Die intratracheale Applikation von Perfluorcarbonen (PFC) in ungeschädigte Lungen, z.B. als Röntgenkontrastmittel und zur PFC-induzierten cerebralen Kühlung, wird derzeit diskutiert. Ob es aufgrund der Dichte und Sauerstofflöslichkeit der PFC zu einer Beeinflussung der cerebralen Oxygenierung und Hämodynamik durch die pulmonale PFC Applikation kommt, ist bisher unbekannt. Änderungen der Konzentration von cerebralem oxygeniertem und totalem Hb koennen mittels Near-infrared Spectroscopy gemessen werden. I.) Effekt durch die PFC-Applikation in gesunde Lungen neugeborener Ferkel: Es wurden zwei verschiedene Applikationsgeschwindigkeiten (30 ml PFC pro kg Körpergewicht als Bolusgabe versus 1,5 ml/min pro kg) und zwei Füllvolumen (30 versus 10 ml/kg) verglichen. Die Bolusgabe bewirkt einen sofortigen Abfall des PaO2 und der cerebralen Oxygenierung, bei langsamer Gabe des gleichen Volumens ist dies weniger ausgeprägt. Mit 10 ml/kg PFC fand sich nahezu keine Beeinflussung der Parameter. II.) Effekte der Änderung der FiO2 in PFC-gefüllten Lungen: Hierfür wurden Änderungen der FiO2 unter konventioneller Druckbeatmung vor PFC-Applikation und unter PFC-Füllung (30 oder 10 ml/kg PFC) verglichen. Beide PFC-Volumen (mit FiO2 1,0) bedingten PaO2-Werte wie unter CMV mit FiO2 von 0,5. Mit 30 ml/kg PFC kam es unter FiO2 von 0,5 zur Abnahme des cerebralen oxygenierten Hb. Zusammenfassend ergibt sich, dass die Applikation von 10 ml PFC/kg bevorzugt werden sollte. Bei kompletter Füllung der Lungen werden durch langsame Applikation cerebrale Nebenwirkungen minimiert. In PFC-gefüllten gesunden Lungen ist zum Erhalt der systemischen und cerebralen Oxygenierung die FiO2 zu erhöhen. / Intratracheal administration of perfluorochemicals (PFC) has been suggested for reasons other than respiratory insufficiency, such as pulmonary imaging and PFC-associated brain cooling. Due to their high density and oxygen solubility, PFC application has been described to affect systemic hemodynamics and oxygenation during liquid ventilation. Whether the PFC application into healthy lungs or changes in inspired oxygen fraction (FiO2) in PFC-filled healthy lungs affects cerebral hemodynamics is not known. Changes in the concentration of cerebral oxygenated and total Hb can be measured by near-infrared spectroscopy (NIRS). I.) Initial effects of PFC application into healthy lungs of newborn piglets: Two different filling modes (rapid versus slow) and two different filling volumes (slow filling of 30 versus 10 ml PFC/kg body weight) were compared. Rapid filling caused an immediate drop of systemic and cerebrale oxygenation, which was less prominent by filling 30 ml/kg PFC slowly. Almost no changes for all parameters were found with 10 ml kg/PFC. II.) Effects of variations in FiO2 in the PFC filled lungs of healthy piglets: Changes in FiO2 during conventional mechanical ventilation (CMV) prior to PFC-application and in the PFC-filled lungs (30 ml/kg or 10 ml/kg PFC) were compared. Both PFC-volumes (at a FiO2 of 1.0) caused PaO2-values that were similar to CMV with FiO2 of 0.5. In the 30 ml/kg PFC group a reduction of cerebral oxygenated Hb was found at FiO2 of 0.5. According to the data application of 10 ml/kg PFC should be preferred. If complete filling of the lung is needed, the slow administration of PFC minimizes cerebral side effects. In PFC- filled healthy lungs an increase in FiO2 is necessary to maintain systemic and cerebral oxygenation.

Thesis submitted in fulfilment of the requirements for the degree Master of Technology Chemistry in the Faculty of (Science) Supervisor: Professor T.N. van der Walt Bellville campus Date submitted: October 2011 / It is important to quantify polymeric components in a coating because they greatly influence the performance of a coating. The difficulty associated with analysis of polymers by Fourier transform infrared (FTIR) analysis’s is that colinearities arise from similar or overlapping spectral features. A quantitative FTIR method with attenuated total reflectance coupled to multivariate/ chemometric analysis is presented. It allows for simultaneous quantification of 3 polymeric components; a rheology modifier, organic opacifier and styrene acrylic binder, with no prior extraction or separation from the paint. The factor based methods partial least squares (PLS) and principle component regression (PCR) permit colinearities by decomposing the spectral data into smaller matrices with principle scores and loading vectors. For model building spectral information from calibrators and validation samples at different analysis regions were incorporated. PCR and PLS were used to inspect the variation within the sample set. The PLS algorithms were found to predict the polymeric components the best. The concentrations of the polymeric components in a coating were predicted with the calibration model. Three PLS models each with different analysis regions yielded a coefficient of correlation R2 close to 1 for each of the components. The root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) was less than 5%. The best out-put was obtained where spectral features of water was included (Trial 3). The prediction residual values for the three models ranged from 2 to -2 and 10 to -10. The method allows paint samples to be analysed in pure form and opens many opportunities for other coating components to be analysed in the same way.

