Thesis (MScAgric)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--Columbia University, 1938. / Vita. Bibliography: p. [23].

Thesis (M.App.Sc.) - University of Queensland, 2005. / Includes bibliography.

Proefschrift--Groningen. / English summary. "Literatuuroverzicht": p. [3]-10.

Effects of different weed control practices on soil quality in mediterranean crops This research approaches the question of weed control sustainability, from the point of view of soil quality maintenance and enhancing. A big choice of practices and products for weed control are available nowadays, but the actual definition of "sustainable practice" not always considers soil fertility. Soil processes timescale is wider than the productive, commercial and legislative ones. Also the definition of survey protocols is a process slower than the evolution of weed control methods. The faster reaction in the soil ecosystem after an external pressure is given by the organisms living in it, and the microbial community is finally the most effective agent in nutrient recycling processes. In this investigation, the same soil analysis protocol was applied on soil samples exposed to different weed management and control methods. Using soil quality indexes and bioindicators, soil properties variations after the different weed control treatments were compared. In particular soil carbon pool and how microbial community recycles was surveyed. A standard protocol to both find variations in long-term soil quality and survey the short-term impact of weed control practices on soil biological processes was defined. Weed management practices can interact with the nutrients recycling processes performed by the microorganisms living in the soil. These processes have a central role in maintaining soil fertility, one of the most important resources for agriculture. Three weed management practices were compared: the use of synthetic (oxyfluorfen) or natural (essential oils and aqueous extracts) herbicides and two mechanical methods (tillage and mulching). Soil fertility was monitored measuring soil physical-chemical values and elaborating soil quality indexes and bioindicators. / Efectos de diferentes prácticas de control de arvenses sobre la calidad del suelo en cultivos mediterráneos Esta investigación aborda la cuestión de la sostenibilidad del control de las plantas arvenses, desde el punto de vista del mantenimiento y mejora de la calidad del suelo. Una gran variedad de prácticas y productos para el control de las arvenses están disponibles hoy en día, pero la definición real de "práctica sostenible" no siempre considera la fertilidad del suelo. La escala de tiempo de los procesos del suelo es más amplia que los procesos productivos, comerciales y legislativos. También la definición de protocolos para la investigación es un proceso más lento que la evolución comercial de los métodos de control de malas hierbas. La reacción más rápida en el ecosistema del suelo después de una presión externa es dada por los organismos que viven en ella, y la comunidad microbiana es el agente más eficaz en los procesos de reciclaje de nutrientes. En esta investigación se aplicó el mismo protocolo de análisis de suelo en muestras de suelo expuestas a diferentes métodos de manejo y control de arvenses. Utilizando índices de calidad del suelo y bioindicadores, se compararon las variaciones de propiedades del suelo después de los diferentes tratamientos de control de arvenses. En particular se estudiaron la reserva de carbono en el suelo y la forma en que la comunidad microbiana recicla. Se definió un protocolo estándar para encontrar variaciones en la calidad del suelo a largo plazo y para analizar el impacto a corto plazo de las prácticas de control de arvenses en los procesos biológicos del suelo. Las prácticas de manejo de malas hierbas pueden interactuar con los procesos de reciclaje de nutrientes realizados por los microorganismos que viven en el suelo. Estos procesos tienen un papel central en el mantenimiento de la fertilidad del suelo, uno de los recursos más importantes para la agricultura. Se compararon las prácticas de manejo de arvenses de frutales: el uso de herbicidas sintéticos (oxyfluorfen) o naturales (aceites esenciales y extractos acuosos) y dos métodos mecánicos (labranza y mulching). Se monitoreó la fertilidad del suelo midiendo los valores físico-químicos del suelo y elaborando índices de calidad del suelo y bioindicadores. / Efectes de diferents pràctiques de control d'arvenses sobre la qualitat del sòl en cultures mediterrànies Aquesta investigació aborda la qüestió de la sostenibilitat del control de les plantes arvenses, des del punt de vista del manteniment i millora de la qualitat del sòl. Una gran varietat de pràctiques i productes per al control de les arvenses estan disponibles avui en dia, però la definició real de "pràctica sostenible" no sempre considera la fertilitat del sòl. L'escala de temps dels processos del sòl és més àmplia que els processos productius, comercials i legislatius. També la definició de protocols per a la investigació és un procés més lent que l'evolució comercial dels mètodes de control de males herbes. La reacció més ràpida en l'ecosistema del sòl després d'una pressió externa és donada pels organismes que hi viuen, i la comunitat microbiana és l'agent més eficaç en els processos de reciclatge de nutrients. En aquesta investigació es va aplicar el mateix protocol d'anàlisi de sòl en mostres de sòl exposades a diferents mètodes de maneig i control d'arvenses. Utilitzant índexs de qualitat del sòl i bioindicadors, es van comparar les variacions de propietats del sòl després dels diferents tractaments de control d'arvenses. En particular es van estudiar la reserva de carboni en el sòl i la forma en què la comunitat microbiana el recicla. Es va definir un protocol estàndard per trobar variacions en la qualitat del sòl a llarg termini i per analitzar l'impacte a curt termini de les pràctiques de control d'arvenses en els processos biològics del sòl. Les pràctiques de maneig de males herbes poden interactuar amb els processos de reciclatge de nutrients realitzats pels microorganismes que viuen a terra. Aquests processos tenen un paper central en el manteniment de la fertilitat del sòl, un dels recursos més importants per a l'agricultura. Es van comparar les pràctiques de maneig d'arvenses de fruiters: l'ús d'herbicides sintètics (oxyfluorfè) o naturals (olis essencials i extractes aquosos) i dos mètodes mecànics (conreu i mulching). Es va monitorejar la fertilitat del sòl mesurant els valors fisicoquímics del sòl i elaborant índexs de qualitat del sòl i bioindicadors. / Oddo, M. (2017). Effects of different weed control practices on soil quality in Mediterranean crops [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90655 / TESIS

