Development of iron fortified cassava mahewu

Abstract

In Mozambique 97% of the small scale farmers grow cassava in 43% of the total cultivated land. In 2012 cassava production was estimated at 10.05 million tons. Cassava is the second most important staple food after maize. Consumption of cassava is estimated at 85 kg per person per year. In Mozambique the diet is poor in micronutrients and the prevalence of under-nutrition is estimated at 38%. Anaemia is a serious public health concern, affecting more than 40% of young children, pregnant and nursing mothers. Cassava mahewu a fermented nonalcoholic beverage prepared using indigenous traditional technology. Fermentation is known to reduce the toxicity of cyanogenic glycosides in both leaves and cassava roots. It also results in higher levels of vitamins, especially the B group, essential amino acids, improves the digestibility of protein and increases the bioavailability of minerals. The aim of the present study was to investigate whether cassava, in the form of mahewu, can be fortified with iron. Bitter and sweet cassava roots and soil samples, were collected from small scale farmers in four Districts of Mozambique. The four Districts are located in intermediate and high production areas of cassava. The concentrations of iron and other minerals such as aluminum, calcium, copper, manganese, phosphorus, lead and zinc in cassava roots and soil, were determined using an inductively coupled-plasma optical emission spectrometer (ICP-OES), after microwave digestion. Sweet and bitter varieties of cassava from four Districts in Mozambique were fermented in a food laboratory, under controlled conditions (45°C for 24 hours) and the optimal stage for iron fortification was determined. Samples were collected at hour 0 and hour 24 for microbial analysis, acid concentration and total solids determination. Fortification with ferrous sulfate (FeSO4.7H2O) and ferrous fumarate (C4H2FeO4) were investigated. The total iron content of the fortified cassava mahewu was determined using Microwave Digestion Accelerated Reaction System (MARS) and ICP-OES, while the bioaccessibility of iron in fortified cassava mahewu was assessed using the in vitro dialysability procedure. Results showed that the mineral content of soil from the four districts differed significantly (p ˂ 0.05). There was also a significant difference (p ˂ 0.05) in the mineral concentration of the cassava roots from the four varieties, but no difference between sweet or bitter types. The concentration of minerals was found to be significantly higher in soil, than in roots. This difference was greatest for iron concentration, which was not detectable in the root samples, although soil concentration was up to 24.78 mg/kg. Although the reason for this was not determined, this lack of iron in the roots supported iron fortification of mahewu. A significant difference (p ˂ 0.05) in pH was observed between mahewu fortified with ferrous sulfate (4.5) and ferrous fumarate (4.3), with the latter being similar to the control. At the beginning of fermentation the acidity was 0.06% and at the end 0.30%. The total solids of fermented mahewu were 9.6%. The microorganisms responsible for fermentation were predominantly lactic acid bacteria (LAB) and yeast. The pH and acidity was different to that reported in the fermentation of maize mahewu. The fermenting microorganisms and total solids were similar to previous findings for maize mahewu. The total iron content of mahewu fortified with ferrous sulfate was significantly higher (p ˂ 0.05) than mahewu fortified with ferrous fumarate. Both the amount and percentage of bioaccessible iron were higher in mahewu fortified with ferrous sulfate compared to mahewu fortified with ferrous fumarate. It was found that mahewu made using the bitter variety of cassava and fortified with ferrous sulfate provided a more bioaccessible source of iron. The stage of fortification was not found to affect the total iron content nor the iron bioaccessibility. It was concluded that cassava roots do not take up iron, even when soils are high in this metal. Thus the selection of varieties with better uptake of minerals and fertilization of soils is recommended, but may not increase concentration of essential minerals sufficiently to maintain health in vulnerable communities where cassava is the main staple. This was the first study in which fermentation of traditional cassava mahewu was carried out under repeatable, controlled conditions. It is recommended that fortification occurs at the end of the fermentation when done at household level. However, when flour is being milled in larger villages, it could be fortified prior to sale in informal markets. There is also the possibility of large scale commercial applications. It is concluded that bitter varieties of cassava will deliver more bioaccessible iron to the consumer. Ferrous sulfate is more suitable as iron fortification source for cassava mahewu than ferrous fumarate and also is more stable in mahewu. Fortification of cassava mahewu could contribute to the iron intake of vulnerable population. In addition, although fortification at the end of fermentation would probably be ideal for rural communities, as it could be made available in sugar sprinkled into the traditional product, it was shown that fortification of flour used to make mahewu would result in significantly higher availability. It is recommended that iron fortification of mahewu is implemented both at subsistence and commercial level. This should form part of a communication strategy at community level by the state, in order to improve public health in vulnerable communities in Mozambique.