Orientador: Carlos Alberto R. Anjos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-07-28T20:55:36Z (GMT). No. of bitstreams: 1 Duarte_GiseleMaraBertolazzo_M.pdf: 5637351 bytes, checksum: 31cc0c411ac10a3fe95906ed0b2bb30b (MD5) Previous issue date: 2001 / Resumo: O consumo de águas minerais no Brasil vem aumentando significativamente nos últimos anos. Os consumidores estão se tornando mais exigentes em relação aos hábitos de compra, qualidade, praticidade e conveniência. Dentro deste cenário e devido a uma série de vantagens técnicas e comerciais, as embalagens tradicionais de vidro, polietileno de alta densidade (PEAD) e policloreto de vinila (PVC) para águas minerais vem sendo substituídas pelas embalagens de polietileno tereftalato (PET). A resina de PET é susceptível à termodegradação durante o processo de injeção de pré-formas, ocorrendo a formação de acetaldeído que pode alterar o aroma e sabor de águas minerais e diversos outros produtos acondicionados em embalagens de PET, dependendo dos níveis existentes deste composto. Todos os setores envolvidos na fabricação de garrafas de PET, tais como fabricantes de resinas, pré-formas, garrafas e de equipamentos, vem trabalhando em conjunto com o objetivo de minimizar a formação de acetaldeído durante o processo de fabricação. Muitas dessas empresas possuem dados relativos aos seus processos, porém não são divulgados ao público. Por outro lado, as empresas envasadoras de águas minerais preocupam-se e desconhecem os níveis residuais de acetaldeído capazes de promover alteração de sabor e aroma, em seus produtos, comprometendo a qualidade após o envase. O presente trabalho teve como objetivos principais determinar o limiar de detecção ou threshold absoluto de acetaldeído em águas minerais, ou seja, determinar a concentração mínima de acetaldeído que promove diferença sensorial significativa, medir os níveis residuais de acetaldeído, através de cromatografia a gás em diferentes águas de fontes brasileiras acondicionadas em PET e verificar se as mesmas apresentam diferença sensorial significativa quando comparadas com as respectivas águas envasadas em garrafas de vidro / Abstract: The consumption of mineral water in Brazil has been increasing significantly in the last few years. Consumers are becoming more demanding with respect to their buying habits and convenience for use. Due to a series of technical advantages the traditional glass package, high-density polyethylene and PVC for mineral waters have been replaced by the PET package. The PET resin is susceptible to thermal degradation during the injection process, resulting in the formation of acetaldehyde, which can alter the flavor of the mineral waters and many other products packaged in PET. Many sectors involved in the production of PET bottles, like the resin producers, pre forms, bottles and equipment producers have been working together aiming to minimize the formation of acetaldehyde during the production processo On the other hand, the mineral water companies are concerned about the residuallevels of acetaldehyde that can promote flavor modification in their products, which could compromise the quality of the product after bottling. The present work aimed at determining the absolute acetaldehyde lhreshold in mineral water and acetaldehyde residue using gas chromatography in different brands, packaged in PET bottles. Also, to verify if the mineral water bottled in PET bottles showed any significant sensory difference when compared with the same waters packaged in glass bottles / Mestrado / Mestre em Tecnologia de Alimentos

In an attempt to determine mechanisms of certain aspects of ethanol- induced fetal damage, I have established a mouse model of the fetal alcohol syndrome based on the work of Chernoff (1977), using inbred C3H mice. Ethanol or its metabolite, acetaldehyde, was administered to female mice prior to and throughout gestation. Ethanol in doses of 6%, 10% and 20% ethanol derived calories and acetaldehyde 3. 9 mg and 11. 8 mg were administered daily in a nutritionally balanced liquid diet. An acute dose study was also undertaken, in which pregnant C3H mice were given. "binge" doses of 1ml of a 7. 35% solution of ethanol, twice daily through an orogastric tube, on days one and eight or four and twelve of gestation. The mice were sacrificed on day eighteen of gestation and the fetuses weighed and examined macroscopically. Some were sectioned using Wilson's method of free-hand razor blade sectioning (Barrow and Taylor, 1969), and the skeletons of the others were examined using a modified Dawson's method of skeletal preparation (Richmond and Bennett, 1938). A separate in vitro model based on the work of New (1967) was established, in which embryos of eight or nine days' gestation were explanted with visceral yolk sac intact from normal C3H mice. They were cultured for twenty-eight hours in rat serum containing various concentrations of ethanol or acetaldehyde (ethanol 1500, 3000 and 6000mg/l and acetaldehyde 7.4, 19. 