This thesis is concerned with the derivation, development, and validation of a model for the dynamic behaviour of gas bubbles in molten instant coffee, in response to changes in pressure and temperature. Initially, the material properties of molten instant coffee were investigated. The primary technique used was capillary rheometry, as the viscous behaviour of molten instant coffee is a major contributor to the behaviour of bubbles within the fluid. The experimental technique was supplemented by analytical and computational modelling of the pressure losses in the system, to improve data processing accuracy. Additional thermal and mechanical tests were performed to obtain as much of the necessary material information as possible for the system. The modelling of bubble behaviour was performed using a combination of analytical and computational methods. The relationship between the pressure driving force for bubble growth or shrinkage and the rate of change of bubble size was derived analytically for a number of common generalised Newtonian fluid models. Heat and mass transfer between the bubble and the surrounding fluid was calculated using a finite difference approximation of the governing partial differential equations. The model was written in MATLAB and initial validation was carried out by comparison with existing models for bubble dynamics. Experimental observations of bubble dynamics in flows of molten instant coffee were recorded and used for an extended validation of the model. Bubbles were exposed to step changes in pressure and oscillatory pressure profiles at a range of temperatures, and the observations of 130 individual bubbles were used to validate the model using the same material parameters for each. A final case study in using the bubble model to predict the bubble size and pressure distribution created by an extrusion process is presented as an example of the use of the model, and highlights the additional information about a process that is required to effectively use the model.

Master of Science / Department of Human Nutrition / Edgar Chambers IV / The sensory properties of coffee are impacted by various factors such as coffee origin, degree of roasting and ways of consumption. This study analyzed impact of ways of consumption (1. consumption temperatures and 2. milk and/or sugar additions) on 38 flavor attributes of hot brewed coffee by descriptive sensory analysis. Different type of coffee samples (2 Arabica, 1 Robusta, and 1 Blended) were consumed at 50ºC, 60ºC and 70ºC. Results showed significant interactions of temperature and coffee samples for coffee like attributes such as coffee identity, fidelity, and blended. The consumption temperature played a major impact on perceived flavor attributes of coffee and influenced Arabica, Blended and Robusta coffee differently and we have to consider that when blending coffees. Coffee identity and fidelity significantly increased with an increase in all temperatures, but most attributes showed significantly higher intensity only for samples served at 70ºC regardless of insignificant differences at 60ºC and 50ºC. Three coffee samples (light, medium, and dark roasted) were tasted with and without milk or sugar. The data were submitted to principal component analysis and cluster analysis. The first 2 PC’s allowed to separate coffee into three categories and CA revealed similar distribution of coffee into three clusters. Coffee like attributes were seemed to play a more important role in the determination of clusters as the addition of milk and sugar decreased the intensity of key flavor attributes such as coffee identity, bitterness, fidelity, roasted, blended, and longevity. The flavor attributes of dark roasted coffee was more impacted by the addition of milk and sugar. Results suggested that the effect of addition (milk and/or sugar) is correlated to the degree of roasting and we have to consider the milk and sugar additions according to degree of roasting.

Cultured tissues derived from the coffee plant, Coffea arabica L., were grown in vitro in the form of both callus and suspension cultures. The suspension cultures grew rapidly and appeared healthy. Microscopic examination showed that the cells characteristically grew in long filamentous chains. Suspension cultures were examined for the presence of three components - free amino acids, caffeine and chlorogenic acid. By examining these components the species specificity could be determined. The free amino acids of the coffee bean are thought to be one of the major precursors of coffee aroma on roasting. The coffee suspension cultures were shown to contain a similar pattern of free amino acids although the total content was much higher in the cultures than in the intact green coffee bean. Aspartic acid, glutamic acid, phenylalanine, alanine, valine, threonine, serine, and glycine were the predominant amino acids present in the coffee suspension culture. Threonine, serine, glycine, alanine and phenylalanine were the major free amino acids in the green coffee bean. The free amino acid content in the suspension culture exhibited an initial rise, decreased during active growth, then increased rapidly to the maximum level during the decline of the culture. Roasted coffee bean extracts were investigated to ascertain whether one solvent could in preference extract some of the major precursors of coffee aroma. Methanol was found to extract material from green coffee beans which on roasting produced coffee aroma. Caffeine was detected in the cell suspension cultures. However, problems with the analytical methods gave rise to questionable results. The suspension cultures, at maximum caffeine yield, contained 0.03% caffeine (dry weight) whereas the green coffee bean contained considerably more caffeine (1.15%, dry weight). The caffeine content of the tissues increased during the lag phase, decreased during the rapid phase and then increased again in the stationary phase and ultimately production levelled off during the deline phase of growth. The cell cultures produced chlorogenic acid in low concentrations at the maximum 0.14% dry weight in contrast to the green coffee bean which contains 6.5% dry weight. The production or accumulation of chlorogenic acid followed a similar pattern to that of the cell caffeine production over the growth curve. Caffeic acid was also detected. The cell suspension cultures of Coffea arabica L. were shown to be species specific in their biochemical capabilities. / Land and Food Systems, Faculty of / Graduate

