Chemical Composition and Physico-chemical Properties of Traditional Alkaline Salts (Lake Deposits and Plant-based Ash Salts) Sampled in Cameroon and Nigeria

Abstract

Lake deposits and plant-based ash salts are food additives used in a variety of food preparations throughout the world. They exist in many colours and are found in market stalls in many countries. In the literature, they have been named traditional alkaline salts (TAS). Their colours (as identified by users) are their major quality determinant and are associated with their efficiency when used in food preparations. Up to now, no relationship has been established between their colours and their chemical composition and/or physico-chemical properties. Lake deposits (sampled in Cameroon and Nigeria), "white" plant-based ashes and evaporites of plant-based ash filtrates (sampled in Cameroon) found from the market have a buffer behaviour (pH of 10 and 11) while "green" and "black" plant-based ashes do not (pH = 12 to 14). The buffer behaviour is due to the simultaneous presence of carbonates and bicarbonates, combined with the absence of oxides, the pH of the resulting solutions was increased with increasing carbonates/bicarbonates ratio. The colours of evaporites of plant-based ash filtrates are similar (less than 6% of difference) in their chemical composition (sodium, potassium, carbonates and bicarbonates) and physico-chemical properties while the other TAS are not. "White" lake deposits have higher major ions (sodium, potassium, carbonates and bicarbonates) content than the "black" ones. There is always a toxicity risk (lead and cadmium) associated with the use of plant-based ash salts and sometimes "black" lake deposits while there is not a toxic risk associated with the use of the "white" colour of lake deposits. "Black" lake deposits sampled in Abuja, Nigeria have one and a half times more cadmium and lead than those sampled all over Cameroon when they contain these metals.