Thesis (MSc Food Sc) (Food Science)--University of Stellenbosch, 2005. / Near infrared spectroscopy (NIRS) and UV/Vis spectrophotometric methods were investigated as rapid and/or more economical methods to quantify the major monomeric phenolic compounds, soluble solid content (SSC), total polyphenol content (TPC) and total antioxidant activity (TAA) of green rooibos and Cyclopia genistoides.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2005. / Near infrared (NIR) spectroscopy prediction models were developed for the rapid determination of the peroxide value, free fatty acid content, specific extinction coefficients at 232 and 270 nm, thiobarbituric acid reactive substances value, pigment, total polyphenol, oleic acid, linoleic acid and saturated fatty acid contents ...

Thesis (MSc Food Sc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Hectolitre mass (HLM) measurements allow rapid and accurate determination of grain density. HLM devices from different countries (Australia, Canada, France, Germany, South Africa, the United Kingdom and the United States of America [USA]) have been investigated for their effect on the HLM measurements of oats. In addition, the potential of near infrared (NIR) hyperspectral imaging has been evaluated to distinguish between oat samples with different HLM values. Comparing HLM measurements obtained from the respective devices, the USA and the South African devices resulted in significantly (P<0.05) lower HLM values compared to the other devices where as the German device resulted in higher values (P<0.05) than the other devices. HLM values from all the devices were highly correlated with intra-class correlation (ICC) consistency values of at least 0.90. These high correlations would allow direct replacement of the South African device with any of the other devices. The equipment selected as replacement should ideally be calibrated according to the ISO 7971-3 standard (i.e. the device currently used in Germany). HLM values significantly (P<0.05) increased when oat samples were rubbed before measurements were made, indicating the importance of continuation of this sample preparation step. The investigation on the effect of the operator on HLM determinations showed that the unskilled operator measured HLM values significantly different to those obtained by the skilled operator. This emphasises the importance of training in spite of HLM measurements being a simple procedure. A poor correlation (r = 0.18) was found between protein content and HLM values of oat samples. Moisture content significantly affected the HLM values of oats and results clearly showed a decrease in HLM values with increasing moisture content. Scanning electron microscope (SEM) micrographs revealed that the starch granules became swollen and that they increased in size with an increase in moisture content, resulting in a decrease in HLM. NIR hyperspectral imaging offers the testing of individual grains non-destructively. This is often required by plant breeders because they subsequently need to plant selected grains. NIR offers this option to plant breeders. NIR hyperspectral imaging, which combines NIR spectroscopy with digital imaging, was used to distinguish between six oat samples with varying HLM values. NIR spectroscopic differences were observed between the images of the two samples with the highest and lowest HLM values (60.2 and 49.35 kg.hL-1). Less distinct differences were observed in the NIR hyperspectral images of two samples differing by less than 2.0 kg.hL-1. Although mixed oat samples were used, these preliminary results established the possible use of NIR hyperspectral imaging in evaluating oat samples from breeding trials. The use of this technique could also be extended to evaluation of other quality characteristics of oats. / AFRIKAANSE OPSOMMING: Hektolitermassa- (HLM-)metings maak snelle en akkurate bepaling van korreldigtheid moontlik. HLM-toestelle van verskillende lande (Australië, Kanada, Frankryk, Duitsland, Suid-Afrika, die Verenigde Koninkryk en die Verenigde State van Amerika) is ondersoek vir hulle uitwerking op die HLM-metings van hawer. Daarby is die potensiaal van nabyinfrarooi- (NIR-)hiperspektrale beelding geëvalueer om tussen hawermonsters met verskillende HLM-waardes te onderskei. Tydens vergelyking van HLM-metings verkry van die onderskeie toestelle, het die Amerikaanse en die Suid-Afrikaanse toestelle beduidend (P<0.05) laer HLM-waardes opgelewer in vergelyking met die ander toestelle terwyl die Duitse toestel hoër waardes (P<0.05) as die ander toestelle getoon het. Daar was hoë korrelasies tussen die HLM waardes verkry van die apparate met intraklaskorrelasie (IKK) konsekwentheidwaardes van ten minste 0.90. Hierdie hoë korrelasies sou direkte vervanging van die Suid-Afrikaanse toestel met enige van die ander toestelle moontlik maak. Die toerusting gekies as vervanging sou ideaal gesproke in ooreenstemming met die ISO 7971-3 standaard gekalibreer kon word (bv. die toestel wat tans in Duitsland gebruik word). HLM-waardes het beduidend (P<0.05) verhoog toe hawermonsters gevryf is voor metings gemaak is, wat dui op die belang van verlengde gebruik van hierdie stap tydens