Pelchem, a commercial subsidiary of Necsa (South African Nuclear Energy Corporation), produces a range of commercial fluorocarbon products while driving research and development initiatives to support the fluorine product portfolio. One such initiative is to develop improved analytical techniques to analyse product composition during development and to quality assure produce. Generally the C–F type products produced by Necsa are in a solution of anhydrous HF, and cannot be directly analyzed with traditional techniques without derivatisation. A technique such as vibrational spectroscopy, that can analyze these products directly without further preparation, will have a distinct advantage. However, spectra of mixtures of similar compounds are complex and not suitable for traditional quantitative regression analysis. Multivariate data analysis (MVA) can be used in such instances to exploit the complex nature of spectra to extract quantitative information on the composition of mixtures. A selection of fluorocarbon alcohols was made to act as representatives for fluorocarbon compounds. Experimental design theory was used to create a calibration range of mixtures of these compounds. Raman and infrared (NIR and ATR–IR) spectroscopy were used to generate spectral data of the mixtures and this data was analyzed with MVA techniques by the construction of regression and prediction models. Selected samples from the mixture range were chosen to test the predictive ability of the models. Analysis and regression models (PCR, PLS2 and PLS1) gave good model fits (R2 values larger than 0.9). Raman spectroscopy was the most efficient technique and gave a high prediction accuracy (at 10% accepted standard deviation), provided the minimum mass of a component exceeded 16% of the total sample. The infrared techniques also performed well in terms of fit and prediction. The NIR spectra were subjected to signal saturation as a result of using long path length sample cells. This was shown to be the main reason for the loss in efficiency of this technique compared to Raman and ATR–IR spectroscopy. It was shown that multivariate data analysis of spectroscopic data of the selected fluorocarbon compounds could be used to quantitatively analyse mixtures with the possibility of further optimization of the method. The study was a representative study indicating that the combination of MVA and spectroscopy can be used successfully in the quantitative analysis of other fluorocarbon compound mixtures. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2012.

Pelchem, a commercial subsidiary of Necsa (South African Nuclear Energy Corporation), produces a range of commercial fluorocarbon products while driving research and development initiatives to support the fluorine product portfolio. One such initiative is to develop improved analytical techniques to analyse product composition during development and to quality assure produce. Generally the C–F type products produced by Necsa are in a solution of anhydrous HF, and cannot be directly analyzed with traditional techniques without derivatisation. A technique such as vibrational spectroscopy, that can analyze these products directly without further preparation, will have a distinct advantage. However, spectra of mixtures of similar compounds are complex and not suitable for traditional quantitative regression analysis. Multivariate data analysis (MVA) can be used in such instances to exploit the complex nature of spectra to extract quantitative information on the composition of mixtures. A selection of fluorocarbon alcohols was made to act as representatives for fluorocarbon compounds. Experimental design theory was used to create a calibration range of mixtures of these compounds. Raman and infrared (NIR and ATR–IR) spectroscopy were used to generate spectral data of the mixtures and this data was analyzed with MVA techniques by the construction of regression and prediction models. Selected samples from the mixture range were chosen to test the predictive ability of the models. Analysis and regression models (PCR, PLS2 and PLS1) gave good model fits (R2 values larger than 0.9). Raman spectroscopy was the most efficient technique and gave a high prediction accuracy (at 10% accepted standard deviation), provided the minimum mass of a component exceeded 16% of the total sample. The infrared techniques also performed well in terms of fit and prediction. The NIR spectra were subjected to signal saturation as a result of using long path length sample cells. This was shown to be the main reason for the loss in efficiency of this technique compared to Raman and ATR–IR spectroscopy. It was shown that multivariate data analysis of spectroscopic data of the selected fluorocarbon compounds could be used to quantitatively analyse mixtures with the possibility of further optimization of the method. The study was a representative study indicating that the combination of MVA and spectroscopy can be used successfully in the quantitative analysis of other fluorocarbon compound mixtures. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2012.

Afin de progresser dans la compréhension de la structure de vibration-rotation de l'acétylène dans son état électronique fondamental, un modèle global a été développé avec succès pour trois de ses isotopologues, permettant d'attribuer de nouvelles données de spectres enregistrés sous diverses conditions expérimentales. L'ensemble des programmes d'analyse rovibrationnelle globale conçus à l'Université Catholique de Louvain par le Pr. A. Fayt et al. ont été utilisés pour répondre aux demandes de collaborateurs tels que les Prs. A. Campargue, A. Jolly ou encore R. Georges dans le cadre de plusieurs problèmes de type spectroscopique, notamment pour des applications astrophysiques. Le modèle global et son pouvoir prédictif mis ainsi à l'épreuve, nous avons démontré la validité de nos jeux de paramètres pour ces trois molécules.<p><p>Concernant l'isotopologue principal, $H^{12}C^{12}CH$, 14 nouvelles bandes ont été mises à jour à partir de spectres enregistrés en CRDS à Grenoble par A. Campargue et al. Une analyse rovibrationnelle globale a été effectuée jusqu'à une énergie de 8600 cm$^{-1}$. 10750 raies ont été ajustées simultanément sur les 12137 attribuées dans la littérature. 