The only treatment for coeliac disease, a common autoimmune disorder, is life-long adherence to a gluten-free diet. However, the replacement of wheat gluten, a key structural and functional component in bread, poses a major technological challenge for food scientists. The use of non-wheat cereal proteins, as alternatives to gluten, shows much promise in gluten-free bread making. Literature has shown that when zein, the maize prolamin protein, is subjected to wet heat above its glass transition temperature (Tg), the protein becomes viscoelastic, rubbery and dough-like. Gluten-like fibrils are visible, which form complex protein networks similar to those found in wheat dough. The resulting zein dough has viscoelastic characteristics and can be successfully used with hydrocolloids to produce gluten-free bread. This project examined the influence of wet heat treatment and dilute organic acids (lactic acid and acetic acid) on the dough-making quality of non-wheat cereal proteins, such as kafirin and zein. Zein was the only non-wheat cereal protein to show any physical change when it was subjected to wet heat treatments, forming a dough-like substance. Acidification of the zein dough prepared at 40°C with concentrations of 0.7, 1.3 and 5.4% (v/v) organic acid in distilled water solutions, showed that the higher the concentration of acid used, the greater its effect on the dough's rheological properties. Tensile tests using a Keifer rig on zein dough showed that as the concentration of organic acid was increased from 0.7 to 1.3 and to 5.4% (v/v) the dough become softer and increasingly more extensible. The dough also exhibited less resistance to extension and reduced elasticity. CLSM revealed that the zein doughs contained a protein network, made up of fine protein fibrils, which became smoother and more homogenous as the concentration of acid was increased. Although SDS-PAGE revealed that no oligomerization took place with acid addition, iv FTIR showed that zein dough prepared with distilled water at 40°C had elevated levels of β-sheets. When organic acids were added in increasing levels, corresponding increases in the quantities of α-helices in the protein were observed. Alveography showed that zein-based doughs prepared with dilute organic acids retained gases well and that the concentration of dilute organic acids influenced dough distensibility (biaxial extensibility) and stability (the ability of the dough to retain gas). Low concentration of acids (0.7 and 1.3%) increased dough stability to levels similar to that of strong wheat flour, 103 mm H2O, but higher concentrations of acids (5.4%) led to a marked reduction in dough stability. Thus, by increasing zein dough functionality to such an extent, the apparent usefulness of the doughs and their ability to retain gases produced during fermentation is reduced. Simple distensibility tests on zein doughs showed that added organic acids promoted ‘clumping’ of the fine protein fibrils in the dough network into pronounced fibres. This would account for the decreased dough stability when high levels (5.4%) of organic acids were used. Baking trials with zein doughs were not successful as adequate leavening was impossible without an acid-tolerant leavening agent. It is believed that dilute organic acids influence the rheological properties of zein dough by creating a positively charged environment, in which the protein is partially solubilized. The higher the level of organic acid used, the greater the positive net charge and the more pronounced the effect on the protein network structure. Organic acids could also improve fluidity of the zein dough by acting as plasticizers. From this work it can be seen that although a protein network is present in all zein-based doughs, the ability of this network to retain gases is dependant on the level of organic acids present. The functional properties of zein-doughs made with low levels of organic acids (0.7 and 1.3%) shows potential in the production of gluten-free bread for individuals suffering from coeliac disease. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Food Science / unrestricted

No description available.