die voorbereiding van monsters. Die ondersoek na die uitwerking van die operateur op HLM-bepalings het getoon dat die onervare operateur HLM-waardes beduidend verskillend gemeet het teenoor dié verkry deur die ervare operateur. Dit beklemtoon die belang van opleiding ten spyte daarvan dat HLM-metings ’n eenvoudige prosedure is. ’n Swak korrelasie (r = 0.18) is aangetref tussen proteïeninhoud en HLM-waardes van hawermonsters. Voginhoud het die HLM-waardes van hawer beduidend beïnvloed en resultate het duidelik ’n styging in HLM-waardes met verhoging van die voginhoud getoon. Aftaselektronmikroskoop- (AEM-)mikrobeelde het aangedui dat die styselgranules swel en in grootte toeneem met verhoging van die voginhoud, wat aanleiding gee tot ’n verlaging in HLM. NIR-hiperspektrale beelding maak die toets van individuele korrels op niedestruktiewe wyse moontlik. Dit word dikwels deur plantkwekers vereis aangesien hulle na toetsing uitgesoekte korrels moet plant. Nabyinfrarooi bied hierdie opsie aan plantkwekers. NIR-hiperspektrale beelding, wat NIRspektroskopie met digitale beelding kombineer, is gebruik om te onderskei tussen ses hawermonsters met wisselende HLM-waardes. NIR-spektroskopiese verskille tussen die beelde van die twee monsters met die hoogste en laagste HLM-waardes (60.2 en 49.35 kg.hL-1) is waargeneem. Minder duidelike verskille is in die NIR-hiperspektrale beelde van twee monsters wat met minder as 2.0 kg.hL-1 verskil het, waargeneem. Alhoewel gemengde hawermonsters gebruik is, het hierdie voorlopige resultate die moontlike gebruik van NIR-hiperspektrale beelding by die evaluering van hawermonsters van kweekproewe vasgestel. Die gebruik van hierdie tegniek sou ook uitgebrei kon word tot die evaluering van ander kwaliteitseienskappe van hawer.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009. / Triticale (X Triticosecale Whittmack), a cross between durum wheat (Triticum sp.) and rye, is a crop with an increasing agronomic and economic potential Though studies on the functional and compositional quality of triticale have been conducted in other parts of the world, little is known regarding cultivars developed in South Africa in terms of these aspects. South African triticale cultivars from various localities in the Western Cape, obtained for two subsequent harvest seasons, were analysed for moisture, protein and ash contents, as well as falling number (an indication of α-amylase activity), hardness (particle size index), 1000-kernel mass and baking potential (SDS sedimentation). These triticale samples were derived from a breeding program that was not focused on baking quality. The results obtained were found to compare well with those reported on in previous studies. Significant differences were observed between both cultivars and localities within years, illustrating the effect of genetic as well as environmental factors. Significant differences were also observed between localities when comparing the two harvest seasons, whereas differences between the cultivars for the two seasons were in most cases not significant; illustrating the effect of environment. Interactions between cultivars and localities were found to be significant for all parameters, and trends were observed between protein content and both particle size index (PSI) (negative) as well as SDS sedimentation (positive) results for both years. Near infrared (NIR) spectroscopy is a rapid method of analysis and is widely used for the quality evaluation of wheat. Limited research has been reported on calibration models for the quality evaluation of triticale, and thus NIR spectroscopy was applied to develop models for the prediction of moisture, protein and ash contents, as well as hardness and baking potential for South African cultivars. Spectra were collected in diffuse reflectance mode and partial least squares (PLS) models developed for both triticale flour and wholegrain using two different instruments (Büchi NIRFlex N-500 and Bruker MPA Fourier transform NIR spectrophometers) and software packages (The Unscrambler and OPUS). Full cross-validations were performed, after which the best prediction models obtained (R2 > 0.66) were validated using an independent test set (n = 50). The best prediction results were obtained with flour for moisture (Bruker: SEP = 0.08%; R2 = 0.95; RPD = 4.65) and protein (Büchi: SEP = 0.44%; R2 = 0.96; RPD = 5.23 and Bruker: SEP = 0.32%; R2 = 0.96; RPD = 4.88). For whole grain, acceptable results were obtained for protein (Büchi: SEP = 0.55%; R2 = 0.94; RPD = 4.18 and Bruker: SEP = 0.70%; R2 = 0.90; RPD = 3.23). Though results for ash content, PSI and SDS sedimentation prediction did not yield models that can be applied as yet, these models form a good basis for further calibration model development and possibly use in early generation screening. The current limited ranges could be expanded by adding samples from subsequent harvest seasons. By adding more data, a better quality profile for South African triticale can be obtained, which will facilitate better interpretation in terms of the effect of genetic and environmental factors. It would also enable the development of improved NIR prediction models.

