Managing the hard-to-cook (HTC) phenomenon in bambara groundnut (Vigna subterranea (L.) Verdc.) processing for resource limited communities in Zimbabwe

Bambara groundnut (Vigna subterranea (L.) Verdc.) is a legume crop with great agronomic and nutritional potential to alleviate malnutrition and improve food security of many rural communities in semi-arid regions of sub-Saharan Africa. Optimal use of bambara groundnut is limited due to the hard-to-cook (HTC) phenomenon and the lack of adequate processing and cooking techniques. To optimise use, this thesis explored various methods of managing the hard-to-cook phenomenon in the context of resource-limited communities. Long cooking time, milling challenges and firewood and water shortages were the constraints to processing and consumption of bambara groundnut. Useful techniques to process HTC legumes found include cooking with alkaline salts; and soaking, roasting and milling in the production of grits and flour. Results on reviewed published data implicated microstructural and compositional changes as factors leading to the development HTC phenomenon. Cooking bambara groundnut seeds with alkaline rock salts (0.5% NaHCO­3 and 0.5% gowa) caused 13 and 20% reduction in cooking time, respectively. The contribution of bambara groundnut phenolic compounds to salt softening effects was evaluated by monitoring phenolic compounds solubilisation pattern in relation to cooking time reduction. Protocatechuic acid, catechin and epicatechin were indicators of softening in relation to cooking time reduction. Grit production was an efficient sustainable way of circumventing the HTC phenomenon as shown by a better processing aptitude as compared to traditional boiling of whole seeds. Different methods of grit processing had a similar dehulling efficiency with no significant varietal influence. Both traditional boiling and grit production improved IVSD, IVPD and mineral bioaccessibility. Dry roasted grits had the lowest IVPD (42%), followed by the combined soaking and roasting (45%), soaking (48%) and boiling (68%). Additionally, grit production was superior in improving mineral bioaccessibility, i.e. Zn, K, P and Mg. Bambara groundnut grits were found to be healthy and sustainable as they contribute to dietary diversity and the RDI values for protein, starch and minerals. Bambara groundnut flour produced by different pre-treatment methods i.e., roasting, soaking and combined soaking and roasting was regarded as nutritious and comparable to other legume flours. The soaked and combined soaked and roasted flours was recommended for further research in product development and consumer acceptance of locally consumed food products such as porridge, soups, bread, cakes and fritters. Overall, insights provided by this thesis is useful in designing effective interventions for sustainably managing processing problems for legume crops for resource-limited communities, thereby contributing to improved food and nutrition security.</p

Effect of processing on the microstructure and composition of Bambara groundnut (Vigna subterranea (L.) Verdc.) seeds, flour and protein isolates

Pre-processing treatments are generally employed to circumvent negating effects, such as the hard-to-cook and hard-to-mill properties, associated with legume seeds. Several studies have investigated the effects of soaking and roasting on the macroscopic qualities of Bambara groundnut (Vigna subterranea (L.) Verdc.) [BGN] seeds, yet knowledge is lacking on the effects of these treatments on the microstructural and molecular properties of the seeds and resulting fractions (i.e. flour and protein isolates). Size-exclusion chromatography coupled with light scattering results have shown that roasting induces thermal aggregation in BGN proteins, resulting in the formation of insoluble aggregates. To that end, the molecular composition of the roasted and soaked-roasted samples were comparable, yet different to the control (untreated seeds), whereas the samples which were subjected to soaking compared favourably to the control. The morphology of the seeds were also well characterized by microscopic techniques, including a confocal imaging technique which appears novel for legume seeds, revealing cotyledon cells with several starch granules embedded in a matrix of protein bodies. The findings of this study provide valuable insights on the microstructural and molecular compositional changes occurring in BGN seeds and fractions when subjected to soaking and/or roasting, which could be linked to some macroscopic properties as previously reported.</p

Agro-Ecological Distribution and Consumption of Wild Harvested Edible Insects, Fruits, and Vegetables in Rural Zimbabwe

