O experimento avaliou os efeitos da ensilagem, da maturidade e do genótipo na matriz amido-protéica e no valor nutritivo de silagens de grão de milho com alta umidade. O delineamento experimental foi blocos ao acaso, com esquema fatorial 2×3×5: dois genótipos (duro ou dentado), três pontos de maturação (ponto de ensilagem de planta inteira, ponto de grão úmido e ponto de grão seco) e cinco tempos de armazenamento (0, 7, 21, 60 e 120 dias), com 4 repetições. Os tratamentos foram constituídos por híbridos de milho AG 1051 (dentado) e IAC 8390 (duro). Os dados foram submetidos à análise de variância e as suas médias comparadas pelo Teste Tukey (5%). Foram avaliadas as características físicas dos grãos ao longo da maturidade, características físico-químicas, composição química e perfil fermentativo das silagens, extração e quantificação de proteínas prolaminas (zeínas) e degradabilidade ruminal in situ da matéria seca e de amido das silagens. Nos grãos, as concentrações de proteínas prolaminas foram maiores para o híbrido duro (P < 0,01) e aumentaram conforme a maturidade, sendo que a vitreosidade teve alta correlação com a concentração dessas proteínas. Já na silagem, os teores de proteínas prolaminas foram similares para grão úmido e grão seco reconstituído ao longo do período de armazenamento, independentemente do híbrido ensilado. O teor de nitrogênio amoniacal e proteína solúvel das silagens aumentaram (P < 0,01) ao longo do período de armazenamento. Silagens de grão seco reconstituído apresentaram maiores valores de pH, maiores teores de ácido butírico, etanol, acetona e 2,3-butanodiol. A maior degradabilidade ruminal de amido foi correlacionada negativamente (P < 0,01) com a concentração de proteínas prolaminas e positivamente relacionada (P < 0,01) aos teores de proteína solúvel e nitrogênio amoniacal. O efeito de genótipo e maturidade foram superados por tempos de armazenamento superiores a 60 dias, no tocante à degradabilidade ruminal das silagens. Silagens de grão seco reconstituído apresentaram maiores perdas de matéria seca e qualidade higiênica inferior às silagens de grão úmido. / The experiment evaluated the effects of silage maturity and genotype on starch-protein matrix and nutritive values of corn grain silage with high moisture. The experiment design was randomized blocks with 2 × 3 × 5 factorial: two genotypes (flint or dent), three maturity stages (whole plant silage stage, moisture grain stage and dry grain stage) and five lengths of storage (0, 7, 21, 60 and 120 days), with four replications. The treatments were composed by two corn hybrids - AG 1051 (dent) and IAC 8390 (flint). The data were subjected to analysis of variance and the averages were compared by Tukey test (5%). Corn grains physical characteristics along the maturity, physicochemical characteristics, chemical composition and fermentation characteristics of silages, extraction and quantitation of prolamin protein (zein) and dry matter and starch in situ silage degradability were evaluated. In corn grains, the concentration of prolamin protein was higher for hybrid flint (P < 0.01) and also increased with maturity, and the vitreousness had higher correlation with the concentration of these proteins. Furthermore in silages, prolamin proteins were similar to high moisture grain and dry grain reconstituted, along with storage, regardless of the hybrid. In silage, the ammonia nitrogen and soluble crude protein contents increased (P < 0.01) during the length of storage. Reconstituted dry grain silages had higher pH, higher concentrations of butyric acid, ethanol, acetone and 2,3 - butanediol. The highest ruminal starch degradability was negatively correlated (P < 0.01) with the prolamin protein concentration and positively (P < 0.01) related to soluble crude protein and ammonia nitrogen protein levels. The effect of genotype and maturity were overcome by 60 days length of storage, according to ruminal degradability of silages. Reconstituted dry grain silages had higher DM losses and the hygienic quality was lower compared with high moisture corn silages.

No description available.