266 paramètres ont été déterminés par la méthode de moindres-carrés. La déviation standard sans dimension du fit est de 0.92. La bande $u_{5}$-$u_{4}$, centrée vers 117 cm$^{-1}$ a été simulée. La valeur du moment de transition associé, $ / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Non-invasive methods to evaluate skeletal muscle oxidative capacity have beenemerging as a viable substitute for invasive methods in recent years. One ofthose methods utilises near-infrared spectroscopy (NIRS) to calculate V O2mrecovery off-kinetics following an exercise. The data analysis of the measuredsignals from the NIRS is still done manually in a time-consuming and dauntingprocess. The present thesis aimed to develop software, associated with theNIRS method, capable of analysing the recovery from a repeated arterialocclusion protocol following an exercise to assess muscle oxidative capacity.Additionally, to analyse the recovery from ischemic preconditioning as a singletest to assess muscle oxidative capacity. A method that has never been utilisedbefore.11 active, healthy subjects were analysed to calculate their recovery rate.Subjects underwent ischemic preconditioning before exercising for 6 minutesat 80% of gas exchange threshold. A repeated arterial occlusion protocol wascarried out after the exercise. A software was developed in R that utilised linearregression as well as exponential fitting to calculate the recovery rate of eachsubject during both the ischemic preconditioning and the occlusion protocol.The calculated results were compared to predetermined recovery rate results ofeach subject. The calculated results of the repeated arterial occlusion protocolgave similar results to the predetermined ones and even more data on eachsubject’s recovery from an exercise. The calculated results of the ischemicpreconditioning were promising and implied that ischemic preconditioning asa single test can be utilised as a method to assess muscle oxidative capacity.However, further research is required to confirm it. / Icke-invasiva metoder för att utvärdera skelettmuskulaturens oxidativa förmågahar på senare år blivit en användbar ersättning för invasiva metoder. Nearinfrared spectroscopy (NIRS) är en utav dessa metoder och har använts föratt beräkna V O2m återhämtning off-kinetics efter träning. Dataanalysen av deuppmätta signalerna från NIRS görs fortfarande manuellt i en tidskrävandeoch felbenägen process. Syftet med den här uppsatsen var att utveckla enprogramvara som kopplad till NIRS metoden, kan analysera återhämtningenfrån ett protokoll med upprepade arteriella ocklusioner efter träning för attutvärdera skelettmuskulaturens oxidativa förmåga. Dessutom att analyseraåterhämtningen från ischemic preconditioning som ett enda test för att utvärderaskelettmuskulaturens oxidativa förmåga. En metod som aldrig tidigare använts.11 aktiva, friska försökspersoner analyserades för att beräkna deras återhämtningshastighet.Försökspersonerna genomgick ischemic preconditioning innan de tränadei 6 minuter med 80% av gasutbyteströskeln. Ett protokoll med upprepadearteriella ocklusioner genomfördes efter träningen. En programvara utveckladesi R som använde sig av linjär regression och monoexponentiell funktionsanpassningför att beräkna återhämtningshastigheten för varje försöksperson under bådeichemic preconditioning och ocklusionprotokollet. De beräknade resultatenjämfördes med förutbestämda resultat av återhämtningshastigheten för varjeförsöksperson. De beräknade resultaten av ocklusionprotokollet gav liknanderesultat som de förutbestämda och gav ännu fler uppgifter om varje försökspersonåterhämtning efter träning. De beräknade resultaten av ischemic preconditioningvar lovande och indikerade att ischemic preconditioning som ett enda testkan användas som en metod för att utvärdera skelettmuskulaturens oxidativaförmåga. Det krävs dock ytterligare forskning för att bekräfta detta.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / Two cationic polymerizable surfactants (surfmers), (11-acryloyloxyundecyl)dimethyl-(2-hydroxyethyl)ammonium bromide (Ethanol surfmer) and (11-acryloyloxyundecyl)-dimethylethylammonium bromide (Ethyl surfmer) were synthesized and characterized. Characterization was done using, conductivity, Fourier transform infra-red spectroscopy (FT-IR), electrospray mass spectrometry (ESMS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), small angle X-ray scattering (SAXS) and polarized light microscopy with a heating stage. These surfmers and the commercial surfactant cetyltrimethylammonium bromide (CTAB) were used for functionalization of sodium montmorillonite (Na+-MMT), thereby forming organophilic MMT. The functionalization of MMT dispersions was carried out by ion exchange of the sodium ions in Na+-MMT by surfactants in aqueous media. Organophilic MMT clays were then dispersed in styrene and subsequently polymerized by a free radical reaction to yield polystyrene-clay nanocomposites. This in-situ intercalative polymerization process resulted in an exfoliated structure for Ethyl surfmer modified clay, a partially exfoliated structure for Ethanol surfmer modified clay and an intercalated structure for CTAB modified clay. These nanocomposite structures were confirmed by SAXS and transmission electron microscopy (TEM). The nanocomposites exhibited enhanced thermal stability. All the nanocomposites exhibited an inferior storage modulus (GI) at low clay contents relative to polystyrene. At higher clay loadings there was an increase in GI which was dependent on the level of clay dispersion and the clay content. All the nanocomposites showed an increase in glass transition temperature (Tg), regardless of the amount of clay and the level of clay dispersion. There was a shift towards higher temperatures and broadening of the tan δ peak, which was in turn dependent on the amount of clay and level of clay dispersion. Molecular masses of polystyrene-clay nanocomposites were in the range 105 g/mol for bulk polymerization relative to 103 g/mol for solution polymerization as revealed by gel permeation chromatography (GPC).

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / This thesis begins with the description of the preparation of thirteen dithioesters (of the form Z- (C=S)-S-R) which were characterized via Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR) and ultraviolet spectroscopy (UV). The dithioesters were then used as reversible addition-fragmentation chain transfer (RAFT) mediating agents in the bulk polymerization of styrene, in order to observe differences in the kinetic behaviour of the polymerizations and, as a result, the efficiencies of the dithioesters in mediating the polymerizations.

