Vitamin C content in leaves and roots of horseradish (Armoracia rusticana): Seasonal variation in fresh tissues and retention as affected by storage conditions

Since antiquity, horseradish is known as folk medicinal herb and food condiment. The richness in phytochemicals has recently encouraged its use in the medical field and as functional food. In this study, vitamin C content by HPLC analysis in young and mature leaves and roots of two horseradish accessions collected at different developmental stages was evaluated. The effect of freezing and freeze-drying on vitamin C loss after different storage time was also analyzed. The vitamin C content varied in fresh tissues depending on accessions and developmental stages. Roots contained the highest values of vitamin C when plant approximated to senescence (about 80 mg 100 g-1 fw). A great content of vitamin C was found in young leaves during the full developmental stages (up to 350 mg 100 g-1 fw) and in mature ones toward plant senescence (up to 280 mg 100 g-1 fw). By freezing tissues at −20°C, a monthly vitamin C loss of 5% was estimated, while by freezing at −80°C the losses did not exceed 6% after 8 months of storage. By freeze-drying tissues, a loss of vitamin C of about 40% was found after 4 months of storage at 4°C. Despite the losses associated with food processing, the residual content of vitamin C in horseradish remains still higher compared to other vegetables.