we occasionally add a few ice cubes, which turns the shake into something almost like a cold cucumber soup. If you like, you can chop a piece of cucumber (about 50 g, peeled and deseeded) together with the radishes. That stretches the shake, makes it fresher and adds more water content without diluting the flavour. For our green smoothie Tiffin we use a similar logic with spinach instead of radishes.

The recipe originally comes from our book Mix dich schlank, published by Suedwest Verlag. Daniela collected a whole series of savoury snack shakes there, all working on the same principle: high volume, low calories, always with one clear flavour anchor. The buttermilk radish shake has remained the favourite among readers.

Keeping it fresh if there is any left over

Fridge: in a sealed glass the shake keeps for 24 hours, after which the radishes start to lose their sharpness and the cress turns brown. Give it a good shake before drinking, as the fine splinters settle to the bottom. Freezing does not work. Buttermilk separates on thawing and the texture becomes grainy rather than creamy. We prefer to make small, fresh portions rather than large batches.

If you only want one portion, simply halve the recipe; the Thermomix® handles 250 g buttermilk just as well and the blending times remain the same. This works in the TM31, TM5 and TM6 alike, because no special temperatures or modes are needed, only reverse direction and low speeds.

Also worth trying: Apricot, Banana and Almond Smoothie with the Thermomix®.

More Thermomix® recipes for weight-conscious cooking and snacking: Green Smoothie Tiffin with the Thermomix®, Varoma Salmon with Broccoli with the Thermomix®, and our full recipe collection.