The extract of quillaia is used in the manufacture of food additives (E number 999). It is used as a humectant in baked goods, frozen dairy products, and puddings and as a foaming agent in soft drinks. It also applied in some "natural" spray adjuvant formulations for agricultural uses.
In particular the saponins from Quillaja saponaria are used in veterinary vaccines as adjuvant (e.g., foot-and-mouth disease vaccines, helping to enhance the immune response). Initially the crude fraction was used. Later on a purified mixture, called Quil A was developed by Dalsgaard which was more effective and caused less local side reactions. Still Quil A is a mixture of more than 25 different saponin molecules. One of them, the saponin QS21, is being investigated for possible beneficial adjuvant effects on the human immune system.