Cocoa butter is a highly complex system of triacyglycerides which has been shown to crystallize in a markedly different fashion under the application of shear. A rheometer insert was developed to enable the intact extraction of sheared samples for study of melting properties, crystal orientation and breaking stress. Samples were created by ramping from 50°C at three different cooling rates (0.5, 1 and 2°C/min) to three different end point temperatures (16, 18 and 20°C), creating nine different temperature sets. Viscosities of the cocoa butter samples under shear were recorded during sample creation and large jumps in viscosity were identified as form II and form V crystallization. Comparison of crystallization times for the nine different temperature profiles allowed for the conclusion that over a shear range of 90 – 1000 s^-1 there was no further appreciable shear acceleration of the form V transformation for the 16 and 18°C temperatures and only a slight increase up to 500 s^-1 for the 20°C temperature. Sheared samples were also examined with differential scanning calorimetry. Samples were examined for peak melting temperature on each of day 0, day 1, day 7 and day 28. Six of the nine different temperature conditions examined yielded a critical shear rate, above which the melting points of the samples were dramatically different than for low shear and no shear samples. For the day 0 and day 1 samples, above 500 s^-1 the melting temperatures were ~2°C higher than for 360 s-1 and below. For the day 7 and day 28 samples, above 500 s^-1 the peak melting temperatures were ~2°C lower than for the lower shear and no shear samples. The orientation of sheared samples was also examined using x-ray diffraction. In all of the nine temperature sets, orientation was present for shear rates of 360 s^-1 and higher. Breaking stress measurements were performed on sheared and non-sheared samples. These tests showed results remarkably similar to those seen in the DSC tests, with a critical shear rate existing in six of the nine temperature sets, above which an increase in the breaking strength occurs. Examination of samples on either side of the critical shear rate with x-ray diffraction yielded two distinct x-ray patterns leading to speculation that the application of high shear rates causes a change in the crystallization of cocoa butter leading to selective crystallization and the formation of a compositionally different form V crystal with fewer defects than its lower/no shear counterparts.

Cocoa butter is a highly complex system of triacyglycerides which has been shown to crystallize in a markedly different fashion under the application of shear. A rheometer insert was developed to enable the intact extraction of sheared samples for study of melting properties, crystal orientation and breaking stress. Samples were created by ramping from 50°C at three different cooling rates (0.5, 1 and 2°C/min) to three different end point temperatures (16, 18 and 20°C), creating nine different temperature sets. Viscosities of the cocoa butter samples under shear were recorded during sample creation and large jumps in viscosity were identified as form II and form V crystallization. Comparison of crystallization times for the nine different temperature profiles allowed for the conclusion that over a shear range of 90 – 1000 s^-1 there was no further appreciable shear acceleration of the form V transformation for the 16 and 18°C temperatures and only a slight increase up to 500 s^-1 for the 20°C temperature. Sheared samples were also examined with differential scanning calorimetry. Samples were examined for peak melting temperature on each of day 0, day 1, day 7 and day 28. Six of the nine different temperature conditions examined yielded a critical shear rate, above which the melting points of the samples were dramatically different than for low shear and no shear samples. For the day 0 and day 1 samples, above 500 s^-1 the melting temperatures were ~2°C higher than for 360 s-1 and below. For the day 7 and day 28 samples, above 500 s^-1 the peak melting temperatures were ~2°C lower than for the lower shear and no shear samples. The orientation of sheared samples was also examined using x-ray diffraction. In all of the nine temperature sets, orientation was present for shear rates of 360 s^-1 and higher. Breaking stress measurements were performed on sheared and non-sheared samples. These tests showed results remarkably similar to those seen in the DSC tests, with a critical shear rate existing in six of the nine temperature sets, above which an increase in the breaking strength occurs. Examination of samples on either side of the critical shear rate with x-ray diffraction yielded two distinct x-ray patterns leading to speculation that the application of high shear rates causes a change in the crystallization of cocoa butter leading to selective crystallization and the formation of a compositionally different form V crystal with fewer defects than its lower/no shear counterparts.

Originally presented as the author's thesis, Basel. / Lebenslauf. "Literaturverzeichnis": p. 172-174.

