Soups made in Vitamix blenders, high-performance blenders that puree just about anything including hot foods, fall prey to the same froth and foam as soups blended in a food processors and with immersion blenders. Vegetables and proteins commonly release impurities during the first few minutes of cooking them. When you blend hot soups in a Vitamix, however, the intense shearing force of the blade ejects impurities to the surface, where they're more visible but also easier to remove.
Blend the soup on high until smooth. Spoon as much froth and foam as possible from the top of the soup using a spoon or ladle.
Allow 1 minute for the soup to settle.
Skim any remaining impurities from the surface. Pour the remaining soup into a gravy separator and filter it if you see fat pooling on the top.
Mix soup ingredients at a lower speed than usual to reduce the amount of air that gets into the mixture.