Zechmeister [168] has been reported that a high con- centration of acid can results in isomerization of b-caro- tene. However, in some other papers, pH has been reported to have only a minor effect of b-carotene isomerization in solvents or in food systems [124, 128]. Apparently, the effect of pH on b-carotene stability can be attributed to time of exposure to acid, concentration of acid, and the system in which b-carotene exists.