Propylene glycol alginate is widely used in the food industry as an emulsifier, as a stabilizer and as a thickener. It is represented by the E number E405. It is an ester of alginic acid which is derived from large brown sea-weed called kelp. It is white to yellowish filamentous powder available in the market and it is also used in cosmetics.
Propylene glycol alginate is made by taking moist alginic acid (20 percent or greater solids) that has been partially reacted with sodium carbonate, and treating it with liquid propylene oxide in a pressure vessel for 2 hours at about 80°C. The product is dried and milled.
It is used in salad dressings as emulsifier. It can be used to hold food components together or thicken them during and after processing. It dissolves other food additives or nutrients to be used in processing, such as colors, flavors or antioxidants. It helps prevent food components from sticking to one another and forming clumps, such as in dried soups or grated cheese. One application is as an emulsion stabilizer for salad dressings where PGA is used in combination with xanthan gum. Another application is a dispersion stabilizer for acid milk beverages, where PGA is used to avoid precipitation.