Thesis (MTech (Food Technology))--Cape Peninsula University of Technology, 2018. / The aim of this study was to produce Bambara groundnut (BGN) starch-catechin complex using chemical initiators (ascorbic acid and hydrogen peroxide) and cyclodextrin (alpha and beta) with the view to obtain a functional ingredient for the food industry. BGN starch was successfully extracted from BGN flour through dry milling method, yielding 32% of BGN starch. Native BGN starch was chemically modified using ascorbic acid (1% w/w) and hydrogen peroxide (165% w/w) as redox, biocompatible initiator for grafting catechin to the BGN starch. In addition, cyclodextrin (alpha and beta) were also used as initiators for modifying BGN starch through complexation methods. Complexation methods used included the microwave, co-evaporation and kneading. The characterization of native and modified BGN starches was carried out by performing scanning electron microscopy, powder X-ray diffraction, Fourier Transform Infrared (FTIR) and fluorescence spectroscopy analysis. Functional, thermal and rheological properties of native and modified BGN starches were evaluated. The pasting properties of BGN starches were determined using the Rapid Visco Analyser (RVA). According to the SEM profile, native BGN starch had round, oval and elliptical shapes typical for legume starches. Native BGN starch displayed a typical type-C crystallinity which is common among legumes with strong peaks at 2θ of 15o, 17o and 23o. BGN starches modified through complexation methods had sharper peaks indicating an increase in starch crystallinity; however, following chemical modification there was loss in starch crystallinity which was evidenced by the amorphous region in the chemically modified BGN starches. Structure of native and modified BGN starches was confirmed by FTIR. The FTIR spectra of native BGN starch showed variable peaks at 3285.34 cm-1, 2931.69 cm-1, 1634.36 cm-1, 1336.77 cm-1 which are attributed to OH stretching, C-H stretching, water bending vibrations and C-O stretching, respectively. Furthermore, the FTIR results confirmed that native BGN starch is made up of glucose molecules just like all other starches. All modified BGN starches displayed a new absorption peak at 1020 cm-1 wavelength, thus indicating that starch modification was successful. On the other hand, all BGN starch-catechin complexes displayed a new absorption peak in the range of 1520 -1560 cm-1, attributed to the C-C stretching within the aromatic ring of the catechin. The successful grafting of catechin to BGN starch was also confirmed by the fluorescence spectroscopy results, where all the BGN starch-catechin complexes had an emission peak at 320 nm while native BGN starch had an emission peak at 270 nm. Antioxidant capacity of BGN starch was determined through DPPH and ORAC antioxidant assays. Within the DPPH assay, the antioxidant activity ranged from 2.26 to 38.31 μmol TE/g. The antioxidant activity of modified BGN starch-catechin complexes was significantly (p ≤ 0.05) higher than the ones modified without catechin. On the other hand, within the ORAC assay, the antioxidant activity ranged from 0.07 to 126.71 μmol TE/g. As opposed to the results obtained in DPPH assay, the antioxidant activity of chemically modified BGN starch-catechin complexes was significantly (p ≤ 0.05) higher than that of complexed BGN starch-catechin complexes. Chemical modification significantly increased the swelling capacity of native BGN starch while complexation methods significantly reduced it.

No description available.

No description available.

Groundnut production is vital to the Senegalese agricultural economy, particularly in the Groundnut Basin. However the region is increasingly affected by climate change and associated rising temperatures. This study investigates long-term changes in the frequency of extreme temperatures in the Groundnut Basin and the impact of extreme temperatures on groundnut production. The current economic costs of extreme temperatures on groundnut farmers and potential future additional economic costs associated with climate change are then calculated. The study uses a two-year panel dataset from 1,123 households in the Groundnut Basin and weather data from meteorological stations and the ERA5 climate database. Results identify a significant increasing trend in extreme temperatures across the Groundnut Basin and a negative relationship between extreme temperatures and groundnut yield. This leads to financial losses for farmers, with adaptation strategies such as input level adjustments providing partial mitigation. Future projections indicate further increases in extreme heat degrees days, resulting in significant yield losses by 2050. But the implications of extreme heat also extend beyond agriculture, affecting human habitation and exacerbating societal inequalities. The findings highlight the potential long-term effects of increasing temperatures on agricultural practices in the Groundnut Basin and underscore the need for adaptation and mitigation strategies to cope with the impacts of climate change. / Master of Science / Groundnut production plays an important role in Senegal's agricultural economy, particularly in the Groundnut Basin. However, the region is facing growing challenges due to climate change and rising temperatures. This study examines the long-term changes in extreme temperatures in the Groundnut Basin and their impact on groundnut production. By analyzing data from 1,123 households and temperature records, the study calculates the current economic costs of extreme temperatures on groundnut farmers and predicts potential future costs associated with climate change. The findings reveal a significant increase in extreme temperatures across the Groundnut Basin, which has a negative effect on groundnut yields. As a result, farmers face financial losses. However, they are employing adaptation strategies, such as adjusting input levels, to partially mitigate these losses. In the future, projections indicate that extreme heat will continue to rise, leading to substantial yield losses by 2050. But the implications of these findings also go beyond agriculture, impacting human settlements and exacerbating existing societal inequalities. The study emphasizes the potential long-term consequences of increasing temperatures on groundnut farming in the Groundnut Basin and highlights the urgency of implementing adaptation and mitigation strategies to address the impacts of climate change.

