The antioxidant capacity and antioxidant system of Jerusalem artichoke (Helianthus tuberosus L.) tubers in relation to inulin during storage at different low temperatures

Jerusalem artichoke (Helianthus tuberosus L.) tubers are rich in inulin and have a much higher resistance to abiotic stress. Previous literatures have focused on changes of inulin in the tubers during postharvest storage, but little is known about the relationships between the antioxidant capacity, antioxidant system and inulin in Jerusalem artichoke tubers during storage. In this work, the inulin profiles and their in vitro radical scavenging abilities, phenolic content and its antioxidant capacity and the antioxidant systems-related enzymes activity in the tubers stored at 4, 0, -5, -12 and -18 degrees C were investigated to explore the correlations between the antioxidant capacity, antioxidant system and inulin in the tubers during storage. Compared with storage at relatively high temperature (4 degrees C), the tubers stored at relatively low temperatures (-18 - 0 degrees C) could effectively enhance the degree of polymerisation (DP), content and antioxidant capacity of inulin, the content and antioxidant capacity of polyphenols and the activity of catalases (CAT). The antioxidant capacity of the tubers stored at below 0 degrees C had no significant differences. Principle component analysis (PCA) was employed to examine the correlations between the antioxidant capacity, antioxidant system and inulin in the tubers during storage. These observations demonstrated the beneficial effects of the content and DP of inulin on antioxidant capacity and antioxidant system of Jerusalem artichoke tubers during storage and indicated that Jerusalem artichoke tubers stored at -5 to 0 degrees C should be considered as a suitable storage temperatures for different uses.