Lemon oil quality is affected by numerous factors including lemon variety, climate, soil type, extraction method, etc.. Therefore, quality largely depends upon the lemons' origin, and aroma profiles of oils obtained throughout the world have potential to vary considerably. This research was conducted to identify differences in the aroma profiles of lemon oil samples from a variety of sources (Argentina, Brazil, California coast, California desert, Spain, South Africa). Two sensory methods commonly used to identify such differences are descriptive analysis and gas chromatography/olfactometry (GCO). A trained sensory panel identified significant differences (p<0.05) in the aroma profiles of the nine tested lemon oils in terms of overall intensity, peel, lime, orange, and sweet aromas. While descriptive analysis is useful in identifying perceived product differences, it does not provide information regarding the chemical components responsible for product differences. GCO is an effective method for identifying a flavor system's important odorants and their odor quality, but there are numerous methods by which it may be performed. Two different GCO methods, Osme and aroma extract dilution analysis with flavor dilution (FD) factors, were used to analyze cold-pressed lemon oil, and results obtained from each method were compared. Conclusions drawn from each method regarding the most critical odorants were slightly different, and better agreement among subjects was found to be present with Osme. Upon concluding that Osme provides a less variable method of identifying critical odorants, the relationship between Osme and descriptive analysis data was examined to determine if samples were characterized similarly by both sensory methods. Considerable agreement between methods was evident. In addition, neral, geranial, limonene, linalool, and gamma-terpinene were identified as important base contributors to lemon oil aroma. / Graduation date: 1998

Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Essential oils are derived from volatile natural oils in plants and have been used by mankind for millennia. Citrus essential oils are widely used in various applications and lemon [Citrus limon (L.) Burm. f.] rind oil is the most important citrus oil in commerce. Rind oil glands are located in the exocarp, or flavedo, of the fruit and are formed schizogenously. The purpose of this study was to quantify the factors affecting rind oil content of lemons. The factors studied were light exposure and canopy position, growing region in South Africa, genotype, i.e. scion and rootstock, as well as the relationship between seedless clones of cultivars and the cultivars from which the seedless clones were derived, and various plant growth regulators were screened to determine whether they influenced rind oil content. Following the sampling of fruit from different positions in the tree's canopy, light exposure was found to affect rind oil content of 'Eureka' lemon fruit. Fruit borne on the outside of trees, higher in the tree, north-facing or not within the hedgerow had the highest rind oil content. Photosynthetically active radiation data supports the hypothesis that rind oil content is correlated with light exposure. To optimise rind oil content of lemons, trees should not be too dense or too high as to overshadow the lower parts of adjacent trees. South Africa has a diverse climate, and rind oil content from fruit produced in different growing regions was compared. 'Eureka' lemon fruit from Upington had the highest rind oil content in all seasons sampled. Fruit from Malelane and Marble Hall ranked second to Upington and rind oil content for fruit from Karino was intermediate. Rind oil content for fruit from Vaalharts was the lowest at each sampling time. When rind oil content was regressed against cumulative heat units there was a positive linear relationship in 2003, but in 2004 the relationship was weak. However, III general, rind oil content increased with increasing heat unit accumulation. A large variation exists among citrus cultivars and rootstocks and their effect on fruit growth and quality. 'Lirnoneira 8A', followed by 'Cicily', 'Lisbon' and 'Genoa' had the highest rind oil content. 