O conhecimento de propriedades termofísicas é importante na modelagem, na otimização e no projeto de equipamentos para processos como a fabricação de massa de pão congelada. Neste trabalho, as propriedades termofísicas condutividade térmica, difusividade térmica e calor específico foram determinadas experimentalmente ao longo do processo de congelamento da massa de pão, pois influenciam diretamente a cinética do processo que, por sua vez, determina a qualidade do pão produzido. Os resultados obtidos mostraram que algumas destas propriedades variaram em função do conteúdo inicial de água e principalmente devido à mudança da temperatura. O valor médio encontrado através da atividade de água das massas (aw = 0,950), para temperatura inicial de congelamento, pode explicar alguns desvios no ajuste dos dados experimentais a modelos disponíveis na literatura baseados na lei de Raoult, que são estritamente relacionados à fração de gelo formada. O uso combinado de goma guar e xantana reduziu a entalpia de fusão ao longo do tempo de armazenamento congelado (87,4 J.g-1 e 81,2 J.g-1 para a formulação sem gomas, não congelada e após 28 dias de armazenamento congelado; 84,4 J.g-1 e 76,9 J.g-1 para a formulação com 0,25% de goma guar e 0,25% de goma xantana na massa não congelada e após 28 dias de armazenamento congelado), indicando uma interação entre as gomas na capacidade de ligar água ao longo do tempo de congelamento. Porém, apesar do tempo de congelamento ter reduzido a entalpia de fusão, o processo de congelamento foi o principal fator na queda da taxa de fermentação e da produção de gás pelas leveduras independentemente do tempo de armazenamento congelado. / The knowledge of thermophysical properties is important to model and optimize equipment design for frozen food processes. In this work, the thermophysical bread dough properties, such as, thermal conductivity, thermal diffusivity and specific heat were experimentally determined during freezing process, due to their influence on the kinetics process, and therefore on bread quality. The results showed that some properties varied according to the initial water content and mainly due to temperature changes. The average value of initial freezing temperature found by water activity (aw = 0.950) explains the deviations between experimental data and available models in the literature based on Raoults law, which is related to the ice mass fraction. The combined use of guar and xanthan gums reduced the fusion enthalpy along frozen storage time (87.4 J.g-1 and 81.2 J.g-1 for formulation without gum, non-frozen and after 28 frozen storage days; 84.4 J.g-1 and 76.9 J.g-1 for formulation with 0.25 % of guar gum and 0.25 % of xanthan gum in non-frozen and after 28 frozen storage days). It indicated the interaction between gums and their ability to hold water along frozen storage. Despite frozen storage reduced the fusion enthalpy, the freezing process itself was the main factor in the decrease in proofing rate and gas production by yeast cells.

A qualidade global da massa de pão congelada por um longo período é um desafio para indústria de panificação. O uso de diferentes técnicas pode ajudar a explicar os danos sofridos à massa de pão durante o congelamento e armazenamento congelado. A presença de água na forma de cristais de gelo foi vista como a principal causa de defeitos à estrutura da massa. Gomas guar e xantana foram incorporadas às massas para contornar os danos causados pelo congelamento. Das análises térmicas conduzidas em calorímetro de varredura diferencial foi possível quantificar a quantidade de gelo presente na massa. A adição de (0,125 a 0,250) g/100g de goma guar e de (0,214 e 0,250) g/100g de goma xantana diminuíram os valores de entalpia na massa ao longo do armazenamento congelado. A fração de gelo foi menor e mais estável nas massas contendo (0,125 e 0,250) g/100g de goma guar ou xantana. O valor da atividade de água diminuiu nas massas contendo goma guar e com níveis mais altos de goma xantana, após o ciclo de congelamento e descongelamento e 170 dias de armazenamento. Alterações na estrutura das massas foram medidas e visualizadas pela análise de textura e por microscopia eletrônica de varredura (MEV). Adição de goma xantana e principalmente de goma guar às massas aumentaram a resistência à extensão após 170 dias de armazenamento congelado. A extensibilidade não foi influenciada pela adição de gomas e manteve estabilidade nos períodos de armazenamento estudados. A MEV ajudou a explicar os danos causados à rede de glúten pelos cristais de gelo ao longo do armazenamento congelado. A massa sem gomas apareceu com pequenos danos na rede de glúten com 21 dias de armazenamento e estes danos aumentaram progressivamente por até 170 dias, mostrando um glúten menos contínuo, mais rompido e separado dos grânulos de amido. As massas contendo gomas minimizaram, mas não evitaram os danos causados ao longo do armazenamento congelado. / The global quality of the frozen bread dough for long periods of frozen storage is the challenge to bakery industry. The use of different techniques could help to explain the damages caused in the frozen dough during the freezing and along frozen storage time. The presence of water as ice crystals was the main cause of damage on the dough structure. In order to minimize the freezing damages, guar and xanthan gums were incorporated in the dough. From thermal analysis by DSC technique, the amount of ice present in the dough was determined. The addition of (0.125 to 0.250) g/100g guar gum and (0.214 and 0.250) g/100g xanthan gum presented lower values of fusion enthalpy. The addition of (0.125 and 0.250) g/100g of guar gum decreased or stabilized the frozen water content, suggesting minimal damage on the dough structure along frozen storage time. The water activity in the dough samples with guar gum and higher quantities of xanthan gum decreased after the freezing-thawed cycle and after a period of frozen storage of 170 days. The incorporation of xanthan gum and mainly the incorporation of guar gum increased the maximum resistance of the dough after 170 days. The extensibility was not affected by addition of gums along frozen storage time. The MEV technical helped to explain the damaged dough structure caused by ice crystals along frozen storage time. Dough samples without gums presented structure damage only after 21 days and increased after 170 days, resulting in less continuous gluten, more disrupted and separated from starch granules. The doughs with gums suffered less damage in the gluten matrix, but did not avoid the problems caused by frozen storage.

