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Characterisation and quantification of microstructure, physicochemical and functional properties of oven and forced convection continuous tumble roasted cereal grains
No full textThe use of roasted cereal grains in foods can improve organoleptic properties, enhance shelf life,
ease incorporation into ready-to-eat products and increase antioxidant activity. Structural,
physicochemical and functional changes will inevitably occur during roasting and this study aimed
to investigate these properties. X-ray micro-computed tomography (μCT) was used as a nondestructive
technique for characterising and quantifying microstructural changes in individual
cereal grains induced by conventional oven and forced convection continuous tumble (FCCT)
roasting at 180°C for 140 s. X-ray μCT uses differences in X-ray attenuation arising from
differences in density within a sample.
X-ray tomograms of the raw and roasted wheat and maize kernels were obtained, using a
General Electric Phoenix model V|Tome|X L240 X-ray μCT system with a source voltage of 60 kV
and an electron current set at 240 μA. Analysis of the whole kernel and regions-of-interest (ROIs)
was performed with VGStudio Max 2.2 three-dimensional (3D) software. Qualitative results were
depicted as two-dimensional (2D) transmission images and 3D volumes. Internal structural
changes were observed as a loss of endosperm integrity, detected as a decrease in attenuation.
For both cereal grains oven roasting was associated with a larger increase in kernel volume
(wheat=4.47%; maize=10.76%) than FCCT roasting (wheat=1.57%; maize=3.41%), as well as
larger relative density decreases (wheat=2.76%; maize=6.33%) in comparison to FCCT roasting
(wheat=0.55%; maize=1.92%). During FCCT roasting the material density (excluding air) remained
unaffected.
Structural changes can strongly influence physicochemical and functional properties. Kernel
hardness and hectolitre mass (HLM) can be helpful to assess the milling yield, which was not
affected (P>0.05) by either roasting methods. Scanning electron microscopy (SEM) illustrated the
starch-protein morphology, where both roasting methods resulted in a partially disintegrated
protein network and swollen and/or ruptured starch granules in the oven-roasted samples.
Quantification of these structural differences included crystallinity determinations using X-ray
diffraction (XRD), thermal properties using differential scanning calorimetry (DSC) and pasting
properties employing a Rapid Visco Analyser (RVA). The reduction in crystallinity for both FCCT
(wheat=0.12%; maize=0.45%) and oven (wheat=0.16%; maize=1.83%) roasting was consistent
with the decrease in gelatinisation enthalpy (ΔH). Only partial gelatinisation occurred in both the
oven (wheat=17.16%; maize=25.27%) and FCCT-roasted (wheat=10.14%; maize=16.23%)
samples.
Oven roasting caused more adverse changes in most of the measured properties, being a
more destructive process. With FCCT roasting the samples are continuously moving, resulting in
an even heat transfer in comparison to oven roasting where the samples are stationary. FCCT
roasting maintained more of the favourable characteristics, i.e. microstructure, hardness and
milling yield and will thus result in a more acceptable final product.
This study demonstrated the capability of X-ray μCT in combination with image analysis as a
non-invasive technique to study microstructural changes in cereal grains, induced by roasting, both
in a qualitative and quantitative manner and at a relatively high spatial resolution of 12 micron. The
results integrate qualitative and quantitative information that could be useful for understanding
structure-property relationships in terms of further processing and utilisation, e.g. the development
of value-added products with improved digestibility and viscosity or delayed staling phenomenon.National Research Foundatio
Characterisation of whole white maize kernels using spectral imaging
No full textMaize (Zea mays L.) is the most important cereal crop grown in South Africa. It is produced widely
across the country under diverse environments, and thus a variety of defects tend to occur. Grading
is an important quality and safety control step where these defective materials are identified and
quantified. This study considered the most important defective material classes, namely 6 types of
defective white maize kernels, 5 types of foreign matter, other colour kernels (yellow maize) and
pinked white maize kernels. Current maize grading is manual and tedious, and modern analytical
methods could improve this process. This study aimed to investigate the viability of using spectral
imaging with multivariate data analysis for maize grading by separating sound maize from the 13
defective materials classes.
