2.3. Starch isolation
For starch isolation modified method of Singh and Singh (2001) was used. Potatoes were washed carefully in tap water, brushed and peeled. The eyes and all bruises were pitted out. For the actual process half of each potato tuber was used. Separation of tubers was carried out in the longitudinal direction from the stolon end to the apical end of tubers. On the laboratory grater approximately 1.5 kg of potato tubers was processed. Grated tubers were poured with 5 L of distilled water and left to stand with occasional stirring for 4 h. Thereafter, after decantation, the starch was washed with distilled water through the filter into the sedimentation beaker. Starch sediment in the vessel was stirred and then filtered through a sieve (mesh 125 μm), which captured the remainder impurities. Thereafter, the beaker containing filtrate with starch suspension was kept undisturbed to settle overnight. The next day supernatant liquid was carefully decanted and to the sediment 2 L of distilled water was added, stirred and left to settle overnight. A solid layer of starch settled down. The supernatant liquid was decanted, the starch layer was reslurried in distilled water and, again, starch was allowed to settle. This was repeated 4–5 times until the supernatant became transparent. Starch was then left to dry in the beaker for 2–3 days. Starch cake was then collected onto the filter paper and for several days freely dried at room temperature to constant weight. The samples were finally lightly pulverised and kept in resealable air-tight plastic bags at room temperature until further use.