Aflatoxin contamination of crops is frequent in warm regions across the globe, including large areas in sub-Saharan Africa. Crop contamination with these dangerous toxins transcends health, food security, and trade sectors. It cuts across the value chain, affecting farmers, traders, markets, and finally consumers. Diverse fungi within Aspergillus section Flavi contaminate crops with aflatoxins. Within these Aspergillus communities, several genotypes are not capable of producing aflatoxins (atoxigenic). Carefully selected atoxigenic genotypes in biological control (biocontrol) formulations efficiently reduce aflatoxin contamination of crops when applied prior to flowering in the field. This safe and environmentally friendly, effective technology was pioneered in the US, where well over a million acres of susceptible crops are treated annually. The technology has been improved for use in sub-Saharan Africa, where efforts are under way to develop biocontrol products, under the trade name Aflasafe, for 11 African nations. The number of participating nations is expected to increase. In parallel, state of the art technology has been developed for large-scale inexpensive manufacture of Aflasafe products under the conditions present in many African nations. Results to date indicate that all Aflasafe products, registered and under experimental use, reduce aflatoxin concentrations in treated crops by > 80% in comparison to untreated crops in both field and storage conditions. Benefits of aflatoxin biocontrol technologies are discussed along with potential challenges, including climate change, likely to be faced during the scaling-up of Aflasafe products. Lastly, we respond to several apprehensions expressed in the literature about the use of atoxigenic genotypes in biocontrol formulations. These responses relate to the following apprehensions: sorghum as carrier, distribution costs, aflatoxin-conscious markets, efficacy during drought, post-harvest benefits, risk of allergies and/or aspergillosis, influence of Aflasafe on other mycotoxins and on soil microenvironment, dynamics of Aspergillus genotypes, and recombination between atoxigenic and toxigenic genotypes in natural conditions.

The fungi Sclerotinia minor and S. sclerotiorum are the causal agents of two similar diseases of peanut (Arachis hypogaea L.). Both diseases cause significant losses in the Australian peanut industry. Chemical and cultural control methods will not provide complete control. Development of cultivars with resistance to Sclerotinia will be an important component of integrated control. The capacity to breed and select for such resistance efficiently must be established before serious investment of resources is made to develop Sclerotinia resistant cultivars. The aims of this project are: (1) to generate information that will assist in the improvement of Sclerotinia resistance in peanut; (2) to develop screening techniques; (3) to identify Sclerotinia resistant peanut germplasm; (4) to understand the inheritance and estimate heritability of resistance to S. minor; (5) to assess response to selection for resistance; and (6) to test the effectiveness of identified sources of resistance against both S. minor and S. sclerotiorum. Experiments were conducted to develop screening techniques applicable for this project and a full scale breeding program. A previously unpublished technique for evaluating physiological resistance was described and modified. The artificial inoculation technique using colonised bean pod segments was found to be more robust than using colonised agar disks: discriminating among the physiological resistance of peanut genotypes to Sclerotinia whether used in controlled environment cabinets or the simple tent structures, and working well with both whole plants and detached stems. Cultivars and lines with the shortest lesion length in this test have demonstrated resistance to S. minor in field experiments in both Australia and in the USA. The use of a tent structure in place of a controlled environment cabinet (CEC) to create a high humidity environment allowed larger numbers of individuals to be tested at one time. With this technique, glasshouse space and labour costs, rather than the size of the available CECs, are the limits to the number of individuals that can be tested at one time. This will allow