EFFECTS OF STORAGE-TEMPERATURE OF POTATO-TUBERS ON SPROUTING, RESPIRATION RATE, SUGAR CONTENT, AND POLYPHENOL OXIDASE ACTIVITY

Potato tubers were stored at 4 degrees, 20 degrees, or 33 degrees C, and the sprouting time, respiration rate, sugar content, and polyphenol oxidase activity were examined. Sprouting was observed after about 70 days of storage at 20 degrees C but was not found when storage was at 4 or 33 degrees C after 160 days. Tubers transferred to 33 degrees C after 70 days of storage at 20 degrees C did not sprout during the next 160 days. When tubers were stored at 33 degrees C for 42 days and then transferred to 20 degrees-C, sprouting was observed after 27 days. The respiration rates of potato tubers stored at 4 degrees or 20 degrees C were low. At 33 degrees C, the respiration rate was initially high, but decreased during storage. The total sugar content of tubers stored at 22 degrees C was low. At 4 degrees or 33 degrees C, however, this content increased rapidly to about 2%. The reducing-sugar content of tubers stored at 33 degrees C was lower than when storage was at 4 degrees C. Polyphenol oxidase activity in potato tubers stored at 20 degrees C increased twofold during storage, but rapidly decreased during storage at 33 degrees C.