'Villafranca', 'Messina' and 'Yen Ben Lisbon' had the lowest rind oil content. Rind oil content from 'Eureka' lemon fruit was disappointingly low. Seedless cultivars, 'Eureka SL' and 'Lisbon SL', had ~18.0% higher rind oil content than the seeded cultivars from which they were derived. With regards to rootstock, fruit from lemon trees budded on non-invigorating rootstocks, e.g. X639 [e. reshni Hort. ex Tan. x P. trifoliata (L.) Raf.], had the highest rind oil content, whereas rind oil content was low on invigorating rootstocks such as rough lemon (e. jambhiri Lush.). Synthetic gibberellins, cytokinins, ethylene and auxins were applied on lemon trees at different times and concentrations to screen their ability to enhance rind oil content. Of all the gibberellins and cytokinins applied, Promalin®, a combination of gibberellic acid 4/7 and benzyl adenine-phosphate, a cytokinin, had a small, but nonsignificant effect on rind oil content. Ethephon, which induces ethylene synthesis, affected rind oil content in 2004, when applied 8 weeks before harvest. However, ethephon and aminoethoxyvinylglycine (AVG, an ethylene biosynthesis inhibitor) had an inconsistent effect on lemon rind oil content. Auxins did not affect rind oil content. Further experiments should be conducted, especially on the timing and concentration of applied gibberellins, e.g. Promalin®, and ethephon. / AFRIKAANSE OPSOMMING: Essensiële olies is vlugtige, natuurlike plantolies wat al vir eeue deur die mens gebruik word. Sitrus essensiële olies het verskeie toepassings en van hierdie sitrus olies is dié verkry uit suurlemoenskil [Citrus limon (L.) Burm. f.] die belangrikste. Skiloliekliere is in die eksokarp, of flavedo, van die vrug geleë en vorm skisogenies. Die doelwit van hierdie navorsing was om faktore wat die olie-inhoud van suurlemoenskil affekteer te kwantifiseer. Faktore wat bestudeer is sluit ligblootstelling en posisie in die boom, produksiearea in Suid-Afrika, en genotipe (bo- en onderstam) in. Ook is saadlose klone vergelyk met die kultivars waaruit dit ontwikkel is. Verskeie plantgroeireguleerders se effek op skilolie-inhoud is ook geëvalueer. Ligblootstelling het skilolie-inhoud van 'Eureka' suurlemoene affekteer toe monsters van verskillende posisies in die boomtop vergelyk is. Vrugte aan die noorde- en buitekant, of hoër in die boom het die hoogste skilolie-inhoud gehad. Vrugte binne die plantry het minder skilolie bevat. Fotosinteties-aktiewe ligvlakmetings ondersteun die hipotese dat skilolieinhoud korreleer met ligblootstelling. Vir opitmale skilolie-inhoud in suurlemoene is dit dus belangrik dat bome nie te dig of te hoog moet wees nie, sodat dit nie die onderste dele van aangrensende bome oorskadu nie. Sitrus word in diverse klimaatstreke in Suid-Afrika verbou. Gevolglik is die skilolie-inhoud van vrugte uit verskillende produksieareas vergelyk. 'Eureka' suurlemoenvrugte uit Upington het met elke monsterneming die hoogste skilolie-inhoud gehad, gevolg deur vrugte uit Malelane en Marble Hall. Skilolie-inhoud van vrugte uit Karino was gemiddeld, terwyl vrugte van Vaalhaarts met elke monsterneming die laagste skilolie-inhoud gehad het. Regressie van skilolie-inhoud op kumulatiewe hitte-eenhede het 'n positiewe lineêre verwantskap in 2003 getoon. Hoewel die verwantskap swakker was in 2004, neem skilolieinhoud oor die algemeen toe met toenemende akkumulasie van hitte-eenhede. Sitruskultivars en -onderstamme varieer aansienlik in groeikrag en vrugkwaliteit. 'Lirnoneira 8A', gevolg deur 'Cicily', 'Lisbon' en 'Genoa' het die hoogste skilolie-inhoud gehad, terwyl 'Villafranca', 'Messina' en 'Yen Ben Lisbon' die laagste skilolie-inhoud gehad het. Die skilolie-inhoud van 'Eureka' suurlemoene was teleurstellend laag. Die skilolie-inhoud van die saadlose kultivars, 'Eureka SL' en 'Lisbon SL', was -18% hoër as die skilolie-inhoud van die kultivars waaruit dit ontwikkel is. Vrugte van bome wat op minder groeikragtige onderstamme geënt is, bv. X639 [C reshni Hort. ex Tan. x P. trifoliata (L.) Raf.], het 'n hoë skilolie-inhoud gehad, terwyl vrugte van bome op groeikragtige onderstamme, bv. growweskilsuurlemoen (C jambhiri Lush.), minder skilolie bevat het. Sintetiese gibberelliene, sitokiniene, etileen en ouksiene is op verskillende tye en teen verskillende dosisse op suurlemoenbome toegedien om die effek daarvan op skilolie-inhoud te bepaal. Promalin® (G~+7 en bensieladenienfosfaat) het 'n klein effek op skilolie-inhoud gehad, maar die effek was nie statisties beduidend nie. Ethephon, wat etileensintese induseer, het skilolie-inhoud in 2004 geaffekteer toe dit 8 weke voor oes toegedien is. Ethephon en aminoetoksievinielglisien (AVG, 'n etileenbiosintese inhibeerder) het egter nie 'n konstante effek op suurlemoen skilolie-inhoud gehad nie. Ouksiene het nie skilolie-inhoud geaffekteer me. Verdere eksperimente is veral nodig op die toedieningstyd en konsentrasie van toegediende gibberelliene, bv. Promalin®, en ethephon.