The most common cause for revision total hip replacement surgey is aseptic loosening of the acetabular component. This thesis explores the effect of three techniques to improve the depth and quality of cemented acetabular component fixation in primary total hip replacement. This may have beneficial effects on the longevity of cemented acetabular components and reduce the rate of revision surgery for aseptic loosening. Aims: 1. Determine the effect of the rim cutter on cement pressure during cup insertion. 2. Examine the effect of the rim cutter on cement penetration distance. 3. Evaluate the effect of bone grafting of the acetabular notch. 4. Determine the effect of iliac suction during cement pressurisation. 5. Compare the behaviour of bone cement with Play Dough. Materials and Methods: 1. Sawbones hemi pelvis models were fitted with pressure transducers at the rim and apex of the acetabulum. Peak pressure was measured upon insertion of cups with different flange sizes and when the acetabulum was prepared with the rim cutter. 2. Foam cavities were used to measure the depth of cement penetration when the same cups and rim cutter were used. 3. Hemi pelvis models were modified to simulate bone grafting of the acetabular notch. Again, pressure sensors were mounted at the apex and rim of the acetabulum. Intra-acetabular cement pressure was compared with native acetabulae. 4. A back bleeding model of the acetabulum was fitted with a suction catheter. The effect on cement penetration into cancellous bone was measured compared with no suction. 5. Play Dough pressurisation and penetration into hemi pelvises and foam was compared to bone cement. Results: 1. Significant increase in peak apex and rim pressures when flanged cup inserted into an acetabulum prepared with the rim cutter compared with both flanged and unflanged cups alone. 2. Significant increase in cement penetration at the rim of the acetabulum when rim cutter used and flanged cup inserted when compared with flanged and unflanged cups alone. 3. Significant increase in intra-acetabular pressure when cement pressurised in presence of simulated acetabular notch bone grafting compared with normal acetabulae. 4. Significant increase in cement penetration distance when suction used compared with no suction. 5. Significant differences in the flow characteristics between bone cement and Play Dough. Conclusion: The authors recommend preparation of the acetabular rim with the rim cutter and bone grafting of the acetabular notch to improve the depth and uniformity of the cement mantle in cemented primary THA. Play Dough at room temperature is not a suitable substitute for bone cement in in-vitro cementing studies.