NIR hyperspectral imaging with pixel-wise and object-wise data analysis were used for twoway
discrimination of the sound and defective material classes. The average spectra indicated
prominent bands at 1219 and 1476 (related to starch), 1941 (related to moisture), and 2117 nm
(related to protein). The loadings of principal component (PC) 1 exhibited similar bands. The objectwise
approach performed superiorly to the pixel-wise approach across all 13 analyses. Little
separation was observed in the principal component analysis (PCA) score plots in the pixel-wise
results due to a large similarity between classes. The object-wise approach utilised the average
spectrum for each maize kernel, and the overlap was reduced. Partial least squares discriminant
analysis (PLS-DA) models were calculated and used to classify an independent validation set of 30
sound kernels and 30 defective materials. The pixel-wise analyses achieved classification
accuracies ranging 75-99%. This approach was not able to accurately distinguish closely related
classes. The object-wise analyses performed well, with 8 of the 13 achieving 100% classification
accuracy, and the remaining 5 classes incurring only one error per analysis of 60 kernels.
Multispectral imaging followed to compare the two imaging techniques. Pixel-wise PCA was
applied to pre-process the spectral imaging data, followed by object-wise two-way PLS-DA
modelling using 17 sound kernels and 18 defective material objects. The PCA loadings revealed
that colour played a role in separating the classes, with a wide band appearing across 505, 525,
570 and 590 nm. Classification accuracies of 83-100% were achieved, and were generally slightly
lower than the results obtained for all classes using the NIR hyperspectral imaging instrument.
Spectral imaging was shown to be capable of separating white maize from 13 commonly
occurring defective materials. NIR hyperspectral imaging performed superiorly to multispectral
imaging, and the use of an object-wise data analysis approach further improved the accuracy of the
separations. These techniques have the potential to offer the maize industry a rapid, accurate and
objective alternative grading method.National Research Foundatio
Genetic diversity in a commercial black soldier fly, Hermetia illucens (Diptera: Stratiomydiae), population
No full textNational Research Foundatio
A revaluation of tolerance and toleration : a selective incorporation of classical conceptions of tolerance
No full textThis dissertation aims to revitalise and revalue a currently disregarded conceptual field of tolerance, and explores the prospect of it - and its respective practice (toleration) - satisfying Nietzsche"s criteria of life-affirmation and flourishing. The project of revaluation undertaken within this dissertation entails an evaluative re-appraisal and a critically selective incorporation of the particular concepts of tolerance and toleration once highly esteemed during the Hellenistic period. This inquiry centres on the axiological, ethical and psychological perspectives on tolerance and toleration, whilst investigating their compatibility within a Nietzschean valuation. Considerations of a few overlapping epistemological perspectives which are apposite to the aforesaid are articulated. Including the effects on the affective and cognitive accompaniments to toleration, possible formulations of tolerance that undermine life-affirmation and flourishing are also considered from a meta-ethical perspective. In order to do so, a critical analysis of the incorporated aspects of tolerance and toleration is conducted in relation to resentment and ressentiment. The primary questions I address are: „what is it to tolerate?", „how would tolerance and toleration read within a Nietzschean valuation?‟, „what are the psychological - i.e. affective and cognitive - intricacies of tolerating and how do they feature in its procedure?", „what kinds of psychological attachment does one qua human being create in connection with the entities one tolerates?" and „are there possible psychological dangers regarding tolerance and toleration that a Nietzschean valuation can help identify?"National Research Foundatio
Exploring stakeholder inclusivity in the development of the South African national policy on basic education