mass screening of segregating populations or replicated testing of progenies in a breeding program context that would not be possible with limited CEC facilities. Calculating a Moderated Lesion Length (MLL) by eliminating the failed or very small lesions was found to improve precision in measuring resistance responses of genotypes. Compared to average lesion length, the MLL had a stronger association with foci count (FC), a measure of resistance in the field. In cases where the small lesions do not occur independently of peanut genotype, a small lesion count (SLC) can be used to describe that variation. The detached stem technique examined in this thesis was another useful tool for screening, particularly in situations where seed production by the plants is deemed critical, or where the seed quantity available would not provide sufficient replication for the pot-based glasshouse test. This study has clearly established that material which shows resistance to S. minor in the USA, is resistant to S. minor and quite likely to be resistant to S. sclerotiorum in Australia. The high level of resistance to both S. minor and S. sclerotiorum in germplasm from Texas, particularly TxAG-4, was confirmed. The component lines of Virginia 93 Bunch showed good resistance in the field, which is primarily architectural resistance. Physiological resistance to S. minor was also identified in a cultivar and a landrace from Indonesia and three rust resistant breeding lines from Queensland. All germplasm found to have high physiological resistance to S. minor belonged to the Spanish type. Inheritance of physiological resistance to S. minor was studied using a Generation Means Analysis (GMA) of the cross TxAG-4/VA 861102 and its reciprocal. The broad-sense heritability of physiological resistance on a single plant basis was estimated at 47%, much higher than earlier estimates obtained in field studies. The average gene action of Sclerotinia resistance genes from TxAG-4 was found to be additive. No dominance effects were detected in the GMA. A small but significant reciprocal effect between TxAG-4 and VA 861102 indicated that VA 861102 passed on some physiological resistance maternally. Selection of single F2 and F3 plants successfully achieved an improvement in physiological resistance as measured by MLL. Selection was based on both MLL and seed production and further work should be conducted to quantify the comparative contribution of these two criteria. To estimate a realised heritability of physiological resistance in early generation selection it may be necessary to use a detached stem technique so that seed production occurs independently of expression of disease resistance. Successful selection of highly resistant genotypes from small F2 and F3 populations was taken as a possible indication of oligogenic control of resistance. An experiment was conducted to confirm the value of resistance against both S. minor and S. sclerotiorum. TxAG-4 was found to have physiological resistance to both S. minor and S. sclerotiorum. This resistance was expressed against both Sclerotinia species by progeny that were selected for resistance to S. minor. On the basis of the information obtained, the comparative advantages of three strategies for Sclerotinia resistant cultivar development are described: (1) introduction of germplasm; (2) recurrent backcrossing with screening and crossing in the BCnF1 generation; and (3) pedigree selection. At present introduction and backcrossing are recommended as the preferred strategies. Pedigree selection for Sclerotinia resistance is expected to become increasingly valuable after the development, by introduction and backcrossing, of Sclerotinia resistant cultivars with other desirable