Thesis (MSc Food Sc )--Stellenbosch University, 2003. / ENGLISH ABSTRACT: This study shows the potential of near infrared spectroscopy for both qualitative and quantitative analyses of wine and brandy in the distilling industry. Wines intended for further processing by the distillation industry have to meet certain specifications to ensure an efficient and cost-effective distilling process with a suitable product yield. Certain compounds have, therefore, been recognised as significant quality parameters and through their regulation, a product of consistent quality can be ensured. These quality parameters include alcohol, total acid, volatile acid, total sulphur dioxide, total phenolics, reducing sugars and acetaldehyde concentrations and pH. The effective control of all these compounds in the wines prior to distillation, is critical to maintain the feasibility and efficiency of the process. Fourier transform near infrared spectroscopy (FT-NIRS) can be used as a rapid and accurate analytical method for the determination of alcohol concentrations in distilling and brandy base wine. The choice of path length for the liquid sampling cell is an important consideration. In this study, alcohol with its strong absorption of OH bands in the near infrared region was not significantly affected, but difference in path length showed a significant influence on the prediction of the volatile acid concentration in distilling wine. Very strong correlations were found between the spectral data and the alcohol concentration data in distilling wine (r = 0.99, SEP = 0.18% v/v, RER =30) and brandy base wine (r = 0.92, SEP = 0.18% v/v, RER = 11.1). Good predictions were obtained for the volatile acid content of brandy base wine (r = 0.85, SEP = 0.04 g.L-1 ) but better accuracy could be obtained by incorporating a wider concentration range and more sensitive, although not the accepted reference methods, such as HPLC and GC, into the modelling. In contrast to the brandy base wine, the much cruder, turbid distilling wine (r = 0.67, SEP = 0.33 g.L-1 ) yielded poor calibration results for volatile acid. FT-NIRS can also be used as a rapid screening method to measure the total acid content, pH and total phenol levels in brandy base wine samples. Satisfactory predictions were obtained for the total acid content (r = 0.89, SECV = 0.38 g.L-1 ), pH (r = 0.84, SEP = 0.09) and total phenol levels (r = 0.71, SEP = 16.4 mq.L" GAE). The SEP of all the parameters compared well with the SEL and were within acceptable limits. The range of the concentration measurements were, however, very narrow and the accuracy of these models (measured as the ratio of the range to the standard error of prediction) were all below 10, indicating that modelling of these parameters in brandy base wine should be attempted with reference values covering a wider range. Poor correlations and predictions were obtained between the wine spectral data and the acetaldehyde (r = 0.39 , SECV =1.45 rnq.L"), residual sugar (r = 0.58, SECV =0.49 mq.L" ) and total sulphur dioxide (r = 0.35, SEP = 10.9 mq.L" ) concentration data. The unique character of potstill distillates, originating from the grape cultivar, type and age of the oak casks, lends itself to the development and blending of different brandies. The process of blending and correcting the brandy is necessary to obtain a product and brand of established and recognised character. The brandy is generally divided into different classes prior to blending based on the degree of "smoothness" or "hardness" of the matured distillate as determined by a sensorial panel. The ideal would, however, be to replace this subjective evaluation method with a more objective approach, such as an instrumental method like NIRS. Near infrared spectroscopy showed potential to successfully discriminate and classify brandy samples in terms of their sensorial classification status. The near infrared spectra of unblended three-year old brandies were measured and discriminant analysis performed using the subjective sensory classification data of the brandy. SIMCA (soft independent modelling of class analogy) models were developed by calculating separate peA (principal component analysis) models for each of the classes for which qualitative analysis were required. An assessment of class membership of an unknown sample was made on the basis of the distance to the cluster centroid. Two types of NIRS instruments, a Fourier transform near infrared system and a diode array spectrophotometer were employed to examine the discriminatory abilities of NIRS. Excellent predictions (90.9%-100%) were obtained for the "smoothest" and "hardest" classes within the 2000 and 2001 seasons with FT-NIRS. For the diode array spectra reasonable classification data were obtained for all the classes within the 2000 and 2001 seasons, as well as an excellent classification rate (100%) of the smoothest class in the 1999 season. Prediction