A qualidade global da massa de pão congelada por um longo período é um desafio para indústria de panificação. O uso de diferentes técnicas pode ajudar a explicar os danos sofridos à massa de pão durante o congelamento e armazenamento congelado. A presença de água na forma de cristais de gelo foi vista como a principal causa de defeitos à estrutura da massa. Gomas guar e xantana foram incorporadas às massas para contornar os danos causados pelo congelamento. Das análises térmicas conduzidas em calorímetro de varredura diferencial foi possível quantificar a quantidade de gelo presente na massa. A adição de (0,125 a 0,250) g/100g de goma guar e de (0,214 e 0,250) g/100g de goma xantana diminuíram os valores de entalpia na massa ao longo do armazenamento congelado. A fração de gelo foi menor e mais estável nas massas contendo (0,125 e 0,250) g/100g de goma guar ou xantana. O valor da atividade de água diminuiu nas massas contendo goma guar e com níveis mais altos de goma xantana, após o ciclo de congelamento e descongelamento e 170 dias de armazenamento. Alterações na estrutura das massas foram medidas e visualizadas pela análise de textura e por microscopia eletrônica de varredura (MEV). Adição de goma xantana e principalmente de goma guar às massas aumentaram a resistência à extensão após 170 dias de armazenamento congelado. A extensibilidade não foi influenciada pela adição de gomas e manteve estabilidade nos períodos de armazenamento estudados. A MEV ajudou a explicar os danos causados à rede de glúten pelos cristais de gelo ao longo do armazenamento congelado. A massa sem gomas apareceu com pequenos danos na rede de glúten com 21 dias de armazenamento e estes danos aumentaram progressivamente por até 170 dias, mostrando um glúten menos contínuo, mais rompido e separado dos grânulos de amido. As massas contendo gomas minimizaram, mas não evitaram os danos causados ao longo do armazenamento congelado. / The global quality of the frozen bread dough for long periods of frozen storage is the challenge to bakery industry. The use of different techniques could help to explain the damages caused in the frozen dough during the freezing and along frozen storage time. The presence of water as ice crystals was the main cause of damage on the dough structure. In order to minimize the freezing damages, guar and xanthan gums were incorporated in the dough. From thermal analysis by DSC technique, the amount of ice present in the dough was determined. The addition of (0.125 to 0.250) g/100g guar gum and (0.214 and 0.250) g/100g xanthan gum presented lower values of fusion enthalpy. The addition of (0.125 and 0.250) g/100g of guar gum decreased or stabilized the frozen water content, suggesting minimal damage on the dough structure along frozen storage time. The water activity in the dough samples with guar gum and higher quantities of xanthan gum decreased after the freezing-thawed cycle and after a period of frozen storage of 170 days. The incorporation of xanthan gum and mainly the incorporation of guar gum increased the maximum resistance of the dough after 170 days. The extensibility was not affected by addition of gums along frozen storage time. The MEV technical helped to explain the damaged dough structure caused by ice crystals along frozen storage time. Dough samples without gums presented structure damage only after 21 days and increased after 170 days, resulting in less continuous gluten, more disrupted and separated from starch granules. The doughs with gums suffered less damage in the gluten matrix, but did not avoid the problems caused by frozen storage.

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No. of bitstreams: 1 Dissertação - Luciana Pereira Cardoso Fares.pdf: 1569580 bytes, checksum: 10253bca7a72e98fc553c010eee86d63 (MD5) Previous issue date: 2010-07-22 / OUTRAS / In the Amazon there are numerous plant species with potential economic, technological and nutrition, among which stands out cubiu (Solanum sessiliflorum Dunal) a herbaceous plant, present in the Brazilian Amazon, and Peruvian Colombiana23. It is an exotic fruit, and has nice flavor, used in food with multiple possibilities of exploitation of the fruit as in the form of juice, nectars, jams, candies and other guloseimas19; 22. Sweet paste or mass is the product of the proper processing of edible parts of vegetables with crumbled sugar, with or 24 without addition of water, pectin, pH adjuster and other ingredients and additives permitidos5. The work aimed at the preparation, characterization and sensory evaluation of fresh mass cubiu (Cubil) using the pulp cubiu, bringing the consumer a product with organoleptic and nutritional qualities through the application of food technology. The physico-chemical and chemical candy, such as pH, titratable acidity, soluble solids in °Brix, reducing sugar glucose, total sugars and non reducing sugars in sucrose, were performed using methods described by IAL11, since the pectin was determined According PEARSON16. The