One of the two soft resins in hops; it consists of a mixture of three closely related chemical compounds--lupulone, co-lupulone, and ad-lupulone. Contrary to alpha acid, it contributes very little (10 percent) to the bitterness of beer and accounts for approximately one-third of its preservative quality. Beta acids constitute about 25 percent of soft resins. They are present in larger quantities than alpha acids, but because of their low solubility (soluble in water only if oxidized) their content level is usually insignificant. Abbrev: b-acid. Syn: lupulon(e); beta resin. See also: alpha acid; lupulin; soft resin.