Maize is the staple food for a majority of people in Southern Africa, but plant diseases are responsible for at least 10% of crop production losses. Bacterial leaf streak (BLS) of maize was first reported in South Africa in 1949 and has not been reported elsewhere. Very little is known about the pathogen involved and therefore it is deemed necessary to compile a characteristic profile for the pathogen to prevent the possibility of major crop losses as a result of this disease. This study aimed to use biochemical and phenotypic methods to determine the specific characteristics of the causal agent of BLS. Diseased plant material showing symptoms of BLS were collected during the maize production seasons of 2012 and 2013 within South Africa’s maize production regions namely the North West, Free State, Gauteng and Northern Cape provinces. To prevent contamination, maize leaves were surface sterilised thoroughly before bacterial isolation commenced. Sections of the infected maize leaves were placed on GYC agar plates on which yellow, mucoid bacterial colonies after incubation for 24 to 48 hrs. The isolated bacteria were purified and the molecular identification of the bacteria was conducted in a related study. Although literature indicates that Xanthomonas campestris pv. zeae is the causal agent of BLS, pure cultures obtained from maize leaves showing characteristic symptoms of BLS were identified as species of Xanthomonas, Pantoea, and Enterobacter. To elucidate the pathogenicity of the isolated strains, pathogenicity tests based on Koch’s postulates were performed. Results from the pathogenicity tests confirmed that only the isolate Xanthomonas species was capable of inducing the characteristic BLS symptoms when healthy maize plants were inoculated with the suspected pathogens. It is important to inoculate the maize seedlings at the correct age (four-leaf stage) and the spray method is recommended. Re-isolation was repeated from the same plant material used during the initial isolation process but the isolation method was amended. The optimised isolation method involved the use of a dilution range and spread plate method. Colonies from this isolation technique grew as bright yellow colonies that were identified as Xanthomonas spp. This outcome indicates the importance of surface sterilisation, pulverisation and subsequent dilution of plant materials for isolation of bacterial pathogens from diseases plants. These isolates were used to create protein profiles with SDS-PAGE electrophoresis and carbon utilisation patterns with the Biolog® GN2 system. Protein profiling banding patterns was assessed based on presence/absence criteria. Highly similar protein profiles were observed among the X. campestris pv. zeae isolates but groupings of different protein profiles were determined when minor differences in the protein profiles was taken into account. Xanthomonas campestris pv. zeae was successfully distinguished from the X. axonopodis pv. vasculorum reference strain through unique SDS banding patterns. Banding patterns obtained from cultures grown in a liquid medium (tryptic soy broth) were of a higher quality than the banding patterns obtained from bacteria harvested from solid media (CYG agar plates). Carbon source utilisation data was used to evaluate the average well colour development obtained from each isolate. Statistically significant differences were found among some of the isolates, with some isolates being metabolically more active than other isolates. Substrate utilisation patterns produced by the isolates corresponded to previously published studies on various Xanthomonas species. The cell count of the samples used during carbon utilisation patterns must be standardised in order to obtain reliable results. During this study, the application of Koch’s postulates and two inoculation techniques confirmed that Xanthomonas campestris pv. zeae is the pathogen responsible for bacterial leaf streak of maize. Members of the Pantoea and Enterobacter genera were found on the leaf surface of maize plants infected with BLS but inoculations of healthy maize plants with these bacteria did not result in bacterial leaf streak symptoms on the maize plants. These bacteria were not pathogenic and were considered endophytes. The identified pathogen was characterised through protein and metabolic profiling. The protein profiles of the pathogen obtained through analysis of the major bands of the SDS-PAGE gels were highly similar and distinguishable from the Xanthomonas reference culture. Groupings within the X. campestris pv. zeae group was found when major and minor bands were considered, this may however be altered when the intensities of the bands are used during analysis. Carbon utilisation patterns were assessed using Biolog® GN2 plates. A metabolic fingerprint was created for the pathogen of BLS, it was possible to distinguish between X. campestris pv. zeae and other Xanthomonas strains based on the fingerprint. This fingerprint could be used to identify the pathogen. