Cowpea (Vigna unguiculata L. Walp) is an important source of protein in some parts of sub Saharan Africa. In southern Africa, it is mainly boiled into a stew, and long cooking time is a concern. Micronisation of preconditioned seeds has been used to reduce the cooking time of other dry legume seeds such as lentils. Hence micronisation (moisture conditioning and infrared heating) presents an opportunity for processing cowpeas to alleviate long cooking time and provide a convenient product as well as diversify cowpea products. In addition, potential exists for using flour milled from micronised (moisture conditioned and infrared heated) seeds in food systems. However, variations in raw material physicochemical properties (seeds) and micronisation temperature would affect the efficacy of the process to produce products with desired properties. Mild (130 and 153°C) and severe (170°C) final surface temperatures were used to determine the extent of micronisation-induced changes in cowpea structure and physicochemical properties and functionality of the resultant flours. Two cowpea varieties (Bechuana white and Var. 462; 41% moisture) micronised to 153 °C were used to study the effect of micronisation on physicochemical and structural properties of cowpea seeds. Bechuana white (41% moisture) micronised to three temperatures (130, 153 and 170°C) was used to study the micronisation temperature effect on physicochemical properties of cowpeas and functional properties of resultant flours. Scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) were used to study seed structure, while light microscopy was used for the flour. Gel permeation high performance liquid chromatography (GP-HPLC), differential scanning calorimetry (DSC), and a rapid visco-analyser (RVA) were used to study starch-related properties, while fluorescence spectroscopy and electrophoresis (SDS-PAGE) were used to study physicochemical properties of isolated proteins. These physicochemical and structural properties were determined to aid in explaining the possible micronisation-induced changes in cooking characteristics of seeds and functional properties of the resultant flours. Micronisation (41% moisture, 153°C) reduced cooking time (Bechuana white > Var. 462) and increased splitting (Var. 462 >Bechuana white) of the cowpeas during subsequent cooking. The micronised (41% moisture, 153°C) seeds were relatively softer than the unmicronised samples following subsequent cooking. The mild temperatures (130, 153°C) were more effective in reducing cooking time than the higher temperature (170 °C). Micronisation (41% moisture, 153 and 170°C) caused physical fissuring of the seed coat, cotyledon, and parenchyma cell wall and reduced the bulk density of treated seeds. These changes in the physical structure improved the hydration rate of the seeds during cooking. There is a possibility that micronisation (41% moisture, 130, 153, 170°C) also caused the degradation of pectic substances of the middle lamella, since shorter cooking time was required for cotyledon parenchyma cells to separate during cooking. Mild micronisation (41% moisture, 130 and 153°C) temperatures caused the disruption of the native starch granular order leading to retrogradation of amylose, while at higher micronisation (41% moisture, 170°C) temperatures the retrogradation of amylose was possibly accompanied by endodegradation of starch. Simultaneously, micronisation (41% moisture, 130 and 170°C) led to increased surface hydrophobicity and crosslinking of protein, which was more pronounced in M-170°C samples. SDS-PAGE indicated that disulphide bonds were formed in micronised (41% moisture, 130 and 170°C) samples; while isopeptide bonds, dityrosyl bonds and Maillard derived crosslinks are possibilities especially in the M-170°C sample. The pronounced crosslinking of protein and possible depolymerisation of starch contributed to hardening of the cotyledon structure, consequently impacting negatively on the effectiveness of the micronisation (41% moisture, 170°C) treatment in reducing cooking time. These changes in seed structure and physicochemical properties of starch and protein contributed towards the reduction in cooking time and increased splitting of seeds and modified flour functionality. Cowpea flour foaming capacity was lost following micronisation (41% moisture, 130 and 170°C) possibly due to reduced solubility and crosslinking of protein. Micronisation (41% moisture, 130 and 170°C) reduced flour gelling and pasting properties while increasing the water absorption capacity, more so in M-170 °C samples than in M-130°C. Hence micronisation to mild temperatures (130°C) has the potential of producing cowpeas with shorter cooking time, which can also be milled into flour with modified functionality. Thus micronisation of moistureconditioned cowpeas to mild temperatures would contribute towards increased utilisation of cowpeas as well as improving household nutrition status. / Thesis (PhD)--University of Pretoria, 2008. / Food Science / unrestricted

