My understanding of the esterification process between a carboxyl (acid) and a hydroxyl (Alcohol) group is that the carboxyl loses an OH and the alcohol just loses an H - contrary to the mechanism for an (Bronsted-Lowry) acid-base reaction - where the acid loses an H+. Water is eliminated in formation of ester bond.
Why? The lone pairs of electrons on the oxygen of the alcohol are attracted to the delta-negative carbon in the carboxyl (nucleophilic) group. This mechanism is more apparent when reacting an acyl-chloride (-COCl) with an alcohol, as HCl is eliminated. The presence of Cl in acyl chloride makes C in COCl more negative - and the source for the H in the elimiated HCl must have been the hydroxyl group, OH, in the alcohol.
Clive