results for class membership of the brandy samples from the three season's combined data did not deliver satisfactory discriminatory results. By applying NIRS and SIMCA, rapid and objective classification of brandy samples within seasonal context can be established to enhance the blending processes. Having accurate reference data in the calibration set is essential in near infrared spectroscopy (NIRS). The precision (usually decided by blind duplicate determination) of the reference data serves as the performance target for correlation-based near infrared analysis. The differences between reference values obtained from two independent laboratories and the Foss Winescan FT 120, which is also a predictive method, for the alcohol and volatile acid determinations in distilling wine and between two independent laboratories for the measurement of the total sulphur dioxide content, were investigated. ANOVA and post-hoc analysis (Bonferroni testing) revealed statistically significant differences (p<O.OS)between all three measurements for the volatile acid analysis. One laboratory differed significantly from the other two measurements in its measurement of the alcohol content in distilling wine. A paired t-test performed on the two laboratories' values obtained for total sulphur dioxide revealed statistically significant differences (p<O.OS) between the two sets of results. This study restated the importance of obtaining reliable reference data for calibration purposes to maintain the efficiency and accuracy and therefore the reputability of NIRS as an accurate and reliable analytical method. / AFRIKAANSE OPSOMMING: Hierdie studie dui op die potensiaal van naby infrarooi spektroskopie (NIRS) vir beide die kwalitatiewe en kwantitatiewe analise van wyn en brandewyn in die distillasie industrie. Sekere spesifikasies word gestel waaraan wyn met voldoen voor dit verdere prosessering tydens distillasie kan ondergaan. Die regulering van wynkwaliteit is noodsaaklik om die distilleringsproses ekonomies volhoubaar te maak. Sekere komponente in die wyn het 'n direkte invloed op die kwaliteit van die eindproduk en word beskou as betekenisvolle parameters wat beheer moet word om 'n produk van konstante hoë kwaliteit te lewer. Hierdie parameters sluit alkohol, titreerbare suur- en vlugtige suurinhoud, asook die pH, totale swaweidioksied, totale fenol vlakke, reduserende suikers en asetaldehied konsentrasies in. Die regulering van al hierdie komponente in die wyne is essensieel voor die aanvang van distillasie om die effektiwiteit en produktiwiteit van die proses te verseker. Fourier transformasie naby-infrarooi spektroskopie (FT-NIRS) kan benut word as 'n vinnige en akkurate analitiese metode om die alkohol konsentrasie in stook- en rabatwyn te bepaal. 'n Geskikte padlengte kuvet moet gekies word vir die ontleding van vloeistof monsters met NIRS. In hierdie studie is gevind dat die voorspelling van alkoholkonsentrasie in wyn, nie soseer beïnvloed is deur die keuse van padlengte nie. 'n Vlugtige komponent soos asynsuur, wat die maatstaf van die vlugtige suurinhoud van die wyn is, word egter regstreeks beïnvloed deur die keuse van padlengte. 'n Sterk korrelasie is gevind in die datastel vir die alkoholinhoud van die stookwyn (r = 0.99, SEP = 0.18% v/v, RER = 30) en rabatwyn (r = 0.92, SECV = 0.18% v/v, RER = 11.1). Baie goeie voorspellings is ook gevind vir die vlugtige suurinhoud van rabatwyn (r = 0.85, SEP = 0.04 g.L-1). Die akkuraatheid van die metode (uitgedruk as die RER waarde) het egter aangedui dat 'n wyer konsentrasie omvang en meer akkurate verwysingswaardes gebruik moet word om 'n geskikte model vir vlugtige suur kwantifikasie in rabatwyn te bewerkstellig. In teenstelling met die resultate verkry vir die rabatwyn, het die ruwer, turbiede stookwyn swak gekalibreer vir die vlugtige suurinhoud (r = 0.67, SEP = 0.33 g.L-1 ). FT-NIRS kan ook gebruik word as 'n vinnige seleksie metode om titreerbare suur vlakke, pH en totale fenolinhoud van rabatwyn monsters te bepaal. Sterk korrelasies is in die datastel gevind vir die titreerbare suurinhoud (r = 0.89, SECV = 0.38 g.L-1 ), pH (r = 0.84, SEP = 0.09) en totale fenol vlakke (r = 0.71, SEP = 16.4 rnq.L" GAE) van rabatwyn. Die SEP waardes verkry vanaf die NIRS bepalings het baie goed vergelyk met die standaard foute wat verkry is vir die chemiese bepalings. Die konsentrasie omvang van die verwysingswaardes was, egter, beperk en die akkuraatheid van die NIRS modelle (uitgedruk as die verhouding tussen die konsentrasie omvang en die standaard fout van voorspelling) was laer as 10. Dit het daarop gedui dat die NIRS kalibrasie van die parameters eerder uitgevoer moet word met monsters wat 'n wyer konsentrasie omvang dek en gemeet is met meer sensitiewe analitiese metodes soos HPLC en GC. Die kalibrasie en voorspelling van die asetaldehied inhoud (r = 0.39 , SECV =1.45 rnq.L"), reduserende suiker konsentrasie (r = 0.58, SECV =0.49 mq.L" ) en totale