Improvement of maize-based foods in Sub-Saharan Africa

Feeding 2.4 billion mouths in Africa by 2050 will require all hands on deck as the demand for cereals may triple. Viable options to feeding Africa include measures with respect to (a) food technology, e.g. improved utilization of the available crops and their by-products, (b) plant breeding, e.g. through bio-fortification, and (c) agronomy, e.g. yield improvement and sustainable crop intensification. Although the latter two options have received most research traction, the current cereal yields in sub-Saharan Africa (SSA) is about 20% of its potential. Crop intensification has huge economic and environmental implications while biofortified crops have not received the expected adoption. This reinforces the importance of strategies aimed at optimizing crop utilization such as the prevention of food and nutrient losses as well as enhancing product diversification from existing climate-resilient crops to feed the ever-rising population. Matching consumer preferences and enhancing the ease of processing of maize into different food types will support better use, with positive consequences on reducing malnutrition and alleviating poverty.

Many high potential maize products that are localized or confined to particular communities can be scaled up across the continent and beyond for prosperity, as elaborated in chapter 2. This will require standardization of the processing conditions for effective monitoring and evaluation. Curbing nutrient loss during post-harvest handling of maize will enhance the nutritional status of Africans relying on maize as a staple crop. Furthermore, research on more effective ways to enhance the protein quality i.e. tryptophan and lysine as well as vitamin content of maize-based foods especially through novel fermentation technique is important. Novel fermentation techniques such as the use of microbial fortification or bio-enrichment using high lysine producing microorganism could help to ameliorate the poor protein quality of maize foods. This was briefly highlighted in the pilot test carried out with three strains of bacteria in this thesis discussion. Microbial fortification has potential to produce healthy maize food with quality protein but must be through methods that are feasible for use, safe, meet organoleptic preferences of consumers, work under sustainable energy sources, independent of the harsh climatic condition and environmental friendly.

Chapter 3 stressed that tackling malnutrition in Africa requires a holistic strategy that stretches across the entire agricultural value chain - Crop-to-Health strategy i.e. from agronomy to beyond plate. Maize value chain improvement with a keen consideration of end user preferences will have a broader impact on the target population. Matching the flavour and taste preference, and enhancing the ease of processing of maize into different food types will guarantee a better consumption of maize in the future, with a better contribution to reducing malnutrition. Therefore, an adequate understanding of the needs of the consumers and incorporating it into breeding programs will help to properly harness research resources, increase adoption of new varieties, improves nutrition and also protects the traditions of the local communities. Six clusters of maize breeding objectives were identified in chapter 3. We develop a framework which identifies the relationship between the breeding objectives and how it impacts farmers, food processors and consumers to achieve sustainable food security. This will help breeders to examine in detail how to establish those priorities.

In aroma analysis presented in chapter 4 and 5, PTRMS gives signals of the headspace while GCMS gives signals of headspace/fibre system hence signal differences in both instruments were found. PTRMS was very useful to give a quick “snapshot” of differences among maize varieties while GCMS was efficient for the identification of VOCs. Generally, vast volatile differences were found in maize genotypes which could help to further improve the flavour of the crop. PTR-QiTOF-MS used for the first time on maize successfully clustered the 22 maize varieties in four nutritionally distinct categories while 69 volatile compounds were identified for quality protein maize, provitamin A maize, white and yellow maize. The nutritional contribution of biofortified maize varieties is significantly limited by loss of the provitamin A content even at the earliest stage of post-harvest handling such as storage; more deteriorations of nutrient occur after processing, as shown in chapter 5. Furthermore, the carotenoid-rich varieties are prone to aroma deterioration during storage which may negatively influence consumer perception.

Chapter 6 showed significant differences in maize genotypes (landraces and hydrides) for bread making performance. Suitable maize flour can be obtained for gluten free bread through selection of appropriate genotypes. Similarly, sourdough technology can help to further improve the functional properties of the flour for better bread-making performance, as observed in chapter 7. Fermentation is a common practice for maize food in SSA and cereal associated bacteria are known to produce exopolysaccharides (EPS) in large quantities which can enhance dough quality. Screening for EPS producing bacteria in ogi and munkoyo generated 10% producers and 22% producers respectively, chapter 7. Isolated EPS producing lactic acid bacteria were identified using morphological, biochemical and microscopic observations as W. confusa, a common EPS producer. EPS can serve as hydrocolloids to enhance textural properties of gluten-free bread such as specific volume, gas retention, crumb structure, taste as well as reduce hardness and staling rate. Availability of suitable maize flour for bread making could replace or reduce Africa’s reliance on wheat for bread making which would certainly improve the socioeconomic status of people.