This diploma thesis deals with the questions of determination of aroma active compounds present in yoghurts. These compounds are crucial for flavour of these fermented dairy products. Four types of yoghurts were analyzed, creamy (10 % of fat), medium-fat and medium-fat Bio (3 % of fat) and light (0,1 % of fat), produced by Mlékárna Valašské Meziříčí, spol. s r.o. Analysis was carried out by gas chromatography with extraction of analytes by SPME - solid phase microextraction. Five groups of different aroma active compounds such as ketones, aldehydes, organic acids and their esters and alcohols in different amounts were determined. These compounds are mostly metabolic products of Streptococcus salivarius subsp. thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, dairy yoghurt cultures usually used for yoghurt production. Less amounts are present in cow's milk or in dairy additives. Yoghurts were simultaneously sensorially evaluated using ranking test and scale test for determination of acceptability and flavour. The assessors were students and staffs of faculty of chemistry BUT.

The aim of the diploma thesis was to determine the influence of different kinds of fats on the content of aromatic active compounds and total flavour of processed cheese analogues. Samples of the cheese were produced by Tomas Bata University in Zlín from concentrated milk fat, butter, palm fat, coconut fat and sunflower oil. The aromatic compounds were isolated from samples of fats and processed cheese analogues via HS-SPME-GC method. A fibre with polar stationary phase CAR/PDMS was used for capturing of aromatic active compounds. In different contents, total of 32 aromatic compounds were determined. The cheese from concentrated milk fat and butter had the highest content and cheese from sunflower oil had the lowest. For determination of acceptability and flavour, the cheese analogues were sensory evaluated at the same time. Ordinal test, evaluation via scale and profile test were used. Cheese made from concentrated milk fat and coconut fat were always evaluated as the best, cheese made from sunflower oil were evaluated as the worst. Finally results between SPME-GC and sensory analysis were compared. It was stated that the kind of fat used for production of processed cheese analogues significantly influences the content of aromatic compounds and thus influences flavour of the cheese analogues.

The aim of this diploma work is to characterise processed cheeses and their analogues, to identify and quantify aroma active substances in the samples of cheese analogues, to evaluate their flavour using selected sensory methods and to compare the acquired results with the flavour of corresponding classic cheeses. The theoretical part is focused on general characteristic, classification, production technology of the processed cheeses and their analogues and on the list of aroma active substances occurring in cheeses. Furthermore, the summary of the methods suitable for sensory and analytic evaluation of cheese flavour and for the isolation of aroma active substances is given here. The samples of cheese analogues were made in Tomas Bata University in Zlín from coconut fat, butter, palm fat, milk fat and sunflower-seed oil. The classic processed cheeses were acquired commercially in the chain-store Billa. The aromatic substances were isolated and quantified using SPME-GC method, the fibre with the polar stationary phase CARTM/PDMS was used. Overall, 44 aroma substances were assessed: 9 aldehydes, 17 alcohols, 3 esters, 10 ketones and 5 acids. Classic processed cheeses contained the largest amount of aroma substances, Edam cheese, used for the production of cheese analogues, the smallest. Aroma compounds found in cheese analogues were then compared with raw materials used (Edam cheese and various fats), with the analogues produced last year and with classic processed cheeses. Finally, the results of the SPME-GC method and the sensory analysis were compared. It is possible to state that there are noticeable extensive differences between classic processed cheeses and cheese analogues, especially in taste.

The aim of this diploma thesis was to identify and quantify the content of taste and aroma active compounds and to evaluate flavour of cheese analogue samples with various vegetable fats (coconut, palm, butter and mixed oils and butter) and differently matured Edam cheese using selected sensory methods. The samples were produced at Tomas Bata University in Zlín. Aroma compounds were extracted using SPME and assessed using gas chromatography. In total 43 compounds were identified, 14 alcohols, 9 aldehydes, 7 ketones, 8 acids, 5 esters and 1 terpene. Simultaneously the analogues were sensorially evaluated using scale, profile and ranking tests. The influence of storage time, type of fat and Edam cheese used on content of aroma compounds and sensory quality of analogues were evaluated. The cheese analogues with butter were sensorially evaluated as the best, with mixed oil as the worst. From the point of view of aroma compounds content, the significant differences between samples were evident. Using more matured Edam cheese, the content of aroma compounds declined, however, these samples were sensorially evaluated as better. The content of aroma compounds decreased also with storage time, which is more obvious in less matured Edam cheese. So all above mentioned factors influence the content of aroma compounds and thus the flavour of cheese analogues.

