Effects of level of nitrogen fertilizer, processing conditions and period of storage of frozen broccoli and cauliflower on vitamin C retention

Directly after harvesting, broccoli contained 116.3–116.4 mg of vitamin C in 100 g of fresh matter, and cauliflower contained 60.5–64.7 mg. Increasing the amount of nitrogen fertilizer from 80 to 120 kg N ha−1 decreased the content of vitamin C only in cauliflower (by 7%), at the same time raising the level of nitrates by 44% in broccoli and by 33% in cauliflower. During the course of processing, the greatest losses in vitamin C content occurred during blanching: in broccoli by 41–42% and in cauliflower by 28–32%. Freezing resulted in little change of the vitamin C content, which was reduced by 15–18% in broccoli and by 6–13% in cauliflower during freeze-storage. After 12 months of storage, the level of vitamin C was 54.9–57.4 mg per 100 g of frozen product in broccoli and 38.5–41.9 mg per 100 g in cauliflower, being slightly higher at a storage temperature of −30 °C than at −20 °C.