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Food Technology in the Faculty of Applied Sciences at the Cape Peninsula University of Technology / The aim of this study was to evaluate bambara groundnut [BGN] non-starch polysaccharides [NSP] subject to the incorporation into model and food systems with a view to establish their functional and physicochemical properties. BGN insoluble dietary fibre [BGNIF] and soluble dietary fibre [BGNSF] were successfully extracted from four varieties (black-eye: BLE, red: RED, brown: BRN and brown-eye: BRE). Physicochemical properties evaluated revealed the high bulk density of all BGNIF and BGNSF varieties, which could contribute to cost-effective packaging. The microstructures of BGNIFs were irregular in shape with different sizes. The colour parameters (lightness, redness, yellowness, chroma and hue angle) differed significantly [p ≤ 0.05] across all BGNIF and BGNSF varieties; and indicated a yellowish-red colour for BGNIFs and a light yellow colour for BGNSFs. Negligible amounts of condensed tannins [CT] were found in BGNIFs (0.014 – 0.160 mg.g-1). Higher amounts polyphenols [PP] were present in BGNSFs (45.42 – 55.90 mg.g-1 gallic acid equivalents [GAE]) compared to the amount PP in BGNIFs (6.14 – 15.56 mg.g-1 GAE). Major sugars identified were arabinose/galactose, xylose and mannose in BGNIFs, and xylose and mannose in BGNSFs. The functional properties evaluated revealed high swelling capacity of BGNIFs (6.37 – 7.72 ml.g-1) and no significant [p > 0.05] difference in water retention capacity. Fat absorption capacity ranged from 1.38 – 1.52 g oil.g-1 dry weight for BGNIFs and 4.04 – 4.55 g oil.g-1 dry weight for BGNSFs. Variability in BGNIF (91.2%) and BGNSF (79.4%) physicochemical and functional properties could both be explained by two principal components (BGNIF component 1: PP, redness, yield; and component 2: xylose, yellowness and chroma; BGNSF component 1: yellowness, chroma, mannose content; and component 2: redness, fat absorption and fructose content). Following an IV optimal mixture design, an optimum white bread formulation was obtained using 59.5% water, 4.3% yeast and 8.5% BGNIF. Bread enriched with the four BGNIF varieties (BLE, RED, BRN and BRE) were tested for several physicochemical properties. Significant [p ≤ 0.05] differences existed between the control and BGNIF enriched loaves for crumb grain characteristics (including pore area distribution, feret angle, circularity, roundness and aspect ratio). Specific loaf volume of BGNIF enriched loaves ranged from 3.33 – 3.85 ml.g-1 and were significantly [p ≤ 0.05] lower compared to the control bread (4.16 ml.g-1). Favourable texture characteristics obtained with the BGNIF enriched breads were lower hardness, chewiness and gumminess compared to the control loaf. Crust and crumb colour parameters (lightness, redness, yellowness, chroma and hue angle) were significantly [p ≤ 0.05] different across all loaves. BRE BGNIF bread (3.43 ± 0.20) had the significantly [p ≤ 0.05] lowest crumb colour difference compared to the control bread; whilst BRN (1.72 ± 0.42) and BRE (2.44 ± 0.78) loaves had the lowest significant [p ≤ 0.05] crust colour difference compared to the control. Favourable chemical properties were the high total dietary fibre [TDF] (7.14 – 8.33%) content of all BGNIF enriched loaves compared to the control loaf (4.96%). Significant [p ≤ 0.05] differences were also observed for some loaves for moisture content, condensed tannins and polyphenol content. Variability in bread physicochemical properties was differentiated by three components (component 1: bread textural properties; component 2: specific loaf volume and bread lightness; component 3: crumb colour parameters) which accounted for a cumulative variation of 92.8%. All bread loaves were also sensorially acceptable as rated moderately like to like very much (>3 rating on a 5-point hedonic scale) by consumers for all parameters (appearance, crust and crumb colour, aroma, taste, texture and overall acceptability) evaluated. Furthermore, brown BGNSF was tested for stabilising effects in an orange beverage emulsion. BGNSF and orange oil were varied at two levels each based on a 22 augmented factorial design and the effects determined on the equilibrium backscattering [BS] flux as emulsion stability indicator. The BS profiles which resulted from the Turbiscan stability analysis revealed flocculation at low rates as the major destabilisation mechanism. The optimal formulation producing a stable emulsion was identified as low oil (6%) and high BGNSF (30%) concentrations. The objective of this study was therefore achieved and showed that positive physicochemical and functional properties are associated with BGNIF and BGNSF from black-eye, red, brown and brown-eye varieties. Furthermore, the incorporation of BGN fibres in white bread and a beverage emulsion was shown to contribute positive technological properties in these systems.