Thesis (MSc (Wine Biotechnology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Fermentation is a complex process in which raw materials are transformed into high-value products, in this case, grape juice into wine. In this modern and economically competitive society, it is increasingly important to consistently produce wine to definable specifications and styles. Process management throughout the production stage is therefore crucial to achieve effective control over the process and consistent wine quality. Problematic wine fermentations directly impact on cellar productivity and the quality of wine. Anticipating stuck or sluggish fermentations, or simply being able to foresee the progress of a given fermentation, would be extremely useful for an enologist or winemaker, who could then take suitable corrective steps where necessary, and ensure that vinifications conclude successfully. Conventional methods of fermentation monitoring are time consuming, sometimes unreliable, and the information limited to a few parameters only. The current effectiveness of fermentation monitoring in industrial wine production can be much improved. Winemakers currently lack the tools to identify early signs of undesirable fermentation behaviour and to take preventive actions. This study investigated the application of Fourier transform mid infrared (FT-IR) spectroscopy in transmission mode, for the quantitative and qualitative monitoring of alcoholic fermentation during industrial wine production. The major research objectives were firstly to establish a portfolio of quantitative calibration models suitable for quantification of the major quality determining parameters in fermenting must. The second major research objective focused on a pilot study aimed at exploring the use of off-line batch multivariate statistical process control (MSPC) charts for actively fermenting must. This approach used FT-IR spectra only, for the purpose of qualitative monitoring of alcoholic fermentation in industrial wine production. Towards these objectives, a total of 284 industrial-scale, individual, actively fermenting tanks of the seven major white cultivars and blends, and nine major red cultivars, of Namaqua Wines, Vredendal, South Africa, were sampled and analysed with FT-IR spectroscopy and appropriate reference methods during vintages 2007 to 2009. For the quantitative strategy, partial least squares regression (PLS1) calibration models for determination of the classic wine parameters ethanol, pH, volatile acidity (VA), titratable acidity (TA) and the total content of glucose plus fructose, were redeveloped to provide a better fit to local South African samples. New PLS1 models were developed for the must components glucose, fructose and yeast assimilable nitrogen (YAN), all of which are frequently implicated in problem fermentations. The regression statistics, that included the standard error of prediction (SEP), coefficient of determination (R2) and bias, were used to evaluate the performance of the redeveloped calibration models on local South African samples. Ethanol (SEP = 0.15 %v/v, R2 = 0.999, bias = 0.04 %v/v) showed very good prediction and with a residual predictive deviation (RPD) of 30, rendered an excellent model for quantitative purposes in fermenting must. The models for pH (SEP = 0.04, R2 = 0.923, bias = -0.01) and VA (SEP = 0.07 g/L, R2 = 0.894, bias = -0.01 g/L) with RPD values of 4 and 3 respectively, showed that the models were suitable for screening purposes. The calibration model for TA (SEP = 0.35 g/L, R2 = 0.797, bias = -0.004 g/L) with a RPD of 2, proved unsatisfactory for quantification purposes, but reasonable for screening purposes. The calibration model for the total content of glucose plus fructose (SEP = 0.6.19 g/L, R2 = 0.993, bias = 0.02 g/L) with a RPD of 13, showed very good prediction and can be used to quantify total glucose plus fructose content in fermenting must. The newly developed calibration models for glucose (SEP = 4.88 g/L, R2 = 0.985, bias = -0.31 g/L) and fructose (SEP = 4.14 g/L, R2 = 0.989, bias = 0.64 g/L) with RPD values of 8 and 10 respectively, also proved fit for quantification of these important parameters. The new calibration models of ethanol, total glucose plus fructose; and glucose and fructose individually, showed an excellent relation to local South African samples and can be easily implemented by the wider wine industry. Two calibration models were developed to determine YAN in fermenting must by using different reference methods, namely the enzyme-linked spectrophotometric assay and Formol titration method, respectively. The results showed that enzyme-linked assays provided a good quantitative model for white fermenting must (SEP = 14.10 mg/L, R2 = 0.909, bias = -2.55 mg/L, RPD = 6), but the regression statistics for predicting YAN in red fermenting must, were less satisfactory (data not shown). The Formol titration method could be used successfully in both red- and white fermenting must (SEP = 16.37 mg/L, R2 = 0.912, bias = -1.01 mg/L, RPD = 4). A minor, but very important finding was made with respect to the storage of must samples that were taken from tanks, but that could not immediately be analysed with FT-IR spectroscopy or reference values. Principal component analysis (PCA) of frozen samples showed that must samples could be stored frozen for up to 3 months and still be used to expand the calibration sample sets when needed. Therefore, samples can be kept frozen to a later stage if immediate analyses are not possible. For the purpose of the pilot study that focused on the use of FT-IR spectroscopy for qualitative off-line monitoring of alcoholic fermentation, a total of 21 industrial-scale fermentation tanks were monitored at 8- or 12-hourly intervals, from the onset of fermentation to complete consumption of the grape sugars. This part of the work excluded quantitative data, and only used FT-IR spectra. MSPC charts were constructed on the PLS scores of all the FT-IR spectra taken at the various time intervals of the different batches, using time as the y-variable. The primary aim of this research objective was to evaluate if the PLS batch models could be used to discriminate between normal and problem alcoholic fermentations. The models that were constructed clearly showed the variations in patterns over time, between red- and white wine alcoholic fermentations. One Colombar tank that was fermented at very low temperature in order to achieve a specific wine style, was characterised by a fermentation pattern that clearly differed form the rest of the Colombar fermentations. This atypical fermentation was identified by the batch models constructed in this study. PLS batch models over all the Colombar fermentations clearly identified the normal and problem fermentations. The results obtained in this study showed that FT-IR spectroscopy showed great potential for effective quantitative and qualitative monitoring of alcoholic fermentation during industrial wine production. The work done in this project resulted in the development of a portfolio