No full textThis study explores the necessity of stakeholder inclusivity, particularly the inclusivity of teachers, in the development of the national policy pertaining to the programme and promotion requirements of the National Curriculum Statement Grades R – 12 in the Department of Basic Education. Through the qualitative exploration of data drawn from in-depth interviews, the study found that bureaucracy and a top-down approach drives policy development in the basic education system of South Africa. While most of the stakeholders indicated that they are only consulted at a public comment phase of the policy development, they viewed this as asking for their endorsement as opposed to genuine and constructive inputs. As such, educational policy developer’s end up missing an opportunity to engage and learn from stakeholders and ultimately the policy reaches the implementation phase with loopholes. Therefore, adopting a consultative approach throughout the life cycle of the policy development with not only the body of stakeholders who have a say by virtue of their power, but also with those whose say was initially restricted as a result of having less influential power in the formulation of educational objectives, might be the breakthrough being strived for in developing policies that will lead to the achievement of quality learner outcomes.National Research Foundatio
South African mathematics foundation validity and diagnostic attributes of the SAMO junior second round
No full textAssessing nutritional quality and consumer acceptability of Moringa oleifera leaf powder (MOLP)-based snacks for improved children's food and nutrition security
No full textGlobally, 16 million children were reported to be severely wasted, and 159 million children
had stunted growth (United Nations International Children’s Emergency Fund et al., 2015).
Nearly 2.3 million children in South Africa were undernourished with 21-48%; 8-15% and 3.7%
being stunted; underweight and wasted, respectively (Gitau, 2009; Shisana et al., 2013). The
mortality rate of children, globally is estimated to be 3.1 million children, annually, and
micronutrient deficiencies contribute to 1.1 million deaths of children. Micronutrient
deficiencies or hidden hunger is mostly prevalent in Africa, specifically, Sub-Saharan Africa
and Southern Asia (Weisstaub & Araya, 2008; Black et al., 2013; Black et al., 2008).
A possible intervention could be to fortify snacks with Moringa oleifera leaf powder, since the
consumption of processed snacks is rising in middle-income countries and in South Africa
(Huffman et al., 2014; Ronquest-Ross et al., 2014). Moringa oleifera originated from South
Asia, in the Himalayan foothills, located from north-eastern Pakistan to Northern West Bengal
in India but now is also found in many tropics and sub-tropics of the world. (Fahey, 2005;
Jideani et al., 2014). Moringa oleifera is known as the “miracle tree” because of its nutritive
value (Fahey, 2005) and according to Fuglie (2001), a 100 g of Moringa oleifera leaf powder
contains 10 times the vitamin A of carrots, half the vitamin C of oranges, 17 times the calcium
of milk, 15 times the potassium of bananas, 25 times the iron of spinach and 9 times the
protein of yoghurt. The overall aim of the study was to assess whether Moringa oleifera-based
snacks could contribute to food and nutrition security for children through the acceptability
of caregivers.National Research Foundatio
Guest effects on the solid-state dynamics of selected inclusion compounds
No full textGuest inclusion has always been a central feature of supramolecular chemistry. The present work describes guest effects on particular properties of selected inclusion compounds. Guest replacement is demonstrated as a means of modifying thermal expansion behaviour and porosity. The body of this thesis consists of three manuscripts (two published and one under review).
The first manuscript describes a nitromethane solvate of 18-crown-6 that was investigated by means of temperature-resolved single-crystal X-ray diffraction. The compound exhibits exceptionally large positive thermal expansion in two axial directions and exceptionally large negative thermal expansion along the third. The underlying mechanism relies exclusively on weak electrostatic interactions to yield a linear thermal expansion coefficient of −129×10−6 −1, which is, to the best of our knowledge, the largest negative value yet recorded for an organic inclusion compound. Our discovery of a reported analogue with acetonitrile led us to prepare an isoskeletal series of compounds for further inquiry.