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Maize is the staple food for a majority of people in Southern Africa, but plant diseases are responsible for at least 10% of crop production losses. Bacterial leaf streak (BLS) of maize was first reported in South Africa in 1949 and has not been reported elsewhere. Very little is known about the pathogen involved and therefore it is deemed necessary to compile a characteristic profile for the pathogen to prevent the possibility of major crop losses as a result of this disease. This study aimed to use biochemical and phenotypic methods to determine the specific characteristics of the causal agent of BLS. Diseased plant material showing symptoms of BLS were collected during the maize production seasons of 2012 and 2013 within South Africa’s maize production regions namely the North West, Free State, Gauteng and Northern Cape provinces. To prevent contamination, maize leaves were surface sterilised thoroughly before bacterial isolation commenced. Sections of the infected maize leaves were placed on GYC agar plates on which yellow, mucoid bacterial colonies after incubation for 24 to 48 hrs. The isolated bacteria were purified and the molecular identification of the bacteria was conducted in a related study. Although literature indicates that Xanthomonas campestris pv. zeae is the causal agent of BLS, pure cultures obtained from maize leaves showing characteristic symptoms of BLS were identified as species of Xanthomonas, Pantoea, and Enterobacter. To elucidate the pathogenicity of the isolated strains, pathogenicity tests based on Koch’s postulates were performed. Results from the pathogenicity tests confirmed that only the isolate Xanthomonas species was capable of inducing the characteristic BLS symptoms when healthy maize plants were inoculated with the suspected pathogens. It is important to inoculate the maize seedlings at the correct age (four-leaf stage) and the spray method is recommended. Re-isolation was repeated from the same plant material used during the initial isolation process but the isolation method was amended. The optimised isolation method involved the use of a dilution range and spread plate method. Colonies from this isolation technique grew as bright yellow colonies that were identified as Xanthomonas spp. This outcome indicates the importance of surface sterilisation, pulverisation and subsequent dilution of plant materials for isolation of bacterial pathogens from diseases plants. These isolates were used to create protein profiles with SDS-PAGE electrophoresis and carbon utilisation patterns with the Biolog® GN2 system. Protein profiling banding patterns was assessed based on presence/absence criteria. Highly similar protein profiles were observed among the X. campestris pv. zeae isolates but groupings of different protein profiles were determined when minor differences in the protein profiles was taken into account. Xanthomonas campestris pv. zeae was successfully distinguished from the X. axonopodis pv. vasculorum reference strain through unique SDS banding patterns. Banding patterns obtained from cultures grown in a liquid medium (tryptic soy broth) were of a higher quality than the banding patterns obtained from bacteria harvested from solid media (CYG agar plates). Carbon source utilisation data was used to evaluate the average well colour development obtained from each isolate. Statistically significant differences were found among some of the isolates, with some isolates being metabolically more active than other isolates. Substrate utilisation patterns produced by the isolates corresponded to previously published studies on various Xanthomonas species. The cell count of the samples used during carbon utilisation patterns must be standardised in order to obtain reliable results. During this study, the application of Koch’s postulates and two inoculation techniques confirmed that Xanthomonas campestris pv. zeae is the pathogen responsible for bacterial leaf streak of maize. Members of the Pantoea and Enterobacter genera were found on the leaf surface of maize plants infected with BLS but inoculations of healthy maize plants with these bacteria did not result in bacterial leaf streak symptoms on the maize plants. These bacteria were not pathogenic and were considered endophytes. The identified pathogen was characterised through protein and metabolic profiling. The protein profiles of the pathogen obtained through analysis of the major bands of the SDS-PAGE gels were highly similar and distinguishable from the Xanthomonas reference culture. Groupings within the X. campestris pv. zeae group was found when major and minor bands were considered, this may however be altered when the intensities of the bands are used during analysis. Carbon utilisation patterns were assessed using Biolog® GN2 plates. A metabolic fingerprint was created for the pathogen of BLS, it was possible to distinguish between X. campestris pv. zeae and other Xanthomonas strains based on the fingerprint. This fingerprint could be used to identify the pathogen. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Modern genetics have improved maize hybrids to better tolerate stress, use nutrients more efficiently and potentially yield higher. Management practices, such as narrow row technology and high plant population density (PPD) may further improve yields in modern maize under irrigated, non-limiting conditions. High PPD (74, 99, 124, 148 K seeds ha-1) were tested in narrow rows with up to four nitrogen (N) rates in three locations over two years in Kentucky with a modern maize hybrid in irrigated, non-limiting conditions. Results indicate that optimal seeding rates were 99,000 to 124,000 seeds ha-1, providing maximum yield and highest partial return, likely due to increasing seed number ha-1 and greater canopy closure, although seed size declined and pollination was more asynchronous as PPD increased. Excess N did not overcome silking delay or the decline in kernel mass associated with higher PPD, indicating 252 kg N ha-1 was adequate for high yields at any population, although data indicates better utilization of supplied N at higher populations. Implications can be used to implement better management techniques in high-yielding maize to supplement use of improved genetics.

