Theses and dissertations (Applied Sciences)

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Characterisation and application of bambara protein-polysaccharide complex coacervates in encapsulation of bioactive compounds
(2019) Busu, Nyasha M.; Amonsou, Eric Oscar
Bambara groundnut (Vigna subterranea) is a leguminous crop that is indigenous to Africa. In South Africa, the legume is cultivated in KZN, Limpopo and Mpumalanga where it is considered a traditional food. Bambara groundnut is a good source of protein (15 – 28 %) and contains substantial amounts of starch. The legume thrives well in areas of low agricultural input. Despite its good protein content, bambara groundnut is mostly cultivated in rural areas for by subsistence farmers. In recent years, there has been increased interest in bambara groundnut protein as an alternative protein source. The purpose of this study is to investigate the complexation behavior of bambara protein with gum Arabic and test the application of the formed complexes in encapsulation and delivery of bioactive compounds. In the first part of this study, four protein fractions extracted at different pH including the salt-solubilisation method were complexed with gum Arabic. The protein content as well as physicochemical properties (SDS-PAGE, FTIR, Zeta potential, SEM) of the protein fractions and resulting bambara protein-gum Arabic (BPI-GA) complexes were then investigated. In subsequent parts of the study, bambara protein extracted by the salt-solubilisation method was complexed with gum Arabic. The influence of ionic strength and biopolymer mixing ratio on complex formation was investigated. Subsequently, the emulsification properties, foaming properties, encapsulation efficiency and release properties of the formed complexes were also investigated under simulated gastric and intestinal pH conditions. The salt-soluble fraction showed the highest protein content (82%) whilst the lowest protein content (76%) was recorded at pH 2. The FTIR analyses revealed an increase in β-sheet content with decrease in pH of extraction. Complexation of the protein fractions with GA resulted in the optimal pHs of interaction shifting towards acidic regions (pHopt: 4.8 to 2.9) as pH of protein extraction became more acidic. Upon complexation, protein fractions produced coacervate yields ranging between 41 - 68%, with the pH 2 fraction recording the lowest (41%) yield. Further, addition of gum arabic seemed to broaden the turbidity profiles. When assessed by SEM, the particles appeared as spherical and aggregated structures between 100-200 nm.
Characterization and application of amadumbe starch nanocrystals in biocomposite films
(2017) Mukurumbira, Agnes R.; Amonsou, Eric Oscar; Mellem, John Jason
Amadumbe (Colocasia Esculenta) commonly known as Taro is an underutilized tuber crop that produces underground corms. It is a promising tropical tuber grown in various parts of the world including South Africa, where it is regarded as a traditional food. It is a significant subsistence crop, mostly cultivated in rural areas and by small scale farmers. Amadumbe is adapted to growing in warm and moist conditions. The tubers are characterised by a high moisture content and consequently high post-harvest losses. The losses can be minimized through the utilization of various preservation techniques such as flour and starch production. Amadumbe corms may contain up to 70-80% starch. The starch granules are characterised by a small size and relatively low amylose content. The combination of high starch content, low amylose and small starch granules thus make amadumbe a potentially good candidate for nanocrystal production. In this study two amadumbe varieties were utilized to extract starch. Amadumbe starch nanocrystals (SNC) were produced using an optimized hydrolysis method. The physicochemical properties (morphology, crystallinity, thermal properties) of the resulting SNC were investigated. The SNC were then applied as fillers in three different matrices namely, amadumbe starch, potato starch and soy protein. The influence of the SNC at varying concentrations (2.5, 5 and 10%) on the physicochemical properties of bio-composite films was examined. Amadumbe starch produced a substantially high yield (25%) of SNCs. The nanocrystals appeared as aggregated as well as individual particles. The individual nanocrystals exhibited a square-like platelet morphology with sizes ranging from 50-100 nm. FTIR revealed high peak intensities corresponding to O-H stretch, C-H stretch and H2O bending vibrations for SNCs compared to their native starch counterparts. Both the native starch and SNC exhibited the A–type crystalline pattern. However, amadumbe SNCs showed a higher degree of crystallinity possibly due to the removal of the armorphous material during acid hydrolysis to produce SNCs. Amadumbe SNC showed slightly reduced melting temperatures compared to their native starches. The SNC presented similar thermal decomposition properties as compared to their native starches. In general, the inclusion of SNCs significantly decreased water vapour permeability (WVP) of composite films whilst thermal stability and tensile strength were increased. The degree of improvement in the physicochemical properties of the films varied with the type of matrix as well as the concentration of the nanocrystals. It generally seemed that the enhancement of the physicochemical properties of starch matrices occurred at a lower SNC concentration in comparison to that of soy protein films. Amadumbe SNC can indeed potentially be used as a filler to improve the properties of biodegradable starch and protein films
Characterization and application of bambara groundnut starch-lipid complexes
(2017) Oyeyinka, Samson Adeoye; Amonsou, Eric Oscar; Singh, Suren
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.