Deterpenation by concentration of the flavor bearing oxygenated compounds present in Citrus Essential Oils using the column chromatographic method and the parameters affecting the adsorption of these oxygenated compounds at maximum economy versus reasonable efficiency in separation from the non-oxygenated compounds have been studied. Particular attention was given to the maximum number of adsorption-desorption-regeneration cycles that a single column charge could be subjected to before the adsorbent should be replaced. The results of this study suggested the following conditions are of importance with regard to the development of an efficient and economic operation: 1) deactivation of the silica gel column by passage of a raffinate; 2) chilling of the column and feed oil to 5°C; 3) use of minimum silica gel/oil ratio; 4) in-place regeneration of the silica gel. The results of this study also demonstrates that no rearrangements of the non-oxygenated terpenes occurred.

Microemulsions (MEs) are dispersed systems, thermodynamically stable, isotropic, transparent, and stabilized by an interfacial film of surfactant compounds. In this study were obtained MEs from differents co - surfactant (ethanol - ET, isopropanol-ISO and propylene glycol - PG), Citrus sinensis (L.) Osbeck essential oil (CSEO), Tween 80 ® and phosphate buffer (pH 5.0). The co - surfactants were selected because they are tolerated by the skin. Therefore, the aim of the study was to evaluate the influence of co - surfactants in the formation of MEs containing Tween 80, CSEO and evaluate the influence of nifedipine (NFD) in the structure of systems formed. The MEs were obtained by constructing diagrams of pseudo-ternary phase in order to evaluate the influence of co-surfactant in the formation of MEs. The structural characterization of these systems was obtained by Polarized Light Microscopy (MLP), test electrical conductivity and Small angle X-ray scattering (SAXS). In each diagram, two formulations were selected, which was the criterion sense phase, in the O / A and bicontinuous, in which the NFD is incorporated. The formulations were evaluated by the techniques mentioned, to observe the influence of NFD and characterized by pH, droplet size, polydispersity index (PDI), surface tension and rheology. Interaction studies with model stratum corneum (SC) were performed using the techniques of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). In the diagrams showed the greatest formation region of the MEs to the ISO (above 40 % T / Cot) instead of the co- surfactants ET and PG. When assessing the electrical conductivity has been observed that increasing the aqueous fraction resulted in an increase in conductivity. The SAXS curves demonstrated that all systems are characteristic of micellar structures and as the water content was added, it was observed the formation of larger structures. Therefore, from the results obtained, the NFD has been incorporated in the formulations selected. The MEs presented as stable systems, isotropic, translucent droplet size between 16 and 34 nm, PDI below 0.5 and pH in the range of 5.64 to 6.7, compatible with the skin and pH stability of the NFD. In conductivity tests for each co - surfactant, the MEs were classified as bicontinuous and O / A. The MEs exhibited reduced surface tension and the formulations containing ISO submitted a surface tension value (24,764 mN / m) lower than the other co - surfactants (ET - 29.512 mN/m PG - 31.784 mN/m), confirmed by the evaluation of the droplet diameter and obtaining the phase diagram. The MEs exhibited Newtonian behavior, with consistency indices (k) higher in formulations with higher proportions of T / Cot, result