The second manuscript demonstrates that guest replacement in a series of isoskeletal organic inclusion compounds can produce remarkable changes in thermal expansion behaviour. The three inclusion compounds have 18-crown-6 as host molecule and nitromethane, acetonitrile or iodomethane as guests. Along principal axis X1 the linear component of thermal expansion is negative for the nitromethane and acetonitrile solvates but zero for the iodomethane solvate. The compounds show varying degrees of large volumetric thermal expansion, with coefficients of 378(22), 226(3) and 256(8)×10−6 −1 for the nitromethane, acetonitrile and iodomethane solvates, respectively. Crystal structure analysis and computational methods were used to elucidate general features of the underlying mechanism of thermal expansion for the series. Interestingly, the thermosalient effect was observed for the acetonitrile version. To our knowledge this is the first example of thermosalience reported for an inclusion compound.
The success with molecular organic crystals prompted similar experimentation with a different class of materials. As inorganic inclusion compounds, MOFs are an obvious choice for experiments involving guest replacement because of their proven capability for guest exchange, and the great interest in MOFs as potential porous sorbents for molecular storage and separation in industry.
The final manuscript describes a non-interpenetrated MOF with a paddle-wheel SBU that has been activated by direct thermal evacuation, guest exchange with a volatile solvent, and supercritical CO2 drying. Conventional thermal activation results in a mixture of crystalline phases and some amorphous content. Exchange with a volatile solvent and subsequent vacuum activation produces a pure breathing phase with high sorption capacity, selectivity for CO2 over N2 and CH4, and substantial hysteresis. Supercritical drying can be used to access a guest-free open phase. Pressure-resolved differential scanning calorimetry was used to investigate the systematic loss of sorption capacity by the breathing phase as a function of successive cycles of sorption and desorption.National Research Foundatio
Moringa oleifera crude aqueous leaf extract induces apoptosis in human hepatocellular carcinoma cells via the upregulation of NF-kB and IL-6/STAT3 pathway
No full textNational Research Foundatio
The correlation of the morphology of the medial patellofemoral ligament (MPFL) with the dimensions of the patella, the patellar tendon, the q-angle and femoral trochlear groove
No full textThe medial patellofemoral ligament (MPFL) is an essential contributing component to a stable patellofemoral joint (PFJ). The PFJ is a complex structure that has balanced forces acting on the stable joint. The aim of this study was to correlate the morphology of the MPFL with the Q-angle, the patellar tendon, the patella and the femoral trochlear groove (FTG) in a stable PFJ. Thirty-four cadaver knees were dissected. The Q-angle for each knee was measured with a goniometer. Dimensions of the MPFL, patella and patellar tendon were measured with a Vernier calliper. The femoral trochlear groove was photographed and photometrically measured with the use of the computer program ImageJ. The data collected were statistically analysed to determine Spearman’s Rank correlations coefficient (rs). A correlation coefficient of rs = 0.482 was considered significant. Firstly, it was found that the length of the MPFL correlated with eleven other measurements. These correlations include the proximal width of the patellar tendon; the length of the patellar tendon; the medial facet width of the patella; the articulating height of the patella; the osseous length of the patella; all the osseous measurements of the FTG; and the mathematically-derived depth of the FTG. Secondly, eight correlations were found with the femoral attachment width of the MPFL. These correlations include both the proximal and distal widths of the patellar tendon; the osseous length and width of the patella; the lateral patellar groove width of the FTG; both the medial and lateral altitudes of the FTG; and the altitude of the deepest point of the FTG. Lastly, the width of the attachment of the MPFL to the vastus intermedius tendon only correlated with the length of the patellar tendon. The morphology of the MPFL positively correlated with specific measurements of the patella, patellar tendon and the FTG in a stable PFJ. This may be explained by the gradual increase in size of the structures in the joint. The findings suggest that the MPFL forms part of a harmonious interplay and disrupting this balance, either by pathology or reconstructive surgery, may alter the delicate harmony in the joint.National Research Foundatio