Characterization and modification of Bambara groundnut globulin fractions for the enhancement of functional properties
(2023-05) Alabi, Opeyemi Olaitan; Amonsou, Eric Oscar
There is a growing interest in the utilization of leguminous grain proteins for food and industrial applications. Bambara groundnut is a xerophyte pulse grain and a potential source of protein that can replace soybean protein, a trusted and widely used food ingredient in the food industry. However, the use of Bambara groundnut proteins including the subunits (legumin and vicilin) is limited in food applications. The understanding of the composition of Bambara groundnut proteins at the subunit level is vital to unlocking their potential and facilitating utilization. In this study, Bambara groundnut globulin is characterized in terms of the structures, composition, and physicochemical properties at the subunit level, and then modified using atmospheric plasma and enzymatic hydrolysis. Bambara globulin consisted of about 70% vicilin, whilst legumin protein was found in relatively low quantity. Gel electrophoresis revealed three major protein bands in globulin similar to vicilin with predominant β-sheet structures. The presence of a disulfide bond was also revealed in legumin. Bambara globulin showed major vicilin (7S, Mw: 120 kDa) and minor legumin (11S, Mw: 410 kDa) components. Fluorescence and hydrophobicity data suggested a folded structure for the legumin fraction dominated by the helical secondary structure compared to the vicilin fraction. Bambara proteins contain an appreciable amount of methionine that is even higher than the FAO/WHO recommended value. Bambara vicilin had the highest amount of negatively and positively charged amino acids compared to globulin and legumin. This coincides with its high solubility profile (approximately 82% at pH 3.5). The least gelation concentration (LGC) significantly increased in the order of globulin (8%) < legumin (18%) < vicilin (20%) at pH 7. Bambara groundnut proteins formed weakly structured gels as indicated by the frequencydependent behaviours of both the storage (Gʹ) and loss (Gʺ) moduli with a difference of lesser than 1 log cycle. The highest Gʹ of vicilin gel indicated more firmness of the gel compared to the gel formed by globulin and legumin. The sol-gel transition temperatures increased in the order of globulin (40℃) < legumin (50℃) < vicilin (80℃). The Gʹ and Gʺ of globulin showed relatively low dependency on heating time beyond the gel point compared to legumin and vicilin subfractions, suggesting a more rapid establishment of its gel network during gelation. Vicilin gel consisted of a microporous structure with a small lath sheet-like structure compared to globulin and legumin. Emulsifying stability of the proteins significantly differed (p < 0.05) at pH 7. The foaming capacity of the vicilin fraction was significantly (p < 0.05) higher than that of the storage protein at pH 3, 7, and 9. Atmospheric cold plasma-activated water (PAW) and enzymatic modification of Bambara groundnut globulin were further assessed. The cold plasma treatment resulted in the loss of the helical structure of Bambara globulin. The plasma treatment increased the hydrophobicity of Bambara globulin indicating an unfolded structure that was also reflected in the observed redshift in fluorescence intensity. No major changes were observed in gel electrophoresis, protein surface charge, and solubility profiles, except for about a 20% reduction in the glutamic acid content of the amino acid profile. Bambara globulin had reduced emulsifying capacity after treatment with PAW. However, foaming capacities were significantly better and stable at up to 15 mg protein/mL. Hydrolysates produced from Bambara groundnut globulin and vicilin, respectively using a combination of pepsin and pancreatin were investigated for ACE and renin inhibitory activities. The hydrophobic amino acid residues in both globulin and vicilin hydrolysates are high, improving the entry of their peptides into target organs via hydrophobic associations. Surface hydrophobicity increased significantly (p<0.05) with an increase in peptide size from <1 to <3 kDa with that of vicilin hydrolysate and membrane fractions having the highest values. The low molecular weight peptide (<1 kDa) membrane fractions from globulin at 1 mg/mL exhibited significantly higher (p<0.05) invitro ACE inhibitory activities compared to vicilin hydrolysate and its fractions. However, higher molecular peptide fraction (<3 kDa) favoured renin inhibitory activity at the same concentration. Vicilin is the major protein fraction of Bambara groundnut globulin. Bambara groundnut globulin was stabilized by disulfide linkages from the legumin, a minor fraction of the storage protein. Bambara globulin and its subfractions formed a weakly structured gel with the dominance of an elastic structure. The dominancy of the β-sheet structure in vicilin protein and the high crosslink density of the vicilin gel could be related to the firmness of the vicilin gel. The variations in the gel points of Bambara globulin and the subfractions were linked to the differences in their amino acid and subunit composition, the thermal unfolding properties of the protein fractions, and the presence of disulfide linkages. Modification of Bambara groundnut globulin using cold plasma-activated water treatment and enzymatic hydrolysis, respectively increased the hydrophobicity of the protein and influenced the emulsifying and foaming properties and the invitro angiotensin-converting enzyme (ACE) and renin inhibitory activities. Therefore, Bambara groundnut globulin could be a potential functional ingredient in the food system. The low molecular weight peptide (<1 kDa and <3 kDa) membrane fractions from globulin have the potential to serve as functional bioactive peptides against hypertension.
Composition and functional bioactive properties of bambara groundnut protein and hydrolysates
(2016) Arise, Abimbola Kemisola; Amonsou, Eric Oscar; Ijabadeniyi, Oluwatosin Ademola
Bambara groundnut (Vigna substerranea) is an indigenous legume of African origin which is currently experiencing a low level utilisation. It is tolerant to drought and can grow under poor soil conditions in which other lucrative crops such as groundnut cannot grow. Bambara is a good source of protein comparable to that of cowpea and slightly lower than soya bean. In order to assess the potential use of bambara protein as a functional ingredient in food systems and as an important ingredient for the formulation of therapeutic product, the knowledge of its protein composition, structure and functionality becomes important. The main goal of this thesis was to determine the composition and bioactive properties of bambara protein and its hydrolysates. Specifically, a comparative study was carried out on the protein content, yield and functional properties of protein concentrates prepared from three different bambara landraces using different extraction methods (Salt solubilisation and Acid precipitation). There was no significant difference in protein content, yield and functional properties of the landraces. However, the method of extraction had an influence on their physicochemical and functional properties. Acid precipitation produced bambara protein concentrates with high protein content and yield (79% and 52% respectively) when compared to salt solubilisation (protein content - 57% and yield - 25%). Protein concentrates prepared through salt solubilisation method exhibited better functional properties in terms of water absorption capacity, oil absorption capacity, foaming capacity, foaming stability and emulsion activities when compared to concentrates obtained through acid precipitation. Furthermore, the composition of bambara proteins produced through isoelectric precipitation was determined. SDS PAGE revealed four major bands; a broad band at 55 kDa which was analysed to be vicilin, two medium bands at 62 kDa and 80 kDa and a high molecular weight (HMW) protein at 141 kDa. Further investigation of bambara protein revealed vicilin (55 kDa) with two sub units as the major protein in bambara and this was also confirmed by the proteomic map. The proteomic map revealed acidic amino acids as