swaweldioksiedinhoud (r = 0.35, SEP = 10.9 rnq.L" ) het onaanvaarbare voorspellings gelewer. Die unieke karakter van potketel distillate wat bepaal word deur die druifkultivar, tipe en ouderdom van die eikehoutvate, bied die potensiaal vir die ontwikkeling en versnyding van verskillende style brandewyn. In 'n poging om 'n produk en handelsnaam van erkende en gevestigde karakter te verkry, moet die brandewyn eers versny word na veroudering. Die brandewyn word geklassifiseer in verskillende style op grond van sensoriese gehalte. NIRS is gebruik as 'n vinnige tegniek om te onderskei tussen verskillende style onversnyde drie jaar-oue brandewyn. SIMCA (soft independent modelling of class analogy) modelle is ontwerp deur aparte PCA (hoof komponent analise) modelle vir elke klas waarvoor kwalitatiewe analise vereis is, te ontwikkel. 'n Skating van klas lidmaatskap van 'n onbekende monster is gemaak deur die afstand van die monster na die groepsmiddelpunt te bereken. Twee soorte NIRS instrumente, 'n FT-NIR en 'n diode array spektrofotometer is gebruik tydens die studie om die diskrimineringsvermoë van elk te ondersoek. Uitstekende voorspellings (90.9%-100%) is gekry vir die "sagste" en "hardste" klasse binne die 2000 en 2001 seisoene met FTStellenbosch NIRS. Met die diode array spektra is redelike klassifikasie resultate verkry vir al die klasse binne die 2000 en 2001 seisoene, asook 'n uitstekende klassifikasie (100%) vir die sagste klas binne die 1999 seisoen. Voorspellings vir klas lidmaatskap van die brandewyn monsters vir die drie seisoene se gekombineerde data het egter onaanvaarbare diskriminasie resultate gelewer. NIRS en SIMCA sal 'n vinnige en objektiewe klassifikasie proses van onversnyde brandewyn monsters kan meebring wat tot voordeel van die versnydings- en produksieproses sal wees. Hierdie voorspellings sal egter binne seisoensverband moet geskied. Akkurate verwysingsdata in die kalibrasie datastel is 'n essensiële fasset van naby infrarooi spektroskopie. Die presisie (bepaal deur blinde duplikaat bepalngs) van die verwysingsdata dien as 'n prestasie teiken vir korrelasie-gebaseerde naby infrarooi voorspellings. Die verskille tussen die data verkry vir die alkohol- en vlugtige suurinhoud van stookwyn deur twee onafhanklike laboratoriums en 'n instrumentele metode (Foss Winescan FT 120) asook die verskille tussen die data verkry van twee laboratoriums vir die totale swaweidioksied metings, is ondersoek. ANOVA en post-hoc toetse het aangedui dat al die data verkry vir die vlugtige suur bepalings, statisties betekenisvol van mekaar verskil het (p<0.05). Vir die alkohol bepalings in stookwyn, het die data verkry van een laboratorium betekensvol verskil van die ander twee datastelle. Gepaarde t-toetse uitgevoer op die data verkry vir totale swaweldioksiedinhoud, het ook betekinisvolle verskille aangedui tussen die twee laboratoriums. Hierdie studie het die belangrikheid van betroubare verwysingsdata vir kalibrasie doeleindes beklemtoon, veral waar 'n tegniek soos NIRS se werksverrigting afhang van die akkuraatheid van dié waardes.

Thesis (MSc Food Sc )--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The effect of drying conditions on the retention of harpagoside, a glucoside iridoid found in the indigenous Southern African plant Harpagophytum procumbens (Devil's Claw), was investigated. Additionally, the feasibility of using near infrared spectroscopy (NIRS) as a rapid and nondestructive analytical tool for the prediction of the iridoids harpagoside (HS), 8-p-coumaroyl harpagide (8pCHG) and moisture contents, as well as the HS:8pCHG ratio in Devil's Claw was also studied. Due to the purported medicinal activity ofthe tuberous secondary roots, Devil's Claw is of commercial interest with a well established export market in Germany. The stability of HS during processing has, however, never been investigated and the current study evaluated the effect of three drying methods (sun, tunnel and freeze-drying), as well as three tunnel-drying temperatures (40°C, 50°C and 60°C, dry bulb temperature) on HS content. Methanolic extracts (70% methanol-water) were analysed by high-performance liquid chromatography (HPLC) and a multiple extraction test (n = 12) indicated a 91.70% recovery for HS. The comparative drying results showed significant (P < 0.05) differences between tunnel and freeze drying on the one hand and sun-drying on the other, with the latter being the most detrimental technique. In comparing tunnel-drying temperatures, at a constant relative humidity (RH) of30%, drying at 40°C showed the lowest retention ofHS, differing significantly (P < 0.05) from that at 50°C. Drying at 60°C did not differ significantly (P > 0.05) from either of the other two conditions, but also resulted in lower retentions ofHS content than drying at 50°C. Overall, freeze-drying showed excellent results for HS retention (1.565% ± 0.394%; mean ± standard deviation), but economic constraints