theory of sweetness enjoyed little further academic attention until 1963, when Robert Shallenberger and Terry Acree proposed the AH-B theory of sweetness. Simply put, they proposed that to be sweet, a compound must contain a hydrogen bond donor (AH) and a Lewis base (B) separated by about 0.3 nanometres. According to this theory, the AH-B unit of a sweetener binds with a corresponding AH-B unit on the biological sweetness receptor to produce the sensation of sweetness. B-X theory proposed by Lemont Kier in 1972. While previous researchers had noted that among some groups of compounds, there seemed to be a correlation between hydrophobicity and sweetness, this theory formalized these observations by proposing that to be sweet, a compound must have a third binding site (labeled X) that could interact with a hydrophobic site on the sweetness receptor via London dispersion forces. Later researchers have statistically analyzed the distances between the presumed AH, B, and X sites in several families of sweet substances to estimate the distances between these interaction sites on the sweetness receptor. MPA theory The most elaborate theory of sweetness to date is the multipoint attachment theory (MPA) proposed by Jean-Marie Tinti and Claude Nofre in 1991. This theory involves a total of eight interaction sites between a sweetener and the sweetness receptor, although not all sweeteners interact with all eight sites. This model has successfully directed efforts aimed at finding highly potent sweeteners, including the most potent family of sweeteners known to date, the guanidine sweeteners. The most potent of these, lugduname, is about 225,000 times sweeter than sucrose. References Cited General Further reading Gustation Culinary terminology