the major protein of bambara which is characteristic of vicilin, the map also showed that there were differences in the number of spots across the landraces with 77 spots matching each other. Circular dichroism spectroscopy exhibited reductions in α-helix, and β-pleated sheet conformations as pH varies. In addition, the tertiary structures as observed from the near-UV CD spectra were also influenced by shifts in pH conditions. Differential scanning calorimetry thermograms showed two endothermic peaks at around 67 and 81oC respectively. These can be attributed to thermal denaturation of vicilin and the HMW protein. Subsequent studies used isolates from red bambara since the composition of the landraces were similar. Bambara protein isolate was subjected to enzymatic hydrolysis using three proteases (alcalase, pepsin and trypsin) to produce various bambara protein hydrolysates (BPHs). BPHs were investigated for antioxidant and antihypertensive activities. The in vitro structural and functional characteristics of bambara protein and its enzymatic protein hydrolysate revealed that bambara groundnut possessed antioxidant properties against a variety of physiologically relevant free radicals. High surface hydrophobicity and the molecular size of the peptide seem to be important for scavenging of hydroxyl radicals, ferric reducing power and metal chelation. BPHs and peptide fractions were able to scavenge DPPH radicals with greater affinity for smaller size. Less than 1 and 1-3 kDa pepsin fraction was able to scavenge DPPH radical more than glutathione, BPHs and its fractions scavenge ABTS•+ three folds than the isolate. Scavenging of superoxide radicals was generally weak except for 5-10 kDa peptide fractions. All BPHs inhibited linolenic acid oxidation with greater affinity for the lower molecular size peptide. BPHs showed potential antihypertensive properties because of the in vitro inhibition of activities of angiotensin converting enzyme (ACE) and renin inhibition. The molecular size had significant effect on the ACE inhibitory properties with low molecular weight peptide (<1 kDa) fractions exhibiting significantly higher (p<0.05) inhibitory activities. However, enzyme type had synergistic effects on renin inhibition with alcalase hydrolysate showing highest inhibition at 59% when compared to other hydrolysates and their membrane fractions. The fractions with <1 and 1-3 kDa peptides showed a higher potential as antihypertensive and antioxidant peptides. Based on this study, incorporation of bambara protein isolate as an ingredient may be useful for the manufacture of high quality food products. Likewise, the bambara protein hydrolysates, especially the <1 kDa and 1-3 kDa fraction represent a potential source of bioactive peptides in formulating functional foods and nutraceuticals.
The effects of laccase and xanthan gum on the quality of glutten-free amadumbe bread
(2018) Seke, Faith; Kudanga, Tukayi; Amonsou, Eric Oscar
Celiac disease (CD) is an auto-immune disorder that is triggered by the consumption of gluten in predisposed individuals. The only remedy that has been proposed thus far is total exclusion of gluten from the diet. This may be the most difficult task to most celiac disease patients for most of the convenient and widely consumed baked products such as bread are prepared using ingredients that contain gluten. The replacement of gluten in the baking industry comes with some implications on the overall quality of the baked products, especially bread. It has been observed that gluten-free baked products currently on the market are of poor texture, less volume, not visually appealing and have a bad taste. Hence, the need for polymeric substances that can mimic gluten properties, yielding baked products with similar characteristics as the gluten-containing counterparts. Various crops such as rice, sorghum, sweet potato and cassava have been used and additives such as hydrocolloids, protein-based ingredients, emulsifiers and enzymes included to improve gluten-free bread quality. The use of carbohydrate-rich tubers and protein-rich legumes as gluten-free ingredients shows great potential in the food industry. Amadumbe (Colocasia esculenta) is a carbohydrate rich tuber which is highly underutilized in South Africa and contains vast amounts of mucilage, a hydrocolloid which can be of great help to improve dough rheology. Hydrocolloids have been reported in literature to have the ability of improving dough water holding capacity and improving dough viscosity hence facilitating gas retention and impacting on the overall quality of the baked product. However, despite the presence of mucilage, amadumbe is very low in protein and it is difficult to produce bread with properties that resemble gluten-containing bread. Hence the need for protein supplementation which may also potentially facilitate protein cross-linking during bread making. Legume proteins from crops such as soy bean and bambara groundnuts contain abundant quantities of lysine, tyrosine and cysteine which could potentially be manipulated through the use of enzymes such as laccase in order to initiate the formation of a network similar to gluten. The project investigated the effect of laccase and xanthan gum (a hydrocolloid) on the quality of gluten-free bread supplemented with bambara groundnut flour and soy protein isolate as protein sources. Flour blends were prepared using a ratio of 70:30 (amadumbe flour: bambara groundnut flour) and 88:12 (amadumbe flour: soy protein isolate) based on a targeted protein content of 16 g/100 g and the quality properties were determined. Colour analysis showed that amadumbe flour had a higher L* value compared to the other flours and the blends, showing that amadumbe can be used in applications where food colour contributes to food perceptions. However, when bambara groundnut flour and soy protein isolate were added the L* value decreased. The nutritional profile of the individual flours and the blends showed that amadumbe flour protein content was improved with the addition of bambara groundnut flour and soy protein isolate in the above-mentioned ratios. The protein content of amadumbe increased from 2.36 g/100 g to 15.87 g when bambara groundnut flour was added and to 16.10 g/100 g when soy protein isolate was added, values that were close to the targeted protein content. Incorporating bambara groundnut flour and soy protein isolate in amadumbe flour resulted in improved water absorption capacity, foam capacity and stability as well as emulsion capacity and stability of the amadumbe flour. However, there was no significant difference in oil absorption capacity between amadumbe flour and the blends. The blends were then used to formulate different bread samples incorporating the enzyme laccase (25 nkat/g flour) and a hydrocolloid, xanthan gum (1%). Laccase-mediated treatment of gluten-free amadumbe dough resulted in a 30% decrease in the free sulfhydryl groups and a 40% decrease in phenolic content indicating that crosslinking had occurred. Laccase action resulted in a 64% increase in bread specific volume and a 32% decrease in bread crumb hardness. Sensory analysis showed that laccase-treated bread samples were more acceptable compared to the non-treated bread samples in terms of appearance, texture, aroma and taste. The acceptability index varied between 46% and 86.2%. This study showed that there is great potential of laccase in gluten-free bread making. The addition of 1% xanthan gum to amadumbe dough supplemented with bambara groundnut flour and soy protein isolate resulted in gluten-free amadumbe bread with improved crumb texture and specific volume, and decreased the rate of moisture loss. Sensory analysis also revealed that gluten-free amadumbe bread with added xanthan gum was more acceptable compared to the bread samples without xanthan gum. The acceptability index of the bread samples ranged between 40% and 85%. The resulting bread with xanthan gum showed that hydrocolloids such as xanthan gum can be successfully used in the development of gluten-free baked products. Overall, this study has shown that the incorporation of laccase and xanthan gum to gluten-free amadumbe bread results in bread with improved and acceptable bread properties.
