SCREENING THE NEW-ZEALAND POTATO GERMPLASM COLLECTION FOR RESISTANCE TO SUGAR ACCUMULATION DURING LOW-TEMPERATURE STORAGE

The ability of potato (Solanum tuberosum) cultivars to withstand cool storage without accumulating reducing sugars would allow manufacturers of fried potato products to process potatoes year-round without the d evelopment of undesirable Maillard browning compounds. More than 600 p otato cultivars and selections held by the New Zealand Institute for C rop & Food Research Limited were screened over three seasons (1991-93) to identify material with resistance to cold-induced sweetening. Pota to lines were tested 1-2 weeks after harvest using diabetic glucose te st tape, and those with glucose levels below 0.1% (1 g/litre) in the p otato juices were stored at 4 degrees C for 2 and 4 months. The effect of any changes in sugar levels on chip colour was then reassessed by frying thin slices in oil and measuring the development of Maillard br owning in individual crisps by image analysis. Tubers which failed to produce crisps of an acceptable colour were reconditioned at 18-20 deg rees C for up to 4 weeks and retested. Lines with potential to resist cold-induced sweetening or with reconditioning potential were retested for an additional two seasons. Over the three seasons, three cultivar s and four breeding selections consistently produced the lightest colo ured crisps: 'ADX248-16', 'ND860-2', 'Red Dakota', and 'Atlantic' from the United States; and 'Torridon','V99', and 'V489' from the United K ingdom. Lines that improved to an acceptable reducing sugar level afte r reconditioning were: 'Agria', 'Fianna', and 'Darwina' from The Nethe rlands; 'Lindsey', 'V401', 'V402', and 'V424' from the United Kingdom; and 'Gladiator', '1975.12', '354/12', and '472/8' from Crop & Food Re search.