Thesis (MSc Food Sc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Near infrared hyperspectral imaging (NIR HSI) in conjunction with multivariate image analysis was
evaluated for the detection of millet and buckwheat flour in ground black pepper. Additionally, midinfrared
(MIR) spectroscopy was used for the quantification of millet and buckwheat flour in ground
black pepper. These techniques were applied as they allow non-destructive, invasive and rapid
analysis.
Black pepper and adulterant (either millet or buckwheat flour) mixtures were made in 5% (w/w)
increments spanning the range 0-100% (w/w). The mixtures were transferred to eppendorf tube
holders and imaged with a sisuChema short wave infrared (SWIR) pushbroom imaging system
across the spectral range of 1000–2498 nm. Principal component analysis (PCA) was applied to
pseudo-absorbance images for the removal of unwanted data (e.g. background, shading effects
and bad pixels). PCA was subsequently applied to the ‘cleaned’ data. An adulterant concentration
related gradient was observed in principal component one (PC1) and a difference between black
pepper adulterated with buckwheat and millet was noted in PC4. Four absorption peaks (1461,
2241, 2303 and 2347 nm) were identified in the loading line plot of PC1 that are associated with
protein and oil. The loading line plot of PC4 revealed absorption peaks at 1955, 1999, 2136 and
2303 nm, that are related to protein and oil. Partial least squares discriminant analysis (PLS-DA)
was applied to NIR HSI images for discrimination between black pepper adulterated with varying
amounts of adulterant (millet or buckwheat). The model created with millet adulterated black
pepper samples had a classification accuracy of 77%; a classification accuracy of 70% was
obtained for the buckwheat adulterated black pepper samples.
An average spectrum was calculated for each sample in the NIR HSI images and the resultant
spectra were used for the quantification of adulterant (millet or buckwheat) in ground black pepper.
All samples were also analysed using an attenuated total reflectance (ATR) Fourier transform (FT)
– infrared (IR) instrument and MIR spectra were collected between 576 and 3999 cm-1. PLS
regression was employed. NIR based predictions (r2 = 0.99, RMSEP = 3.02% (w/w), PLS factor =
4) were more accurate than MIR based predictions (r2 = 0.56, RMSEP = 19.94% (w/w), PLS factors
= 7). Preprocessed NIR spectra revealed adulterant specific absorption bands (1743, 2112 and
2167 nm) whereas preprocessed MIR spectra revealed a buckwheat specific signal at 1574 cm-1.
NIR HSI has great promise for both the qualitative and quantitative analysis of powdered food
products. Our study signals the beginning of incorporating hyperspectral imaging in the analysis of
powdered food substances and results can be improved with advances in instrumental
development and better sample preparation. / AFRIKAANSE OPSOMMING: Die gebruik van naby infrarooi hiperspektrale beelding (NIR HB) tesame met veelvoudige
beeldanalise is ondersoek vir die opsporing van stysel-verwante produkte (giers en bokwiet) in
gemaalde swart pepper. Middel-infrarooi (MIR) spektroskopie is addisioneel gebruik vir die
kwantifisering van hierdie stysel-verwante produkte in swart pepper. Albei hierdie tegnieke is
toegepas aangesien dit deurdringend van aard is en dit bied nie-destruktiewe sowel as spoedige
analise.
Swart pepper en vervalsingsmiddel (giers of bokwiet) mengsels is uitgevoer in 5% (m/m)
inkremente tussen 0 en 100% (m/m). Eppendorfbuishouers is met die mengsels gevul en
hiperspektrale beelde is verkry deur die gebruik van ‘n sisuChema SWIR (kortgolf infrarooi)
kamera met ‘n spektrale reikwydte van 1000–2498 nm. Hoofkomponent-analise (HK) is toegepas
op pseudo-absorbansie beelde vir die verwydering van ongewenste data (bv. agtergrond, skadu en
dooie piksels). Hoofkomponent-analise is vervolgens toegepas op die ‘skoon’ data.
Hoofkomponent (HK) een (HK1) het die aanwesigheid van ‘n vervalsingsmiddel konsentrasie
verwante gradient getoon terwyl HK4 ‘n verskil getoon het tussen swart pepper vervals met giers
en bokwiet. Vier absorpsiepieke (1461, 2241, 2303 en 2347 nm) was geïdentifiseer binne die HK
lading stip van HK1 wat met proteïen en olie geassosieer kon word. Die HK lading stip van HK4
het absorpsipieke by 1955, 1999, 2136 en 2303 nm aangedui wat verband hou met proteïen en
olie. Parsiële kleinste waarde diskriminant-analise (PKW-DA) is toegepas op die hiperspektrale
beelde vir die moontlike onderskeiding tussen swart pepper vervals met verskeie hoeveelhede
vervalsingsmiddel (giers of bokwiet). ‘n Klassifikasie koers van 77% is verkry vir die model
ontwikkel met giers vervalsde swart pepper terwyl die model ontwikkel met bokwiet vervalsde
swarte pepper ‘n klassifikasie koers van 70% bereik het.
‘n Gemiddelde spektrum is bereken vir elke monster in die hiperspektrale beelde en die
resulterende spektra is gebruik vir die kwantifisering van vervalsingsmiddels (giers of bokwiet) in
gemaalde swart pepper. ‘n ATR FT-IR instrument met spektrale reikwydte van 576-3999 cm-1 is
additioneel gebruik vir die analise van alle monsters. Parsiële kleinste waarde regressie is gebruik
vir kwantifikasie doeleindes. NIR gebasseerde voorspellings (r2 = 0.99, RMSEP = 3.02% (m/m),
PLS faktore = 4) was meer akkuraat as die MIR gebasseerde voorspellings (r2 = 0.56, RMSEP =
19.94% (m/m), PLS faktore = 7). Vooraf behandelde NIR spektra het vervalsingsmiddel verwante
absorpsiepieke (1743, 2112 en 2167 nm) aangetoon terwyl vooraf behandelde MIR spektra ‘n
bokwiet verwante absorpsiepiek by 1574 cm-1 aangedui het.
NIR HB toon goeie potensiaal vir beide kwalitatiewe en kwantitatiewe analise van gepoeierde
voedsel produkte. Ons studie kan gesien word as die begin van die inkorporasie van
hiperspektrale beelding in die analise van gepoeierde voedsel material en verbeterde resulte kan
verkry word deur die vordering in instrumentasie ontwikkeling en verbeterde monstervoorbereiding.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6624 |
| Date | 03 1900 |
| Creators | September, Danwille Jacqwin Franco |
| Contributors | Manley, Marena, Geladi, Paul, University of Stellenbosch. Faculty of AgriSciences. Dept. of Food Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 97 p. : ill. |
| Rights | University of Stellenbosch |
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