Malic acid and citric acid were identified in raw and boiled Jerusalem
artichoke tubers by 1H NMR (Table 3). Ascorbic acid was also
identified, but only in boiled tubers and in a content too low to
quantify. The contents of malic acid and citric acid were not quantified
but given as peak areas relative to TMSP. There were no significant
differences (p > 0.05), regardless of harvest time, between
varieties in relative contents of malic and citric acid. The relative
content of citric acid was higher in autumn than in spring, whereas
the opposite was seen for malic acid (Table 3). Findings of Clausen
et al. (2012) showed similar results. The relative contents of malic
and citric acid remained almost unchanged during boiling