Natural resources are a valuable component of traditional food systems that contributes to food and nutrition. The distribution and consumption patterns of these natural resources still needs exploration for follow-up research and optimum utilisation. The aim of this study was to investigate the agro-ecological distribution and the consumption of wild harvested edible insects, indigenous fruits and vegetables in rural Zimbabwe. Secondary data generated from a cross-sectional survey targeting 11,973 randomly selected households rural districts was used. The results revealed that at least 14 wild harvested edible insect species, 26 indigenous fruits and 10 indigenous vegetables are commonly consumed. The results showed that the highly consumed indigenous fruits, vegetables and insects were widely distributed in all provinces irrespective of the agro-ecological region and varied due to rainfall pattern and also due to soil type. However, their distribution was in some cases restricted to specific administrative boundaries or provinces. Consumption pattern and preference for some insects, fruits and vegetables varied with province. The distribution and consumption data presented in this study offers an opportunity to advocate for the conservation, production, processing and promotion of specific species in districts by relevant stakeholders and can be used as an advocacy tool for policymakers

Contribution of edible insects to improved food and nutrition security:a review

The consumption of insects “entomophagy” or insect-based foods is increasingly being recognised as an emerging solution to promote diet diversification and address the multiple burden of malnutrition. Although several studies suggest edible insects as valuable nutrient sources, few have evaluated the effects of processing on nutrient bioavailability and bioaccessibility and provided actual evidence on human nutrition. Moreover, there is limited evidence of their actual contribution to improved food and nutrition security. Therefore, the review evaluated existing evidence on human interventions and the effects of processing methods on bioavailability and bioaccessibility of key nutrients since these directly influence food and nutrition security outcomes. Seven human efficacy studies have been conducted to date and these show limited observable effects on nutrition status therefore more research is required. Findings also suggest that the processing method, insect matrix, composition of the food matrix and interaction with other food components can influence nutrient bioavailability and bioaccessibility. Hence, these should be considered during formulation and upscaling for entomophagy and insect-based foods to be viable intervention strategies against malnutrition.</p

Mopane worm value chain in Zimbabwe:evidence on knowledge, practices and processes in Gwanda district

Consumption of edible insects is a potential solution to the growing need for protein. However, the wild harvested edible insects’ value chain faces several challenges including limited knowledge on indigenous practices in the harvesting and processing and lack of information on roles of the different actors in the chain. A case study of Gonimbrasia belina, colloquially referred to as the ’mopane worm’, was conducted to understand and identify determinants of participation in the value chain of the edible caterpillar. A cross sectional study was conducted in Gwanda (a rural district in Zimbabwe) to (a) understand the indigenous knowledge on harvesting and processing methods, (b) explore value addition and the traditional beliefs surrounding the utilisation of the mopane worm. Results showed that consumers (81.7%), and harvesters (76.6%) were the main actors in the mopane worm value chain. Using the Ordinary Least Squares (OLS) model, the following were shown to be determinants of participation in the mopane worm value chain: (a) gender (b) household size (c) marital status (d) religion and (e) household assets. Two primary processing methods of harvested mopane worm were distinguished i.e., boiling and roasting on ambers. Results showed lack of diversity in mopane worm-based products. Current culturally acceptable processing techniques need improvement and standardization to support sustainable mopane worm processing while optimising nutrient bio-accessibility

Development of a nutritious cereal-based instant porridge by the incorporation of protein-rich insect powder - an example from Zimbabwe

Maize in Zimbabwe lacks essential nutrients like protein, iron, and zinc. This study explored alternative ingredients, including climate smart cereals used in porridge, to address this issue. A fortified porridge was developed by adding mopane worm powder, known for its high protein content. Consumer analysis in the UK and Zimbabwe confirmed acceptability of the fortified porridge. The study also assessed the nutritional quality by examining protein, iron, and zinc bioaccessibility after digestion. Results showed a significant increase in the porridge's nutritional profile. A 20 kg child consuming a 50 g portion of the fortified porridge had a potential 230 % increase in protein uptake and 164 % and 109 % increases in iron and zinc uptake, respectively. Acknowledging dietary diversity and use of local raw materials, the study concludes that food-to-food fortification offers a recommended and sustainable solution to address food security challenges in sub-Saharan African nations

Hard-to-cook phenomenon in bambara groundnut (Vigna subterranea (L.) Verdc.) processing : Options to improve its role in providing food security

Indigenous legume crops are pivotal in providing proteins and food security to sub-Saharan African rural communities, but most of these crops are underutilized because of the so-called hard-to-cook (HTC) phenomenon in combination with inadequate processing techniques. This review studies the case of bambara groundnut, which is third in importance after groundnut and cowpea and especially adapted to semi-arid areas. Published data on the HTC phenomenon implicate microstructural and compositional changes as factors leading to its development. Useful and sustainable techniques to process HTC legumes in developing countries include cooking with alkaline salts, milling, roasting, fermentation, and malting. Improvement of these processing techniques in relation to nutrient bioaccessibility, safety, and consumer acceptance of the products is urgently needed. Recommendations are to lessen the problems of food security in sub-Saharan African countries through, amongst other means, the optimization of bambara groundnut processing methods.</p

Bambara groundnut (Vigna subterranea (L.) Verdc.) flour: A functional ingredient to favour the use of an unexploited sustainable protein source.

