Potato Review

www.potatoreview.com POTATO REVIEW NOVEMBER/DECEMBER 2020 11 STORAGE to avoid bringing in outside air warmer than the temperature of the tubers already in store. Where an air-mixing system is used that combines outside and inside air, aim for no more than 4°C di erence between the air used for ventilation and the tuber temperature. Recirculation starting point In a fridge store where bringing air from outside is not possible, start recirculation from the point of store loading. e temperature of the cooling air should be kept in a range between 1°C and 4°C below the crop temperature, but no cooler. Ideally, the fridge can be set at 2°C below the tuber temperature to equalise the tubers in store as they are loaded. Once wound healing has occurred, cooling rates should aim for a maximum of 0.5°C pull-down per day until the target holding temperature is achieved. Adequate ventilation is required during pull-down to remove surface moisture. While a relatively small temperature di erential may reduce the cooling rate, a larger one can cause excessive temperature di erences within boxes. is can result in condensation when humid air within the centre of the box rises and condenses on the cooled surface tubers unless positive ventilation is used. Once the target temperature is achieved, recirculation can be reduced to 10 to 20 minutes every two to four hours depending on the store. Fungi and bacteria risks Mechanical wounds allow fungi and bacteria to develop in the esh of the tuber. Rate of wound healing is in uenced by temperature, in cooler stores the time taken to wound heal is increased. Wound healing and temperature pull- down strategy in ware crops depends on nal market and likelihood of disease development. In general, longer curing will be required for mechanically damaged crops or skin spot susceptible varieties ie Cultra and King Edward. For these varieties, it is preferable to hold the tubers above 10oC for at least 10-14 days. It is also important to dry the crop properly to ensure that rots do not develop. If preventing the development of silver scurf and black dot are essential, as soon as wound healing of the last crop loaded is complete, the store should be brought down to its target holding temperature as quickly as possible, unless skin spot is the primary concern. Piper and Estima require starting temperature pull-down as soon as possible after store loading. “Adequate ventilation is required during pull-down to remove surface moisture.” Rate of wound healing and relationship with temperature Some varieties will require starting temperature pull-down as soon as possible after store loading. Longer curing will be required for skin spot susceptible varieties such as King Edward.