Postharvest sweetening can improve the quality of sweet potatoes. Although exposure to low temperature has been observed to increase sweetness, sweet potatoes are susceptible to chilling injury (CI). Therefore, an effective method to increase sweetness without causing CI is necessary. Tuberous roots of the sweet potato "Naruto-Kintoki" were subjected to heat treatment followed by low-temperature conditioning prior to exposure to chilling stress under cold storage at 5 ℃ for 30 days. Following chilling stress, the roots were incubated at 20 ℃ for 20 days. External and internal deterioration induced by chilling was evaluated and total soluble solids were analyzed. The results showed that the combination of heat treatment at 40 ℃ for 2 days and stepwise low-temperature conditioning of 1 ℃ per day from 10 - 5 ℃ enhanced sweetness and chilling tolerance. Therefore, storage at low temperature following pre-storage temperature manipulations is a feasible approach for increasing sweetness and reducing CI of Naruto-Kintoki tuberous roots.