Bambara groundnut (Vigna subterranea [L.] Verdc.) is an under-utilized indigenous African legume crop which has substantial potential to contribute to food security in sub-Saharan Africa. The crop is well adapted to severe agro-ecologies and grows where other legumes may not survive. The seed is highly nutritious with an ideal balance of carbohydrate (55-72%), protein (18-20%) and fats (6-7% oil), which is particularly beneficial in balancing protein deficiencies in cereals. Also, the seed contains essential and non-essential amino acids of about 33% and 66%, respectively. These attributes make Bambara groundnut an ideal crop to alleviate food insecurity, and to reduce protein malnutrition in rural communities of Africa. However, small-scale farmers grow low-yielding landraces in most production regions in sub-Saharan Africa. Bambara groundnut landraces exist as heterogeneous mixtures of seeds of a few to several seed morpho-types that embrace wide genetic potential for breeding. The objectives of this study were: 1) to determine the production status and constraints associated with Bambara groundnut production in Kano State of Nigeria through the use of a participatory rural appraisal (PRA); 2) to determine the genetic diversity of Bambara groundnut landraces through seed morphology; 3) to assess the inter- and intra-genetic diversity of the Bambara groundnut landraces; 4) to determine the yield and yield component responses among selected Bambara groundnut genotypes, 5) to determine the genomic diversity in Bambara groundnut landraces, using simple sequence repeat (SSR) markers; and 6) to develop a crossing protocol. Using a structured questionnaire, 150 Bambara groundnut farmers were interviewed. The respondents interviewed were male and aged between 36 to 50 years, while Qur’anic education was the most popular among them. Most of the farmers practiced a combination of sole and mixed cropping, and allocated between 0.38 to 1.68 hectares of land to Bambara groundnut growing. They selected Bambara groundnut landraces, especially looking for large seeds that were pure and oval in shape, with a cream seed coat colour and which were early maturing. A total of 27 diverse landraces bearing different names were identified in the hands of the farmers. Most popular among them were Gurjiya, Kurasa, Hawayen-Zaki, Fara Mai-Bargo and Silva. Production was largely for home consumption and for sale on local markets. Common production constraints of the crop were identified as a lack of improved varieties (70.7%), frequent droughts (9.3%), low yield (4%) and limited access to large markets (3.3%). Diverse collections of Bambara groundnut landraces from seven geographic origins were characterized using seed morphology, including seed coat, seed eye colour and pattern, and hilum colour and pattern. Out of 58 original seedlots, a total of 353 different seed morpho-types were further identified. The selected morpho-types- can be used for large-scale production or true-to-type lines could be used in genetic improvement of the crop. Genetic variability within- and between-landraces was investigated among 262 Bambara groundnut landraces, forty nine were studied for agronomic traits, and 213 were investigated for pod and seed variability. Most (47.9%) of the landraces developed pods with a point on one pole, and a round end on the other. Most had a creamy (37.1%) and yellow (76.1%) pod colour, and the pods were usually rough textured, and contained an oval seed. A further 158 landraces were evaluated for leaf morphology where 49.4% had round leaves, while 21.5% had elliptic leaves, with 55.7% of the landraces being heterogeneous, possessing more than one form of leaf shapes. These discrete characters can be utilized for genetic studies and improvement of Bambara groundnut. Single plant selections of 49 Bambara groundnut genotypes were evaluated for yield and yield components using 26 yield and yield related traits. Highly significant variations (P<0.001) were detected among the genotypes for canopy spread, petiole length, weight of biomass, seed weight and seed height. Principal component analysis (PCA) identified nine useful components, where two components, PC1 and PC2, contributed strongly to the total variation, at 19% and 14%, respectively. The PCA revealed that leaf colour at emergence, petiole colour, leaf joint pigmentation and calyx colour were highly correlated with PC1, while seed length, seed width and seed height had strong association with PC2. Both the principal component and cluster analyses showed that most genotypes associated with one another with respect to agronomic and seed yield traits, irrespective of geographical location. The genotypes 211-57, MO9-4 and TV-27 displayed high seed yield performances, while TV-93 and 45-2 had higher biomass production. These genotypes can be used as breeding lines to enhance productivity of Bambara groundnut. Fifty Bambara groundnut genotypes, representing seven geographical regions across Africa, were genotyped using five pre-selected polymorphic simple sequence repeat (SSR) markers developed specifically for Bambara groundnut. The results detected a total of 53 alleles among the 50 Bambara groundnut genotypes, while the neighbor-joining analysis generated seven major genetic groups, which were clustered regardless of their geographic origin. Close relationship were found between 211-68 on one hand and 211-83-2, N211K and M09-3 with 211-68 on the other. Genotypes M02-3, 211-55-1 and 211-57 displayed close similarities. These associations suggested the likelihood that the two pair groups had common origins or may possess similar genes. A preliminary protocol was developed for crossing Bambara groundnut using eight selected parents, using the diallel mating system. Emasculation and crossing of Bambara groundnut was effective when conducted on the same day, with the two procedures being carried out sequentially between 4:30 am and 9:00 am. This protocol generated a number of F1 seeds, with the most success being from crosses between 211-40-1 x N211-2, N212-8 x 211-40-1 and M09-3 x 211-82-1. These F1 seeds can be advanced to confirm whether they are true F1 or selfs. The most important production constraint of Bambara groundnut production is the lack of improved varieties, suggesting that further breeding is needed to enhance productivity. Bambara groundnut landraces need to be sorted using discrete morphological features before breeding for genetic enhancement. The SSR markers used in the study demonstrated their ability to distinguish the existing diversity among the Bambara groundnut genotypes, which could be useful for both germplasm conservation and for breeding. Genotypes that displayed outstanding performance in seed yield and biomass can be used as breeding lines for the genetic improvement of Bambara groundnut. Overall, the study generated valuable and novel Bambara groundnut genetic material, useful in the development of improved cultivars for large-scale production in sub-Saharan Africa. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2014.