Die doel van hierdie studie is om `n omvattende prysbepalingsmodel te ontwikkel vir vinnige bewegende voedselsoorte, met spesifieke verwysing na die mieliemeelbedryf. Deur navorsing wat gedoen is het dit aan die lig gekom dat daar nie `n enkele model bestaan wat prysbepaling in totaal aanspreek nie. Die model wat in hierdie verhandeling ontwikkel is, sal kan dien as `n omvattende prysbepalingsmodel en ook diegene wat nie bekend is met die prysbepalingsproses nie, tot voordeel strek. Hoofstuk 2 bied `n literatuurstudie van die faktore of komponente wat tydens prysbepaling verantwoord moet word. Hoofstuk 3 bied `n empiriese oorsig van die prysbepalingsmetodes wat TWK meulens aangewend het om die pryse van hulle klaarprodukte te bepaal, en hoe `n prysbepalingsmodel aangewend is om die winsgewendheid van die meulens te verhoog. Hoofstuk 4 word gewy aan die ontwikkeling van `n omvattende prysbepalingsmodel wat deur die mieliemeulebedryf en ander vervaardigers van vinnig bewegende voedselsoorte aangewend kan word. Hoofstuk 5 verskaf `n samevatting en riglyne vir verdere navorsing. / Business Management / M.Com. (Business Management)

Da oltre vent’anni l’Unione Europea (UE) è protagonista di un acceso dibattito circa l’orami vasta adozione di OGM in agricoltura. Laddove la maggior parte dei paesi Nord e Sud americani ha già largamente introdotto tali colture, l’UE è invece in forte ritardo, complice una legislazione basata sul Principio di Precauzione. Queste discrepanze nei i processi legislativi hanno portato a galla alcune problematiche di carattere commerciale: primo, la riduzione delle disponibilità di materia prima non-OGM costituisce un problema per la stabilità delle filiere ad essa dedicate; secondo, il commercio di prodotti convenzionali è compromesso dalla possibilità di riscontrare varietà OGM non approvate in UE all’interno delle partite provenienti da paesi terzi. In ultimo, data l’ampia diffusione di OGM nelle Americhe, è lecito porsi il quesito di come tale tendenza abbia influito sui prezzi delle materie prime agricole. In questa tesi si cercherà di analizzare queste tematiche. Per prima cosa, ci occupiamo di capire come la filiera della soia non-OGM italiana sia organizzata e gestita in modo da minimizzare i rischi di presenza avventizia. La conclusione è che le forme di governance ibride garantiscono la migliore forma di gestione. Successivamente ci domandiamo se le diversità legislative in materia di OGM abbiamo un impatto sull’import Europeo di mais e soia. Utilizzando l’analisi della domanda, riscontriamo che i paesi esportatori competono o sul prezzo o in base alla disponibilità stagionale di prodotto. In ultimo, utilizzando serie storiche, analizziamo il ruolo del tasso di adozione di soia OGM sui prezzi reali; ciò che osserviamo indica che questo ha un effetto deflattivo di breve periodo, ma di scarso peso. / The debate on the increasing adoption of GMOs in agriculture has been in vogue for the last twenty years. Whereas most North and South American countries have largely adopted GMOs, the European Union (EU) has not. Since the EU legislation is based on the Precautionary Principle, the introduction of new GM varieties has been slow. These discrepancies put forward some fundamental issues: first, the decreasing availability of non-GM raw materials poses the sustainability of these supply chains at risk; second, the trade of conventional products is undermined by the possible occurrence of unauthorized GMOs in overseas. Last, the wide adoption of GM crops in North and Latin America poses the question of what effect the spreading of biotechnology in agriculture has exerted on market prices. In this thesis, we try to answer these three research questions. First of all, we investigate how the Italian supply chain for non-GM soybean meal is framed and managed in order to reduce the risk of adventitious presence. We find that hybrid organizations represent the best governance form. Next, we assess the role of legislative diversities (regarding GMOs) on EU import decisions through import demand analysis. We conclude that competition among exporters is solely based on price and seasonality. Last, we disentangle the role of GMOs adoption on the variability of US soybean prices. Results indicate that a higher rate of adoption reduces real soybean market prices, yet the effect is short lived and not much relevant.