Effects of processing on the characteristics of flour and protein isolates produced from Lablab purpureus
(2020) Naiker, Tremayne Sheldon; Mellem, John Jason; Amonsou, Eric Oscar; Baijnath, Himansu
The utilization of legumes by food industries has grown considerably in intermediate forms other than whole grains. Thus, continuous work is focused on modifying legume-based raw materials for improving its techno-functional properties whilst preserving its nutritive value. The study conducted was aimed at analyzing the effects of processing treatments on the characteristics of flour and protein isolates produced from Lablab purpureus (L.) Sweet (hyacinth bean). Flour was produced from legume grains subjected to steaming (S+A) and dehydration (S+A+D) treatments, following soaking (S). Protein isolates were produced from respective flour fractions using isoelectric precipitation. Samples produced from steaming and dehydration was found useful for potential application as functional food ingredients for nutritional intervention. The respective flour samples contained improved resistant starch (23.44 g/100 g dry starch) content. Swelling and solubility indices were found to be greater at lower temperatures mainly attributed to the pre-gelatinization of starch granules. Thus, they may be potentially suitable for ingredient application in texture modified foods. Protein isolates produced displayed traits typical of high-quality proteins and demonstrated exceptional functionality. The rapid increase in predicted biological values observed suggested improved protein digestibility potential. Samples contained significant concentrations of branched chain and aromatic amino acids highlighting potential health benefits. Protein nanoparticles were produced using Ca2+-induced aggregation (0.00-6.50 mM) from hyacinth bean protein isolate (2% m/v, pH 7). This was to examine its potential for development as food- grade Pickering emulsion stabilizers. Protein solutions containing high Ca2+ concentrations resulted in higher dynamic viscosities (mPa.s). Protein nanoparticles (~172.38 nm) were formed at 3.50 mM Ca2+. The z-average diameter of aggregates was dependent on Ca2+ concentration. Results satisfied certain criteria for nanoparticles to potentially function as Pickering stabilizers. However, nanoparticles were susceptible to 4 M Urea and emulsion creaming became more apparent as storage progressed. The study conducted provides valuable information on how processing could be useful for obtaining value-added legume grain ingredients for potential food applications. Such approach could diversify the use of hyacinth bean and help improve the competitiveness of the legume grain sector.
Enzymatic modification of amadumbe flour for gluten-free applications
(2018) Manhivi, Vimbainashe Edina; Kudanga, Tukayi; Amonsou, Eric Oscar
The production of gluten-free bread from gluten-free flours remains a technological challenge. Different strategies have been employed to improve the dough rheological properties. Enzymatic modification of the proteins in dough may result in polymers that mimic gluten. In this study gluten-free amadumbe flour was modified using single and optimised multiple crosslinking enzyme systems for the improvement of rheological properties and bread quality. Specifically, compositional, rheological and thermal properties of amadumbe and cactus mucilages were investigated as potential hydrocolloids and as substrates for crosslinking enzymes in gluten-free bread production. The effects of laccase, tyrosinase and transglutaminase on amadumbe dough rheology were also investigated. Model reactions were used to demonstrate the different enzymatic reactions occurring in amadumbe dough treated with the crosslinking enzymes. The combination of enzymes was then optimised using response surface methodology (RSM), to produce dough with improved G’ and G”. Xanthan gum, amadumbe mucilage or cactus mucilage were then added to the dough with an optimum enzyme combination. The effect of these enzymes and hydrocolloids were studied on the bread properties. The mucilages had a similar composition of monosaccharides and amino acids, except for the absence of rhamnose in amadumbe mucilage. Cactus mucilage showed a pseudoplastic flow behaviour whilst amadumbe mucilage showed a Newtonian flow behaviour at up to 5% (w/v) concentrations. The mucilages contained phenolics and amino acids such as lysine, tyrosine and glutamine, which are potential enzyme substrates. Trametes versicolor laccase catalysed the crosslinking of phenolics and thiols producing a wide range of crosslinking products which included homo- and hetero-conjugates, as demonstrated by mass spectroscopy. Thiol and total phenolic contents of dough decreased by up to 28% and 93%, respectively, as laccase activity was increased (0-3 U/g flour), confirming crosslinking reactions. Laccase-catalysed modification of amadumbe dough increased dough viscoelasticity, as shown by the increase in G’ and G”. Tan δ decreased with increase in laccase activity indicating an increase in the elastic character of the dough. Tyrosinase oxidation resulted in a 7.7 – 39.4% decrease in dough free amine and a 16.8 – 46.3% decrease in the dough thiol content as activity was increased (0-80 U/g flour). Transglutaminase treatment decreased the dough free amino groups by 10 – 38.1% as activity was increased from 0 to 2 U/g flour. An increase in dough G’ and G”, showed that both transglutaminase and tyrosinase improved dough viscoelasticity. Evidence of transglutaminase and tyrosinase crosslinking was provided by relevant model reactions monitored by mass spectrometry. Reaction model data showed the formation of the glutamyl-lysine bond due to transglutaminase crosslinking, whilst tyrosinase crosslinking resulted in disulphide and dityrosine bond formation. The viscosity and elasticity of amadumbe dough containing soy protein were optimised using a central composite design and the enzyme combination resulting in maximum G’ and G”, and minimum Tan δ was selected and verified. The predicted optimal enzyme activities (LAC, 1.78 U/g flour), (TYR, 79 U/g flour) and TG, 1.97 U/g flour) resulted in amadumbe dough that had a higher G’ and G”, as well as bread with a higher specific volume and lower crumb hardness compared to the dough without enzymes or with a single enzyme system. Addition of cactus and or amadumbe mucilage to the dough containing the optimum enzyme combination further improved dough viscoelasticity, improved bread specific volume, and significantly (p < 0.05) reduced bake loss and crumb moisture loss. The better bread was produced from dough with an optimum enzyme combination and 2% cactus mucilage. Sensory evaluation revealed that enzymes and cactus mucilage improved bread texture, appearance and overall acceptability but did not significantly affect bread aroma and taste. Overall, the combined effect of multiple enzyme-catalysed modification of gluten-free amadumbe flour and amendment with hydrocolloid resulted in more acceptable bread quality than single enzyme systems or unmodified flour. Therefore the optimised combination of enzymes have potential for application in gluten-free bread production.