7 and 39.4mg/l). During the last four hours of the culture period the embryos were labelled with one microcurie of tritiated thymidine (specific activity 5curies/mmol). At the end of the culture period the embryos were assessed morphologically, and then prepared for liquid-scintillation counting to determine DNA synthesis by measuring tritiated thymidine uptake. Small numbers of embryos from each group were used for autoradiographic studies in an attempt to quantitate the uptake of label in the various parts of the embryo. I found that ethanol given in chronic dosage in vivo was embryotoxic in all three doses studied. There was no evidence of ma tern al toxicity other than hyperactivity at the highest dose used and maternal jaundice in a small number of the 10% EDC and 20% EDC mice. Acetaldehyde given in chronic dosage in vivo produced no toxic effects on mothers or fetuses, other than a reduction in placental weights. Acute "binge" ethanol dosage of mothers on days one and eight or four and twelve of gestation did not appear to have any adverse effects on mothers or fetuses, apart from changes in placental weights. These findings should be viewed with caution, as the in vitro studies did not produce a corresponding result. In the latter study there was a marked time-related response, particularly for acetaldehyde. Ethanol given in vitro produced little evidence of toxicity except at dose levels which in the corresponding in vivo situation were extremely toxic to the mothers. Acetaldehyde, given in vitro in minute fractions of the harmless doses given to mothers in vivo, proved to be highly toxic to 8-day embryos and relatively non-toxic to 9-day embryos. This difference in sensitivity indicates that there must be some protective factor intervening between eight and ten days gestation - possibly the developing placenta may have a role here. From these findings I would suggest that acetaldehyde is a true teratogen, and the abnormalities produced in the chronic ethanol in vivo study were probably largely due to the action of acetaldehyde.

In this study photocatalytic oxidation was investigated as a potential treatment method of VOC emissions from industrial plants. This was done by designing an experimental setup and a photocatalytic reactor for screening of photocatalysts (TiO2). The performance of commercial TiO2 and synthesized TiO2 (pure and Ni-doped) for degrading acetaldehyde when exposed to UV-C light was evaluated at fix reaction conditions. Also, procedure of coating TiO2 on aluminum and stainless steel as well as their stability performance was investigated in the study. For comparison of photocatalysts aluminum was chosen as support material since it showed highest stability at reaction conditions.  The results show that photocatalysts with a high anatase content and high specific surface area present enhanced photocatalytic performance. Commercial TiO2 show significantly higher photocatalytic performance than synthesized TiO2. This may be influenced by higher coating stability presented for commercial TiO2. For synthesized TiO2 non-doped samples present significantly higher performance than Ni-doped TiO2. However, because of coating instabilities it is difficult to determine if this was observed difference in performance was only caused by photocatalytic performance. / I detta arbete undersöktes fotokatalytisk oxidation som potentiell gasreningsteknik för industriella utsläpp av flyktiga organiska kolväten. En experimentell uppsättning konstruerades tillsammans med en fotokatalytisk reaktor designad för att jämföra olika fotokatalysatorers (TiO2) prestanda. Prestandan för både kommersiella fotokatalysatorer samt fotokatalysatorer syntetiserade i arbetet (TiO2 samt Ni-dopad TiO2) jämfördes för att bryta ned acetaldehyd under konstanta reaktionsförhållanden samt bestrålning av UV-C. Aluminum och rostfritt stål undersöktes som supportmaterial för TiO2. För undersökning av olika fotokatalytorers prestanda användes aluminum på grund av en högre stabilitet vid undersökta reaktionsförhållanden. Resultaten från jämförelsen av olika fotokatalysatorer visar att en hög andel anatas form av TiO2 samt en hög specifik ytarea ger en förbättrad fotokatalytisk prestanda. Kommersiell TiO2 visade signifikant högre fotokatalytisk effekt än syntetiserad TiO2. Detta kan bero på en högre stabilitet av TiO2-beläggning på aluminum för kommersiell TiO2 gentemot syntetiserad och inte nödvändigtvis bero av enbart fotokatalytisk aktivitet. För syntetiserad TiO2 visar dopning med Ni signifikant lägre aktivitet än för icke dopad TiO2. På grund av instabilitet i beläggningen av TiO2 på supportmaterialet kan en påverkan av detta inte uteslutas.