Thesis (MTech (Agriculture))--Cape Peninsula University of Technology, 2014. / Plants require nitrogen (N) to support desired production levels. Nitrogen fertilization strategy is a major consideration in field management with regard to achieving both economic and environmental objectives. For instance, in potato, insufficient N supply reduces tuber size and overall yield while excessive N supply can reduce tuber quality and increase environmental risk through nitrate (NO3-) leaching and nitrous oxide emission. Selection of an adequate N fertilizer application rate for crops is difficult, due to marked variations in soil N supply and crop N demand in both the field and over time. This research was conducted to characterise the ammonium transporter gene (AMT1) of Bambara groundnut and potato using molecular biology and bioinformatics methods. Nucleotide database sequences were used to design AMT1-specific primers which were used to amplify and sequence the core-region of the gene from Bambara groundnut and potato. Bioinformatics techniques were used to predict the structure and infer properties of the proteins. Nucleotide sequence alignment and phylogenetic analysis indicate that BgAMT1 and PoAMT1 are indeed from the AMT1 family, due to the clade and high similarity they respectively shared with other plant AMT1 genes. Amino acid sequence alignment showed that BgAMT1 is 92%, 89% and 87% similar to PvAMT1.1, GlycineAMT1 and LjAMT1.1 respectively, while PoAMT1 is 92%, 83% and 76% similar to LeAMT1.1, LjAMT1.1 and LeAMT1.2 respectively. BgAMT1 and PoAMT1 fragments were shown to correspond to the 5th - 10th transmembrane spanning-domains. Mutation of Bg W1A-L and S28A (for BgAMT1) and Po S70A (for PoAMT1) is predicted to enhance ammonium (NH4+) transport activity. Residues Bg D23 (for BgAMT1) and Po D16 (for PoAMT1) must be preserved otherwise NH4+ transport activity is inhibited. In all, BgAMT1 and PoAMT1 play a role in N uptake from the root while BgAMT1 may contribute more in different steps of rhizobia interaction. In an investigation of the correlation between AMT1 gene expression levels and leaf chlorophyll content index (CCI) with plant N status, potato plants were grown in a hydroponic greenhouse with 0.75 or 7.5 mM NO3- and 0.75 or 7.5 mM NH4+ as forms of N supply in a completely randomized design. Leaf CCI as measured by chlorophyll content meter, showed that an increase in N supply results in increased leaf CCI in response to both forms of N. Total RNA was isolated from leaf sampled at 28 days after treatment and expression level of the AMT1 gene was determined by reverse transcription-qPCR using a second set of primers designed for qPCR. The results showed that expression levels of AMT1 increased from 8.731 ± 2.606 when NO3- supply was high to 24.655 ± 2.93 when NO3- supply was low. However, there was no significant response in AMT1 expression levels to changes in NH4+. This result suggested that AMT1 transports NO3- less efficiently than NH4+, and thus more transport channels are required in the cell membrane when NO3- levels are low. Such variation in AMT1 expression levels are not necessary for NH4+ transport since the transport mechanism for NH4+ is efficient even at low NH4+ levels.

