Oca (Oxalis tuberosa Mol.) or New Zealand yam, in common with other members
of this genus, contains oxalate, an antinutritive factor. Twelve South Ame
rican and two New Zealand cultivars of oca were analysed for the total oxal
ate contents of tubers. Total oxalate levels ranged from 80 to 194mg/100g w
et matter (WM). As these tubers are normally cooked before consumption, the
oxalate levels were measured after they had been cooked by three conventio
nal cooking methods, Oxalate levels ranged from 77 to 220mg/100g WM for boi
led and steamed tubers, while the levels of oxalate found in baked tubers w
ere significantly increased when compared to the raw tubers. The oxalate co
ntent of the baked tubers ranged from 164 to 335mg/100g WM. Total calcium c
ontent of the raw tubers ranged from 7.5 to 15.5mg/100g WM; cooking had lit
tle effect on the calcium content. Among cultivars mean oxalate/calcium rat
io of the raw, boiled and steamed tubers ranged from 2.5 to 9.9. Baked tube
rs had a significantly increased oxalate/calcium ratio (mean for all cultiv
ars 9.5). (C) 2001 Academic Press.