chemical composition, moisture, protein, lipid, ash, total carbohydrate and total energy were determined according AOAC1. The crude fiber content was determined by the method Weende, according to manufacturer's recommendation. Microbiological analysis was based on legislation específica4;6. Was also performed to evaluate the shelf life of fresh mass cubiu was performed during a period of 90 days, ie immediately after preparation, at time zero, 30, 45, 60 and 90 days after preparation. All analysis proposed in this paper were performed in triplicate and the results were averaged and standard deviation, being held estatístico treatment3. For sensory evaluation was carried out in a first step the affective preference test by testing preferência10-ordination, and later the acceptance test by a 5-point hedonic scale (with scores ranging from 1: I really liked until 5: dislike very much ), numerical, verbal and bipolar, to candy, to determine how much he liked it or not the sample oferecida23, besides the emotional scale test of intent to purchase the product, structured verbal, and five bipolar pontos11vvv. Cubil The product is a viable technology, providing consumers with a sweet and exotic taste great and can be stored at room temperature (up to 28 ° C) for up to 90 days, and maintaining its quality from the point of view of microbiological and physico-chemical without losing their original organoleptic characteristics (flavor, color and texture). Samples of fresh mass Cubiu was well accepted by the judges, and the fourth formulation (F4) the more accepted (34.17%), which was evaluated in the parameter enjoyed by over 50% of the panelists on the characteristics flavor color, texture, and 50% indicated that they certainly would buy the product and could be a good investment on their marketing. / Na Amazônia existem inúmeras espécies vegetais com potencial econômico, tecnológico e nutricional, dentre os quais se destaca o cubiu (Solanum sessiliflorum Dunal) uma planta herbácea, presente na Amazônia Brasileira, Peruana e Colombiana22. É um fruto exótico, possui sabor característico e agradável, utilizado na alimentação com possibilidades múltiplas de aproveitamento do fruto como na forma de suco, néctares, compotas, doces e outras guloseimas18; 21. Doce em pasta ou massa é o produto resultante do processamento adequado das partes comestíveis desintegradas de vegetais com açúcares, com ou sem adição de água, pectina, ajustador do pH e outros ingredientes e aditivos permitidos5. O trabalho teve como objetivo a elaboração, caracterização e avaliação sensorial do doce em massa de cubiu (Cubilada), utilizando a polpa de cubiu, trazendo ao consumidor um produto com qualidades organolépticas e nutricionais, mediante a aplicação da tecnologia de alimentos. As análises físico-quimicas e químicas do doce, como pH, Acidez titulável, sólidos solúveis em °Brix, Açucares Redutores em glicose, Açucares Totais e açucares não Redutores em Sacarose, foram realizadas segundo metodologia descrita pelo IAL11, já a Pectina foi determinada de acordo com PEARSON16. A composição centesimal, umidade, proteínas, lipídios totais, cinzas, carboidratos totais e valor energético total foram determinados segundo AOAC1. A teor de fibra total foi determinado, mediante o método Weende, segundo recomendação do fabricante. A análise microbiológica foi baseada em legislação específica4; 6. Foi realizado também a avaliação da vida de prateleira do doce em massa de cubiu durante um período de 90 dias, ou seja, logo após a elaboração, no tempo zero, 30, 45, 60 e 90 dias depois da preparação. Todas as análises propostas neste trabalho foram executadas em triplicata, e para os resultados encontrados foram calculadas a média e o desvio padrão, sendo realizado tratamento estatístico3. Para avaliação sensorial realizou-se numa primeira etapa o teste afetivo de preferência através do teste de ordenação-preferência23, e posteriormente o teste de aceitação através de escala hedônica de 5 pontos, (com escores variando de 1: gostei muito até 5: desgostei muito), numérica, verbal e bipolar, para os doces, a fim de determinar o quanto gostou ou não da amostra oferecida23, além do teste afetivo de escala de intenção de compra do produto, estruturada verbal, bipolar e de cinco pontos11. A Cubilada é um produto viável tecnologicamente, fornecendo aos consumidores um doce com sabor exótico e excelente, podendo ser armazenado em temperatura ambiente (até 28°C) por até 90 dias, mantendo sua qualidade sob o ponto de vista microbiológico e fisíco-químico, sem a perda de suas características organolépticas originais (sabor, cor e textura). As amostras de doce em massa de Cubiu foi bem aceita pelos provadores, sendo a formulação 4 (F4) a mais bem aceita (34,17%), na qual foi avaliada no parâmetro gostou muito por mais de 50% dos provadores nas características sabor, cor, textura e aparência, e 50% indicaram que certamente comprariam o produto, indicando ser um bom investimento a sua comercialização.