corroborated the structures observed by SAXS. The DSC and FTIR techniques have demonstrated the use of the MEs as permeation promoters, provided from interactions with SC model. Therefore, the diagrams have elucidated the effect of co- surfactant in the formation of MEs and the same interference suffered no NFD, suggesting their use as permeation enhancers on the skin on application. / As microemulsões (MEs) são sistemas dispersos, termodinamicamente estáveis, isotrópicos, transparentes, estabilizados por um filme interfacial de compostos tensoativos. Neste trabalho foram obtidas MEs a partir de diferentes co-tensoativos (etanol-ET, isopropanol-ISO e propilenoglicol-PG), óleo essencial de Citrus sinensis (L.) Osbeck (OECS), Tween 80® e tampão fosfato (pH 5.0). Os co-tensoativos foram selecionados por serem toleráveis pela pele. Assim, o objetivo deste trabalho foi avaliar a influência dos co-tensoativos na formação de MEs contendo Tween 80, OECS bem como avaliar a influência da nifedipina (NFD) na estrutura dos sistemas formados. As MEs foram obtidas pela construção de diagramas de fase pseudoternário com o propósito de avaliar a influência do co-tensoativo na zona de formação das MEs. A caracterização estrutural desses sistemas foi realizada por Microscopia de Luz Polarizada (MLP), ensaios de condutividade elétrica e espalhamento de raios-X a baixo ângulo (SAXS). De cada diagrama, foram selecionadas duas formulações, cujo critério foi o sentido de fases, na região de óleo-água (O/A) e bicontínuas, nas quais a NFD foi incorporada. As formulações foram reavaliadas pelas técnicas citadas, a fim de observar a influência da NFD, além de caracterizadas por pH, tamanho de gotícula, índice de polidispersividade (IPD), tensão superficial e reologia. Estudos de interação com modelo de estrato córneo (EC) foram realizados através das técnicas de Calorimetria exploratória diferencial (DSC) e Espectroscopia na região de infravermelho com transformada de Fourier (FTIR). Nos diagramas foi observada uma maior região de formação das MEs para o ISO (acima de 40% de T/Cot) ao contrário dos co-tensoativos ET e PG. Ao avaliar a condutividade elétrica foi observado que o aumento da fração aquosa proporcionou um aumento na condutividade. As curvas de SAXS demonstraram que todos os sistemas foram característicos de estruturas micelares e à medida que o conteúdo aquoso foi adicionado, observou-se a formação de estruturas com maiores dimensões. Logo, a partir dos resultados obtidos, a NFD foi incorporada nas formulações selecionadas. As MEs apresentaram-se como sistemas estáveis, isotrópicos, translúcidos, tamanho de gotículas entre 16 e 34 nm, IPD abaixo de 0,5 e pH na faixa de 5,64 a 6,07, compatíveis com a pele e pH de estabilidade da NFD. Nos ensaios de condutividade para cada co-tensoativo, as MEs foram classificadas como bicontínuas e O/A. As MEs apresentaram redução da tensão superficial, sendo que as formulações contendo ISO apresentaram um valor de tensão (24,764 mN/m) inferior aos demais co-tensoativos (ET- 29,512 mN/m e PG- 31,784 mN/m), confirmado pela avaliação do diâmetro de gotas e obtenção do diagrama de fases. As MEs apresentaram comportamento newtoniano, com os índices de consistência (k) maiores nas formulações com proporções mais elevadas de T/Cot, resultado que corroborou com as estruturas observadas por SAXS. As técnicas de DSC e FTIR demonstraram a utilização das MEs como promotores de permeação, a partir das interações proporcionadas com modelo de EC. Logo, os diagramas elucidaram a influência do co-tensoativo na área de formação de MEs e os mesmos não sofreram interferência da NFD, sugerindo a sua utilização como promotores de permeação em aplicação sobre a pele.