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Thesis (Ph. D.)--University of Missouri--Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 172-205). Also available on the Internet.

Este trabalho apresenta a preparação e caracterização de eletrodos de óxidos do tipo ânodos dimensionalmente estáveis (ADE) de composição nominal Ti/Ru0,3Ti0,7O2, modificados pela adição de metais em sua superfície. A introdução de um metal modulador permitiu alterar de forma significativa o comportamento eletroquímico de todo o recobrimento. A modificação do ADE foi realizada através de eletrodeposição de Pt e PbO2 e de deposição química de catalisadores nanodivididos (Pt e Pt-Ni). O objetivo desta preparação foi modular as propriedades dos ânodos visando melhorar as propriedades eletrocatalíticas e a resistência mecânica e com isto, introduzir uma nova classe de materiais para aplicá-los na eletrooxidação de formaldeído, acetaldeído e ácido oxálico. Para caracterizar os eletrodos foram utilizadas as técnicas de microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva de raios X (EDX), voltametria cíclica (VC), eletrólises com acompanhamento por cromatografia líquida de alta eficiência (CLAE), espectrometria de massas eletroquímica diferencial (DEMS). Os experimentos com DEMS foram realizados na Universidade de Poitiers, França. As micrografias e as análises de EDX mostraram que o rutênio concentra-se em pequenas ?ilhas? na camada de óxidos e a modificação com platina, eletrodepositada ou depositada quimicamente, ocorre preferencialmente nas regiões ricas em rutênio. O eletrodepósito de PbO2 apresentou uma distribuição mais uniforme sobre toda a camada de óxido. As eletrólises foram realizadas aplicando um programa de pulsos de potenciais. Os resultados mostraram que a eficiência para formação do produto mais oxidado (CO2) está intimamente ligada à quantidade e distribuição da platina adicionada na superfície do ADE. Os eletrodos mais eficientes foram os de composições nominais: Ti/ADE modificado com eletrodeposição de Pt (100 ?g cm-2) e Ti/ADE modificado com deposição química do catalisador nanodividido de Pt-Ni (1:1) (60 ?g cm-2). Estes resultados foram confirmados pelos experimentos utilizando DEMS. O eletrodo Ti/ADE modificado com eletrodeposição de PbO2 (100 ?g cm-2) apresentou uma melhora na eficiência eletrocatalítica em relação ao ADE, porém inferior aos eletrodos modificados com platina. O desempenho do ADE na oxidação das pequenas moléculas orgânicas foi estudado em comparação com um eletrodo de platina eletrodepositada diretamente na placa de titânio. Os resultados de eletrólise mostraram que o ADE não funciona somente como um substrato inerte e sim auxilia na reação de oxidação, desempenhando um importante papel na eficiência catalítica total destes materiais. / This work presents the preparation and characterization of dimensionally stable anodes (DSA) of nominal composition Ti/Ru0.3Ti0.7O2, modified by the addition of metals to their surface. The introduction of the modulator metal allowed us to change the coating of the electrochemical behavior in a significant way. The DSAâ surface was modified by electrodeposition of Pt and PbO2, and chemical deposition of highly nanodispersive supported catalysts (Pt and Pt-Ni). The objective of this preparation was to modulate the anode properties in order to enhance the electrocatalytic properties and mechanical resistance of these materials. This new class of materials was applied in the electrooxidadtion of formaldehyde, acetaldehyde and oxalic acid. The electrode characterization was carried out by Scanning Electron Microscopy (SEM), Energy-dispersive X-ray Spectroscopy (EDS), cyclic voltammetry (CV), long-term electrolysis followed by high performance liquid chromatography (HPLC) and the differential electrochemical mass spectrometry (DEMS) which was performed at the University of Poitiers, France. The micrographs and EDS analyses showed that the ruthenium is concentrated in small ?islands? in the oxide layer, and the modification with platinum, either electrodeposited or chemically deposited, occurs preferable over the ruthenium-rich regions. The PbO2 electrodeposit was more uniformly distributed along the oxide layer. Bulk electrolysis experiments were carried out applying a potentiostatic program. The efficiency toward the formation of the more oxidized compound (CO2) is related with the amount and distribution of the platinum deposited on the DSAâ surface. The most efficient materials were: Ti/ADE modified with electrodeposited Pt (100 ?g cm-2) and Ti/ADE modified with chemically deposited Pt-Ni (1:1) (60 ?g cm-2). Through the DEMS experiments these results were confirmed. The DSAâ modified with PbO2 (100 ?g cm-2) was more efficient than the bare DSAâ. However, the amount of CO2 obtained with the former electrode is still lower than that obtained with the platinum-modified ones. The role of DSAâ on the direct activation of the oxidation of small organic molecules was studied applying an electrode containing the platinum directly electrodeposited over the titanium. The bulk electrolysis results showed that DSAâ is not just an inert substrate since it does play an important role in the overall efficiency of these materials.