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Orientadores: Lireny Aparecida Guaraldo Gonçalves, Renato Grimaldi / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-27T17:41:44Z (GMT). No. of bitstreams: 1 Silva_ThaisLomonacoTeodoroda_M.pdf: 4781686 bytes, checksum: 71da04b9cf4bdf2b971bd669e6c631c5 (MD5) Previous issue date: 2015 / Resumo: A manteiga de cacau (MC) é uma gordura natural extremamente importante para formulação de chocolate, mas devido à dificuldade em seu acesso e volatilidade de seus preços outras gorduras alternativas têm sido estudadas e produzidas a fim de substituí-las, como as gorduras equivalentes (Cocoa Butter Equivalent-CBE) e as substitutas (Cocoa Butter Substitutes-CBS). Entretanto as características de cristalização e sensoriais da MC promovidas no chocolate são muito peculiares, além disto, pode ocorrer uma incompatibilidade entre as gorduras sucedâneas o que ocasionará defeitos no chocolate como o fat bloom. O objetivo desse trabalho foi estudar a cristalização da MC, CBE, CBS, bem como entre estas misturas, a fim de se obter uma fração o mais semelhante possível à MC pura para elaboração de chocolates amargos, e a partir da avaliação destes chocolates, estudar a influência dessas gorduras na formação do fat bloom. As misturas elaboradas foram baseadas no teor total de MC presente no chocolate (MC adicionada e do liquor) e as concentrações estudadas variaram de 5%, 10%, 15%, 20% e 37,5% da CBE ou CBS na MC. As matérias-primas e as misturas foram caracterizadas mediante composição em ácidos graxos, composição triacilglicerólica, isotermas de cristalização, teor de sólidos, microestrutura, comportamento térmico, polimorfismo, consistência e ponto de fusão. Para verificar o efeito da adição dessas gorduras na qualidade do chocolate e resistência ao fat bloom amostras produzidas foram armazenados sob duas condições, 100 dias por 20°C e seis ciclos de 48h com 24h a 20°C e 24h a 33°C, sendo periodicamente avaliados quanto ao, índice de brancura, tensão de ruptura, configuração visual, polimorfismo e comportamento térmico. As misturas entre CBS e MC apresentaram grandes alterações na cristalização e plasticidade à medida que se aumentou o teor de CBS, e o principal efeito desta foi a formação de uma mistura eutética entre as duas gorduras. Já misturas entre CBE e MC são completamente compatíveis e poucas alterações são encontradas para estas misturas mesmo em altas concentrações de CBE. Por isso foi possível utilizar concentrações de até 20% de CBE e 10% de CBS, na produção dos chocolates. Os chocolates armazenados a 20°C apresentaram ótima resistência ao fat bloom e nenhum apresentou sinais da ocorrência deste defeito após 100 dias. Dentre os chocolates submetidos a flutuações de temperatura, após 3 ciclos o chocolate padrão apresentou alterações polimórficas e visuais características de fat bloom que foram intensificadas à medida que os ciclos foram prosseguindo. Os demais chocolates não sofreram influência da variação de temperatura, principalmente o chocolate com CBE que não apresentou nenhuma alteração visual ou estrutural característica de fat bloom, e o com CBS apenas após o sexto ciclo apresentou os primeiros sinais deste fenômeno. Através destes resultados foi possível concluir que apesar da incompatibilidade entre CBS e MC observada pelo estudo da cristalização destas misturas, esta incompatibilidade não foi determinante para acelerar a formação de fat bloom nos chocolates com esta gordura, sendo estes mais resistentes do que o chocolate padrão. A utilização de CBE em chocolates além de não ocasionar alterações de cristalização significativas ainda aumenta a resistência do chocolate ao fat bloom / Abstract: Cocoa butter (CB) is an extremely important natural fat for chocolate formulation, but due to the difficulty access and volatility of its price, alternative fats have been studied and produced to replace them as the Cocoa Butter Equivalent (CBE) and Cocoa Butter Substitutes (CBS). However, the crystallization and sensory characteristics that CB promoted in chocolate are very singular. Moreover, there may be an incompatibility between the alternative fats and CB which will cause defects in chocolate as fat bloom. The aim of this work was study the crystallization of CB, CBE, CBS, and their mixtures, in order to obtain a fraction as similar as possible to the pure CB for the preparation of dark chocolates, and study the influence of these fats on fat bloom formation. The mixtures were prepared based on the total content of CB on chocolate (CB added and CB inside the liquor), and the studied concentrations ranging from 5%, 10%, 15%, 20% and 37.5% of the CBE or CBS on CB. Raw materials and mixtures were characterized by fatty acid composition, triacylglycerol composition, isothermal crystallization, solid fat content, microstructure, thermal behavior, polymorphism, consistency and melting point. To check the effect of the addition of these fats in chocolate quality and resistance to fat bloom, the samples were produced and stored under two conditions, 100 days at 20° C and by temperature cycling for six cycles of 48h, 24h at 20°C and 24h at 33°C, periodically evaluated for, whiteness index, snap, microstructure, polymorphism and thermal behavior. The mixtures between CBS and CB showed large changes in the crystallization and plasticity as the CBS content was increased and the main effect is the formation of an eutectic mixture between the two fats. CBE and CB mixtures are fully compatible and little changes on crystallization of these mixtures are found even at high concentrations of CBE. Therefore it was possible to use 20% of CBE and 10% of CBS in chocolate production. All chocolates stored at 20°C showed excellent resistance to fat bloom and showed no signs occurrence of this defect during the 100 days. Nevertheless, the chocolate standard under temperature cycling, after 3 cycles showed modifications polymorphic and visual characteristics of fat bloom, and these characteristics were enhanced as the cycles were proceeding. Other chocolates were not so influenced by the variation of temperature, especially chocolate with CBE that showed no visual change or structural feature of fat bloom, and with CBS only showed after the sixth cycle the first small signs of this phenomenon. Through these results was concluded that despite the incompatibility between CBS and MC observed in the study of crystallization of these mixtures, this incompatibility was not decisive to accelerate the formation of fat bloom in chocolates with this fat, which are more resistant than standard chocolate. The addition of CBE on chocolates did not result on significant crystallization changes and also increased the resistance of chocolate to fat bloom / Mestrado / Tecnologia de Alimentos / Mestra em Tecnologia de Alimentos

Thesis (Ph. D.)--University of Wisconsin, 1973. / Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 303-310).