of calibration models for the most important quality determining parameters in fermenting must. The quantitative models were subjected to extensive independent test set validation, and have subsequently been implemented for industrial use at Namaqua Wines. Multivariate batch monitoring models were established that show good discriminatory power to detect problem fermentations. This is a very useful diagnostic tool that can be further developed by monitoring more normal and problem fermentations. Future work in this regard, will focus on further optimisation and expansion of the quantitative and qualitative calibration models and implementation of these in the respective wineries of Namaqua Wines. / AFRIKAANSE OPSOMMING: Fermentasie is ‘n komplekse proses waartydens rou material getransformeer word na produkte van hoë waarde, in hierdie geval, druiwesap na wyn. In die huidige ekonomies-kompeterende samelewing, is dit al hoe meer belangrik om volhoubaar wyn te produseer wat voldoen aan definieerbare spesifikasies en style. Goeie prosesbestuur tydens die wynproduksie stadium is baie belangrik om herhaalbaarheid en gehaltebeheer te verseker. Problematiese wynfermentasies het ’n direkte impak op beide kelderproduktiwiteit en wynkwaliteit. Die voorkoming van slepende- of steekfermentasies, of selfs net om probleme te voorsien, sou uiters bruikbaar wees vir ‘n wynkundige of wynmaker, wat dan die toepaslike regstellende stappe kan neem waar nodig, om te verseker dat die wynbereiding suksesvol voltooi word. Konvensionele metodes van monitering van alkoholiese fermentasie is tydrowend, soms onbetroubaar en die inligting beperk tot ‘n paar parameters. Die huidige effektiwiteit van fermentasie monitering in industriële wynproduksie kan heelwat verbeter word. Wynmakers ervaar tans ’n behoete aan tegnologië wat die vroeë tekens van ongunstige fermentasiepatrone kan identifiseer, en hul doeltreffendheid om moontlike regstellende aksies te neem, is dus beperk. Hierdie studie het die toepassing van Fourier transformasie mid-infrarooi (FT-IR) spektroskopie in transmissie, ondersoek met die oog op kwantitatiewe en kwalitatiewe monitering van alkoholiese gisting tydens industriële wynproduksie. Die vernaamste navorsingsdoelwitte was eerstens om ’n portefeulje van kwantitatiewe kalibrasiemodelle te vestig, wat geskik is om die belangrikste kwaliteitsbepalende parameters in gistende mos te kwantifiseer. Die tweede hoofnavorsingsdoelwit was ’n loodsstudie wat ondersoek ingestel het na die opstel van multiveranderlike statistiese proseskontrole grafieke van aktief-gistende mos, met die oog op aflyn-kwalitatiewe monitering van alkoholiese gisting in industriële wynproduksie. Hiervoor is slegs FT-IR spektra gebruik. Vir die doel van hierdie studie is monsters van ’n totaal van 284 individuele, aktief-gistende tenke van die sewe hoof wit kultivars en hul versnydings en nege hoof rooi kultivars van Namaqua Wyne, Vredendal, Suid Afrika, geneem. Al die monsters is met toepaslike chemiese metodes en FT-IR spektroskopie analiseer tydens die parsseisoene van 2007 tot 2009. Vir die kwantitatiewe strategie is parsiële kleinste kwadraat (PKK1) kalibrasiemodelle vir die bepaling van die klassieke wynparameters etanol, pH, vlugtige suur (VS), titreerbare suur (TS) en die totale konsentrasie van glukose plus fruktose herontwikkel, om beter te pas op plaaslike Suid-Afrikaanse monsters. Nuwe PKK1 kalibrasiemodelle is ontwikkel vir die komponente glukose, fruktose en gis-assimileerbare stikstof, aangesien hierdie komponente gereelde aanduidings van probleemgisting is. Die regressiestatistieke het die standaardvoorspellingsfout (SVF), bepalingskoëffisiënt (R2) en sydigheid ingesluit en was gebruik om die prestasie van die herontwikkelde kalibrasiemodelle vir plaaslike Suid-Afrikaanse monsters te evalueer. Etanol (SVF = 0.15 %v/v, R2 = 0.999, sydigheid = 0.04 %v/v) het baie goeie regressiestatistiek getoon en met ‘n relatiewe voorspellingsafwyking (RVA) van 30, was dit ‘n uitstekende model vir kwantifisering in gistende mos. Die modelle vir pH en VS met RVA waardes van 4 en 3 onderskeidelik, is geskik vir semi-kwantitatiewe toepassings. Die kalibrasiemodel vir TS met ‘n RVA waarde van 2, was nie geskik vir akkurate kwantifisering nie, maar wel vir semikwantitatiewe analises. Die kalibrasiemodel vir die totale glukose plus fruktose inhoud in gistende mos, met ‘n RVA waarde van 13, het uitstekende regressiestatistiek gegee en is geskik vir akkurate kwantifiseringsdoeleindes. Die nuut-ontwikkelde kalibrasiemodelle vir glukose en fruktose, met RVA waardes van onderskeidelik 8 en 10, is geskik vir akkurate kwantifisering van hierdie belangrike parameters. Die kalibrasiemodelle vir etanol, totale glukose plus fruktose, en glukose en fruktose afsonderlik, het uitstekende korrelasies getoon met plaaslike Suid-Afrikaanse monsters en is gereed om toepassing te vind in die wyer wynindustrie. Twee kalibrasiemodelle is ontwikkel om gis-assimileerbare stikstof in gistende mos te bepaal, deur gebruik te maak van verskillende verwysingsmetodes van analise; hierdie metodes was ‘n ensiem-gekoppelde spektrofotometriese toets en die Formoltitrasie metode. Resultate het getoon dat goeie regressiestatistiek vir FT-IR spektroskopie-gebaseerde kalibrasiemodelle waar data wat met die ensiem-gekoppelde toetse verkry is, as verwysingwaardes gebruik is, in wit gistende mos (SVP = 14.10 mg/L, R2 = 0.909, sydigheid = -2.55 mg/L, RVA = 6), maar nie in rooi gistende mos nie. Die Formoltitrasie metode as verwysingsmetode, was geskik vir die ontwikkeling van goeie kalibrasiemodelle in beide rooi- en wit gistende mos (SVP = 16.37 mg/L, R2 = 0.912, sydigheid = -1.01 mg/L, RVA = 4). ’n Sekondêre, maar baie belangrike bevinding is gemaak met betrekking tot die stoor van mosmonsters wat geneem is van tenke, maar wat nie dadelik met die verwysingsmetodes en FT-IR spektroskopie analiseer kon word nie. Multiveranderlike hoofkomponentanalise op vars en gevriesde sapmonsters het getoon dat gevriesde monsters gebruik kan word om die kalibrasie datastel uit te brei, wanneer benodig. Dus, sapmonsters kan gevries word tot ’n later stadium as onmiddelike analises nie moontlik is nie. Vir die doel van die tweede navorsingsdoelwit van die studie, naamlik kwalitatiewe af-lyn monitering van alkoholiese fermentasie met FT-IR spektroskopie, is ‘n totaal van 21 industriëlegrootte fermentasietenks ge-monitor deur sapmonsters met 8- tot 12-uurlikse intervalle te trek, vanaf die begin van fermentasie, totdat al die druifsuiker gemetaboliseer is. Vir hierdie deel van die werk is die kwantitatiewe data nie gebruik nie; slegs die FT-IR spektra. Multiveranderlike statistiese proseskontrole grafieke is