Monitoring of the vitamin C content of frozen green beans and Padrón peppers by HPLC

Abstract

Abstract: HPLC (using a C18 column, water at pH 2E2 as mobile phase, and UVdetection) was used to monitor the vitamin C content of deep-frozen ([22iC)green beans and Padro“ n peppers over 12 months. Unblanched beans andpeppers lost P97% of their vitamin C within 1 month of freezing, whether or notthey were contained in bags sealed under vacuum. Blanching reduced the beansIvitamin C content by 28%, but limited further decreases to between 3 (vacuumsealed) and 10% (no vacuum) in 12 months. These results conÐrm the utility ofblanching in the preservation of vegetables by deep-freezing. 1998 SCI.(J Sci Food Agric 76, 477E480 (1998)Key words: deep-freezing; HPLC; ascorbic acid; green beans; peppers INTRODUCTIONHumans are among the few mammals incapable of bio-synthesis of ascorbic acid, or vitamin C. The amount ofthis vitamin in foodstu†s should therefore be carefullymonitored with a view to avoiding deÐciency, which inextreme cases causes scurvy and, moreover, leads toreduced resistance to infection (Anderson et al 1987).Vitamin C is almost exclusively found in fruit andvegetables although the amount present varies amongvarieties (Morrison 1975) according to factors such asthe stage of development and size of the produce(Selman and Rolfe 1982), and the time between harvest-ing and processing (Kozar et al 1988). This variation isreNected in the diversity of vitamin C content reportedin the literature for fresh produce.The seasonality and high perishability of fruit andvegetables provides opportunity to apply preservation