beta-carotene and ascorbic acid retention in fresh and processed vegetables

Broccoli, carrots, and green beans (grown in 2 consecutive years) were randomly divided into 3 treatments: fresh-refrigerated (F-R), frozen (FZ) or canned (C) (carrots only). FZ or C vegetables were processed within 24 h and stored for up to 1 yr. F-R vegetables were held at 4 degrees C for 3 wk (broccoli and green beans) or 6 mo (carrots). Trans beta-carotene (T beta-C) and total ascorbic acid (AA) were determined at specified times, before and after microwave cooking. Vitamin content differed between years due to environmental conditions; Blanching resulted in AA loss, but retention remained stable after freezing broccoli and green beans. F-R green beans lost >90% AA after 16 d storage. Linear decreases in AA were found in most F-R or FZ vegetables. T beta-C decreased slightly during freezer storage. Reductions in T beta-C occurred in canned carrots. Microwave cooking had minimal effects on AA or T beta-C.