Aquafaba (literally the amalgamation of the Latin words for water and bean) is the liquid that remains after boiling legumes. In 2014 a French musician discovered this liquid’s ability to create a foam similar to egg whites, and started a vegan revolution of sorts.
See, for those who do not consume eggs (whether by choice or necessity) certain foods become really difficult to make. Meringues, angel food cake, marshmallows, macarons and some cocktails all rely on eggs for their creation. Egg replacers are common at this point, but they aren’t all the same, and not all of them work for all things. Aquafaba may be just another egg replacer, but it’s got some unique properties that other replacers don’t possess.
The problem is that eggs don’t serve only one purpose in a food. They are what’s called a polyfunctional ingredient, since they serve three distinct and culinarily important functions outside of their taste and nutritional roles: emulsifying, coagulating and foaming. Each of these functions is affected by different conditions like temperature and pH, and each relies on different chemical processes.
Eggs as emulsifiers are the simplest to emulate. In this role the egg serves to stabilize a mixture between two immiscible liquids. Silken tofu, flax or chia seeds, bananas, mustard (for savoury recipes) or applesauce can all be used as egg substitutes in recipes in which the egg functions only as an emulsifier. The main factor affecting emulsifiers is concentration, with dilute ingredients emulsifying poorly. I really enjoy baking but have largely stopped baking with eggs since eggs mostly function as emulsifiers in my recipes, and substituting them for bananas or “flax eggs” is much cheaper and works just as well!
Eggs as coagulators are more difficult to replace. Eggs coagulate when either heat, strong acids or strong bases cause the proteins in them to denature (lose their structure). The rate and efficiency at which this happens depends on the salt, sugar, and acid content of the food. In eggs the main proteins that coagulate are conalbumin and ovalbumin in the white, and lipoproteins in the yolk. Lots of other proteins coagulate but under different conditions than typically occur during cooking. Egg replacers for coagulation have been attempted. They were made from lupini beans, whey protein, various gums and wheat products, but they haven’t really worked. Replacers made with chia seeds or soy have been a bit better, while replacers made with proteins isolated from whole bovine blood plasma have debatably worked the best but using cow’s blood isolates as an egg replacer probably wouldn’t sit well with most people who use egg replacers.
The foaming ability of eggs is the hardest to replicate. An ingredient’s ability to foam is affected by the method of beating, temperature, pH and water content. Some foods such as soy milk or whey protein can create foams, but these foams are not stable at high temperatures, which is what you need to make angel food cake or meringues.
That’s where aquafaba comes in! It’s vegan, temperature resistant, and made from what would otherwise be waste.
Legumes, like chickpeas, are usually bought either canned and precooked, or dry and uncooked. To cook dry chickpeas you simply boil them for about an hour and a half (pre-soaking dried beans doesn’t actually made them cook faster, so stop wasting your time doing it). During the cooking process the water-soluble proteins and sugars inside the chickpeas are able to travel into the cooking water. The longer you cook the legumes, the more of this migration will occur, as up to about 5% of the dry weight of each chickpea moves into the water. Once you remove your cooked chickpeas, what you’re left with is aquafaba, a sort of protein- and sugar-enriched water.
A study has found that the main components of aquafaba are polysaccharides, sucrose, and various proteins. Chemically, this mixture has many of the same components as egg whites, so it makes sense that it can function in many of the same ways. The study also found that some of the compounds most important for aquafaba’s foaming ability are saponins. Saponins, as the name suggests, are characterized by the soap-like foam they produce when shaken.
So how do you actually use aquafaba in a recipe? You basically just whip it up! Using a hand or stand mixer, whip the liquid from your can of legumes or your cooking water for about 3-6 minutes to get semi-firm peaks. You can add some cream of tartar to make the peaks firmer for use in macarons or meringues, or skip the whipping and use it as a binder to make vegan mayonnaise or vegan muffins. The application I’m most excited to try? Aquafaba as a replacement for egg whites in cocktails!