O conhecimento de propriedades termofísicas é importante na modelagem, na otimização e no projeto de equipamentos para processos como a fabricação de massa de pão congelada. Neste trabalho, as propriedades termofísicas condutividade térmica, difusividade térmica e calor específico foram determinadas experimentalmente ao longo do processo de congelamento da massa de pão, pois influenciam diretamente a cinética do processo que, por sua vez, determina a qualidade do pão produzido. Os resultados obtidos mostraram que algumas destas propriedades variaram em função do conteúdo inicial de água e principalmente devido à mudança da temperatura. O valor médio encontrado através da atividade de água das massas (aw = 0,950), para temperatura inicial de congelamento, pode explicar alguns desvios no ajuste dos dados experimentais a modelos disponíveis na literatura baseados na lei de Raoult, que são estritamente relacionados à fração de gelo formada. O uso combinado de goma guar e xantana reduziu a entalpia de fusão ao longo do tempo de armazenamento congelado (87,4 J.g-1 e 81,2 J.g-1 para a formulação sem gomas, não congelada e após 28 dias de armazenamento congelado; 84,4 J.g-1 e 76,9 J.g-1 para a formulação com 0,25% de goma guar e 0,25% de goma xantana na massa não congelada e após 28 dias de armazenamento congelado), indicando uma interação entre as gomas na capacidade de ligar água ao longo do tempo de congelamento. Porém, apesar do tempo de congelamento ter reduzido a entalpia de fusão, o processo de congelamento foi o principal fator na queda da taxa de fermentação e da produção de gás pelas leveduras independentemente do tempo de armazenamento congelado. / The knowledge of thermophysical properties is important to model and optimize equipment design for frozen food processes. In this work, the thermophysical bread dough properties, such as, thermal conductivity, thermal diffusivity and specific heat were experimentally determined during freezing process, due to their influence on the kinetics process, and therefore on bread quality. The results showed that some properties varied according to the initial water content and mainly due to temperature changes. The average value of initial freezing temperature found by water activity (aw = 0.950) explains the deviations between experimental data and available models in the literature based on Raoults law, which is related to the ice mass fraction. The combined use of guar and xanthan gums reduced the fusion enthalpy along frozen storage time (87.4 J.g-1 and 81.2 J.g-1 for formulation without gum, non-frozen and after 28 frozen storage days; 84.4 J.g-1 and 76.9 J.g-1 for formulation with 0.25 % of guar gum and 0.25 % of xanthan gum in non-frozen and after 28 frozen storage days). It indicated the interaction between gums and their ability to hold water along frozen storage. Despite frozen storage reduced the fusion enthalpy, the freezing process itself was the main factor in the decrease in proofing rate and gas production by yeast cells.

<p>Савремено пекарство у нашој земљи, још увек, у највећој мери подразумева производњу хлеба и пекарских производа<em> in situ</em>. Припрема пекарских производа у кућним условима своди се, готово искључиво, на мешење према традиционалном<br />моделу. Овакво понашање пекара и потрошача делимично је последица навика, али и изузетно лоше снабдевености нашег тржишта замрзнутим пекарским производима добијеним од квасног теста, као и сировинама намењеним за<br />производњу истих.</p><p>Циљ истраживања обухваћених докторском дисертацијом усмерен је ка дефинисању и унапређењу услова производње и финализације замрзнутих пекарских производа непосредно пред употребу, у близини корисника или од стране самог корисника. Добијени резултати требало би да дају допринос бољем разумевању феномена који се дешавају у поступкузамрзавања/одмрзавања теста. Модификација постојеће, код нас примењиване технологије, у смислу примене одабраних сојева квасца, одабраног режима замрзавања/одмрзавања и дужине чувања теста у замрзнутом стању, као и примене одабраних додатака тесту, требало би да резултује пекарским производима добијеним од замрзаваног теста чије су технолошке и сензорне карактеристике побољшане.</p><p>Испитан је сировински састав теста и квалитет употребљених сировина карактеристичан за наше поднебље са аспекта њихове примене у производњи замрзаваног теста, о чему нема публикованих резултата. Доказана је могућност употребе комерцијалног пекарског квасца и комерцијалног брашна које по садржају и квалитету глутена не одговара у потпуности литературним препорукама.