This diploma thesis deals with the topic of cheese analogues, their characterization and qualitative and quantitative analysis of processed cheese analogues for determination the taste and aroma active compounds. The overall character of processed cheese analogues is theoretically compiled in the introductory part. Their utilization, causes of the production, market introduction, technological production process and microstructure, including their comparison with classical processed cheese are given here. Various kinds of fats were used for production of analyzed cheese analogues, therefore commonly used ingredients for their production, their physical-chemical and sensory properties have been described. Specifically butterfat, milk fat, coconut fat, palm fat and mixed oil. Samples used for the practical part of the diploma thesis were made at Tomas Bata University in Zlín. In the experimental part the profile of aroma compounds in individual cheese analogues samples was assessed by SPME-GC analysis. In total 34 compounds were identified. The results were evaluated and compared, with emphasis put on the influence of storage, different fats, different maturity of Edam cheese on the content of aroma active compounds and on overall sensory quality of the analogues.

Lysine deficiency is a major nutritional problem faced by poor people living in the arid and semi-arid tropics who depend on sorghum as their staple food. This is because of poor lysine content and digestibility of sorghum proteins, which aggravates when sorghum is cooked in food. To address this nutritional problem, compositing with locally available lysine-rich legumes has been proposed. Therefore, this study investigated the effects of compositing with the African grain legume, cowpea, on the protein and functional quality of important traditional African sorghum foods. Two sorghum cultivars, a red, tannin (NS 5511) and a white tan plant, non-tannin (Orbit) composited with cowpea at 70:30 ratio, were used to prepare three traditional sorghum foods, ugali (unfermented thick porridge), uji (fermented thin porridge) and injera (fermented flatbread). The protein quality of the traditional sorghum foods was determined by measuring their protein contents, lysine and reactive lysine contents, and in vitro protein digestibility. The functional properties of the foods were studied using instrumental texture analysis. Other sensory properties of ugali were determined using a trained sensory panel. Compositing with cowpea increased the protein contents of the foods by up to 35% and 57% for NS 5511 and Orbit foods, respectively. Lysine contents of the food proteins increased by 67% to 139%. Reactive lysine content increased by 10% to 75%. Protein digestibility of the foods increased by 13% to 62%. There was approximately three- and two-fold increase in protein digestibility corrected amino score (PDCAAS) of NS 5511 and Orbit foods, respectively, due to addition of cowpea. However, Orbit-plus-cowpea foods still had better protein quality than NS 5511-plus-cowpea foods, primarily because of the tannins in the latter which bind the proteins thereby lowering their digestibility. Compositing reduced paste peak viscosity (PV) and cool paste viscosity (CPV) of uji porridge by 6% to 23%, and 6% to 12%, respectively, probably as a result of decreasing porridge starch content. Principal component analysis (PCA) showed that compositing contributed 38% of the variation in 17 sensory attributes of ugali. Compositing imparted cowpea flavour to ugali. Most of the variation in sensory properties (59%) of ugali was due to the quality characteristics of the sorghum cultivars. Compositing increased the stiffness of NS 5511 injera by up to 25%, while it reduced the stiffness of Orbit injera by up to 12%. These differences in stiffness suggested a weakening effect of weaker H-bonding between tannins and other food polymers such as proteins instead of stronger covalent bonds like those involved in proteins-protein interactions. Compositing important traditional sorghum foods with cowpea has potential for helping to solve lysine deficiency faced by sorghum consumers in the semi-arid tropics. However, it introduces cowpea flavour which may need to be eliminated, in foods intended for consumers not accustomed to cowpea flavour. Copyright / Dissertation (MSc)--University of Pretoria, 2009. / Food Science / unrestricted

This diploma thesis is focused on the problematic of assessment of 26 most important allergenic aroma compounds in foods, flavoured herbal teas were chosen as the model samples. Aroma is the one of the main characteristics of tea, which is closely linked to taste and odour. The theoretical part of this work is focused on the characteristics of tea, tea types, producing technology, classification according to the fermentation and also their undeniable impact on the human organism. In the experimental part, the allergenic aroma compounds in 10 chosen samples of flavoured tea were identified and quantified using the solid phase microextraction (SPME-GC-FID) in conjunction with gas chromatography. The work also includes sensory evaluation of taste and smell of tea samples by qualified assessors.