By virtue of their fragrance and therapeutic nature, essential oils have gained great application in the cosmetic and pharmaceutical industries. These oils, as products consumed by the public for the general health and cosmetics, should be of high quality and unadulterated. In this project comprehensive two-dimensional gas chromatography (GCxGC) was used for the qualitative analysis of some South African essential oils. The main purpose of the project was to evaluate GCxGC for identification of essential oil constituents and for fingerprinting the different essential oils for quality control purposes. Essential oils of the same kind but of different origin were compared and the quantitative variation between their components was studied. Gas chromatography-time-of flight mass spectrometry (GC-TOFMS) as well as comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GCxGC-TOFMS) was used to help identify component peaks separated in the GCxGC instrument. Once certain precautions are taken and the delicate modulator is correctly optimized, the GCxGC results are reproducible and easy to interpret. Overall, the GCxGC technique utilized showed good promise for quality control of essential oils. / Dissertation (MSc)--University of Pretoria, 2006. / Chemistry / unrestricted

Ruminant products, meat and milk, were long ago discovered to contain a high content of saturated fat associated with various chronic diseases in human, including coronary heart disease. Increased consumption of n-3 fatty acids, linolenic (LNA; 18:3n-3), eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) by man has been linked with reduced incidences of these diseases. Therefore, in vitro experiments carried out in this thesis investigated the possibility that the dietary inclusion of essential oil compounds (EOC) might modify ruminal biohydrogenation of polyunsaturated fatty acids (PUFA), and thereby improve the fatty acid profiles of ruminant derived foods. In the first experiment, twenty EOC were screened, of which carvacrol, thymol, cis/trans-citral, geraniol, nerol, (+)-α-pinene, l-menthone, linalyl acetate and (R)-(+)-pulegone were most effective at protecting the PUFA from biohydrogenation. The reduced accumulation of stearic acid with concomitant increases in vaccenic acid following the addition of the EOC confirmed their capacity to inhibit biohydrogenation of both LA and LNA. However, the observed decreases in total volatile fatty acids concentrations suggested that the inclusion of these compounds at 300 mg l-1 also suppressed microbial fermentation. Of these EOC, carvacrol and thymol were the most potent inhibitors of fermentation as they decreased total VFA concentrations by ≥60% from those of the control. In the second experiment, selected EOC, namely linalyl acetate, l-menthone and (+)-α-pinene, were tested at lower doses. It was observed that these EOC when added at 100 and 200 mg l-1 also inhibited biohydrogenation with minimal effect on VFA concentration. In experiment 3, pure culture work was undertaken to assess the effects of EOC on three key Butyrivibrio spp., involved in the biohydrogenation process, namely B. fibrisolvens, B. hungatei and B. proteoclasticus. The EOC inhibited biohydrogenation through their bacteriostatic effects on these bacteria. In conclusion, these studies revealed that EOC have the potential to modify ruminal biohydrogenation to varying extents depending on the type of compound used and the dose applied. Consequently, they might be useful at improving the healthiness of ruminant products, however their effects have to be confirmed in vivo and ensure that they do not cause significant inhibition of fibre digestion.