</p><p>Предложене су математичке релације које омогућавају предвиђање трајања операција замрзавања и одмрзавања квасног теста у дефинисаним условима који су уобичајени у пекарској производњи, о чему нема литературних података.<br />Дефинисани су оптимални услови замрзавања и одмрзавања квасног теста који омогућавају очување активности квасца у замрзаваном тесту на прихватљивом нивоу.<br />На основу активности квасца у замрзаваном тесту са хидроколоидима, матурографских и екстензограмских показатеља квалитета као и његове микроструктуре доказан је позитиван утицај додатка хидроколоида у замрзавано тесто са аспекта његовог квалитета. Јасно изражене промене микроструктуре замрзнутог теста током његовог складиштења доприносе разумевању феномена који се дешавају у тесту услед његовог замрзавања, одмрзавања и складиштења у замрзнутом стању до 28 дана, као и интеракција између конституента теста и додатих хидроколоида.</p><p>Доказано да је за припрему замрзаваног теста могуће користити сировине чији квалитет није оптималан, али да се тиме<br />значајно скраћује период складиштења у коме не долази до неприхватљиве деградације његовог квалитета са неколико седмица колико препоручује литература, на свега 7 до 14 дана. Квалитет готовог пекарског производа добијеног од замрзаваног теста које се састоји од сировина уобичајено присутних<br />на нашем тржишту, а које је припремљено уз предложене минималне модификације традиционалног начина припреме хлеба, задовољавајући је из угла конзумента.</p> / <p>Savremeno pekarstvo u našoj zemlji, još uvek, u najvećoj meri podrazumeva proizvodnju hleba i pekarskih proizvoda<em> in situ</em>. Priprema pekarskih proizvoda u kućnim uslovima svodi se, gotovo isključivo, na mešenje prema tradicionalnom<br />modelu. Ovakvo ponašanje pekara i potrošača delimično je posledica navika, ali i izuzetno loše snabdevenosti našeg tržišta zamrznutim pekarskim proizvodima dobijenim od kvasnog testa, kao i sirovinama namenjenim za<br />proizvodnju istih.</p><p>Cilj istraživanja obuhvaćenih doktorskom disertacijom usmeren je ka definisanju i unapređenju uslova proizvodnje i finalizacije zamrznutih pekarskih proizvoda neposredno pred upotrebu, u blizini korisnika ili od strane samog korisnika. Dobijeni rezultati trebalo bi da daju doprinos boljem razumevanju fenomena koji se dešavaju u postupkuzamrzavanja/odmrzavanja testa. Modifikacija postojeće, kod nas primenjivane tehnologije, u smislu primene odabranih sojeva kvasca, odabranog režima zamrzavanja/odmrzavanja i dužine čuvanja testa u zamrznutom stanju, kao i primene odabranih dodataka testu, trebalo bi da rezultuje pekarskim proizvodima dobijenim od zamrzavanog testa čije su tehnološke i senzorne karakteristike poboljšane.</p><p>Ispitan je sirovinski sastav testa i kvalitet upotrebljenih sirovina karakterističan za naše podneblje sa aspekta njihove primene u proizvodnji zamrzavanog testa, o čemu nema publikovanih rezultata. Dokazana je mogućnost upotrebe komercijalnog pekarskog kvasca i komercijalnog brašna koje po sadržaju i kvalitetu glutena ne odgovara u potpunosti literaturnim preporukama.</p><p>Predložene su matematičke relacije koje omogućavaju predviđanje trajanja operacija zamrzavanja i odmrzavanja kvasnog testa u definisanim uslovima koji su uobičajeni u pekarskoj proizvodnji, o čemu nema literaturnih podataka.<br />Definisani su optimalni uslovi zamrzavanja i odmrzavanja kvasnog testa koji omogućavaju očuvanje aktivnosti kvasca u zamrzavanom testu na prihvatljivom nivou.<br />Na osnovu aktivnosti kvasca u zamrzavanom testu sa hidrokoloidima, maturografskih i ekstenzogramskih pokazatelja kvaliteta kao i njegove mikrostrukture dokazan je pozitivan uticaj dodatka hidrokoloida u zamrzavano testo sa aspekta njegovog kvaliteta. Jasno izražene promene mikrostrukture zamrznutog testa tokom njegovog skladištenja doprinose razumevanju fenomena koji se dešavaju u testu usled njegovog zamrzavanja, odmrzavanja i skladištenja u zamrznutom stanju do 28 dana, kao i interakcija između konstituenta testa i dodatih hidrokoloida.</p><p>Dokazano da je za pripremu zamrzavanog testa moguće koristiti sirovine čiji kvalitet nije optimalan, ali da se time<br />značajno skraćuje period skladištenja u kome ne dolazi do neprihvatljive degradacije njegovog kvaliteta sa nekoliko sedmica koliko preporučuje literatura, na svega 7 do 14 dana. Kvalitet gotovog pekarskog proizvoda dobijenog od zamrzavanog testa koje se sastoji od sirovina uobičajeno prisutnih<br />na našem tržištu, a koje je pripremljeno uz predložene minimalne modifikacije tradicionalnog načina pripreme hleba, zadovoljavajući je iz ugla konzumenta.