RESPIRATORY ENZYME-ACTIVITY IN LOW-TEMPERATURE SWEETENING OF SUSCEPTIBLE AND RESISTANT POTATOES

During storage at 4°C and 12°C, a potato cultivar susceptible to chill‐sweetening (Norchip) accumulated significantly (P≤0.05) higher levels of sucrose, fructose and glucose than a potato selection resistant to chill‐sweetening (ND 860‐2). ND 860‐2 tubers exhibited a significantly (P≤0.05) higher respiration rate throughout storage, reflected in higher activities of phosphofructokinase (PFK), glucose‐6‐phos‐phate dehydrogenase (G6PDH) and 6‐phosphogluconate dehydrogenase (6PGDH). Storage significantly (P≤0.05) reduced respiration rate for both cultivars. G6PDH showed no significant (P>0.05) difference in specific activity or Vmax between 4°C and 12°C for either cultivar. However, Km decreased at 4°C for both cultivars, possibly due to build up of substrate. Copyright © 1990, Wiley Blackwell. All rights reserved