Cowpeas (Vigna unguiculata L. Walp) are legumes recognised as a good source of proteins in developing countries. Cowpeas are mostly utilised as cooked whole seeds. This is often achieved only after boiling for up to 2 hours, resulting in high energy consumption and a long time for food preparation. Micronisation of pre-conditioned cowpeas (± 41 % moisture at 153 °C) reduces their cooking time. During micronisation, cowpea seeds are exposed to electromagnetic radiation with a wavelength range of 1.8 to 3.4μm. For biological materials, the penetration of infrared rays into the food material causes intermolecular vibration, this result in a rapid increase in temperature and water vapour pressure within the seed. Micronisation changes physico-chemical properties of cowpea seeds that may affect sensory properties of cooked cowpeas. Micronisation may also affect cowpea bioactive components such as phenolic compounds and hence their antioxidant properties and bioactive properties. This study aimed at (1) determining the effects of micronisation of pre-conditioned cowpeas on sensory properties of cooked cowpeas and (2) determining the effects of mironisation of pre-conditioned cowpeas on the phenolic compounds, radical scavenging properties and their protective effects against oxidative damage of biomolecules (i.e. low density lipoproteins (LDL), deoxyribonucleic acid (DNA) and red blood cells (RBC). © University of Pretoria vi Micronisation significantly reduced cowpea cooking time by 28 to 49 %, depending on cowpea type. There were significant (P<0.05) increases in roasted aroma and flavour, mushy texture and splitting in all micronised samples. Bechuana white, a light brown cowpea type, was more mushy and split than others. There were significant decreases in firmness, mealiness and coarseness after micronisation for all cowpea types. Micronised cowpeas were darker (lower L* values) than unmicronised cooked cowpeas. Darkening was more evident in light coloured than dark coloured cowpea types. Although micronisation reduces cowpea cooking time, it also affects sensory properties of cowpeas. This might have an influence on consumer acceptance of micronised cowpeas. Twenty seven phenolic compounds were identified in the cowpea types studied: 6 phenolic acids, 14 flavonols and 7 flavan-3-ols. Protocatechuic acid, p-coumaric acid, 4- hydroxybenzoic acid and ferulic acid were the major phenolic acids in cowpeas. Catechin, catechin-3-O-glucoside, myricetin, rutin, quercetin and its mono and diglycosides were present in all cowpea types analysed. Dr Saunders (701.7−849.2 μg/g) (red in colour) and Glenda (571.9−708.1 μg/g) (dark brown in colour) contained the highest total phenolic contents, followed by Bechuana white (361.5−602.3 μg/g) (light brown in colour) and Blackeye (152.0−224.5 μg/g) (cream in colour). More of the flavonols were identified in red and dark brown compared to light brown and cream cowpea types. The red cowpea type contained all the dimers and oligomeric flavan-3-ol species identified in this study. In all cowpea types, extracts from unmicronised (uncooked) cowpeas inhibited copperinduced LDL oxidation in a dose dependent manner. Extracts from all samples analysed exhibited protective effects against AAPH (2, 2'-azobis (2-amidinopropane) hydrochloride) induced RBC haemolysis and DNA damage. Extracts from more pigmented cowpeas, i.e. Dr Saunders, Glenda and Bechuana white, had significantly (P<0.05) higher levels of total phenolics, total flavonoids and radical scavenging properties than Blackeye (less pigmented). Extracts from more pigmented cowpeas also offered higher protection against AAPH-induced DNA and copper-induced LDL oxidation damage than extracts from less pigmented cowpeas. These results indicate protection of biomolecules e.g. DNA, LDL and RBC) from oxidative damage and have a potential to reduce oxidative stress implicated in the development of chronic diseases. This is because cowpea phenolic compounds possess the ability to reduce oxidative damage associated with development of these diseases. © University of Pretoria vii Pigmented cowpea types may be recommended for health applications as they show more potential as source of antioxidants compared to the less pigmented cowpeas. Extracts from micronised (uncooked and cooked) samples of Dr Saunders and Glenda cowpeas had significantly higher concentrations of ferulic acid and p-coumaric acid compared with unmicronised samples. Para-coumaric acid concentrations were higher in all micronised samples of Blackeye cowpeas than in unmicronised samples. The micronisation process could release cell wall bound ferulic acid and p-coumaric, increasing their concentrations in micronised