Milk proteins are known to bind volatile flavour compounds to varying extents, depending on the nature of the protein and flavour compound. Processing conditions, such as temperature and pH, are also known to have an influence on the interactions between milk proteins and flavour compounds. These interactions cause a great challenge for flavour scientists because they influence the perceived aroma profile of food products significantly, in particular in low-fat food products. The objectives of this research were to develop a headspace solid-phase microextraction (SPME) method followed by gas chromatography with flame ionisation detection (GC-FID) for the investigation of protein-flavour interactions, and to determine binding parameters of the hydrophobic flavour compound, 2-nonanone, to individual milk proteins - namely, β-lactoglobulin (β-lg), α-lactalbumin (α-la), bovine serum albumin (BSA), αs1-casein, and β-casein -, whey protein isolate (WPI), and sodium caseinate. Secondly, it was the aim to compare the binding of the structurally similar flavour compounds - 2-nonanone, 1-nonanal, and trans-2-nonenal – to WPI in aqueous solution, and to investigate the effect of heat and high pressure treatment, and pH on the extent of protein-flavour binding. The final objective was to investigate the in vivo release of the reversibly bound flavour compound, 2-nonanone, from WPI and sodium caseinate using proton transfer-reaction mass spectrometry (PTR-MS), and to understand the effect of viscosity on flavour release in vivo. The binding of the model flavour compound 2-nonanone to individual milk proteins, WPI, and sodium caseinate in aqueous solutions was investigated, using headspace SPME followed by GC-FID. The 2-nonanone binding capacities decreased in the order: BSA > β-lg > α-la > αs1-casein > β-casein, and the binding to WPI was stronger than the binding to sodium caseinate. All proteins appeared to have one binding site for 2-nonanone, except for BSA which possessed two classes of binding sites. The influence of heat treatment, high pressure processing and pH of the protein solutions on the binding of 2-nonanone, 1-nonanal, and trans-2-nonenal to WPI was determined. The binding of these compounds to WPI decreased in the order: trans-2-nonenal > 1-nonanal > 2-nonanone. The binding of 2-nonanone appears to involve hydrophobic interactions only, whereas the aldehydes, in particular trans-2-nonenal, also react through covalent binding. Upon both heat and high pressure denaturation, the binding of 2-nonanone to WPI decreased, the binding of 1-nonanal remained unchanged, while the binding of trans-2-nonenal increased. The binding affinity of the flavour compounds and WPI increased with increasing pH, which is likely to result from pH dependent conformational changes of whey proteins. The in vivo flavour (2-nonanone) release from solutions of WPI and sodium caseinate was investigated using proton-transfer-reaction mass spectrometry. During consumption, 2-nonanone was partly released from WPI, whereas there was no significant release from sodium caseinate. Even after swallowing of the samples, a substantial amount of flavour was detected in the breath, suggesting that the milk proteins interact with the mucosa in the mouth and throat, resulting in a further release of flavour from mucosa-bound proteins. An increase in viscosity of the protein solutions by the addition of carboxymethylcellulose enhanced the release of 2-nonanone from WPI, and resulted in 2-nonanone release from sodium caseinate. This may be due to a thicker coating of the mucosa with the sample solution after swallowing due to the higher viscosity, resulting in additional release of protein-bound flavour. These findings contribute to the knowledge of the interactions that occur between flavour compounds and proteins, which is required to improve food flavouring and to make protein based foods, e.g., low-fat dairy products, sensorily more acceptable to the consumer. The results also emphasize a careful choice of food processing conditions, such as temperature, high pressure or pH to obtain a desirable flavour profile.

