Hot water and molybdenum dips: The case of antioxidant assays in lemon flavedo during cold storage

Abstract

Antioxidants are part of the plant’s defense system, protecting tissue against oxidative stress. In citrus fruit, oxidative stress can occur during extended cold storage ultimately result in chilling injury. Citrus fruit contain certain rind antioxidants which occur in different forms (lipophilic and hydrophilic). Previous studies demonstrated a synergistic relationship between hot water dips (HWD) and molybdenum dips (Mo) in mitigating chilling injury in citrus fruit. Therefore, the aim of this study was to investigate the potential of HWD and Mo to alleviate chilling injury by enhancing antioxidant capacity in lemon flavedo of fruit stored at -0.5°C. Fruit from different sources, commonly displaying chilling injury and other seemingly resistant to the development of chilling symptoms, were preconditioned for 2 min with HWD (47 or 53°C) and thereafter soaked in 1 or 10 µM Na2MoO4 solution for 30 min. Fruit were subsequently stored at -0.5°C for 7 or 28 days, moved to ambient temperature for a week and then evaluated for chilling injury symptoms. Chilling susceptible lemon fruit showed low Trolox equivalent total antioxidant capacity (TEAC), phenolics, and flavonoids concentration and high lipid peroxidation. Hot water dips 53°C, as well as 1 and 10 µM Mo plus HWD 53°C treatments mitigated chilling injury by enhancing total antioxidant capacity, and total phenolics and flavonoids concentrations in the flavedo. However, the ability of these treatments to alter lipophilic and hydrophilic antioxidants was fruit source dependent. Key words: Lemon (Citrus limon), chilling injury, antioxidant assays, hot water dips, molybdenum, cold storage.