THE PROCESSING POTENTIAL OF TUBERS OF THE CULTIVATED POTATO, SOLANUM-TUBEROSUM L AFTER STORAGE AT LOW-TEMPERATURES .2. SUGAR CONCENTRATION

Several clones from a potato breeding programme at the Scottish Crop Research Institute (SCRI) produced acceptable (pale) coloured fry products after five months' storage at 4-degrees-C. Chemical analysis of tuber samples taken at five-week intervals during storage at 4-degrees-C and 10-degrees-C gave a substantial variation in glucose, fructose and sucrose concentrations among the 22 clones examined. Several unnamed SCRI clones showed little accumulation of reducing sugars when stored at 4-degrees-C. In marked contrast, the cultivars Record and Pentland Dell, currently the most widely used cultivars for fry processing in the UK, accumulated far greater levels of sugar during low temperature storage. Glucose concentration proved more important than fructose concentration in determining fry colour. Clones with the lowest concentrations of glucose after storage at 4-degrees-C also showed lowest concentrations when stored at 10-degrees-C. These results are in agreement with previous reports on the predictive value of glucose levels at harvest, but this is the first identification of such low temperature, low sweetening variants in agronomically adapted clones of the cultivated tetraploid potato.