Key words Deep-freezing
Springer Online Journal Archives 1860-2000
Process Engineering, Biotechnology, Nutrition Technology
Abstract HPLC (using a C18 column and water at pH 2.2 as the mobile phase) was used to monitor the quantities of oxalic acid (UV detection at 245 nm) and quinic, malic, citric and fumaric acids (UV detection at 215 nm) of deep-frozen (−22 °C) green beans and Padrón peppers over 12 months. Malic, oxalic and citric acid contents decreased considerably in the first month of frozen storage, then oscillated before returning to those one-month levels after 12 months. The amount of fumaric acid increased, most notably in the peppers. Quinic acid was only detected in the peppers; its content also increased. Freezing the vegetables in vacuum-sealed bags did not moderate these changes. Blanching the beans decreased the quantities of all the acids in the vegetable; then, in most cases, values varied similarly to those of the unblanched beans (notably, the citric acid content of the blanched beans doubled during the first 6–8 months of frozen storage, then fell sharply to roughly its initial, post-blanching level). Overall, blanching and then freezing green beans led to greater losses of their organic acids compared to freezing alone.
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