Embora o uso de etanol como combustível venha aumentando no Brasil e em diversos países, há uma grande escassez de dados relacionados à abundância desse álcool e de espécies orgânicas correlatas na atmosfera. O estudo temporal do comportamento do etanol em água de chuva no Brasil é pioneiro, e serve de base para melhor compreender as alterações que possam ocorrer na atmosfera devido ao aumento do uso desse combustível. Neste trabalho foi desenvolvido um novo método utilizando headspace GC-FID para a determinação simultânea de acetaldeído (AA), acetona (AC), metanol (MeOH) e etanol (EtOH), em concentrações ambientalmente relevantes em águas naturais. O método é mais simples do que aqueles apresentados na literatura, robusto e de custo relativamente baixo. O método apresentou boa recuperação, precisão, e sua exatidão foi comprovada pela forte correlação com o método que utiliza HPLC, e que já é bem estabelecido. A concentração de etanol foi determinada em amostras de água de chuva de Ribeirão Preto coletadas de 2012 a 2016 (n = 186). A média ponderada pelo volume (MPV) foi de 5,28 ± 0,49 µmol L-1, que é próxima da concentração esperada no equilíbrio entre a fase gasosa e aquosa. Esse valor de etanol é cerca de 28 vezes maior do que a média encontrada na cidade de Wilmington (EUA), refletindo o elevado uso de etanol combustível no Brasil. As concentrações médias anuais de etanol na chuva nos mais de 4 anos de estudo variaram pouco, e também não apresentaram diferenças significativas de acordo com a estação do ano, sazonalidade das atividades agrícolas, ou com a direção das massas de ar. Para as amostras de água de chuva coletadas de fevereiro a dezembro de 2016 a concentração MPV das espécies analisadas foram: 0,84 ± 0,12 µmol L-1 AA (n= 62); 0,70 ± 0,08 µmol L-1 AC (n = 59);10,9 ± 1,19 µmol L-1 MeOH (n = 62), 15,8 ± 1,64 µmol L-1 ácido fórmico (n = 67); e 9,76 ± 0,95 µmol L-1 ácido acético (n = 67). A massa média de carbono orgânico identificado nas amostras representou cerca de 20% do total de carbono orgânico dissolvido (COD) na água de chuva. O fluxo estimado de carbono orgânico por deposição úmida foi de 5,1 g C m-2 ano-1, sendo 1,0 g C m-2 ano-1identificados neste trabalho. Além da emissão veicular, uma importante fonte de COD para a atmosfera é a queima de biomassa, que ainda ocorre com frequência no estado. As ferramentas estatísticas aqui utilizadas considerando as espécies orgânicas identificadas juntamente com outras espécies inorgânicas majoritárias, não permitiram separar claramente as fontes predominantes de emissão na região. Isso deve ocorrer porque a emissão veicular durante todo o ano é predominante com relação às possíveis emissões biogênicas e por queima de biomassa. A exposição de amostras de água de chuva à irradiação com luz solar artificial mostrou que houve perda de EtOH e formação de AA, porém os processos não ocorreram em proporção estequiométrica, e nem na mesma taxa. No caso do MeOH e formaldeído, a formação e perda dessas espécies ocorreram de forma errática. A ausência de uma tendência clara nas transformações fotoquímicas dos álcoois reflete a complexidade da matriz e das reações envolvidas na atmosfera. / Although there has been a dramatic increase on the use of ethanol fuel in Brazil and in several other countries, there is a great lack of data related to the abundance of ethanol and associated organic species in the atmosphere. The temporal study of the behavior of ethanol in rainwater in Brazil is pioneer, and may serve as a basis to better understand the changes that occur in the atmosphere due to the increasing use of this fuel. This work presents a new headspace GC-FID method to simultaneously determine acetaldehyde (AA), acetone (AC), methanol (MeOH) and ethanol (EtOH) at environmentally relevant concentrations in the atmosphere and in a variety of natural waters. The method is simpler than those presented in the literature, robust and relatively low-cost. The method presented good recovery, precision and good agreement with a HPLC method for determination of acetaldehyde, methanol, and ethanol, which endorsed the accuracy of the proposed method. The ethanol concentration was determined in rainwater samples from Ribeirão Preto from 2012 to 2016 (n = 186). The volume-weighted mean (VWM) was 5.28 ± 0.49 mol L-1, which is close to