Akamu is a lactic acid bacteria fermented cereal-based food that complements infant diets in most African countries. Uncontrolled fermentation increases the variability in quality and safety of akamu. This study was aimed at the controlled fermentation of akamu with selected lactic acid bacteria (LAB), investigation of the probiotic potential of the LAB and the effect of variation in production method on the product quality and sensory properties. PCR-DGGE analysis of traditional akamu samples revealed LAB community dominated by Lactobacillus fermentum, L. plantarum, L. delbrueckii subsp. bulgaricus and L. helveticus. Isolated yeasts were Candida tropicalis, C. albicans, Clavispora lusitaniae and Saccharomyces paradoxus. The isolated Lactobacillus plantarum strains (NGL5 and NGL7) fermented irradiated ground maize slurries and produced significant levels of lactic acid (>73 mmol L-1) and low pH ≤3.63 displaying inhibitory activity against Salmonella enterica serovar Enteritidis NCTC 5188, Escherichia coli 1077 (NCTC 11560), Bacillus cereus NCIMB 11925, Staphylococcus aureus NCTC 3750 and Listeria monocytogenes NCTC 7973 in MRS agar and E. coli 1077 in maize slurry fermentation. Viability of both strains of L. plantarum at pH 2 after 3 h was reduced from ≥8.26±0.05 to ≤4.94±0.49 Log10 CFU mL-1 while incubation in 0.3% bile allowed growth to 5.73±0.13 and 7.93±0.12 Log10 CFU mL-1 after 6 h for NGL5 and NGL7 respectively. Auto-aggregation of the L. plantarum strains at 37oC (≥25 after 5 h) correlated with adhesion to hydrocarbons (<15, 26, 33 and 64% for Hexane, Hexadecane, Ethyl acetate and Chloroform respectively). The strains failed to exhibit gelatinase or haemolytic activity but adhered to porcine mucin (OD403 nm ≥0.63 with viability ≥6.52 Log10 CFU mL-1) and Caco-2 cells (≥5.13 Log10 CFU mL-1). The ash, mineral (Ca, K, Mg, Na, S and Zn), IDF, SDFP and TDF content of the L. plantarum fermented ground maize slurries were significantly (p≤0.05) higher than that of the traditional akamu but the peak and final viscosities (139.5 and 68.5 cP respectively) were significantly (p≤0.05) the least. The aroma, appearance, colour, flavour and texture of the resultant porridges were liked moderately by 75% of the assessors. This study demonstrated that fermentation with the L. plantarum strains would contribute towards product safety and the L. plantarum strains possessed some probiotic potential that could be beneficial to the consumers particularly in those developing countries were the main staple foods are fermented cereals.

