The thermal stability of monomeric and polymeric flavan-3-ols, or proanthocyanidins, was measured in blanching experiments. Monomeric catechin and epicatechin were blanched in 100�C water (HW) for 20 min. (n=3). The initial and final concentrations of catechin were 4.84�0.23 and 4.73�0.60 ppm, respectively, indicating thermal stability. Epicatechin was thermally instable with initial and final concentrations of 2.54�0.08 and 0.29�0.01 ppm, respectively. A corresponding increase in catechin concentration indicated isomerization occurred. Almonds were blanched in 25�C (RT, the control) and 100�C (HW) water for 2 min.  and then removed. Therefore, changes in proanthocyanidins, and their monomers, in the first two minutes were attributed to blanching; changes from 2-20 min. were attributed to thermal instability in the hot blanch water. A constant concentration of proanthocyanidins found in both blanching conditions indicated thermal stability. Proanthocyanidins identified only under HW conditions had variable concentrations and were the result of thermal degradation/isomerization reactions.

Thermal stability of monomeric and oligomeric proanthocyanidins in almonds

245th National Meeting (2013)

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