Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Due to the commercial, nutritional and health value of vegetable oils, seeds and beans, the
analysis of their components is of much interest. In this dissertation oil-containing food
products, specifically vegetable oils, seeds and beans, were investigated.
Selected minor components of three locally produced vegetable oils, namely apricot
kernel, avocado pear and macadamia nut oils were investigated using 31P NMR
spectroscopy. These minor components, including 1,2 diacylglycerols, 1,3 diacylglycerols
and free fatty acids, were identified in the 31P NMR spectra of each of the three vegetable
oils for the first time. Two approaches were used for the quantification of the minor
components present in the spectra. A calibration curve approach used known
concentrations of standard minor components to establish calibration curves while a direct
correlation approach calculated the unknown concentration of minor components in the
vegetable oils using a known amount of standard compound within the analysis solution.
These approaches aided in determining the concentration of minor components during
storage studies in which vegetable oils were stored in five different ways: exposed to light,
in a cupboard, in a cupboard wrapped in tin foil, at -8 °C and at 5 °C. It was found that
determining the best storage condition for each oil was difficult since individual minor
components were affected differently by the various storage conditions. However, in
general the best storage conditions appeared to be 5 °C and -8 °C.
The oil, protein and carbohydrate contents of sesame, sunflower, poppy, and pumpkin
seeds, and soy, mung, black and kidney beans were analysed by thermogravimetric
analysis and 13C NMR solid state NMR spectroscopy. It was shown that the first derivative
of TGA data for seeds and beans can give valuable information about the carbohydrate,
moisture, protein and fat content. This has not been previously demonstrated. For the
seeds, the integration of a region between 270–480 ºC was equal to the sum of the oil and
protein content and compared well to quantitative results obtained by other conventional
methods. For beans the integration of a region between 180-590 ºC, gave a value which
represented the sum of the oil, protein and carbohydrate content.
13C solid state NMR spectroscopy, including SPE-MAS, CP-MAS and variable contact time
experiments, was carried out on these seeds and beans and gave valuable information on
the solid-like and liquid-like components. To our knowledge these seeds and beans have
never been previously analysed using this technique. 13C SPE-MAS NMR spectroscopy
indicated that the seeds contained more liquid-like components than the beans. In turn the
13C CP-MAS NMR spectra indicated that beans had higher levels of solid-like components
than the seeds. These conclusions correlated well with the quantities of liquid-like
components and solid-like components that were determined by conventional methods
and TGA. Preliminary studies using T1pH experiments on the components present in the
seeds and beans led to a few observations. Most interesting is that a model using a two-
phase fit in order to determine T1pH values appears to be more accurate than a one-phase
model. / AFRIKAANSE OPSOMMING: Groente olies, sade en bone is ‘n onderwerp van groot belang omrede hul kommersiële,
voeding en gesondheidswaardes. In hierdie tesis is olie-bevattende voedselprodukte,
spesifiek groente-olies, sade en bone geanaliseer.
Geselekteerde komponente teenwoordig in klein hoeveelhede in drie lokaal
geproduseerde groente-olies, naamlik appelkoos-pit, avokadopeer en makadamia-neut
olies is geanaliseer met behulp van 31P KMR spektroskopie. Hierdie komponente,
insluitend 1,2 diasielglyserole, 1,3 diasielglyserole en ongebonde vetsure, is vir die eerste
keer geïdentifiseer in die 31P KMR spektra van die drie groente olies. Twee benaderings is
gebruik vir die hoeveelheids-bepaling van die komponente in die spektra. ‘n Yking-kurwe
metode het gebruik gemaak van bekende hoeveelhede konsentrasies standaard
komponente vir die opstel van yking-kurwes, terwyl ‘n direkte korrelasie metode gebruik is
om die onbekende konsentrasie van komponente in groente olies te bepaal met behulp
van ‘n bekende hoeveelheid standaard verbinding teenwoordig in die oplossing. Hierdie
metodes het gelei tot die bepaling van die konsentrasies van die komponente gedurende
vyf verskillende berging toestande wat ingesluit het: Blootgestel aan lig, in ‘n donker kas,
in ‘n donker kas toegevou in tin foelie, bevries by -8 °C en in ’n koelkas by 5 °C. Dit was
bevind dat bepaling van die beste bergingstoestand vir elke olie moeilik is aangesien die
individuele komponente verskillend geaffekteer word deur die verskeie berging toestande.
Die beste bergings toestand oor die algemeen blyk egter om by 5 °C en -8 °C te wees.
Sesamsaad, sonneblomsaad, papawersaad en pampoensaad sowel as sojaboontjie,
mungboontjie, swartboontjie en pronkboontjie se olie, protein en koolhidraat komponente
was geanaliseer met behulp van termogravimetriese analise (TGA) en 13C soliede
toestand KMR spektroskopie. Dit was bevind dat die eerste afgeleide van die TGA data
waardevolle inligting lewer oor die komponent inhoud van elk van die sade en bone.
Hierdie is nog nie vantevore bevind nie. Vir die sade, was die integrasie van ‘n area tussen
270–480 ºC gelyk aan die som van die olie en proteïen inhoud en het goed vergelyk met
die waardes verky deur algemene analitiese metodes. Vir die boontjies, was die integrasie
van ‘n area tussen 180-590 ºC gelyk aan die som van die olie, protein en koolhidraat
inhoud.
13C vaste staat KMR spektroskopie, insluitende SPE-MAS, CP-MAS en variëerbare
kontak-tyd eksperimente, was gedoen en het waardevolle inligting gelewer omtrent die
solied-agtige en mobiel-agtige komponente. Hierdie sade en bone is tot ons kennis nog
nie van te vore met die tegnieke ondersoek nie. 13C SPE-MAS NMR spektroskopie het
aangedui dat daar ‘n groter hoeveelheid mobiel-agtige komponente in sade as in bone
teenwoordig is. 13C CP-MAS NMR spektroskopie het weer aangedui dat daar ‘n groter
hoeveelheid solied-agtige komponente in bone as in sade teenwoordig is. Hierdie
gevolgtrekkings het goed vergelyk met die waarnemings verkry deur konvensionele
analitiese metodes en TGA. Voorlopige studies op die komponente van sade en bone deur
T1pH eksperimente het tot ‘n paar gevolgtrekkings gelei waarvan die mees interessantste
was dat ‘n twee-fase model vir die bepaling van T1pH waardes beter resultate lewer as ‘n
een-fase model.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6831 |
| Date | 03 1900 |
| Creators | Retief, Liezel |
| Contributors | Koch, Klaus, McKenzie, Jean, University of Stellenbosch. Faculty of Sciences. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Rights | University of Stellenbosch |
Page generated in 0.003 seconds