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The purpose of this study was to investigate the variation that exists between maize samples regarding particle size separation, in vitro fermentation kinetics and in vitro dry matter (DM) disappearance. A second objective was to quantify possible relationships between the Roff Milling Index (RMI) of maize and any of the measured in vitro parameters. Three trials were conducted: a particle size distribution trial, a gas production trial and an in vitro DM degradability and starch disappearance trial. Overall, nine maize samples, which differed in terms of cultivar and endosperm type, were collected from different origins for the study. The samples were selected in terms of their Milling Index (MI). Three of the nine samples had a high MI that ranged between 109 and 118, three had a low MI that ranged between 67 and 71 and the other three samples had a medium MI that ranged between 85 and 92. Although the MI is not a direct indication of the hardness or softness of the endosperm, it was believed to be indirectly associated with vitreousness. In the first trial, the different maize samples were milled through a 1 mm screen and sieved through a series of three sieves 150, 125 and 106 μm, respectively. It was found that RMI was not a reliable indicator to predict particle size distribution, especially in terms of the coarse (>150 μm) and very fine (<106 μm) particles. In the gas production trial, the nine different maize samples were subjected to a gas production system for a duration of 48 hours. Here gas production and rate of gas production of the different maize types in buffered rumen liquor were measured during incubation. After fitting the gas volume data to the respective models, the non-linear parameters b, c and L were subjected to a main effects ANOVA with the aid of Statistica, version 9 (2009). Main effects were treatment and repetition. Means were separated by means of a Scheffé test and significance was declared at P < 0.05. The results were compared to the RMI of the different maize types and it was concluded that RMI was not a reliable predictor of gas production or rate of gas production of different maize types. In the third trial, in vitro DM degradability and starch disappearance of the different maize types were measured. In vitro DM degradability was conducted in the Ankom DAISYII incubator apparatus and the incubation times were 0, 2, 4, 8, 12 and 24 hours. Starch disappearance was measured on residues of the samples incubated for 0, 2 and 4 hours. After fitting the DM disappearance data to the respective models, the non-linear parameters a, b, c and L were subjected to a main effects ANOVA with the aid of Statistica, version 9 (2009). Main effects were treatment and repetition. Means were separated by means of a Scheffé test and significance was declared at P<0.05. The results indicated variation between maize samples, especially in terms of the a-, b- and L-values. The RMI did not appear to be a reliable predictor of digestibility parameters. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die variasie tussen mieliemonsters te ondersoek ten opsigte van die skeiding van partikelgroottes, in vitro-fermentasiekinetika en in vitro-droëmateriaalverdwyning. ‘n Tweede doel was om te bepaal of daar moontlike verwantskappe tussen die Roff Milling Index (RMI) van mielies en enige van die ander in vitro-parameters bestaan. Drie proewe is gedoen: verspreiding van partikelgrootte, ‘n gasproduksieproef en ‘n droëmateriaal degradeerbaarheid- en stysel verdwyningsproef. Nege mieliemonsters, wat van mekaar verskil ten opsigte van kultivar en endospermtipe, is van verskillende lokaliteite versamel. Die monsters is gekies in terme van hul maal-indeks (MI). Drie van die nege monsters het ‘n hoë MI gehad wat gewissel het tussen 109 en 118, drie het ‘n lae MI gehad wat gewissel het tussen 67 en 71 en die ander drie monsters het ‘n medium MI gehad wat gewissel het tussen 85 en 92. Alhoewel die MI waardes nie ‘n direkte indikasie van ‘n endosperm se hardheid- of sagtheidsgraad is nie, is dit aanvaar dat daar ‘n indirekte verwantskap tussen MI en glasagtigheid van die mielie bestaan. In die eerste proef is die nege verskillende mieliemonsters deur ‘n 1 mm sif gemaal en daarna deur ‘n reeks van drie siwwe met groottes van onderskeidelik 150, 125 en 106 μm gesif. Daar is bevind dat die RMI nie ‘n betroubare