Enzymatic modification of Bambara groudnut protein for the production of hydrogels
(2021) Ruzengwe, Faith Matiza; Kudanga, Tukayi; Amonsou, Eric Oscar
Natural polymer-based, especially plant protein hydrogels have recently been gaining attention because of their biodegradability and biocompatibility. Bambara groundnut is a potential source of protein in hydrogel production. However, the use of Bambara groundnut protein in such applications is limited because it is associated with the formation of inadequate crosslinks between polymer chains. Enzymatic treatment can potentially be used for improving the strength of Bambara groundnut protein hydrogel. In this study, the effect of laccase and transglutaminase (separately and in combination) on the microstructural, structural, rheological and mechanical properties of Bambara groundnut protein hydrogels was investigated for potential application in encapsulation and release of bioactive compounds. In the first part of this study, the effect of pH and NaCl concentration on the rheological and microstructural properties of Bambara groundnut protein gels were optimised using response surface methodology (RSM) to determine ideal starting conditions before enzymatic treatment. The effect of using crosslinking enzymes (transglutaminase and laccase) on the textural, rheological, structural and microstructural properties of Bambara groundnut protein hydrogels were then investigated. Since the effectiveness of enzymatic processes may be limited by using single enzymes, the use of a combination of enzymes was also investigated for the first time in gelation and optimised using RSM. Subsequently, encapsulation efficiency and release properties of the enzymatically crosslinked Bambara groundnut protein hydrogel were investigated using riboflavin as a model bioactive compound. The heat induced Bambara groundnut protein isolate (BPI) gels optimised for pH and NaCl prior to enzymatic treatment showed G’> G’’ over a frequency range of 0-100 rad s-1 . Although BPI gels displayed the characteristics of weak gels, slightly acidic conditions (pH 6) coupled with low NaCI concentration (0.5 M) promoted the formation of more rigid gels. These gels had the lowest water holding capacity and thiol content, suggesting the participation of disulphide linkages during network formation. Their microscopy images showed that the network was composed of porous homogeneous aggregates. Amino acid analysis showed that Bambara groundnut protein contains substantial amounts of amino acids including lysine, glutamic acid, cysteine and tyrosine with potential active sites for transglutaminase and laccase action. Laccase modification of Bambara groundnut protein caused a decrease in the gelation point temperature from approximately 85°C in the absence of laccase to 29°C at an activity of 3 U/g protein. Laccase treated samples showed a sharp increase in the G’ and G” values during the heating ramp as well as a wider gap between the moduli suggesting the formation of a more established network structure. The difference between G’ and G” increased to approximately 1 log and the dependency on angular frequency reduced suggesting improvement in the strength of the formed gels. Bambara groundnut protein crosslinking by laccase, was demonstrated by the decrease in thiol and phenolic content and crosslinking of amino acids (glutathione, cysteine and lysine) in model reactions. Microscopy images of the gel showed an increase in homogeneity and compactness of the lath sheet-like structure with increase in laccase activity up to 2 U/g protein. Transglutaminase crosslinking at 15 U/g protein resulted in the formation of hydrogels with well-organised network structures and small pores. Gel strength improved as observed from the highest G’ (6947 Pa) and hardness (5.60 N) recorded upon use of this activity. Transglutaminase-mediated crosslinking of BPI hydrogel was demonstrated by the reduction in amine and thiol groups and the formation of a new protein band (56 kDa) in crosslinked hydrogels. The combined use of transglutaminase and laccase showed a G’ > 10G” over a frequency range of 0 – 100 rad/s suggesting the dominance of the elastic behaviour. BPI hydrogel with the highest hardness (15.96 N) and encapsulation efficiency (98.8%) was formed at 15 and 0.5 U/g protein of transglutaminase and laccase activities, respectively. The lowest swelling capacity recorded in this hydrogel contributed to the lowest release kinetic constants in both simulated gastric fluid (0.51) and simulated intestinal fluid (0.73) in the presence of digestive enzymes which indicated that riboflavin release was due to diffusion and swelling. Overall, modification of Bambara groundnut protein using a combination of crosslinking enzymes increased the crosslinking density and promoted the formation of strong hydrogels. The hydrogels effectively encapsulated and prevented the early release of a heat sensitive compound (riboflavin) in the stomach while making it available in the small intestines. Therefore, the optimised enzyme combination of laccase and transglutaminase is a potential strategy for application in Bambara groundnut protein gelation.
