Bitterness of cassava: Identification of a new apiosyl glucoside and other compounds that affect its bitter taste

Compounds extracted by methanol from cassava parenchyma and cortex have been separated on a preparative HPLC column and identified by 1H and 13C NMR spectroscopy. A new compound isopropyl‐β‐D‐apiofuranosyl‐(1 → 6)‐β‐D‐glucopyranoside (IAG, structure I) has been found as well as small amounts of phenylalanine and tryptophan. The composition of another HPLC fraction has not been elucidated. The amounts of the identified compounds and of linamarin, lotaustralin, citrate, malate and the various sugars present in cassava have been determined by HPLC methods. The threshold levels of bitterness of aqueous solutions of linamarin, lotaustralin and IAG, have been determined and together with published data on L‐phenylalanine and L‐tryptophan have allowed our evaluation of their contributions to the bitterness of cassava. Linamarin is the sole contributor in the parenchyma but (with two cultivars out of six studied) IAG contributes more to the bitterness of the cortex than does linamarin. The perception of bitterness of linamarin solutions is confounded in the presence of neutral citrate and malate which have a sour taste. These modify the taste of cassava tubers. There are many compounds that contribute to the taste of cassava tubers, hence it is not surprising that the bitterness of cassava is not always correlated positively with the cyanide potential.