opgestel op grond van die PKK tellings wat bereken is op al die FT-IR spektra wat gemeet is by die verskillende tydsintervalle. Vir hierdie analise is tyd as y-veranderlike gebruik. Die vernaamste doel van hierdie ondersoek was om te evalueer of die PKK-gebaseerde modelle kon onderskei tussen normale en slepende gistings. Die modelle wat verkry is, het die variasie oor tyd in die fermentasiepatrone tussen wit- en rooiwyn fermentasies tydens alkoholiese gisting, duidelik uitgewys. Een Colombar tenk wat teen baie lae temperatuur gefermenteer is om ‘n spesifieke wynstyl te verkry, se fermentasiepatroon het aansienlik verskil van die ander Colombar tenks wat gemonitor is, en hierdie atipiese patroon is ook deur die kwalitatiewe modelle identifiseer. ‘n PKK model oor al die Colombar fermentasies kon duidelik tussen normale en slepende gistings onderskei. Die resultate wat in hierdie studie verkry is, het getoon dat FT-IR spektroskopie baie goeie potensiaal toon vir die aanwending van kwantitatiewe en kwalitatiewe monitering van alkoholiese fermentasie tydens industriële wynproduksie. Die werk wat in hierdie projek gedoen is, het gelei tot die vestiging van ‘n portefeulje van kalibrasiemodelle vir die belangrikste kwaliteitsbepalende parameters in fermenterende mos. Die kwantitatiewe modelle is baie deeglik getoets met onafhanlike toets datastelle, en daarna is die kalibrasiemodelle geimplementeer vir industriële gebruik by Namaqua Wyne. Multiveranderlike statistiese proseskontrole grafieke wat baseer is op data wat vanaf 21 verskillende fermentasietenks verkry is, het baie goeie potensiaal getoon om probleemfermentasies vroeg te identifiseer. Dié grafieke is ‘n baie nuttige diagnostiese hulpmiddel wat verder ontwikkel kan word om verskillende tipes probleemfermentasies te monitor. Toekomstige navorsing in hierdie konteks, sal toegespits word op die optimisering en uitbreiding van die kwantitatiewe en kwalitatiewe modelle, sowel as toepassing van die tegnieke in die onderskeie kelders van Namaqua Wyne.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The two white seedless table grape cultivars, Regal Seedless and Thompson Seedless fulfil a very important role in securing foreign income not only for the South African table grape industry, but the South African economy as a whole. These two cultivars, however, are like so many other white table grape cultivars, also prone to browning, especially netlike browning on Regal Seedless and internal browning on Thompson Seedless grapes. This leads to huge financial losses every year, since there is no established way to assess at harvest, during storage or during packaging, whether the grapes will eventually turn brown. In other words, there is no well-known protocol of assessing the browning risk of a particular batch of grapes prior to export. Numerous studies have been undertaken to determine the exact cause of browning and how it should be managed, but to date, no chemical or physical parameter has been firmly associated with the phenomenon. The overall aim of this study was thus to find an alternative way to deal with the problem by investigating the potential of near infrared (NIR) spectroscopy as a fast, non-destructive measurement technique to determine the browning potential of whole white seedless table grapes. A secondary aim was the determination of optimal ripeness of table grapes. In this way harvest maturity and quality indicative parameters namely total soluble solids (TSS), titratable acidity (TA), pH, glucose and fructose, also associated with the browning phenomenon, was quantified using models based on infrared spectra. Three different techniques (a) Fourier transform Near Infrared (FT-NIR), (b) Fourier transform – Mid Infrared (FT-MIR) and (c) Fourier transform – Mid Infrared Attenuated Total Reflectance (FT-MIR ATR) spectroscopy were investigated to determine these parameters. This was done so that a platform of different technologies would be available to the table grape industry. The grapes used in this study were harvested over two years (2008 and 2009) and were sourced from two different commercial vineyards in the Hex River valley, Western Cape, South Africa. Different crop loads (the total amount of bunches on the vines per hectare) were left for Regal Seedless (75 000, 50 000 and 35 000) and for Thompson Seedless (75 000 and 50 000). Three rows were used for Regal Seedless and two rows for Thompson Seedless. Each row had six sections which each represented a repetition for each crop load. In 2008 these cultivars were harvested early at 16°Brix, at optimum ripeness (18°Brix) and late at 20°Brix. In 2009 they were harvested twice at the optimum ripeness level. Berries from harvested bunches were crushed and the juice was used to determine the reference values for the different parameters in the laboratory according to their specific methods. The obtained juice was also scanned on the three different instruments. Different software (OPUS 6.5 for the FT-NIR and FT-MIR ATR instruments and Unscrambler version 9.2 for the FT-MIR instrument) as well as different spectral pre-processing techniques were also evaluated before construction of the models for all the instruments. Partial least squares (PLS) regression was used for the construction of the different calibration models. Different regression statistics, that included the root mean square error for prediction (RMSEP); the coefficient of determination (R2); the residual prediction deviation (RPD) and the bias were used to evaluate the performance of the developed calibration models. Calibration models which are fit for screening purposes were obtained on the FT-NIR and FTMIR ATR instruments for TSS (11.40 - 21.80°Brix) (R2 = 85.92%, RMSEP = 0.71 °Brix RPD = 2.67 and bias = 0.03°Brix), pH (2.94 - 3.9) (R2 = 85.00%, RMSEP = 0.08 RPD = 2.59 and bias = -0.01) and TA (4.3 - 13.1 g/L), (R2 = 90.77%, RMSEP = 0.48 g/L RPD = 3.30 and bias = -0.03 g/L). Models for fructose (46.70 – 176.82 g/L) (R2 = 74.66%, RMSEP = 9.28 g/L RPD = 2.00 and bias = 1.10 g/L) and glucose (20.36 – 386.67 g/L) (R2 = 70.71%, RMSEP = 11.10 g/L RPD = 1.87 and bias = 1.64 g/L) were obtained with the FT-NIR and FT-MIR ATR instruments that were in some instances fit for screening purposes and in some instances unsuitable for quantification purposes. The FT-MIR instrument gave models for all the parameters that were not yet suitable for quantification purposes. Combined spectral ranges used for calibration were often similar for some parameters, namely 12 493 - 5 446.2 for TSS and pH, 6 101.9 - 5 446.2 for TSS, TA and fructose and 4 601.5 - 4 246.7 for pH and fructose on the FT-NIR instrument, 2 993.2 - 2 322.3 for pH, TA