The number of foodborne disease outbreaks related to fresh produce has increased in recent years. This has coincided with a growing public demand for minimally processed fruits and vegetables. Effective produce sanitizers are therefore needed that are at least as effective as chlorine, currently the most commonly used sanitizer. Natural antimicrobials from plant extracts and essential oils are a possible alternative. These are highly effective and may also be used in situations in which chlorine is not advantageous; for instance, in situations in which chlorine has limited efficacy or because of concerns over the production of harmful by-products resulting from chlorine use. Plant derived essential oils have been shown to be antibacterial, antiviral, and antifungal. In this study we examined the use of natural antimicrobials from plant extracts and essential oils as possible alternative sanitizers. We examined these antimicrobials for their efficacy against Escherichia coli. In addition, since many of these natural compounds are believed to be membrane active, silver ions were added to some of the tests to assess the potential for synergy between the antimicrobials. Silver ions, although slow-acting on their own, often exhibit a synergistic antimicrobial effect when combined with other membrane active antimicrobials such as oxidizing agents. These studies reveal that plant derived antimicrobials are effective sanitizers with the potential to replace commonly used chlorine

No description available.

Made available in DSpace on 2014-06-11T19:30:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-01Bitstream added on 2014-06-13T21:01:39Z : No. of bitstreams: 1 feniman_cm_dr_botib.pdf: 616550 bytes, checksum: 9e6cbb3844a5f90133b28c48baf360a5 (MD5) / Os óleos essenciais (OEs) apresentam-se como novas opções tecnológicas para serem aplicados como conservantes em alimentos. Entretanto, o uso nas concentrações necessárias para exercerem ação antimicrobiana provoca alterações sensoriais indesejáveis, além de que a essa ação não é desejável quando aplicado em produtos probióticos. O trabalho objetivou identificar e registrar as preferências do público consumidor para alimentos adicionados de OEs, avaliar a ação antimicrobiana do OE de canela em iogurte, adicionado em concentração máxima aceitável sensorialmente (CMAS) e associado com EDTA e/ou polietilenoglicol, verificar a existência de ação antimicrobiana dos OEs de canela, cravo e menta na CMAS contra o Lactobacillus rhamnosus e cultura starter de iogurte durante a vida de prateleira de leite fermentado, determinar a Concentração Inibitória Mínima (CIM) e visualizar os efeitos do OE de canela contra o L. rhamnosus. Os OEs foram obtidos por destilação a vapor e caracterizados quimicamente por cromatografia gasosa e espectrometria de massa. A primeira parte do projeto consistiu em pesquisa de mercado para determinar a melhor associação de OEs com o sabor de frutas no iogurte e os óleos mais associados ao queijo. A máxima concentração aceitável de OE (estipulado na pesquisa de mercado) para o iogurte foi determinada na análise sensorial pela Escala Hedônica de 0 a 9 pontos, com amostras de concentrações crescentes de OE, tendo-se como referencial de aceitação a mediana mínima igual a 7 pontos, referente ao gostei moderadamente. Nessa concentração foi verificada a ação antimicrobiana do OE sozinho e associado com EDTA, polietilenoglicol e ambos, além do tratamento controle. Foram realizadas as contagens de aeróbios mesófilos totais, psicrotróficos e bolores... / Essential oils (EOs) show as new technology options to be used as preservatives in foods. However, the use in necessary concentrations to exert antimicrobial activity causes undesirable sensory changes, and this action is not desirable when applied to probiotic products. The study aimed to identify and record the preferences of the consuming public to foods added with EOs, to evaluate the antimicrobial action of cinnamon EO in yogurt, added to the higher acceptable sensory concentration (HASC) and associated with EDTA and/or polyethylene glycol, to verify the existence of antimicrobial action of cinnamon, clove and mint EOs in the HASC against Lactobacillus rhamnosus and yogurt starter culture during the shelf life of fermented milk, to determine the minimum inhibitory concentration (MIC) and to view the effects of cinnamon EO against L. rhamnosus. The EOs were obtained by steam distillation and chemically characterized by gas chromatography and mass spectrometry. The first part of project involved in market research to determine the best combination of EOs with the taste of fruit in yogurt and oils associated with cheese. The maximum acceptable concentration of EO (stipulated in market research) to the yogurt was determined by sensory analysis scale of 0 to 9 points, with samples of increasing concentrations of OE, haven been as reference the median minimum acceptance equals 7 points, referring to liked moderately. This concentration was found to antimicrobial action of EO alone and associated with EDTA, polyethylene glycol, and both, beyond a control treatment. Counts were performed total mesophilic aerobic, psychrotrophilics, and yeasts and molds. The second part of the project consisted in the survival curve of L. rhamnosus and starter culture in fermented milk, isolated and associated microbial... (Complete abstract click electronic access below)