When buying alternative milks that you want to froth, make sure gellan is on the ingredient list.
Recently we had some colleagues report that they couldn’t always get alternative milks to froth properly for homemade coffee drinks. To see for ourselves, we purchased several almond, soy, rice, and coconut milks and tried to froth them using our French press method. Indeed, some frothed up just fine. But others couldn’t hold a foam no matter how hard we tried. We found the reason for this on the ingredient label.
Only nondairy milks that contain gellan, a fermented food additive that’s added to help thicken these thinner liquids, could hold a foam. Here’s why: The proteins and water in cow’s milk form the walls of air bubbles in foam. The proteins, which unwind during agitation, buttress and stabilize the walls, slowing the process in which the water drains out and causes the foam to collapse. The proteins in nondairy milks are weaker (and there are fewer of them) and can’t support air bubbles as well. But when gellan is in the mix, it bonds with the calcium in nondairy milks to create a strong matrix that makes up for the lack of strong proteins and results in a more stable foam. So when buying alternative milks that you want to froth, make sure gellan is on the ingredient list.