samples. On the contrary, extracts from all micronised samples of Bechuana white and Glenda cowpeas had lower concentrations of catechin than unmicronised samples. Results indicated that total extractable phenolics were lower in micronised samples of cowpea types than unmicronised samples. Futhermore, extracts from micronised samples of all cowpea types showed less protective effect against LDL oxidation than extracts from unmicronised samples. However, for most cowpea types there was no significant difference in total flavonoid contents (TFC) and Trolox equivalent antioxidant capacity (TEAC) values of cooked samples of both micronised and unmicronised. Micronisation did not affect the protective effects of cowpeas against AAPH-induced RBC haemolysis and oxidative DNA damage. Micronisation, followed by cooking, may have generated heat-induced antioxidants such as Maillard reaction products contributing to radical scavenging properties in micronised (cooked) cowpea samples. Though micronised samples had lower concentrations of some phenolic compounds and total extractable phenolics than unmicronised samples, micronised cowpea samples still exhibited radical scavenging properties and offered protective effects against oxidative damage of LDL, DNA and RBC and therefore may offer potential health benefits to consumers. / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Food Science / Unrestricted

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Thesis (M.S.)--Michigan State University. Dept. of Agricultural, Food, and Resource Economics, 2008. / Title from PDF t.p. (viewed on Aug. 4, 2009) Includes bibliographical references (p. 317-321). Also issued in print.

Cowpeas (Vigna unguiculata L. Walp) are legumes widely consumed in developing countries. Because cowpeas are an important source of proteins, calories and vitamins, they have the potential to alleviate protein-energy malnutrition. However, the consumption of cowpeas is impaired by the hard-to-cook (HTC) defect, which develops when cowpeas are stored at high temperature and humidity conditions. HTC cowpeas require extended time to cook and have decreased protein, starch, vitamin availability and poor textural quality. The extended cooking time and poor textural quality reduce consumer preference and acceptability. Soaking cowpeas in water or in a solution containing monovalent cations have been used by other researchers to reduce the cooking time of normal and HTC cowpeas, while micronization has been used to reduce the cooking time of normal cowpeas. Hence preconditioning in water or in a solution containing monovalent (Na+) cations in combination with micronization, could have the potential to help in alleviating the HTC phenomenon in legume seeds, especially cowpeas. This study was undertaken in two parts. The first part consisted of inducing the hard-tocook (HTC) defect and determining its effect on cooking and physicochemicalcharacteristics of cowpeas. The second part consisted of attempting to alleviate the HTC defect in cowpeas by pre-conditioning cowpeas in water or in a solution with monovalent (Na+) cations and its combination with micronization. The effect of these treatments on cooking and physicochemical characteristics of normal and HTC cowpeas were studied. Storing cowpeas at high temperature and high relative humidity, increased the cooking time of cowpeas (Mogwe-o-Kgotsheng) from 89 to more than 270 min. The increase in the cooking time was associated with reduced pectin solubility, which was coincident with a decrease in phytic acid content and an increase in phytase activity. According to the “phytate-divalent cations-pectins” theory, at adverse storage conditions, phytase probably hydrolysed phytate to release divalent cations which migrated to the middle lamella to bind with pectins, reducing their solubility. Because of the reduced pectin solubility of HTC cowpeas, the hardness of cooked seeds increased, the degree of splitting reduced and water absorbed during cooking consequently reduced as compared with normal cowpeas. This research supports the “phytate-divalent cations-pectins” as an important mechanism to explain the HTC-defect in legume seeds. From a practical standpoint, pre-conditioning cowpeas in water on its own was effective in reducing the cooking time of normal cowpeas from 89 to 44 min. This coincided with an improvement of pectin solubility, degree of splitting and decreased hardness. For HTC cowpeas, a combination of pre-conditioning in a solution containing monovalent (Na+) cations and micronization was needed to optimally reduce the cooking time from more than 270 min to 59 min. This coincided with an improvement of pectin solubility, degree of splitting and decrease in the hardness of cooked cowpeas. Pre-conditioning cowpeas in water induced the solubilization of pectins in the middle lamella of normal