</p> / <p>Currently the baker&#39;s industry in our country is based on the production of bread and bakery products <em>in situ</em>. ln domestic conditions the preparation of bakery products is done solely using the traditional model. This is a consequence of baker and consumer habit in our country as well as the poor market supplies of frozen bakery products from yeast dough and raw material for this production.<br />The aim of research for this dissertation is based on the definition and improvement of the production conditions as well as the flnalization of frozen bakery products prior to use. The results should contribute to the understanding of phenomena that exist in the process of freezing/thawing of dough. In order to preserve the technology commonly<br />used in our country, minor modifications were made using selected yeast types, selected regime of freezing/tharving, frozen dough storage time and additives to dough. These minor changes should result in the improvement of technological and sensor characteristics for baker products obtained from frozen dough. The raw material structure in dough and the quality of used raw material were analyzed from the aspect of the frozen dough production where there is nothing published upon this subject yet. The possibility of the use of commercial baker yeast and flour was proven even though their content and quality of gluten does not correspond to the literature recommendation.<br />Mathematical relations that enable prediction of freezing/thawing of yeast dough operation durance in defined conditions were suggested and has no published results upon this subject yet. Optimal conditions of freezing/thawing yeast dough that preserves the activity of yeast in frozen dough on an accepted level were defined.<br />On the basis of the yeast activity in frozen dough with hydrocolloids, the rheological characteristics and its microstructure, the positive affect of hydrocolloid addition to frozen dough was proven from its quality aspect. Major changes in microstructure of frozen dough during its storage contribute to the understanding of the phenomena that<br />appear in dough during freezing, thawing and storage in frozen state up to 28 days, as well as the interaction between the dough constituents and added hydrocollcids.<br />The possibility of the use of raw material for the dough preparation that has not the optimal quality but shortens the storage time was proven. During this storage time the degradation of its quality does not appear as reconlmended by literature in the period of few weeks but in the period of 7 to 14 days.<br />From the consumerrs point of view the quality of finished bakery product derived from frozen dough with available raw material and with minor modifications of the traditional method of preparation was satisfactorily.</p>

This work presents a new digital cooking process that utilizes heat from lasers to cookfood products. Unlike conventional cooking appliances, which heat an entire area by some uniform amount, lasers are unique in that they provide precision directional heating, they have a small form factor, and they are highly controllable using software. Lasers—as a cooking appliance—are of particular interest since they have a heating resolution that is on the same order of magnitude as the deposition path of a 3D food printer. While food printing is great for customized meal creation, we can print foods to millimeter resolution but we lack the ability to cook at this same resolution. Here, I primarily focus on the characterization of three different types of lasers: (1) a blue laser operating at 445 nm, (2) a near-infrared (NIR) laser operating at 980 nm, and (3) a mid-infrared (MIR) laser operating at 10.6 µm. Initial cooking apparatuses used a set of mirror galvanometers to direct visible blue light for cooking, then future iterations relied on the movement of a 3-axis gantry. Both blue and NIR lasers are diode lasers that can be mounted on a machine and the MIR laser is a standalone CO₂ gas laser. I characterize the heating behavior of the aforementioned lasers using dough, salmon, and chicken as model food systems. Different modes of cooking can be achieved by changing the wavelength of the light: infrared (IR) lasers are more well-suited for non-enzymatic browning and blue lasers are best for subsurface cooking (i.e. starch gelatinization of dough, protein denaturation of salmon and chicken). Precision “pulsed heating” with lasers also allows one to achieve food safe temperatures with greater accuracy and reduces overcooking, which leads to more moist food samples. Laser-baked dough can also achieve starch gelatinization. Food safe temperatures and browning can be achieved in dough, salmon, and chicken. Lastly, color development—as a result of laser exposure—is similar to conventionally cooked foods.