Submitted in fulfillment of the academic requirement for the degree Doctor of Philosophy (Ph.D.) in Food Science and Technology, Durban University of Technology, Durban, South Africa, 2017. / Bambara groundnut (Vigna subterranea) is an indigenous underutilised leguminous crop to Africa. It is a good source of protein and carbohydrate including starch. Bambara groundnut is a traditional crop grown mainly for subsistence in Southern Africa. Bambara groundnut has the advantage of being drought tolerant and can thrive in hot temperatures and poor soil conditions. Therefore, it has great potential as an alternative crop to soya bean and peanuts for cultivation and utilisation. Bambara groundnut starch can potentially be used for various industrial applications. However, native starches are not suitable for most industrial applications, hence the need for modification. Bambara groundnut starch has been previously modified using physical and chemical modification methods. Natural alternatives such as the use of lipids are being sought to modify starches due to the associated risk with chemically modified starch. In this research, Bambara groundnut starch was modified with lipids to improve functional properties, utilisation and application. Specifically, the physicochemical properties of native Bambara groundnut starch obtained from five Bambara groundnut genotypes and three landraces (maroon, brown and cream) were determined. Bambara groundnut starch was modified with lipids (palmitic acid, stearic acid, oleic acid, linoleic acid and lysophosphatidylcholine) and the physicochemical properties of the modified starch were investigated. Further, the influence of high-pressure homogenization on complexation of Bambara groundnut starch with lipids was assessed in comparison with maize and potato starches. Lastly, an application of modified Bambara groundnut starch in biofilm production was also studied. Bambara groundnut landraces generally showed higher amylose contents (approx. 33%) than the genotypes (approx. 28%). Differences were observed in the crystalline patterns of these starches. Bambara groundnut genotypes exhibited the C-type-crystallinity, while the landraces showed the unusual A-type pattern. In terms of functionality, landrace starches showed better swelling than the genotypes. Subsequent studies on modification used maroon Bambara groundnut starch since the amylose content was higher than other landraces and there was a consistent supply of the grains during the period of the study. Generally, Bambara groundnut starch showed higher complexing ability with all the lipids than maize and potato reference samples. These differences in complexing ability among the starches could be due to the variation in amylose contents (Bambara groundnut starch: 31.5%, maize: 22.5% and potato: 24.6%). Fatty acids complexed better with Bambara groundnut starch than lysophosphatidylcholine, which could be due to the structural differences in comparison with the lysophosphatidylcholine molecule. The number of fatty acid in the glycerol backbone and the additional steric hindrance of the polar phosphatidic acid group in the lysophosphatidylcholine may have reduced its complexing ability. Among the fatty acids, palmitic acid complexed better than stearic and the unsaturated fatty acids, possibly due to its short chain length compared to other fatty acids. Bambara groundnut starch showed reduced peak and setback viscosities in the presence of stearic acid, linoleic acid and lysophosphatidylcholine, suggesting the formation of V-amylose complex. Bambara groundnut starch pasted with lipids displayed reduced gelling ability compared to their unmodified counterparts. XRD studies of freeze-dried paste revealed peaks at 2Ѳ = 7.4, 12.9 and 19.9o confirming the formation V-amylose complexes in Bambara groundnut starch. Modification of Bambara groundnut starch with lipids resulted in reduced digestibility. High-pressure homogenization significantly increased the complexing ability of Bambara groundnut starch with lipids. Homogenized Bambara groundnut starch-lipid complexes generally exhibited higher complex index than their unhomogenized counterparts. The higher complexing ability could be attributed to the effect of high-pressure which may have enhanced greater dispersion of lipids in the starch-water system. X-ray diffraction studies also revealed the formation of higher complexes as shown by high intensities at peaks (2Ѳ= 7.4, 12.9 and 19.9o) corresponding to V-amylose complexes. Bambara groundnut starch-lipid complexes displayed significantly higher melting temperatures (95.74-103.82oC) compared to native uncomplexed starch (77.32oC). Homogenized Bambara groundnut starch complexes were non-gelling while the unhomogenized types produced weak gels, with G′ ˃ G″ in the range of 0.1- 10 Hz. Complexation of Bambara groundnut starch with lipids using high-pressure homogenization may be employed in the production of modified starch with non-gelling properties and higher thermal stability suitable for certain industrial application, such as fat replacers in mayonnaise, frozen foods and desserts for a better mouth feel. The physicochemical and mechanical properties of biofilm prepared from Bambara groundnut starch modified with stearic acid at varying concentrations of 0, 2, 4, 6, 7 or 10% were further studied. By SEM, Bambara groundnut starch films containing stearic acid (˃ 2%) showed a progressively rough surface compared to those with 2% stearic acid and the control. The addition of 2% stearic acid to Bambara groundnut starch film reduced water vapour permeability by approximately 17%. However, mechanical properties of starch films were generally negatively affected by stearic acid. Bambara groundnut starch film may be modified with 2% stearic acid for improved water vapour permeability and thermal stability with minimal effect on tensile strength. / D