Since the introduction of coffee to Europe in the early 17th century its popularity has steadily increased and, water apart, is the most widely consumed beverage globally. Being derived from a plant, a cup of coffee represents a complex mixture of naturally occurring chemicals such as caffeine, coffee oils and chlorogenic acid. As the popularity for coffee has grown so too has the interest surrounding its possible biological and pharmacological effects. A small number of studies suggest potential risks and benefits associated with coffee consumption in pregnancy; however these have yet to provide definitive conclusions. Furthermore government advice does not directly address coffee intake during pregnancy and there is no information regarding womens’ and midwives’ views and opinions on this increasingly important issue. This was a mixed-method research study, with both a qualitative and quantitative components. Firstly, I aimed to gain insight into womens’ and midwives’ views and opinions on coffee consumption during pregnancy. Informed written consent was obtained from women attending the hospital for their antenatal care. These women were of varying gestational age, ethnic background, socioeconomic status and age. Informed written consent was also obtained from midwives from varying disciplines and experience levels; those from academia, research and practicing midwives included. I recruited twenty participants in each group. Information and perspectives were gathered through semi-structured face-to-face or telephone interviews. Interviews were analysed with the Framework method of analysis. The second quantitative arm of my study investigated the effect of specific coffee chemicals on placental and myometrial vascular function. Human chorionic plate arteries, isolated from placental biopsies, and maternal myometrial arteries isolated from myometrial biopsies, were assessed by wire myography. Contraction and relaxation were determined to incremental doses of caffeic acid, chlorogenic acid and caffeine. The antioxidative properties of these chemicals were also assessed in response to application of reactive oxygen species. My findings indicated that women and midwives’ were unsure of the information surrounding coffee consumption. Pregnant women and midwives’ discussed the provision of information, sources of information and supplementing information. Findings also indicated that the relationship between health care professional and pregnant women can influence willingness to accept information and womens’ level of pregnancy stress. My laboratory studies indicated that the active coffee chemicals did not significantly impact on placental or myometrial arterial function. The chemicals investigated did not elicit any significant protective antioxidative effects. Combining methods allowed for a more comprehensive primary study to be completed. My literature search indicated that there was a clear gap in the knowledge surrounding coffee and its consumption during pregnancy. There is a clear lack of evidence-based information accessible to women regarding consumption. Midwives feel ill-equipped to provide women with information on coffee but err on the side of caution with their advice. Laboratory studies indicate that the coffee chemicals investigated did not induce an effect and cast doubts on the potential antioxidative effects that have been previously quoted in the literature.

The cells of two plants, Coffea arabica and an unknown Mentha species, were grown as suspension cultures in liquid media, in order to analyse and compare the fatty acids and sterols of the cell cultures to those found in the parent plants. The cell growth, the parameters of pH and conductivity of the media, and the composition of the neutral lipid fraction were examined. In the case of the coffee cell cultures, the cell growth and the media pH and conductivity were studied in three different media, two defined and one undefined, while the mint cell cultures were studied in one other defined medium. Both coffee and mint cell cultures were grown in the absence of light (normal cultural conditions) and in the presence of light. The coffee cells showed no differences in growth rate due to variations in media composition. Exposure to light affected neither the growth rate nor initiated chlorophyll formation in the coffee cell cultures, although a distinct green pigmentation formed in the mint cells. A plot of the ionic conductivity of coffee and mint cell suspension cultures was essentially a mirror image of the growth curve of the respective culture. The fatty acids present in the neutral lipid fraction of the cells were studied via gas chromatography, and were compared to the fatty acids found in the seeds and tissues of the parent plants. Palmitate, stearate, oleate, linoleate and linolenate were found in all coffee and mint cell cultures, independent of the composition of the media and of the presence of absence of light. The appearance of short chain fatty acids (less than C-l6) occurred during the dying phases of culture. The fatty acid composition of the coffee cell cultures resembled the analyses of the leaf and stem tissues of the coffee plant rather than the coffee bean. The cell cultures all contained linolenate, not found in the coffee bean, and lacked arachidate, which was present in the bean. In contrast to the coffee cell, the mint cell fatty acids resembled the fatty acid composition of the mint seed rather than the parent plant tissues which contained substantial quantities of the short chain fatty acids (less than C-16). The total fatty acid content of the coffee and mint cell cultures was lower than the seeds of the parent plant, but was comparable to parent plant tissues. A decrease in the total fatty acid content of the neutral lipid fraction of both cultures was noted during the death phase of culture. The total fatty acid content of the coffee cell cultures was not altered by changes in media composition, nor by growth of the cultures in the presence of light. However, the growth of mint cell cultures ln the presence of light had a marked effect on the fatty acid content, which increased approximately four fold in comparison to cultures grown in the dark. The sterol composition of the unsaponifiable lipid found in the extracts of coffee and mint cell cultures was investigated via gas chromatography and thin layer chromatography. The sterols present were compared to those found in the seeds of the parent plants. The sterols found in large concentration in the coffee cells werep -sitosterol, stigmasterol and campesterol, while in the mint cells only ϐ -sitosterol was conspicuous. The predominant sterols found in the seeds of the parent plants and in the plant cell cultures were identical. However, the cell cultures of both coffee and mint contained larger amounts of sterols in their saponified lipid extracts than found in the seeds. Furthermore, in comparison to the seeds, the lipid extracts of the cell cultures contained greater quantities of unesterified sterols. A wide variety of sterols other than desmethyl sterols were located in the seeds and cell cultures, but were not identified as they constituted only a minor portion of the total plant sterols present. A large portion of the unsaponiflables of the coffee bean was characterized as non-steroidal. This non-steroidal material was identified as a mixture of two diterpenold alcohols, cafestoi and kawheol, both known to be major constituents of the unsaponiflables of coffee bean oil. The coffee cell oil unsaponifiables were also found to contain these two diterpenoid alcohols. / Land and Food Systems, Faculty of / Graduate

The subject of this diploma thesis is the design of a coffee machine. The design focuses on a professional automatic high-load coffee machine intended for use in dayrooms and meeting rooms of companies. The final proposal should meet all constructional, technological, aesthetic and ergonomic requirements. The aim of the thesis is to design a coffee machine following the expected requirements while the visual appearance and functionality of the device corresponds to the individual needs of its users and operators.

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