Complementary porridge based on pearl millet and cow pea : the effect of traditional processing techniques and cooking methods on pasting properties and in vitro starch digestibility

Sammanfattning: In Mozambique, malnutrition in children under 5 years is a serious concern. The condition is thought to be owing to nutritionally inferior diets and improper feeding practices on a mainly cereal-based diet, where porridges from millet- and legume-flours constitute the major staple food. Prior to cooking the porridges, traditional processing techniques are often applied to the cereal grains and grain legumes, such as soaking, germination and fermentation. These processing techniques have been suggested in literature to improve the nutritional quality, by reducing the amount of antinutritional compounds naturally present in both millets and grain legumes. Some of these processing methods have also been reported to modify the starch composition which result in changes in functional properties, e.g. pasting properties, and improve starch digestibility. The objective of this master thesis was to formulate complementary porridges based on cereal grain; pearl millet, and grain legume; cow pea, to evaluate these for changes in cooking quality (i.e., pasting properties) and in vitro starch digestibility due to the effects of cooking method and traditional processing techniques (e.g. germination, fermentation, soaking). Two aims were formulated to meet the objective. The first was to determine the impact of ingredient formulation on product consistency in terms of pasting characteristics. The second was to map the starch digestibility of the formulated porridges. The pasting properties of formulated complementary porridges were analysed with a rapid visco analyzer (RVA) using two costume temperature running profiles, i.e. “slow cooking” and “rapid cooking”. In direct connection to analysing the pasting properties of porridges, the in vitro starch digestibility was analysed using a “Digestible starch assay kit” from Megazyme. The impact of ingredient formulation on product consistency showed that porridges constituting of soaked and germinated pearl millet generally displayed substantially lower viscosities, compared to porridges constituting of only soaked pearl millet. The results also showed that fermentation of cow pea only marginally affected porridge pasting properties. Further, the cooking method, i.e. slow cooking or rapid cooking, did not substantially affect pasting properties of porridges. Lastly, the in vitro starch digestibility was neither impacted by ingredient formulation, nor by cooking methods used. In future research, when formulating complementary porridges based on pearl millet and cow pea for malnourished children, one would optimally utilize the effects of germination as it offers an increase energy- and nutrient density. One would also utilize the effects of fermentation, as literature suggest that the process improves seed nutrient bioavailability. Keywords: cow pea; pearl millet; complementary porridge formulation; traditional processing techniques; germination; fermentation; soaking; pasting properties; starch digestibility; energy density