and glucose and 1 654.3 - 649.4 for pH and glucose on the FT-MIR ATR instrument and sometimes they were adjacent (3 996.6 - 3 661.2, 3 663.5 - 3 327.7 and 3 327.2 - 2 322.3 for TSS and glucose, 1 988.3 - 1 652.8 and 1 654.3 - 649.4 for TSS, pH and TA. Other times they were overlapping (1 654.3 - 649.4 and 1 318.8 - 649.4) for pH, TA and fructose on the FT-MIR ATR instrument. This is a very good sign for transfer of this technology to a handheld device, where adjacent and/ or overlapping wavenumbers are crucial. Instruments which have to determine different parameters over large spectral ranges are not only impractical, because the instrument has to be big, but because it is also very expensive. Another advantage of implementing especially FT-NIR spectroscopy as a fast, accurate and inexpensive technique for determining harvest maturity and quality parameters is because no sample preparation is necessary and very little waste (few single berries tested) is produced. This is a pre-requisite which is highly recommended in the green era that we are currently living in and will do so for aeons to come. A platform of technologies has now been made available through this study for the determination of the respective parameters in future table grape samples by just taking their spectra on one of the instruments. Indeed something that has not been possible or available for the South African table grape industry before. Berries for the browning experiments were scanned on a FT-NIR instrument immediately after harvest (before cold storage) and again after cold storage. Before cold storage they were scanned on each side of the berry and after cold storage they were scanned twice on a brown spot if browning was present and twice on a clear spot, irrespective of whether browning was present or not. Inspection of the berries for the incidence of browning after cold storage revealed that Regal Seedless had a higher incidence of browning (68% in 2008 and 66% in 2009) than Thompson Seedless (21% in 2008 and 25% in 2009). Regal Seedless was also more prone to external browning, specifically netlike browning, whereas Thompson Seedless was more prone to internal browning, despite the different phenotypes of browning that were present on both. Principal component analysis (PCA) done on the spectra obtained before and after cold storage revealed that NIR can capture the changes related to cold storage with the first principal components explaining almost 100% of the variation in the spectra. Classification models also build using PCA was based on spectra of berries that remained clear before and after cold storage and those that turned brown after cold storage. Classification models of berries based on spectra obtained after cold storage (browning present) had a better total accuracy (94% for training- and 87% for test datasets), than the classification models based on spectra obtained before cold storage (79% for training- and 64% for test datasets). The implication of this is that the current models will be able to classify berries in terms of those which have turned brown already and those that remained clear better after cold storage than before cold storage, which is the critical stage where we want to actually know whether the berries will turn brown or not. The potential, however, to use NIR spectroscopy to detect browning before harvest already on white seedless grapes is still present, since all these models were built using the whole NIR spectrum. No variable selection was thus done and all the different browning phenotypes were also used together. Further analysis of the data will thus be based on using variable selection techniques like particle swarm optimization (PSO) to select certain wavelengths strongly associated with the browning phenomenon and only on the main types of browning (netlike on Regal Seedless and internal browning on Thompson Seedless). This study has major implications for the table grape industry, since it is the first time that the possibility to predict browning with other methods than visual inspection, especially before cold storage, is shown. / AFRIKAANSE OPSOMMING: Die twee wit pitlose tafeldruif kultivars, Regal Seedless en Thompson Seedless onderskeidelik, speel 'n baie belangrike rol in die verkryging van buitelandse inkomste, nie net vir die Suid- Afrikaanse tafeldruif industrie nie, maar ook vir die Suid-Afrikaanse ekonomie as 'n geheel. Hierdie twee kultivars is egter, soos baie ander wit kultivars, ook geneig tot verbruining. Dit is veral netagtige verbruining op Regal Seedless en interne verbruining op Thompson Seedless wat pertinent is. Hierdie belangrike kwaliteitsprobleme lei jaarliks tot groot finansiële verliese, aangesien daar huidiglik geen gevestigde prosedure is om voor oes, tydens opberging of tydens verpakking te bepaal of die druiwe uiteindelik gaan verbruin nie. Met ander woorde, daar is geen gevestigde protokol vir die beoordeling van die verbruinings risiko van 'n bepaalde groep druiwe voor dit uitgevoer word nie. Talle studies is alreeds onderneem om vas te stel wat die presiese oorsaak van hierdie verskynsel is en hoe dit bestuur moet word, maar geen enkele aspek wat bestudeer is kon tot op hede, herhaaldelik ge-assosieer word met die presiese oorsaak van verbruining nie. Die oorkoepelende doel van hierdie studie was dus om 'n alternatiewe manier te kry om hierdie probleem aan te spreek. ‘n Ondersoek na die potensiaal van naby infrarooi (NIR) spektroskopie as 'n vinnige en nie-vernietigende metings tegniek om die verbruinings potensiaal van ‘n wit pitlose tafeldruifkorrel wat nog heel is te bepaal, is onderneem. 'n Sekondêre doel was om die bepaling van optimale rypheid van tafeldruiwe te onderosek. Op hierdie manier is oesrypheid, en die kwaliteitsfaktore, naamlik totale oplosbare vastestowwe (TOVS), titreerbare suur (TS), pH, glukose en fruktose, wat ook gekoppel word aan die voorkoms van verbruining, deur middel van infrarooi (IR) spektroskopie modelle gekwantifiseer. Drie verskillende infrarooi metodes naamlik (a) die Fourier transform naby infrarooi (FT-NIR), (b) Fourier transform - Mid Infrarooi (FT-MIR) en (c) Fourier transform - Mid Infrarooi Verswakte Totale Refleksie (FT-MIR VTR) spektroskopie is gebruik om die aspekte te bepaal. Dis gedoen sodat 'n platform van tegnologie beskikbaar sou wees vir die tafeldruif industrie. Die druiwe wat in hierdie studie gebruik is, is oor twee jaar (2008 en 2009) en van twee verskillende kommersiële wingerde in die Hexriviervallei, Wes-Kaap, Suid-Afrika ge-oes. Verskillende oesladings (die totale aantal trosse op die wingerdstokke per hektaar) is vir Regal Seedless (75 000, 50 000 en 35 000) en Thompson Seedless (75 000 en 50 000) gelaat. Daar is drie rye gebruik Regal Seedless en twee vir Thompson Seedless. Elke ry het ses vakkies gehad wat dan verteenwoordigend was van ‘n herhaling vir elke oeslading. In 2008 is hierdie kultivars by vroeë rypwording (16°Brix), by optimale rypheid (18°Brix) en by laat rypheid (20°Brix) geoes. In 2009 is dit twee keer by die optimale rypheidsgraad geoes. Vir die bepaling van oesrypheid, en die kwaliteitsapekte is verskillende sagteware (OPUS 6.5 op die FT-NIR en FT-MIR VTR instrumente en Unscrambler weergawe 9.2 vir die FT-MIR instrument) sowel as verskillende spektrale voor-verwerking tegnieke ëvalueer voor die konstruksie van die kalibrasie modelle op die verskillende instrumente. Parsiële kleinste kwadraat (PKK) regressie is gebruik vir die opstel van kalibrasiemodelle vir die bepaling van laasgenoemde aspekte. Verskillende statistieke gegewens is gebruik om die kalibrasie modelle te evalueer, naamlik die bepalingskoëffisiënt (R2), die vierkantswortelgemiddelde- kwadraat fout vir voorspelling (VGKV), relatiewe voorspellingsafwyking (RVA) en sydigheid. Kalibrasie modelle wat geskik is vir keuring is verkry op die FT-NIR en FT-MIR VTR instrumente vir TOVS (11.40 – 21.80°Brix) (R2 = 85.92%, VGKV = 0.71°Brix, RVA = 2.67 en sydigheid = 0.03°Brix), pH (2.94 – 3.9) (R2 = 85.00%, VGKV = 0.08 g/L, RVA = 2.59 en sydigheid = -0.01 g/L), en TS (4.3 – 13.1 g/L), (R2 = 90.77%, VGKV = 0.48 g/L RVA = 3.30 en sydigheid = -0.03 g/L). Modelle vir fruktose (46.70-176.82 g/L) (R2 = 74.66%, VGKV = 9.28 g/L RVA = 2.00 en sydigheid = 1.10 g/L) en glukose (20.36 – 386.67 g/L) (R2 = 70.71%, VGKV = 11.10 g/L RVA = 1.87 en sydigheid = 1.64 g/L) is verkry met die FT-NIR en FT-MIR VTR instrumente wat in sommige gevalle gepas was vir keuringsdoeleindes en in sommige gevalle nie geskik was vir kwantifiserings doeleindes nie. Die FT-MIR-instrument het modelle vir al die aspekte gegee wat nog nie vir kwantifiserings doeleindes of vir keuringsdoeleindes geskik was nie. Gekombineerde spektrale reekse is gebruik vir die kalibrasies wat dikwels soortgelyk was vir sommige aspekte naamlik 12 493 - 5 446.2 vir TOVS en pH, 6 101.9 - 5 446,2 vir TOVS, TS en fruktose en 4 601.5 - 4 246.7 vir pH en fruktose op die FT-NIR instrument, 2 993.2 - 2 322.3 vir pH, TA en glukose en 1 654.3 – 649.4 vir pH en glukose op die FT-MIR VTR instrument. Andersyds, was dit aangrensend (3 996.6 - 3 661.2, 3 663.5 - 3 327.7 en 3 327.2 - 2 322.3) vir TOVS en glukose, 1 988.3 - 1 652.8, 1 654.3 – 649.4 vir TOVS, pH en TS en ander tye was dit weer oorvleuelend 1 654.3 – 649.4 en 1 318.8 – 649.4 vir pH, TS en fruktose op die FT-MIR VTR instrument. Dit is 'n baie goeie teken vir die oordrag van hierdie tegnologie na ‘n handgedraagde instrument, waar aanliggende en/of oorvleuelende golfnommers noodsaaklik is. Instrumente wat verskillende aspekte oor groot spektrale reekse moet bepaal is nie net onprakties, omdat die instrument groot moet wees nie, maar dit is ook baie duur. Nog 'n voordeel van die implementering van veral FT-NIR spektroskopie as 'n vinnige, akkurate en goedkoop tegniek vir die bepaling van oesrypheid, en die kwaliteit aspekte van druiwe is omdat daar geen monster voorbereiding nodig is nie en baie min afval (paar enkele korrels word gemonster) geproduseer word. 'n Voorvereiste wat sterk aanbeveel kom in die groen era waarin ons tans leef en nog vir eeue van nou af gaan doen. ‘n Platform van tegnologie is nou beskikbaar gestel deur middel van hierdie studie vir die bepaling van die onderskeie aspekte in toekomstige tafeldruif monsters deur net op een van die instrumente hulle spektra te neem. Inderdaad iets wat nie voorheen moontlik of beskikbaar was vir die Suid- Afrikaanse tafeldruif industrie nie. Korrels vir die verbruiningseksperimente is geskandeer direk na oes (voor koelopberging) en weer na koelopberging. Dit was voor koelopberging op elke kant van die korrel skandeer en na koelopberging was dit twee maal skandeer op 'n bruin vlek indien verbruining teenwoordig was en twee keer op 'n helder plek, ongeag of verbruining teenwoordig was of nie. Inspeksie van die korrels vir die voorkoms van verbruining na koelopberging het aan die lig gebring dat Regal Seedless 'n hoër voorkoms van verbruining (68% in 2008 en 66% in 2009) as Thompson Seedless (21% in 2008 en 25% in 2009) gehad het. Regal Seedless was ook meer geneig om eksterne verbruining, spesifiek netagtige verbruining te vertoon, terwyl Thompson Seedless meer geneig was om interne verbruining te vertoon, ten spyte van die verskillende fenotipes van verbruining wat teenwoordig was op beide kultivars. Hoofkomponente analise (HKA) is op die spektra gedoen voor en na koelopberging en naby infrarooi spektroskopie het aan die lig gebring dat die veranderinge wat verband hou met koelopberging met die eerste hoofkomponent (HK) verduidelik kan word met byna 100% van die variasie in die spektra wat daarin vasgevang is. Klassifikasiemodelle is ook deur die gebruik van HKA gebou en was gebaseer op die spektra van korrels wat vekry is voor en na koelopberging asook die wat verkry is nadat korrels verbruin het na koelopberging. Klassifikasiemodelle van korrels wat gebaseer was op spektra na koelopberging (verbruining teenwoordig) het 'n beter algehele akkuraatheid (94% vir opleidingsdata en 87% vir toetsdata), getoon as die klassifikasiemodelle wat gebaseer was op spektra van korrels voor koelopberging (79% vir opleidings data en 64% vir toetsdata). Die implikasie hiervan is dat die huidige modelle in staat sal wees om korrels beter te klassifiseer in terme van diegene wat alreeds verbruin het en die wat nie verbruin het na koelopberging as daardie voor koelopberging, wat juis die kritieke stadium is waar ons wil weet of die korrels wel gaan verbruin of nie. Daar is wel potensiaal wat verder ontgin kan word, aangesien al hierdie modelle gebou is deur gebruik te maak van die hele NIR spektrum. Geen veranderlike seleksie is dus gedoen nie en al die verskillende verbruiningsfenotipes is ook saam gebruik in die opstel van die modelle. Verdere analise van die data sal dus gebaseer word op die gebruik van veranderlike seleksie tegnieke soos deeltjie swerm optimisasie (DSO) wat sekere golflengtes kies wat sterk verband hou met die verbruining verskynsel en slegs die belangrikste tipes van verbruining (netagtig op Regal Seedless en interne verbruining op Thompson Seedless) sal gebruik word. Hierdie studie het 'n baie belangrike implikasie vir die tafeldruifbedryf, want dit is die eerste keer dat die moontlikheid om verbruining te voorspel met ander metodes as visuele inspeksie, veral voor koelopberging, getoon word. / The Postharvest and Innovation Programme, for financing this study