and HTC cowpeas. Pre-conditioning cowpeas in a solution with monovalent (Na+) cations improved pectin solubility due to the solubilization effect of water as well as a conversion of insoluble pectins to soluble pectins by monovalent (Na+) cations. Micronization improved pectin solubility further by breaking pectin molecules into lower and more soluble fractions, probably via the β-elimination reaction. Micronization also decreased the hardness of cooked seeds and increased the degree of splitting for both normal and HTC cowpeas. However, the reduction in hardness and increase in the degree of splitting were more pronounced in normal than in HTC cowpeas, probably becausemore divalent cations were bound to the pectins of HTC cowpeas. For normal cowpeas, the improvement of pectin solubility, decrease in texture of cooked seeds and increase in the splitting as influenced by micronization was reflected in the increase of the amount of water absorbed during cooking, which could have contributed to the reduction in the cooking time. However, for HTC this was not the case as the water absorbed during cooking decreased. The reduction in the amount of water absorbed during cooking could be associated with protein denaturation during storage at adverse conditions and during micronization. The improvement of pectin solubility was at higher levels when all the treatments were applied in HTC cowpeas than in normal cowpeas. However, this was not coincident with reduction in the cooking times. This suggests that factors (i.e. proteins, starch) other than pectin solubility could have contributed to the cooking time of HTC cowpeas. Pre-conditioning cowpeas in a solution with monovalent (Na+) cations in combination with micronization has a definite potential to help alleviate the HTC defect in cowpeas.</P. Copyright 2011, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Salvador, BDV 2007, Improvement in the cooking and physico-chemical characteristics of hard-to-cook cowpeas by pre-conditioning and micronization, MSc(Agric) dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-08042008-132413 / > E846/gm / Dissertation (MSc(Agric))--University of Pretoria, 2007. / Food Science / unrestricted

Cowpea (Vigna unguiculata L. Walp) is an important legume mainly used for human consumption worldwide, particularly in developing countries. Cowpea legume is rich in protein (25%), carbohydrates (70%), dietary fibre, minerals and vitamins. Cowpea comprises a range of varieties that breeders release based primarily on agronomic characteristics, such as yield, early maturity and drought tolerance. However, consumers do not always adopt all the released cowpea varieties. Cooking characteristics such as cooking time and sensory properties (i.e. appearance, texture, flavour) of cooked cowpeas are believed to be quality characteristics for legume acceptability by consumers. Physicochemical characteristics are known to influence cooking characteristics of cowpeas. These characteristics may be influenced by seed coat and cotyledon structure. The present study focuses on the effect of seed coat and cotyledon structure on cooking and sensory characteristics of cowpeas and how this in turn influences consumer acceptability of cowpeas. The influence of seed coat thickness and cotyledon compactness on cooking characteristics of four cowpea types (thick seed coat/compact cotyledon (Bechuana White), thick seed coat/porous cotyledon (IT82E 18), thin seed coat/compact cotyledon (Black Eye) and thin seed coat/porous cotyledon (California Black) was studied. Seed coat thickness was found to influence water absorption during soaking. Cowpeas with thin seed coats had higher rates of water absorption during soaking due to its amorphous cell layer that rendered the seed coat more permeable compared to the palisade cell layer found in cowpeas with thick seed coats. Cotyledon compactness influenced cooking time of cowpeas. Cowpeas with porous cotyledons cooked faster compared to cowpeas with compact cotyledon probably because of the structural arrangement of porous cotyledon cells that provide more intercellular spaces for rapid water entry, cell expansion and separation favouring a faster cooking process compared to compact cotyledon. Seed coat and cotyledon structures directly influenced very few of the cooking and sensory characteristics. Sensory attributes such as cooked cowpea flavour, degree of sweetness, degree of sweet aftertaste, and degree of mushiness positively contributed to consumers’ liking of cowpeas. Raw cowpea flavour, bitter taste, degree of bitter aftertaste and degree of firmness contributed to consumers’ disliking of cowpeas. Chemical composition of cowpeas probably influences sensory characteristics of cowpeas more than seed coat and cotyledon structures. It is recommended that breeders work together with food scientists in order to release cowpeas types that are preferred by consumers (i.e. cowpeas with good appearance (low percentage of splitting), good flavour and soft texture upon cooking. Please cite as follows: Penicela, L 2010, The influence of seed coat and cotyledon structure on cooking characteristics of cowpeas, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-06292011-154445/ > E11/438/gm / Dissertation (MSc)--University of Pretoria, 2010. / Food Science / unrestricted