the expected concentration at the equilibrium between the gas and aqueous phases. The ethanol value is about 28 times higher than the average found in the city of Wilmington (USA), reflecting the high use of ethanol fuel in Brazil. The annual mean concentrations of ethanol in rainwater samples over 4 years of monitoring varied little, and also did not show significant differences according to the season, agricultural activities, or the direction of the air masses. For the rainwater samples collected from February to December 2016 the VWM concentration of the other analyzed species were: 0.84 ± 0.12 mol L-1 AA (n = 62); 0.70 ± 0.08 mol L-1 AC (n = 59), 10.9 ± 1.19 mol L-1MeOH (n = 62), 15.8 ± 1.64 mol L-1formic acid (n = 67); and 9.76 ± 0.95 mol L-1 acetic acid (n = 67). The identified organic carbon average mass in the samples represented about 20% of the total dissolved organic carbon (DOC) in rainwater. The estimated flux of organic carbon by wet deposition was 5.1 g C m-2 year-1, being 1.0 g C m-2 year-1 identified in this work. In addition to the vehicular emission, an important source of DOC to the atmosphere is the biomass burning, which still occurs frequently in the state. The statistical tools used here, considering the organic species identified together with other major inorganic species, did not allow to clearly separate the predominant emission sources in the region. This may occur because the year-round vehicular emission is predominant in relation to the possible biogenic and by biomass burning emissions. Exposure of rainwater samples to irradiation with artificial sunlight showed that there was loss of EtOH and formation of AA, but the processes neither occurred in stoichiometric proportion, nor at the same rate. In the case of MeOH and formaldehyde, the formation and loss of these species occurred erratically. The absence of a clear trend in the photochemical transformations of alcohols reflects the complexity of the matrix and the reactions involved in the atmosphere.

Devido ao efeito estufa, a produção de hidrogênio a partir da reação de reforma do bioetanol tem se tornado um assunto de grande interesse em catálise heterogênea. Os catalisadores à base de Pt são empregados nos processos de purificação de H2 e também em eletrocatalisadores das células a combustível do tipo membrana polimérica (PEMFC). O hidrogênio obtido a partir da reforma do etanol contém como contaminante o acetaldeído e pequenas quantidades de CO. Assim, pode-se prever que muitas reações podem ocorrer na presença de catalisadores de Pt durante o processo de purificação do H2 e mesmo no próprio eletrocatalisador. Desta forma, este trabalho tem como objetivo descrever o comportamento do acetaldeído na presença de catalisadores de Pt. Para tanto foram preparados dois catalisadores, Pt/SiO2 e Pt/USY, contendo 1,5% de metal em ambos. Também foi estudado um eletrocatalisador (comercial) de Pt suportado em carvão (Pt/C). Os catalisadores foram caracterizados através das técnicas de análise textural, difração de raios X (DRX), quimissorção de H2, reação de desidrogenação do ciclohexano, espectroscopia no infravermelho de piridina adsorvida, dessorção a temperatura programada de n-butilamina (TPD de n-butilamina), dessorção a temperatura programada de CO2 (TPD-CO2), análise termogravimétrica, microscopia eletrônica de varredura (MEV) e espectroscopia de dispersão de energia (EDS). Os testes catalíticos foram realizados entre as temperaturas de 50 e 350 C em corrente contendo acetaldeído, H2 e N2. Foi observado que as propriedades ácido-básicas dos suportes promovem as reações de condensação com formação de éter etílico e acetato de etila. O acetaldeído em catalisadores de Pt sofre quebra das ligações C-C e C=O. A primeira ocorre em uma ampla faixa de temperaturas, enquanto a segunda apenas em temperaturas abaixo de 200 C. A quebra da ligação C-C produz metano e CO. Já a quebra da ligação C=O gera carbono residual nos catalisadores, assim como espécies oxigênio, que por sua vez são capazes de eliminar o CO da superfície dos catalisadores. Nota-se que o tipo de suporte utilizado influencia na distribuição de produtos, principalmente a baixas temperaturas. Além disso, constatou-se que a descarbonilação não é uma reação sensível à estrutura do catalisador. Verificou-se também a presença de