Role of invertase activity in processing quality of potatoes: Effect of storage temperature and duration

Invertase activity and processing attributes of three potato cultivars were studied to find the reason for deterioration of processing quality during their prolonged storage in commercial cold stores (4 degrees C) as compared to elevated temperature storage (12 +/- 0.5 degrees C), with CIPC {Isopropyl-N-(3-Cholorophenyl) carbamate}. Lower storage temperature (4 degrees C) tended to be more effective in increasing invertase activity of potato tubers than elevated temperature. Non-processing cultivar viz., Kufri Pukhraj resulted in accumulation of more invertase activity than relatively two processing cultivars. Kufri Chipsona-1 and Kufri Chipsona-3 at 12 +/- 0.5 degrees C possessed basal invertase activity ranging from 39.3 to 79.8 and 54.1 to 93.8 (mu moles hexose h(-1) f.wt.) respectively, during two years. Total invertase activity at 4 degrees C increased abruptly and remained high from 30 to 60 days of storage. The activity progressively reached 90.6 to 106.6 and 81.4 to 101.3 during both the years respectively, after 60 days of storage to that observed initially. Reducing sugar content increased from 23.3 to 105.7 and 389.0 to 1138.2 (mg 100g(-1) f.w.t.) after 90 days of storage at 12 +/- 0.5 degrees C and 4 degrees C, respectively. Studies concluded that basal and total invertase, were responsible for cold induced sweetening and resulted in deterioration of processing quality of potatoes during storage at 4 degrees C. Since this activity is low at 12 +/- 0.5 degrees C, the processing traits remained acceptable to industry and consumers.