limit the commercial application of this drying method. Although further study is required to optimise tunnel-drying conditions, this method indicated acceptable and practical results (1.526% ± 0.396%), especially with conditions set to 50°C and 30% RH (1.750% ± 0.438%). Future research should concentrate on elucidating the degradation mechanisms of HS during processing, transport and storage of dried Devil's Claw root. The analysis of dried, ground Devil's Claw root by NIRS was referenced to HPLC analyses of the same methanolic extracts used in the drying studies. The spectra were generated on two different NIRS instruments by measuring diffuse reflectance of the powder whilst calibrations were performed by partial least squares regression. Both independent data set validation and full cross-validation were used to evaluate the performance and predictive abilities of the various models. Excellent moisture content (MC) calibrations were developed with a standard error of prediction (SEP) ofO.24% (range: 2.44% to 10.43%) and correlation coefficient (r) of 0.99. For the given MC range, the model performed very well against the standard error of laboratory (SEL) ofO.14%. Considering the sensitivity of the HPLC reference method (SEL = 0.035%), the HS content calibration (range: 0.693% to 2.244%) performed admirably with an SEP ofO.134%. The available range was, however, relatively small and future NIRS studies should incorporate a larger range if possible. The 8pCHG model (range: 0.069% to 0.290%) performed similarly, with a standard error of cross-validation of 0.028% and SEL of 0.007%. By inclusion of a second species, H. zeyheri, both the 8pCHG content and especially HS:8pCHG ratio (range: 1.84 to 34.48) calibrations were evaluated as possible methods of distinguishing between species. With 8pCHG values of ca. 0.9%, good separation was achieved for the first model but, contrary to previous studies, the ratio was found to be less successful. Principle component analysis of the spectra, however, showed great potential as a qualitative tool for this purpose. It is believed that NIRS can become an invaluable tool for the division of Devil's Claw into export classes, depending on HS content. This content is, however, dependant on the drying conditions used and drying parameters should be optimised to ensure the best possible quality and retention ofHS. / AFRIKAANSE OPSOMMING: Die invloed van drogingskondisies op die behoud van harpagosied, 'n iridoïed glikosied wat in die inheemse Suider-Afrikaanse plant, Harpagophytum procumbens (Duiwelsklou) voorkom, is ondersoek. Die uitvoerbaarheid van naby infra-rooi spektroskopie (NIRS) as 'n vinnige en niedestruktiewe analitiese metode vir die voorspelling van die inhoud van iridoïede, harpagosied (HS), 8-p-kumaroïel-harpagied (8pCHG) en vog, sowel as die HS:8pCHG verhouding in Duiwelsklou is ook ondersoek. Die beweerde medisinale aktiwiteit van die knolagtige sekondêre wortels van Duiwelsklou het gelei tot 'n gevestigde uitvoermark in Duitsland, en is dus van kommersiële belang. Die stabiliteit van HS gedurende prosessering is nog nooit ondersoek nie. Die huidige studie het die invloed van drie drogingsmetodes (son-, tonnel- en vriesdroging) en drie tonneldrogingstemperature (40°C, 50°C en 60°C, droëbol temperatuur) op die HS inhoud evalueer. Metanolies ekstrakte (70% metanol-water) is met hoë-druk vloeistof chromatografie ("HPLC") geanaliseer en 'n veelvoudige ekstraksie toets (n =12) het 'n 91.70% herwinning van HS getoon. Betekenisvolle (P < 0.05) verskille is gevind tussen tonnel- en vriesdroging enersyds en sondroging andersyds, met laasgenoemde die nadeligste metode. Die vergelyking van tonneldrogingstemperature, by 'n konstante relatiewe humiditeit (RH) van 30%, het getoon dat droging by 40°C die minste HS behou het en betekenisvol (P < 0.05) verskil het van droging by 50°C. Alhoewel die droging by 60°C nie betekenisvol verskil het van die ander twee kondisies nie, het dit laer HS waardes as droging by 50°C getoon. Vriesdroging het uitstekende resultate ten opsigte van die behoud van HS gelewer (1.565% ± 0.394%; gemiddelde ± standaard afwyking), maar ekonomiese beperkings plaas noodgedwonge limiete op die toepaslikheid van hierdie drogingsmetode. Verdere studie om tonneldrogingskondisies te optimiseer word is nodig (1.526% ± 0.396%), maar veral droging by 50°C en 30% RH (1.750% ± 0.438%) het prakties aanvaarbare resultate gelewer. Toekomstige navorsing moet daarop gemik word om die spesifieke degradasie meganismes van HS gedurende die droging, vervoer en opberging van Duiwelsklouwortel te verklaar. Die NIRS ontleding van gedroogde, gemaalde Duiwelsklou wortel is vergelyk met HPLC analises van dieselfde metanolise ekstrakte wat tydens die drogingstudies gebruik is. Twee verskillende NIRS instrumente is gebruik om spektra deur diffuse weerkaatsing in die poeier te meet en kalibrasies is daaropvolgend met gedeeltelike minste vierkante ("PLS") regressie gedoen. Beide onafhanklike data stel validasie en volle kruisvalidasie is gebruik om die prestasie en voorspellingsvermoë van die onderskeie modelle te evalueer. Uitstekende voginhoud (VI) kalibrasies met 'n standaard voorspellings fout (SVF) van 0.24% (klasinterval: 2.44% tot 10.43%) en 'n korrelasie van 0.99 is gevind. Die model het goed vergelyk met die standaard laboratorium fout (SLF) van 0.14%, oor die gegewe klasinterval. Met inagneming van die sensitiwiteit van HDVC as verwysingsmetode (SLF = 0.035%), het die HS inhoud kalibrasie (klasinterval: 0.693% tot 2.244%) aanvaarbaar gepresteer met 'n SVF van 0.134%. Die beskikbare klasinterval was egter relatief klein en toekomstige NIRS studies moet gebruik maak van 'n wyer klasinterval indien moontlik. Die 8pCHG model (klasinterval: 0.069% tot 0.290%) het soortgelyk gepresteer, met 'n standaard kruisvalidasie fout van 0.028% en SLF van 0.007%. Met die insluiting van monsters van 'n tweede spesie, H. zeyheri, is beide die 8pCHG inhoud en HS:8pCHG verhouding (klasinterval: 1.84 tot 34.48) kalibrasies as moontlike metodes vir onderskeiding tussen die spesies geëvalueer. Met'n 8pCHG inhoud van ca. 0.9% het die eerste model 'n goeie skeidingsvermoë getoon. In teenstelling met vorige studies egter, het die verhoudingsmodel minder sukses getoon. Hoofkomponent analise ("PCA") van die spektra was egter baie belowend as 'n kwalitatiewe onderskeidingsmetode. Volgens hierdie studie kan NIRS 'n waardevolle tegniek wees vir die verdeling van Duiwelsklou in uitvoer klasse op grond van HS inhoud. Hierdie inhoud is egter grotendeels afhanklik van die drogingskondisies en drogingsparameters wat verder verfyn behoort te word om 'n produk van die hoogste kwaliteit met behoud van HS te verseker.

Thesis (MSc Food Sc)--University of Stellenbosch, 2011. / Please refer to full text to view abstract.

Cette thèse porte sur l'élaboration de nanoparticules (NPs) à luminescence persistante pour l'imagerie optique dans le domaine du rouge profond et du proche infrarouge. Leur utilisation présente un avantage indéniable, l'étape d'irradiation pour obtenir l'état excité pouvant être réalisée avant injection, il est possible d'éviter tout stress des tissus et autres phénomènes d'autofluorescence. Dans les compositions chimiques étudiées, elles sont par ailleurs ré-excitables in vivo. Nous présentons une synthèse originale pour l'élaboration de " petites " NPs de ZnGa2O4 :Cr3+ par voie hydrothermale assistée par chauffage micro-onde qui peut être suivi d'un traitement thermique. Les caractérisations avancées des propriétés de luminescence persistante et la structure fine du matériau a montré une corrélation directe entre la luminescence et l'ordre local des cations dans la structure (répartition et distorsion des sites cationiques). Ainsi, nous avons montré l'effet bénéfique d'une calcination sans frittage sur l'amélioration des propriétés de luminescence. Nous avons également mis en évidence le gain apporté par l'ajout d'un codopant comme l'ion Bi3+ ou la modification de la matrice avec la substitution d'une partie des ions Ga3+ par des ions Ge4+. Les limites d'optimisation de ce matériau étant atteinte, une toute nouvelle voie a été ouverte dans cette thématique en dopant la matrice avec des ions Ni2+ pour déplacer la luminescence persistante dans le domaine du proche infrarouge. L'exploitation de cette nouvelle fenêtre pour l'imagerie optique devrait permettre d'imager plus profond dans les tissus avec un meilleur rapport signal/bruit. / This thesis aims to develop persistent luminescent nanoparticles (NPs) for optical imaging in the deep red and near infrared range. Their use has a clear advantage as the irradiation step can be performed before injection, avoiding tissue stress and other autofluorescence phenomena. The chemical compositions studied are also re-excitable in vivo. We propose an original way of synthesis for the elaboration of “small” ZnGa2O4:Cr3+ NPs. Hydrothermal synthesis assisted by microwave heating followed by a heat treatment is used to obtain the NPs. The extensive characterization of the persistent luminescence properties and of the material’s fine structure showed a direct correlation between luminescence and local cation order in the structure (distribution and distortion of cationic sites). Thus, we have shown the benefits of a heat treatment without sintering on the improvement of luminescence properties. We have also highlighted the enhancement provided by the addition of a codopant such as Bi3+ ions or the modification of the matrix by substituting a part of Ga3+ ions by Ge4+ ions. The optimization limits of this material being reached, doping the matrix with Ni2+ ions to move the persistent luminescence in the near infrared range, opens a new pathway in this research field. Exploiting this new window for optical imaging should allow imaging deeper into tissue with a better signal-to-noise ratio.