voorspeller is om partikelgrootte-verspreiding aan te dui nie, veral nie ten opsigte van growwe (> 150 μm) en baie fyn (< 106 μm) patikels nie. Tydens die gasproduksieproef is die nege mieliemonsters vir 48 ure blootgestel aan ‘n gasproduksiesisteem, waar gasdruk outomaties aangeteken is. Gasproduksie en tempo van gasproduksie van die verskillende mieliemonsters is gemeet en aangeteken gedurende inkubasie met ‘n gebufferde rumenvloeistofmedium. Nadat die gasvolumedata met behulp van relevante modelle gepas is, is die nie-linêre parameters b, c en L onderwerp aan ‘n hoof-effek ANOVA met die gebruik van Statistica weergawe 9 (2009). Hoof-effekte was behandeling en herhaling. Gemiddeldes is deur ‘n Scheffé-toets geskei en betekenisvolheid is verklaar by P<0.05. Die resultate verkry is vergelyk met die RMI van die verskillende mielietipes. Die gevolgtrekking is gemaak dat Roff MI nie ‘n betroubare voorspeller van totale gasproduksie of gasproduksietempo is nie. Tydens die derde proef is droëmateriaaldegradeerbaarheid en styselverdwyning van die verskillende mielietipes bepaal. In vitro droëmateriaal (DM) degradeerbaarheid is gedoen in die Ankom DAISYII inkubator met inkubasietye van 0, 2, 4, 8, 12 en 24 ure. Styselverdwyning is bepaal deur styselanalises op die residue van die monsters wat geïnkubeer is vir 0, 2 en 4 ure. Nadat die DM-degradeerbaarheid met behulp van relevante modelle gepas is, is die nie-lineêre parameters a, b, c en L onderwerp aan ‘n hoof-effek ANOVA met die gebruik van Statistica weergawe 9 (2009). Hoof-effekte was behandeling en herhaling. Gemiddeldes is deur ‘n Scheffé toets geskei en die betekenisvolheid is verklaar by P<0.05. Die resultate het aangedui dat daar groot variasie tussen mielies bestaan, veral ten opsigte van die a-, b- en L-waardes. Dit het verder geblyk dat die RMI van die verskillende mielietipes nie ‘n betroubare voorspeller van DM-degradeerbaarheid was nie.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Maize (Zea mays L.) is used for human and animal consumption in diverse forms, from specialised foods in developed countries, to staple food in developing countries. Unfortunately, maize is prone to infection by different Fusarium species that can produce harmful mycotoxins. Fusarium verticillioides is capable of asymptomatic infection, where infected kernels show no sign of fungal growth, but are contaminated with mycotoxins. If fungal contamination is not detected early on, mycotoxins can enter the food chain. Rapid and accurate methods are required to detect, identify and distinguish between pathogens to enable swift decisions regarding the fate of a batch or consignment of cereal. Near infrared (NIR) hyperspectral imaging and multivariate image analysis (MIA) were evaluated to investigate the fungal development in maize kernels over time. When plotting principal component (PC) 4 against PC5, with percentages sum of squares (%SS) 0.49% and 0.34%, three distinct clusters were apparent in the score plot and this was associated with degree of infection. Prominent peaks at 1900 nm and 2136 nm confirmed that the source of variation was due to changes in starch and protein. Variable importance plots (VIP) confirmed the peaks observed in the PCA loading line plots. Early detection of fungal contamination and activity (20 h after inoculation) was possible before visual symptoms of infection appeared. Using NIR hyperspectral imaging and MIA it was possible to differentiate between species of Fusarium associated with maize. It was additionally applied to examine the fungal growth kinetics on culture media. Partial least squares discriminant analysis (PLS-DA) prediction results showed that it was possible to discriminate between species, with F. verticillioides the least correctly predicted (between 16-47% pixels correctly predicted). For F. subglutinans 78-100% and for F. proliferatum 60-80% pixels were correctly predicted. Three prominent bands at 1166, 1380 and 1918 nm were considered to be responsible for the differences between the growth zones. Variations in the bands at 1166 and 1380 nm were correlated with the depletion of carbohydrates as the fungus grew while the band at 1918 nm was a possible indication of spore and new mycelial formation. By plotting the pixels from the individual growth zones as a function of time, it was possible to visualise the emergence and interaction of the growth zones as separate growth