Everyone knows the correct way to use a whisk, right? Wrong.
We’ve noticed that different cooks seem to favor different motions when using a whisk. Some prefer side-to-side strokes, others use circular stirring, and others like the looping action of beating that takes the whisk up and out of the bowl. That got us wondering: Is any one of these motions more effective than the others?
We compared stirring, beating, and side-to-side motions in three core whisking applications: emulsifying vinaigrette and whipping small amounts of cream and egg whites. We timed how long the dressing stayed emulsified and how long it took us to whip cream and egg whites to stiff peaks.
In all cases, side-to-side whisking was highly effective. It kept the vinaigrette (made simply of oil and vinegar) fully emulsified for 15 minutes, and it speedily whipped cream to stiff peaks in 4 minutes and egg whites to stiff peaks in 5 minutes. Circular stirring was ineffectual across the board. It never fully emulsified the dressing, which remained thin and separated, and it took more than twice as long as side-to-side whisking to whip cream and egg whites (10 and 12 minutes, respectively). Beating was even less effective than stirring for emulsifying, and whipping cream dragged on with minimal effect for 8 minutes before we threw in the towel. Beating was only effective at whipping egg whites, creating stiff peaks in a record 4 minutes, surpassing the timing of side-to-side strokes.
So why does a side-to-side motion work so well—and the other actions, in the main, work so poorly? The first reason is that side-to-side whisking is simply an easier motion to execute quickly and aggressively—allowing you to carry out more and harder motions per minute than with the other strokes. Second, this action causes more of what scientists call “shear force” to be applied to the liquid. As the whisk moves in one direction across the bowl, the liquid starts to move with it. But then the whisk is dragged in the opposite direction, exerting force against the rest of the liquid still moving toward it. Because stirring and beating take the liquid in the same direction of the whisk, they produce less shear force.
In vinaigrette, the greater shear force of side-to-side whisking helps break oil into tinier droplets that stay suspended in vinegar, keeping the dressing emulsified longer. To create stiff peaks in cream and egg whites, shear force and efficiency are both key. As the tines are dragged through each liquid, they create channels that trap air. Since the faster the channels are created, the faster the cream or whites gain volume, rapid, aggressive side-to-side strokes are very effective. Their greater shear force is also better at keeping each type of foam stable. In cream, shear force disrupts the proteins surrounding the fat molecules, freeing them to form a protective coating around the air bubbles; in egg whites, shear force performs a similar function, unfolding proteins that then create a protective film around the bubbles.
In whipping egg whites, however, beating had an advantage even over side-to-side strokes. Because egg whites are very viscous, more of them will cling to the tines than cream, even at the beginning of whipping. This allows the whisk to create wider channels that trap more air. With side-to-side strokes, the reverse motion will disrupt some of the channels that were just created, slowing the process of trapping air and building volume. Since beating takes the whisk out of the liquid during some of its action, these larger channels can stay open longer, trapping more air. In this case, the effect is more important than shear force in quickly creating volume.