O presente trabalho apresenta proposições para seleção de variáveis em avaliações sensoriais descritivas e de espectro infravermelho que contribuam com a indústria de alimentos e química através da utilização de métodos de análise multivariada. Desta forma, os objetivos desta tese são: (i) Estudar as principais técnicas de análise multivariada de dados, como são comumente organizadas e como podem contribuir no processo de seleção de variáveis; (ii) Identificar e estruturar técnicas de análise multivariada de dados de forma a construir um método que reduza o número de variáveis necessárias para fins de caracterização, classificação e predição dos produtos; (iii) Reduzir a lista de variáveis/atributos, selecionando aqueles relevantes e não redundantes, reduzindo o tempo de execução e a fadiga imposta aos membros de um painel em avaliações sensoriais; (iv) Validar o método proposto utilizando dados reais; e (v) Comparar diferentes abordagens de análise sensorial voltadas ao desenvolvimento de novos produtos. Os métodos desenvolvidos foram avaliados através da aplicação de estudos de caso, em exemplos com dados reais. Os métodos sugeridos variam com as características dos dados analisados, dados altamente multicolineares ou não e, com e sem variável dependente (variável de resposta). Os métodos apresentam bom desempenho, conduzindo a uma redução significativa no número de variáveis e apresentando índices de adequação de ajuste dos modelos ou acurácia satisfatórios quando comparados aos obtidos mediante retenção da totalidade das variáveis ou comparados a outros métodos dispostos na literatura. Conclui-se que os métodos propostos são adequados para a seleção de variáveis sensoriais e de espectro infravermelho. / This dissertation presents propositions for variable selection in data from descriptive sensory evaluations and near-infrared (NIR) spectrum analyses, based on multivariate analysis methods. There are five objectives here: (i) review the main multivariate analysis techniques, their relationships and potential use in variable selection procedures; (ii) propose a variable selection method based on the techniques in (i) that allows product prediction, classification, and description; (iii) reduce the list of variables/attributes to be analyzed in sensory panels identifying those relevant and non-redundant, such that the time to collect panel data and the fatigue imposed on panelists is minimized; (iv) validate methodological propositions using real life data; and (v) compare different sensory analysis approaches used in new product development. Proposed methods were evaluated through case studies, and vary according to characteristics in the datasets analyzed (data with different degrees of multicollinearity, presenting or not dependent variables). All methods presented good performance leading to significant reduction in the number of variables in the datasets, and leading to models with better adequacy of fit. We conclude that the methods are suitable for datasets from descriptive sensory evaluations and NIR analyses.

Avec l'objectif de réduire de la quantité de gaz à effets de serre dans l'atmosphère, les pouvoirs publics encouragent les pratiques ayant vocation à séquestrer du carbone dans les sols (reforestation, changement de pratiques agricoles). Pour en évaluer les réels bénéfices, des outils analytiques rapides, précis et peu coûteux sont nécessaires pour pouvoir comptabiliser précisément les stocks de carbone et leur évolution dans le temps. La Spectroscopie proche infrarouge (SPIR) est une technologie analytique adaptée à ce cahier des charges mais relève encore du domaine de la recherche en science du sol.Cette thèse s'est focalisée sur la première étape de cette méthode analytique: la formation du signal. Les sols étant des milieux très complexes, en termes de composition chimique et de structure physique, le signal spectroscopique est négativement impacté par les phénomènes de diffusion. Les conditions de la loi de Beer-Lambert n'étant plus remplies, les modèles chimiométriques pour prédire la teneur en carbone des sols sont moins précis et robustes. Nous proposons un système optique de mesure spectrale original et adapté aux milieux très diffusants, qui se base sur le principe de polarisation de la lumière. Il permet de sélectionner les photons ayant été moins impactés par le phénomène de diffusion. Ce signal est utilisé pour calculer un signal d'absorbance étant une bonne approximation de l'absorbance de Beer-Lambert.Ce dispositif, appelé PoLiS, a été validée expérimentalement sur des milieux modèles liquides et particulaires. Appliquée des sols pour prédire la teneur en carbone organique, les modèles de prédictions sont meilleurs avec l'absorbance calculée par PoLiS qu'avec l'absorbance calculée classiquement à partir de la mesure de réflectance. / With the goal of reducing the amount of greenhouse gases in the atmosphere, policy makers encourage practices intended to sequester carbon in soils (reforestation, changes in farming practices). New methods are required to rapidly and accurately measure soil C at field- and landscape-scales. Near infrared spectroscopy (NIRS) is an analytical technology adapted to these specifications but remains experimental research in soil science.This thesis has focused on the first step of this analytical method: signal formation. The soils are very complex materials, in terms of chemical composition and physical structure. Hence, the spectroscopic signal is negatively impacted by light scattering. Consequently, the conditions of the Beer-Lambert are no longer fulfilled, and the chemometric models to predict the carbon content of soils are less accurate and robust. We develop an original optical method based on light polarization spectroscopy to measure the absorbance of highly scattering materials. By selecting photons being less scattered, we compute a new absorbance signal which is a good approximation of the Beer-Lambert absorbance.This method, called Polis, was experimentally validated on model materials in liquid and powdered form. Applied on soils to predict Total Organic Content, the model built with the PoLiS absorbance outperform the models built with the classical absorbance computed from the diffuse reflectance signal.