resíduos sobre os catalisadores, possivelmente oriundos não somente da quebra da ligação C=O, mas também de reações de polimerização / Due to the greenhouse effect, hydrogen production from bioethanol reforming is a very important subject in heterogeneous catalysis research. Pt based catalysts are employed in H2 purification processes and also as electrocatalysts of PEM (Proton Exchange Membrane) fuel cells. Hydrogen obtained from ethanol reforming may contain acetaldehyde and small amounts of CO as contaminants. This very reactive aldehyde can interact with Pt based catalysts during purification process, and also with the electrocatalyst. Therefore, this work aims to study the acetaldehyde behavior in the presence of platinum based catalysts under hydrogen atmosphere. Two catalysts named Pt/SiO2 and Pt/USY were prepared, containing 1,5% of Pt. A commercial Pt eletrocatayst supported on carbon (Pt/C) was also studied. The catalysts were characterized by textural analysis, XRD, H2 chemisorption, cyclohexane dehydrogenation reaction, pyridine IR, n-butylamine TPD, CO2 TPD, TGA/DTG, SEM and EDS. The catalytic tests were carried out in a fixed bed reactor at temperature range of 50-350 C, under acetaldehyde, H2 and N2 flow. It was observed that the acid-basic supports properties promoted condensation reactions with the formation of ethylic ether and ethyl acetate. Once in contact with Pt based catalysts, acetaldehyde undergoes C-C and C=O bond scissions. The former occurs at a wide temperature range, whereas the latter occurs only at low temperatures (< 200 C). The C-C bond scission (decarbonylation) produces methane and CO. The C=O bond scission generates carbon residues on the catalyst, as well as oxygen species, which in turn eliminate CO from the catalytic surface. It was noticed that the type of support influences products distribution, mainly at low temperatures. The data also show that decarbonylation is not a structure-sensitive reaction. Residues were observed on Pt/USY which were generated not only from C=O bond rupture, but also from acetaldehyde polymerization

Yoghurt is a fermented milk product which is produced by Streptococcus thermophilus and Lactobacillus delbrueckii spp. bulgaricus. The production of yoghurt has started in Middle East and spread all over the world. The aim of this study is to select the culture combination which is appropriate to Turkish taste and have the best yoghurt characteristics by means of post-acidification and whey separation properties, texture of gel formation, exopolysaccharide and acetaldehyde content / and to observe the effect of freeze-drying of cultures on these yoghurt properties. At the first part of this study, six L.delbrueckii spp. bulgaricus isolates and six S.thermophilus isolates were used with different combinations to produce 36 yoghurt samples. These isolates were selected among a strain collection which contains 111 L.delbrueckii spp. bulgaricus and 56 S.thermophilus isolates which were isolated from traditional Turkish yoghurt according to their acidification activity and acetaldehyde production properties. In addition, two commercial S.thermophilus isolates and one commercial L.delbrueckii spp. bulgaricus isolate were used to produce two commercial yoghurt samples. 38 yoghurt samples were examined in terms of pH and total titratable acidity changes during 21-day storage, syneresis and hardness. According to these three analyses, six yoghurt samples were chosen, which give the best results, for the determination of exopolysaccharide and acetaldehyde content. In addition, two yoghurt samples produced by commercial cultures and one sample, which gives average results in experiments, were also examined for these compounds to provide a good comparison. In the second part of the study the amount of exopolysaccharide and acetaldehyde of nine yoghurt samples were determined. In addition, sensory analysis was conducted to see consumer perception. According to the results, one culture combination was obtained as the best combination which produces the appropriate yoghurt to Turkish taste with the closest chemical analysis results to the commercial samples. In the last part, freeze drying process was examined if this has a significant effect on the selected LAB combination as well as yoghurt produced by using this.