Cassava and bamboo shoots available in Australia and New Zealand are safe to eat provided you prepare them properly. These foods contain cyanogenic glycosides; chemicals that can be broken down to release hydrogen cyanide, which can be harmful to consumers.
Under the Food Standards Code cassava and bamboo shoots must be labelled with (or if unpackaged accompanied by) a statement indicating they must be fully cooked (and peeled in the case of cassava) before eating.
Cassava is a tropical root crop similar to taro and yam and is grown for food in Pacific Island countries, South America, Asia and Africa. It has enlarged starch-filled roots, which contain about 30 per cent starch and very little protein. It is known by many names such as yucca, tapioca (in a processed form), gaplek or manioc.
Only sweet cassava, containing low levels of cyanogenic glycosides (50mg/kg), is permitted to be used for food in Australia and New Zealand.
To make cassava safe to eat, first peel and slice the cassava and then cook it thoroughly either by baking, frying, boiling or roasting. This process reduces the cyanogenic glycosides to safe levels. Frozen cassava and frozen peeled cassava should also be cooked in this way. Discard any cooking water after use.
Processed cassava products, such as cassava flour and tapioca pearls used for tapioca pudding, are safe because the cyanogenic glycosides are reduced to safe levels during manufacture. Ready-to-eat cassava chips are also safe because they are required to comply with a maximum limit of 10 mg/kg of hydrocyanic acid for these foods in the Code.
Bamboo shoots are an Asian food sourced from the underground stems of the bamboo plant. Of the many bamboo species, only a small number are used as food.
Like cassava, unprocessed fresh bamboo shoots contain cyanogenic glycosides.
To make them safe, slice fresh bamboo shoots in half lengthwise, peel the outer leaves away and trim any fibrous tissue at the base. Then slice them thinly into strips and boil in lightly salted water for eight to ten minutes. Discard the cooking water after use.
Canned or dried bamboo shoots are widely available and are safe because processing reduces hydrogen cyanide to safe levels.