- Jaswal (1973) was adapted with modifications. Peeled, fresh potato samples of the Netted Gem cultivar, corresponding to approximately 5 g (dry weight basis), were triturated in 250 mL of 70% ethanol for 2 min, then transferred to an Erlenmeyer, and shaken for 8 h on a Burrell Wrist-Action shaker (Burrell Corp., Pittsburgh, PA). The mixture was then centrifuged for 10 min at loooOg on a Beckman Model 5-21 centrifuge, the precipitate was discarded, and the supernatant was passed through a membrane filter (Millipore) with a pore size of 0.45 pm. The clear filtrate was evaporated to dryness on a rotary evaporator (Biichi/Brinkmann) under reduced pressure with intermittent nitrogen flushes. The residue was dissolved in 0.1 N HC1; final volumes varied between 10 and 20 mL. Each sample was divided into three vials and kept frozen until used for amino acid analysis.