Variability in dehulling efficiency, colour, chemical composition and selected functional properties of raw and pre-treated bambara groundnut (Vigna subterranea (L.) Verdc.) (BG) flour from red and black-eye varieties were studied. Functional properties were water and oil absorption, gelation, pasting, emulsification and foaming capacity. Pre-treatment of seeds (i.e. soaking, roasting and combined soaking and roasting) improved dehulling efficiency of BG varieties. Protein content of flour ranged from 15.6-19.6%, starch from 47.8-52.0% and sucrose from 1.9-5%. An improvement was observed for protein and ash content of pre-treated flour compared to raw flour. Heat treatments increased onset gelatinization temperature of flour. Black-eye BG flours that had higher starch content, also had better gelation capacity than red BG flours. All pre-treatment methods decreased flour emulsification capacity and stability. Dry-roasting caused a greater decline than other methods, whereas soaking had little effect on emulsion stability. Further, soaking increased foaming capacity, whilst a decline was observed in roasted flour. All pre-treatment methods increased oil absorption capacity of both BG flour varieties. Overall, soaked and combined soaked and roasted flour is recommended for BG flour to be incorporated in food products

Utilization of bambara groundnut (Vigna subterranea (L.) Verdc.) for sustainable food and nutrition security in semi-arid regions of Zimbabwe

Bambara groundnut (Vigna subterranea (L.) Verdc.) is an indigenous legume crop, cultivated by subsistence farmers throughout sub-Saharan countries. Research findings indicate that the crop has great nutritional and agronomic potential, but it remains scientifically neglected. A baseline study was conducted in seven districts in semi-arid regions of rural Zimbabwe to gather knowledge on current production and utilization of bambara groundnut, assess its role in providing sustainable food and nutrition security for rural populations and determine priorities for follow-up research. Results revealed a variety of bambara groundnut processing techniques, which included boiling, soaking, roasting and milling across the surveyed districts. Reported constraints to processing and consumption included long cooking time, difficulties with milling and high firewood and water requirements. Fifty to eighty percent of respondents in all districts consumed bambara groundnut once or twice weekly from August to December. Preferred consumer attributes were taste, the satiating effect, nutritional benefits or a combination of these. Current, culturally acceptable processing techniques need improvement to support sustainable bambara groundnut processing while optimising nutrient bio-accessibility. Ultimately, community resilience to food and nutrition insecurity can be promoted by exchange of bambara groundnut processing knowledge amongst the production areas, involving the different stakeholders in the food supply chains.</p

Effect of processing on the microstructure and composition of Bambara groundnut (Vigna subterranea (L.) Verdc.) seeds, flour and protein isolates

Pre-processing treatments are generally employed to circumvent negating effects, such as the hard-to-cook and hard-to-mill properties, associated with legume seeds. Several studies have investigated the effects of soaking and roasting on the macroscopic qualities of Bambara groundnut (Vigna subterranea (L.) Verdc.) [BGN] seeds, yet knowledge is lacking on the effects of these treatments on the microstructural and molecular properties of the seeds and resulting fractions (i.e. flour and protein isolates). Size-exclusion chromatography coupled with light scattering results have shown that roasting induces thermal aggregation in BGN proteins, resulting in the formation of insoluble aggregates. To that end, the molecular composition of the roasted and soaked-roasted samples were comparable, yet different to the control (untreated seeds), whereas the samples which were subjected to soaking compared favourably to the control. The morphology of the seeds were also well characterized by microscopic techniques, including a confocal imaging technique which appears novel for legume seeds, revealing cotyledon cells with several starch granules embedded in a matrix of protein bodies. The findings of this study provide valuable insights on the microstructural and molecular compositional changes occurring in BGN seeds and fractions when subjected to soaking and/or roasting, which could be linked to some macroscopic properties as previously reported.</p