Nutrition in low-income countries
Professor Ulf Svanberg
Professor Marie Alminger
Assoc. professor Thomas Andlid
Serafina Vilanculos, PhD student
The focus of this research unit is on two of the major health problems in low-income countries that are associated with the diet, namely iron and vitamin A deficiency. In a long-term collaboration between countries in Southern Africa and Food Science at Chalmers several research projects have focused on these problems. The projects have been implemented with major support from Sida/SAREC.
In collaboration with Tanzania Food and Nutrition Centre, the research aimed at increasing the bioavailability of iron in cereal-based foods for children, prepared as porridges out of maize, millet and sorghum. These have adequate iron content, but also contain substances (inhibitors) such as phytate and polyphenols, that prevent the uptake of iron into the body. The content of inhibitors may be reduced by different fermentation techniques or by the use of intrinsic enzymes in the plants to increase the availability of iron. We have isolated several yeast species from traditional lactic acid fermented maize gruels from Tanzania and identified some yeast strains with the ability to form an enzyme, phytase, which will degrade phytate. One of the yeast strains had a unique ability to release the enzyme through the cell wall and thereby being able to sufficiently degrade phytate in maize porridge to increase iron absorption. With the help of genetic engineering and classical mutation the aim is to further increase phytase production from this yeast strain, making it suitable for use in a starter culture for fermentation on village level. In another project, we have been investigating ways to decrease the negative effects of polyphenols on iron absorption. The approach was to use enzymes (PPO) that is readily abundant in fruits. Flour from cereal varieties with a high content of polyphenols were incubated with such PPO-enzymes resulting in a reduced content of polyphenols and improved iron availability.
In collaboration with Makerere University in Uganda, research has focused on vitamin A deficiency. Vitamin A is found in animal foods but in most developing countries the staple food is of plant origin. Thus, vitamin A needs must be met by provitamin A carotenoids from plants. The problem is that the absorption of provitamin A from fruits and vegetables is too low to cover this need. Through plant breeding in Uganda, new provitamin A-rich varieties of sweet potatoes were produced and those could provide a high availability of provitamin A by a modified cooking technology. Using a specially developed microscopy technique (CARS and SHG), we have also shown how the provitamin A is released at the cell level from sweet potatoes depending on the cooking method to enable prediction of what is optimal for high availability.
In an ongoing collaboration with the University Eduardo Mondlane in Maputo, Mozambique, we are carrying out three projects in co-operation with the Swedish institute for food and biotechnology (SIK) in Gothenburg. Two of these projects are aimed at baking breads with local flour products to reduce the need to import wheat not grown in Mozambique. The goal is to produce breads with similar characteristics as wheat bread using different baking ingredients and to increase the availability of iron in such breads using high phytase producing yeast strains from the Tanzanian project. We will also include different provitamin A sources in the bread formula and optimize the baking process for a high availability of provitamin A. In a third project, we will dry domestic fruits with modern techniques (osmotic dehydration and hot air/microwave heating) with the aim to preserve a high content of different bioactive components such as provitamin A.