Evaluation of toxicity and biochemical characterisation of a microalgal diatom
(2023-05) Beekrum, Lamees; Amonsou, Eric Oscar; Odhav, Bharti; Lalloo, Raj
One ofthe critical challengesthat we face in the 21st century isthe need to feed an ever-increasing human population with increasingly limited natural resources. Microalgae have emerged as a potentialsolution for global food security as a sustainable biological food source for humans due to their nutrient-rich composition, particularly rich protein and bioactive compoundsthat provide potential benefits for human health. By establishing microalgae as a new food platform, we can increase the supply of these essential productsto address global demandsin a more efficient and environmentally sustainable way. These under-exploited organisms have been consumed in the human diet for thousands of years. Microalgae cultivation does not compete with land and resources required for traditional crops and has a superior yield compared to terrestrial crops. Diatoms are a major group of microalgae in the phytoplankton community and have the potential to be engineered into cell factoriesforthe sustainable production of bioactive compoundsin food and nutraceutical industries. This study aimed to characterise a rapidly growing marine diatom in terms of its toxicity and biochemical profile. This was done by evaluating the safety profile and biochemical composition, characterising the soluble protein, and investigating the carbohydrate profile with specific emphasis of β-glucan and its effect of cardioprotective properties on ferric-induced oxidative cardiac injury in a rat model. Based on Basic Local Alignment Search Tool (BLAST) analysis, the strain showed the closest similarity to Amphora sp. (JF834543.1) with 99.5% and istherefore represented as Amphora sp., accession number MW721231. The bacterial reverse mutation assay found no evidence of mutagenicity on the methanolic, aqueous, and hexane extracts of Amphora sp. and was found to exert low levels of cytotoxicity against Peripheral Blood Mononuclear Cells (PBMC). A 28- day acute oral toxicity assessment on male Wistar rats showed an absence of adverse effects and mortality in the rats. The biomass exhibited a low lipid profile, modest protein content, notable amino acid content, and excellent carbohydrate and mineral content. Results of this study for antioxidant assays displayed low to moderate activities. Protein extracted using three-phase partitioning (TPP) treatment showed that the protein concentration and total amino acid content were substantially higher in the protein-enriched biomass extract when compared to the dried biomass. The solubility of the protein-enriched biomass extract increased with the increase in pH within the range of pH 2 to pH 12. The biomass consisted of a simple monosaccharide profile comprising glucose, rhamnose, and mannose, and a β-glucan content of approximately 9%. The cardioprotective properties ofthe β-glucan extract on ferric-induced oxidative cardiac injury did not improve the glutathione (GSH) level significantly, it led to increased superoxide dismutase (SOD) and catalase activities, while depleting malondialdehyde (MDA), NO (nitric oxide), low-density lipoprotein cholesterol levels, and simultaneously elevating triglycerides and high-density lipoprotein (LDL) cholesterol levels. GC-MS analysis revealed a complete depletion of the lipid metabolites. Our results advocate the protective capabilities of the β-glucan extract against ferric-induced oxidative cardiac injury as portrayed by its ability to stall oxidative stress and modulate cardiac lipid metabolism while inhibiting the acetylcholinesterase and lipase activities. These results display that the β-glucan extract could be utilized as an alternative for the development of nutraceuticals for maintaining cardiac health. The diversity of food bioactive molecules obtained from microalgae makes these microorganisms a bioresource with full potential of exploitation in the food industry. The richness of compounds in microalgae can contribute to develop an algal-based food industry, focusing on producing and utilizing microalgae for innovative functional food products. Overall, this study demonstrated the potential utilization of the diatom, Amphora sp. as a potential ingredient and nutraceutical in foods.
Influence of growth locations on physicochemical properties of starch and flour from amadumbe (Colocasia esculenta) genotypes
(2017) Mawoyo, Bruce; Amonsou, Eric Oscar; Gerrano, Abe S.
Amadumbe commonly, known as taro is a traditionally underutilised tuber crop in Southern Africa. Nutritionally, amadumbe corms contain appreciable levels of carbohydrate mainly in the form of starch which is resistant to digestion. It also contains mucilage, a soluble fibre, which is good for the human digestive health. Thus, amadumbe starch and mucilage can be used as functional ingredients in food formulations. The aim of this research was to investigate the effects of genotypes and growth location on the physicochemical properties of amadumbe flour and starch. Eighteen (18) amadumbe genotypes grown in Roodeplaat, Gauteng and Umbumbulu, Kwazulu-Natal, South Africa, were studied. Roodeplaat received a lower annual average rainfall (514 mm) and high environmental temperature (24oC) compared to Umbumbulu (828 mm, 19oC) during the cropping season. Specifically, the influence of growth location and genotypes on the chemical composition (proximate composition and mineral contents) as well as the functional properties of amadumbe flours were investigated. Furthermore, starch was extracted and its physicochemical and functional properties were also studied. The carbohydrate contents (73-81%) of amadumbe flours were substantially high and varied with growth location. Mucilage contents (6-9%) were very low across genotypes in both locations. Water absorption and oil absorption capacities positively correlated to carbohydrates and mucilage in the flour irrespective of growth locations. Swelling power and solubility index was influenced by the amylose content of the flour. Genotype and growth location significantly affected the pasting properties of amadumbe flour. The pasting temperature was very high (approx. 90oC) across genotypes in both locations, while peak viscosity differed significantly (54-242 RVU) for genotypes grown in different environments. The amylose contents (0-14.4%) of amadumbe starches were low and varied significantly with growth location and among genotypes. Three genotypes, G2, G20, and G21 grown in Roodeplaat lacked amylose. Amadumbe starches showed reflective peaks at 2θ=15o and doublet at 17o, 18o and 24o typical of A-type starches. Amadumbe genotypes had small sized (1-5 µm) and polygonal starch granules. Functional properties including water absorption, swelling power, gelatinisation temperature and peak viscosity significantly positively correlated with amylose content. These findings further suggest that water availability could have a major effect on starch synthesis as the two locations received a different amount of rainfall during the growing season. Findings from this study are important for future improvement programmes and selection of appropriate genotypes for industrial production or food application of amadumbe flour and starch.
