The amounts of chlorophylls
a and
b, β-carotene and lutein in green beans, blanched green beans and Padrón peppers, all frozen at −22 °C, were monitored over
12 months by reverse-phase, gradient HPLC (C18 column, visible detection). In unblanched beans, these amounts of the pigments
decreased considerably during month 1, but were generally stable during the next 11 months (β-carotene content decreased further
in month 2 before stabilizing). Similar results were obtained for blanched beans, but decreases were offset by increases due
to blanching (carotenoids) and lipoxygenase deactivation (β-carotene), or enhanced by blanching-induced decreases (chlorophylls).
In contrast, the amounts of pigments in frozen Padrón peppers fluctuated around more or less constant values over the 12 months.
Freezing in bags sealed under vacuum lead to moderate decreases in chlorophyll
a in Padrón peppers and in β-carotene in blanched green beans.
Key words Pigment compounds - Green beans - Padrón peppers - Frozen storage - Blanching - HPLC
Received: 22 July 1996 / Revised version: 4 December 1996