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Master of Agribusiness / Department of Agricultural Economics / Vincent Amanor-Boadu / Beans and cowpeas are considered nutritionally dense and good sources of protein. In this sense, they are considered excellent food in poor households, especially in those that exhibit high levels of malnutrition or under-nutrition. To address food security and nutrition security in poor countries, there has been an increasing interest in encouraging farmers to grow beans and cowpeas. This has spurred research in value chains for these crops in many countries, especially those that do not traditionally grow them as primary staples. Most of these research efforts have focused on the producer and consumer issues, with little or no attention paid to traders who operated between these two players in the value chain. The objective of this study, therefore, is to contribute to the literature on the bean and cowpea value chain research by identifying the factors influencing the participation decisions of traders in this segment of the agricultural economy in Zambia. Using data collected by the Pulse Value Chain Initiative – Zambia in 2011, a probit model was used to analyze data. The dependent variable trader participation in wholesale marketing of beans and cowpeas in Lusaka and its principal food markets. The explanatory variables encompass trader demographic characteristics and available assets or resources. The research explored the effect of the assets or resources on the choice to trade cowpeas or beans at the wholesale level in Lusaka with and without controlling for traders’ demographic characteristics. Three procurement sources are identified in the study: the local market within which the traders operate; producers/suppliers within Lusaka District; and producers/suppliers outside Lusaka District. The results indicate that the procurement source for beans and cowpeas influenced trader decision to operate at the wholesale level. For example, traders who purchased their produce from locations outside Lusaka District were about 37% more likely to participate in wholesale trade compared to those sourcing their produce within the market in which they operate when demographic characteristics of traders are not controlled for in the model. When the demographic factors are controlled, the likelihood of those procuring from outside Lusaka District participating in the wholesale trade declines slightly to about 34%. These coefficients were both statistically significant at the 1 percent level. The results also showed that traders using credit from friends and family were nearly 18% less likely to participate in wholesale trade than those borrowing from other traders, significant at the 5% level. Controlling for demographic characteristics led to a reduction of this likelihood to about 16.7%, significant only at the 10% level. There were no statistical differences between traders for all education levels and those without any education except for respondents with lower primary and lower secondary education. Traders with lower primary and lower secondary education had a 31% higher likelihood of operating at the wholesale level compared to those without any formal education while those with upper secondary education had about 26.7% higher likelihood of operating at the wholesale level compared to those without any formal education. Marital status was not a discriminant in the decision to operate at the wholesale level. However, males had about a 9% higher probability than females in operating at the wholesale level. Wholesalers tend to move larger volumes of produce and, hence, create wealth much quickly than retailers. Wholesalers are also more likely to be engaging processors when these exist in the supply chain. Given that traders sourcing their produce from outside Lusaka District are more likely to engage in wholesale trading, it recommended that further research into the intricate characteristics of these traders are explored. This future research will do well to explore the factors that specifically differentiate these traders from the others. Understanding these and their potential effects could allow policymakers to provide support and services to this class of traders to engage in structured relationships with larger organizations such as processors and exporters.

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