The prebiotic effects of amadumbe (Colocasia Esculenta) and okra (Abelmoschus esculentus) mucilage
(2023) Gajadhar, Sharmista; Amonsou, Eric Oscar; Mchunu, Nokuthula Peace
Prebiotics have been shown to aid in the improvement and maintenance of human health through positive manipulation of gut microbiota. Diet-induced changes in gut microbial diversity has been recognized as a factor which contributes to the rising epidemics of chronic illnesses in both developed and developing countries. Traditional crops, amadumbe (Colocasia esculenta) and okra (Abelmoschus esculentus (L.) Moench) offer nutritional security to many communities in South Africa. These crops are rich in mucilage and are presumed prebiotics. Structural composition and functional properties of polysaccharides like mucilage are suggested to influence their fermentability by gut microbiota and potential health effects. The purpose of this study was to investigate the prebiotic effects of amadumbe and okra mucilages for potential application as dietary supplements. Mucilage was extracted from amadumbe and okra by cold water extraction. Purified mucilage was obtained by Sevag method, lipid removal and thereafter dialyzed. The composition and structure of crude and purified mucilage were analyzed using Fourier transform infrared spectroscopy (FT-IR), size exclusion chromatography (SEC) and high pressure liquid chromatography (HPLC). Functional properties including water and oil holding capacity, swelling and solubility were determined. The prebiotic potential of amadumbe and okra mucilage was carried out by in- vitro fermentation using human faecal sample. Glucose was the common monosaccharide present in both amadumbe and okra mucilage. Monosaccharides present in amadumbe mucilage were arabinose, mannose and xylose, while galactose, ribose and rhamnose were the main monosaccharides present in okra mucilage. The presence of β-glucan was found to be higher 0.20 g/100 g in amadumbe mucilage than in okra mucilage 0.07 g/100 g. The resistant starch content in amadumbe mucilage was higher 4 g/100 g than in okra mucilage 0.7 g/100 g. Asparagine, proline, glutamine, and threonine were the most common amino acids found in both amadumbe and okra mucilage samples. Purified amadumbe and okra mucilage displayed the same characteristic peaks as crude amadumbe and okra mucilage in the FT-IR spectrum but at a lower intensity suggesting that purification contributed to a more stable and uniform structure. The FT-IR spectrum indicated the presence of uronic acid and hydroxyl groups which confirm the existence of carbohydrate in both amadumbe and okra mucilage. The molecular weight of crude amadumbe and okra mucilages ranged between 219 and 224 kDa while molecular weight of purified amadumbe and okra mucilage ranged between 220 and 244 kDa. The purification process was seen to improve functional properties such as the water holding capacity, swelling and solubility of mucilages. In comparison to okra mucilage, crude and purified amadumbe mucilage showed low water holding capacity 5 and 9 g/100 g and high percentage solubility 61 and 73%. Amadumbe mucilage had a slightly higher oil holding capacity 11 g/100 g in comparison to okra mucilage 10 g/100 g. During in-vitro fermentation, inulin (positive control) rapidly decreased the pH of the fermentation medium from 7.0 to 6.5, in comparison to amadumbe (7.0 to 6.7) and okra (7.0 to 6.8) mucilage. At the end of fermentation inulin had maximum gas production of 233.19 mL, followed by amadumbe mucilage 158.98 mL and okra mucilage 113.98 mL. These results suggest inulin is more easily fermented by microbes compared to amadumbe and okra mucilage. Gut microbiota analysis at phylum level showed that amadumbe mucilage stimulated the proliferation of Actinobacteria and reduced the presence of Firmicutes in comparison to okra mucilage. At species level, okra mucilage promoted the growth of Bacteroidaceae bacteroidetes, Bacteroides ovatus and Bacteroides uniformis. These species are known to assist in protection of the gut and are capable of providing nutrients to other microbial species. This suggest that amadumbe and okra mucilages are fermented differently by gut microbiota possibly due to differences in their structure and composition. This study concluded that amadumbe and okra mucilages has potential to be utilized as an emerging prebiotic in food applications or as supplements.
Production process improvement and characterization of starch nanocrystals
(2023-05) Nzama, Nkosingiphile Lucky; Amonsou, Eric Oscar
Starch nanocrystals (SNCs) are promising biomaterials for novel applications in foods, cosmetics, and medicine. In general, acid hydrolysis below the gelatinization temperature of starch is the most common method used for nanocrystals production. Major drawbacks associated with this method are the extended hydrolysis time required (up to 5 days) and the low yield (4–15%) of SNCs. Different methods, including physical and enzymatic pretreatments of starch prior to acid hydrolysis, have been investigated. Among these methods, enzymatic hydrolysis can be regarded as a promising and green strategy for the creation of pores in starch to enhance acid diffusion into the inner regions during SNCs fabrication. Debranching enzymes such as pullulanase are gaining attention in the food industry due to their ability to modify the starch structure and properties through selective hydrolysis of the branched chain of α-1,6-glycosidic bonds. However, pullulanase has not yet been applied as a pretreatment method aiming at starch nanocrystal preparation. Therefore, the pretreatment of starch granules with pullulanase and β-amylase (i.e., to hydrolyze the linear α-1,4-linkages) concurrently could be a novel technique to modify starch surfaces for faster production of SNCs and improved yield. To improve the efficiency of starch nanocrystals production and properties, pullulanase (15 U/g starch) was used alone or together with β-amylase (50 and 100 U/g starch) to modify the starch before acid hydrolysis. The compound enzyme system of pullulanase:β-amylase (15 : 50 U/g starch) had the most pronounced effect on starch morphology compared to a single enzyme system by creating a dense and more porous structure on starch surfaces as evidenced by microscopy images, a high degree of oil absorption and extent of hydrolysis data. Nanocrystals were produced after 3 days with modified starches instead of 5 days. The yield of SNC was approx. 25 wt.%, which is 3 times greater than that of the conventional SNC preparation method. SNC derived from the modified starches were small in size (less than 50 nm) and appeared mostly as platelet and isolated round particle aggregates. Nanocrystals from modified starches showed the A-type crystalline structure similar to the native starch, but with a significant increase in the degree of crystallinity (from 32.85% to 45.28%.), and the short-range molecular order during the early stage of acid hydrolysis. Starch hydrolysis using compound enzymes consisting of pullulanase and βamylase hydrolysis seems to be the most effective and green to produce SNC in a shorter time and with increased yield and enhanced properties. SNCs were incorporated in different concentrations (0, 5, 10, 15, and 20 wt.% starch) together with stearic acid to improve cassava starch-based nanocomposite film properties using a solution casting method. The addition of SNCs from 5 to 15% in combined with stearic acid into starchbased nanocomposite films presented better water resistance, water vapor permeability, and tensile strength than native cassava starch film. Conversely, beyond 15% SNC content, nanocrystals seem to aggregate which impaired the tensile strength of the nanocomposite films. The surfaces of the nanocomposite films were relatively smooth and homogenous after the addition of nanocrystals at up to 15 wt.% concentration compared to native starch film as demonstrated by the atomic force microscopy (AFM). Furthermore, the opaqueness of the nanocomposite films progressively increased with the SNC content, which might be beneficial in the packaging of foods that are easily degraded when exposed to light and high moisture. XRD analysis revealed sharp peaks at approximately 2θ of 13.5° and 20.3°, which are characteristics of typical V-type crystalline pattern in starch films prepared with added steric acid. This further indicates the formation of amyloselipid complexes in films. The inclusion of SNC in films also enhanced their thermal stability. Therefore, the combined effect of SNC at different concentrations and stearic acid into cassava starch-based films was a successful approach to further improve the mechanical reinforcement and barrier properties of nanocomposite films.