Quarks charm são criados em estágios iniciais da colisão de íons pesados em processos de espalhamento duro. Portanto eles são sondas ideais para o Plasma de Quarks e Glúons (QGP), que é um estado da matéria em que os partons contidos em hadrons, em condições de alta temperatura (150 MeV) ou densidade (cerca de cinco vezes a densidade da matéria ordinária), passam para um estado livre de quarks e glúons. A fragmentação de quarks charm pode produzir mésons D. Jatos contendo um méson D como um de seus constituentes podem ser identificados como originados de uma fragmentação de quark pesado. Jatos contendo mésons D são valiosas ferramentas para caracterizar interações de quarks charm com o plasma. Jatos de charm podem fornecer informações para o estudo da perda de energia dependente da massa pela medida da modificação da produção de jatos de charm em colisões de núcleos de chumbo com respeito a colisões entre prótons em função do momento transversal dos jatos. Além disso, uma visão mais profunda pode ser obtida com a medida da distribuição da fração de momento, que é de particular interesse para investigar a possível influência do meio na fragmentação de quarks charm em jatos. Mésons D são reconstruídos através da análise de massa invariante de seu canal de decaimento hadrônico, rejeitando uma grande quantidade de fundo combinatório com seleções topológicas e explorando o tempo de vida relativamente longo de mésons D e as capacidades de identificação de partículas do detector ALICE. Jatos são reconstruídos com o algoritmo anti-kT usando candidatos a mésons D e partículas carregadas. A medida do espectro de momento transversal de jatos contendo mésons D em colisões de núcleos de chumbo a energias de sNN = 5.02 TeV será apresentada. Esses resultados levam a novas possibilidades de sondagem das propriedades do QGP quando comparados com medidas de referência. Por fim, os métodos desenvolvidos podem ser empregados no estudo das funções de fragmentação de quarks charm em colisões de íons pesados. / Charm quarks are created in the early stages of heavy-ion collisions in hard-scattering processes. Therefore, they are ideal probes of the Quark-Gluon Plasma (QGP), which is a state of matter where partons contained in hadrons, at high temperatures (150 MeV) or density (about five times the density of ordinary matter), change to a deconfined state of quarks and gluons. The fragmentation of charm quarks can produce D mesons. Jets containing a D meson as one of their constituents can be identified as originating from heavy-quark fragmentation. These jets are a valuable tool to characterize the charm interaction with the QGP. Charmed jets can provide information to the study the mass-dependent energy loss by the measurement of the modification of the charm-jet yield in Pb-Pb collisions with respect to pp collisions as a function of the jet transverse momentum. Moreover, a further insight can be obtained with the measurement of the momentum-fraction distribution, which is of particular interest to investigate the possible influence of the medium in the charm-jet fragmentation. D mesons are reconstructed through an invariant mass analysis of their hadronic decay channels, rejecting the large combinatorial background with topological selections exploiting the relatively large lifetime of D mesons and the particle identification capabilities of the ALICE detector. Jets are reconstructed with the anti-kT algorithm using D-meson candidates and charged tracks. The measurement of the transverse momentum spectrum of jets containing D mesons in Pb-Pb collisions at sNN = 5.02 TeV will be presented. These results lead to new possibilities of probing the QGP properties when compared to baseline measurements. Furthermore, the methods developed can be employed in the study of charm-quark fragmentation functions in heavy-ion collisions.

Las Bebidas con Aroma a Limón sufren cambios significativos con el paso del tiempo, que son asociados a deterioro por los consumidores. En la presente Tesis Doctoral se identificaron las causas de la inestabilidad de los Aromas de Limón. Para lograr la aparición de los defectos en forma acelerada se prepararon Bebidas con Aroma a Limón y se expusieron a alta temperatura. La identificación del defecto se realizó en primera instancia mediante técnicas de Evaluación Sensorial, conformando un Panel de Evaluadores Expertos, entrenados con Descriptores Sensoriales y una Rueda del Aroma Limón diseñados en este trabajo. Por otra parte se llevaron a cabo análisis de Cromatografía Gaseosa acoplada a Espectroscopía de Masas, para identificar los cambios químicos que experimentan los Aromas de Limón. La comparación de ambas metodologías presentó resultados que permitieron diseñar Aromas de Limón para uso en Bebidas, estables y con un alto nivel de aceptación por los consumidores. / Lemon Beverages experience significant changes over time, which are perceived as deterioration by consumers. This PhD thesis identifies the causes of Lemon Flavours instability. To achieve the quick appearance of the defects, Lemon Flavoured Beverages were prepared and exposed to high temperature. The identification of the defects was first performed by Sensory Evaluation techniques, training an Expert Panel of Evaluators, with tailor made Sensory Descriptors and a Lemon Flavour Wheel. Moreover analytical methods were performed using Gas Chromatography with Mass Spectroscopy, to identify the chemical changes experienced by Lemon Flavours. The comparison of both methodologies showed results that allowed the design Lemon Flavours to use in beverages, stable and with a high level of consumer acceptance.