profiles. The microstructure of fungal infected maize kernels was studied over time using high resolution X-ray micro-computed tomography (μCT). The presence of voids and airspaces could be seen in two dimensional (2D) X-ray transmission images and in the three dimensional (3D) tomograms. Clear differences were detected between kernels imaged after 20 and 596 h of inoculation. This difference in voids as the fungus progressed showed the effect of fungal damage on the microstructure of the maize kernels. Imaging techniques are important for rapid, accurate and objective evaluation of products for quality and safety. NIR hyperspectral imaging offers rapid chemical evaluation of samples in 2D images while μCT offers 3D microstructural information. By combining these image techniques more value was added and this led to a comprehensive evaluation of Fusarium infection in maize. / AFRIKAANSE OPSOMMING: Mielies (Zea mays L.) word in verskeie vorms deur mens en dier verbruik, van gespesialiseerde voedsel in ontwikkelde lande, tot stapelvoedsel in ontwikkelende lande. Ongelukkig is mielies onderhewig aan besmetting deur verskeie Fusarium spesies wat skadelike mikotoksiene kan produseer. Fusarium verticilloioides is in staat tot asimptomatiese infeksie waar die besmette pit geen teken van fungusgroei toon nie, maar (reeds) met mikotoksiene besmet is. Indien fungusbesmetting nie vroegtydig opgespoor word nie, kan mikotoksiene die voedselketting betree. Vinnige en akkurate metodes word benodig om patogene op te spoor, te identifiseer en ook om onderskeid tussen patogene te tref om sodoende (effektiewe) besluite aangaande die gebruik van ‘n lot of besending graan te neem. Naby-infrarooi (NIR) hiperspektrale beelding en meerveranderlike beeld ontleding (MIA) is geëvalueer om fungusontwikkeling in mieliepitte oor tyd te ondersoek. Wanneer hoofkomponent (PC) 4 teenoor PC5 gestip word, met persentasies som van kwadrate (%SS) 0.49% en 0/34%, is drie afsonderlike groepein die telling grafiek waargeneem. Dit is geassosieer met die graad van besmetting. Prominente pieke by 1900 nm en 2136 nm het bevestig dat veranderinge in stysel en proteïene die bron van die variasie was. Veranderlike belangrikheidsgrafieke (VIP) het die pieke wat in die PCA beladingslyngrafieke waargeneem is, bevestig. Vroegtydige opsporing (bespeuring) van fungusbesmetting en aktiwiteit (20 h na inokulasie) was moontlik voor visuele besmettingsimptome verskyn het. Onderskeid tussen Fusarium spesies wat met mielies geassosieer word, was moontlik deur gebruik te maak van NIR hiperspektrale beelding en MIA. Dit is bykomend toegepas om fungusgroeikinetika op kwekingsmedia te bestudeer. Parsiële kleinste kwadrate diskriminantanalise (PLS-DA) voorspellingsresultate het getoon dat dit moontlik was om tussen spesies te onderskei, met F. verticillioides die minste korrek voorspel (tussen 19-47% beeldelemente korrek voorspel). Vir F. subglutinans is 78-100% en vir F. proliferatum is 60-80% beeldelemente korrek voorspel. Drie prominente bande by 1166, 1380 en 1918 nm is oorweeg as oorsaak vir die verskille tussen die groeisones. Variasies in die bande by 1166 en 1380 nm is gekorreleer met die vermindering van koolhidrate soos die fungus groei, terwyl die band by 1918 nm ‘n moontlike aanduiding van spoor en nuwe miseliale vorming is. Deur die beeldelemente van die individuele groeisones as ‘n funksie van tyd te stip, was dit moontlik om die verskyning en interaksie van die groeisones as aparte groeiprofiele te visualiseer. Hoë-resolusie X-straal mikro-berekende tomografie (μCT) is gebruik om die mikrostruktuur van fungusbesmette mieliepitte oor tyd te ondersoek. Die voorkoms van leemtes en lugruimtes kon in die twee-dimensionele (2D) X-straal transmissie beelde en in die drie-dimensionele (3D) tomogramme gesien word. Duidelike verskille is waargeneem tussen pitte wat na 20 en 596 h na inokulasie verbeeld is. Hierdie verskil in leemtes soos die fungus vorder, het die effek van fungusskade op die mikrostruktuur van mieliepitte getoon. Beeldingstegnieke is belangrik vir vinnige, akkurate en objektiewe evaluasie van produkte vir kwaliteit en veiligheid. NIR hiperspektrale beelding bied vinnige chemiese evaluering van monsters in 2D beelde, terwyl μCT 3D mikrostrukturele inligting gee. Meer waarde is toegevoeg deur hierdie beeldingstegnieke te kombineer en dit het gelei tot ‘n omvangryke evaluering van Fusarium besmetting in mielies.