Quality and storage stability of provitamin A biofortified amahewu, a non-alcoholic cereal beverage
(2015) Awobusuyi, Temitope Deborah; Amonsou, Eric Oscar; Siwela, Muthulisi; Ijabadeniyi, Oluwatosin Ademola
Vitamin A deficiency (VAD) is a major health problem in sub-Saharan Africa where maize is a staple food. Amahewu, a fermented non-alcoholic,maize-based beverage is a popular drink in southern Africa.The aim of this study is to produce a provitamin A enriched and acceptable amahewu, using provitamin A biofortified maize which can be used to alleviate VAD. The optimal processing parameters for the production of amahewu using provitamin A-biofortified maize were determined. Amahewu samples were prepared with reference to a traditional method by boiling a mixture of maize meal and water (rato:1:7) at 90ᴼC, with occasional stirring, for 15 minutes. The resulting porridge was left to cool to approximately 40ᴼC, before inoculation and fermentation at 37oC. Processing parameters investigated were inoculum types (wheat bran (WB), maize malt (MM) and Lactobacillus mixed starter culture) and inoculum concentration (0.5,1 and 2% (w/w)) and varieties of provitamin A maize (PVAH 62 and PVAH 19). Wheat flour (at 2%) was used as reference inoculum to conform to the traditional practice. White maize amahewu samples processed in the same way as those of provitamin A-biofortified maize were used as references. Provitamin A amahewu samples were produced using the optimized processing parameters and then analysed for nutrient composition, including carotenoids, protein, ash, amino acids, mineral profile and invitro protein digestibility. The consumer acceptability of amahewu samples was evaluated using regular consumers of amahewu (n= 54), who rated the acceptability of the samples on a 9-point hedonic scale (1:disliked extremely, 9:liked extremely). The storage stability of the provitamin A biofortified amahewu samples was assessed by subjecting the samples to different storage conditions: 4ᴼC, 25ᴼC and 37ᴼC. The microbiological quality of the stored samples was monitored by taking samples every day for a period of five days to analyse for the presence of aerobic and anaerobic bacterial spore formers, E.coli and moulds. The provitamin A maize variety did not influence pH and Total titratable acidity (TTA) of amahewu samples during fermentation. As expected, there was a substantial drop in pH with fermentation time. After 24 hours, all the samples of amahewu, including those made with white maize, prepared using malted maize and wheat bran inocula reached a pH of 3.3-3.8 and TTA of 0.3-0.6, which were within acceptable range for amahewu. The addition of a starter culture substantially reduced fermentation time, from 24 to six hours. The inoculum of WB and MM, respectively, at a concentration of 0.5%, with or without starter culture (5%), were found to be suitable for the production of amahewu using provitamin A biofortified maize. The total provitamin A content of amahewu samples, produced using optimised parameters (i.e one variety of provitamin A biofortified maize, 0.5% MM, WB with or without starter culture), ranged from 3.3-3.8 μg/g (DW). The percentage retention of total provitamin A ranged from 79%- 90% (DW). The lowest percentage retention was observed in products fermented with the addition of starter culture. The gross energy of the amahewu samples was approx. 20 MJ/kg. There was a slight increase in the lysine content of amahewu after fermentation. The protein digestibility (approx. 91%) of amahewu samples was slightly higher than that of raw provitamin A maize (86%). Amahewu processed using starter cultures had a slightly higher iron content than those processed without a starter culture. Consumer acceptability data showed that amahewu samples made with provitamin A biofortified maize were slightly more acceptable (average rating for overall acceptability was 7.0 ± 1.2), compared to those made with white maize (average rating for overall acceptability was 6.4 ± 0.8). Principal component analysis (PCA) of Amahewu sensory data showed that 71% of variation was due to maize types and 18% of variation may be due to the inoculum used during fermentation. The use of a starter culture improves the taste and aroma acceptability of amahewu. Segmentation of consumers based on overall linking for amahewu revealed three clusters, named A, B and C. Cluster A consisted of most consumers (43%), who liked amahewu moderately. About 60% of these consumers were females. Cluster B consisted of most of the consumers (31%) who were undecided about their liking for the product. Approximately 52% of the consumers in this cluster were female. Cluster C consisted of consumers (26%) who liked amahewu very much. Sixty-four percent (64%) of these consumers were female. It appeared that gender may have some influence on overall liking for amahewu, as cluster B, consisting of undecided consumers, had more male consumers compared to clusters A and C. Age did not seem to be significantly associated with the liking of amahewu. Provitamin A biofortified amahewu samples stored under refrigerated conditions (4ᴼC) had better microbiological quality compared to those stored at 25ᴼC and 37ᴼC. Refrigeration effectively maintains the microbiological quality of amahewu for about three of days. Provitamin A biofortified maize can be used to produce β-carotene enriched amahewu that is acceptable to consumers following the processing method that is traditionally employed for white amahewu at both domestic and commercial level. Provitamin A biofortified amahewu has the potential to make a significant contribution towards alleviating VAD among rural communities, who are the most vulnerable to VAD.