Topic 1. Effects of the biocolorants extracted from dye sorghum leaf sheaths on the antioxidant capacity and in vitro solubility of iron and zinc in infant fermented starchy food.

Koko is a thick fermented porridge usually obtained from ogi, a fermented cereal slurry (Nago et al., 1998). Sorghum, maize and millet are the common cereal used in the processing of koko in West Africa (Kayodé et al., 2005; Lartey et al., 1999; Lei and Jakobsen, 2004). The colour of koko comes from the cereal used in the processing. Koko obtained from red sorghum grains is characterised by its red colour (Kayodé et al., 2005). To meet consumer preference even when sorghum is not accessible, processors use maize and dye sorghum leaf sheaths as ingredients. Dye sorghum is a specific variety of sorghum grown exclusively for the red dye extracted from its leaf sheaths. Dye sorghum leaf sheaths is a rich source of phenolic compounds and thus a source of bioactive compounds. Due to its richness in phenolic compounds, the use of dye sorghum leaf sheaths in infant foods like koko could also decrease the bioavailability of micronutrients such as iron and zinc.

Objective

The objective is to evaluate the effect of watery extract of dye sorghum leaf sheaths on antioxidant capacity and the in vitro solubility of iron and zinc in koko.

 

Topic 2. Managing the hard-to-cook (HTC) phenomenon in bambara groundnut processing for resource limited communities in Zimbabwe.

Bambara groundnuts are grown, harvested, and then stored under sub-tropical conditions that accelerate the development of HTC phenomenon. Cooking time of HTC legumes can be reduced by the use of different salt solutions and cell wall degrading enzymes. Salts are hypothesized to have an effect on denaturation temperature of proteins, pectin solubilisation and gelatinization temperature of starch. Salts have also been reported to affect the digestibility of starch and proteins. The aim of the study is to assess the effect of alkaline salts and cell wall degrading enzymes on nutrient solubilisation, protein denaturation and starch gelatinization leading to reduction in cooking time. In addition the effect of salts and cell wall degrading enzymes on bio-accessibility of nutrients will be assessed.

MSc Topic: Preferred Target student (FQM)
1.    Effect of alkaline salts and cell wall degrading enzymes on nutrient solubilisation, protein denaturation and starch gelatinization in bambara groundnut cooking.

BSc Topic: Preferred Target student (FQM)
2.    Effect of alkaline salts and cell wall degrading enzymes on bio-accessibility of nutrients in bambara groundnut processing. 

Topic 3. Monkey orange processing.

Monkey orange (Strychnos sp.) fruits are well appreciated and consumed in Southern Africa due to their nutritional value (vitamin C, zinc and iron) and taste. The dried MO have a shelf life between two months to five years. Therefore, the optimization of drying processes using locally available resources and its impact on nutritional and sensorial quality of MO fruits warrants further investigation.

• Sub-topic 1. Evaluation of osmotic dehydration on MO.

Osmotic agents limited to sucrose and sodium chloride are readily available cheap materials affordable to the local communities. Osmotic dehydration preserves product texture, decreases water and enzymatic activity thus reducing enzymatic browning and retaining product colour, leaching of small amounts of product-soluble compounds, minerals and vitamins. Thus the effect of osmotic dehydration in MO can be studied with the aim to: (i) assess the effect of osmotic dehydration on sensorial quality, namely texture and colour, and (ii) assess the impact of osmotic dehydration on nutritional quality, namely vitamin C and flavonoid content of monkey oranges.

• Sub-topic 2. Evaluation of hot air drying on MO.

Thermal drying can result in an extremely hard, off-flavour product and nutrients sensible to heat, light, and oxygen are degraded. In other studies dried fruits contained rich and shelf stable dietary polyphenolics and anti-oxidants, explained by concentration of polyphenolic compounds during drying. Contradictory results of literature show high and low anti- oxidant activity, thus studies need to be performed to evaluate the effect of drying MO on nutritional quality and sensory characteristics. Further studies aim to: (i) assess the effect of hot-air drying of monkey orange on colour and texture and (ii) assess the effect of hot-air drying on nutritional quality, namely vitamin C and flavonoid content of monkey orange.

• Sub-topic 3. Osmotic dehydration as a pre-treatment.

Osmotic dehydration as a pre-treatment to hot air drying reduces the drying time and temperature, thereby improving product sensory appeal, nutritional quality and shelf life. This research topic will therefore combine osmotic dehydration followed by hot air drying, where the drying characteristics and constants will be determined, moisture ratio compared to drying time at different temperatures will be utilized for the development of a drying curve. The aim is therefore to assess the impact of osmotic dehydration followed by hot air drying on nutritional and sensorial quality of monkey orange fruits from different varieties (S. cocculoides and S. innocua).