This project has investigated the mechanism of caking of lactose and identified some possible solutions to minimise caking of lactose and dairy powders, additional to those suggested in the literature. A background to lactose and caking is given. The problems of caking are identified and discussed. The project adds information to the knowledge on the polymorphic forms of lactose and their inter-relationships due to moisture sorption and processes such as milling. This information and many others in the literature are used to complete the simplified lactose conversion diagram developed by King [1965] and improved by Walstra, et al. [1999], which has been widely used in the literature as a guide for lactose manufacturing, processing, and storage. / Doctor of Philosophy (PhD)

The plasticity of coal during pyrolysis is of significant importance, since it affects the reactivity, porosity, particle size and the density of the char and thus also the behaviour of the char during further utilisation processes. The main focus of this study was to characterize the chemical and physical changes which the thermally treated coal undergoes, in order to better understand the pyrolysis process of caking and non-caking South African coals. The pyrolysis behaviour of three South African coals with different caking indices was investigated. The coal samples included; (1) Highveld (TWD), a medium rank C coal with a free swelling index (FSI) of 0, (2) Grootegeluk (GG), also a medium rank C coal, with a FSI of 6.5, and (3) Tshikondeni (TSH), a medium rank B coal with the highest FSI of 9. The three coal samples were classified as vitrinite-rich coals consisting of mainly aliphatic structures. Thermogravimetric experiments were used to determine the different temperatures relating to specific percentages of mass loss using set conditions. The pyrolysis process was stopped at various percentages of mass loss (thus at various stages of the reactions) to characterize the chemical structural changes that occurred at the specific mass loss percentages. The results obtained from characterization analyses indicated that the three coals differ in chemical composition and thus were expected to behave differently during pyrolysis. The coal samples consist of different amounts of macerals and minerals according to X-ray Fluorescence (XRF) and X-ray Diffraction (XRD) analyses. The Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT) results indicated that some of the functional groups within the coal samples evolved with the increase in temperature. The highly caking coal (TSH) exhibited the highest aromaticity and ring condensation. The surface areas were determined by CO2 adsorption and an increase in surface area was observed with an increase in temperature. The surface area of the GG and TSH coal-derived char samples decreased at some stage, which is an indication of thermoplastic behaviour and subsequent swelling of the coal samples. Scanning electron microscopy (SEM) images confirm the plastic stage of caking coals at specific temperatures and volatile matter release via the multiple bubble mechanism. All these results are given and discussed extensively in this dissertation. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2015

The plasticity of coal during pyrolysis is of significant importance, since it affects the reactivity, porosity, particle size and the density of the char and thus also the behaviour of the char during further utilisation processes. The main focus of this study was to characterize the chemical and physical changes which the thermally treated coal undergoes, in order to better understand the pyrolysis process of caking and non-caking South African coals. The pyrolysis behaviour of three South African coals with different caking indices was investigated. The coal samples included; (1) Highveld (TWD), a medium rank C coal with a free swelling index (FSI) of 0, (2) Grootegeluk (GG), also a medium rank C coal, with a FSI of 6.5, and (3) Tshikondeni (TSH), a medium rank B coal with the highest FSI of 9. The three coal samples were classified as vitrinite-rich coals consisting of mainly aliphatic structures. Thermogravimetric experiments were used to determine the different temperatures relating to specific percentages of mass loss using set conditions. The pyrolysis process was stopped at various percentages of mass loss (thus at various stages of the reactions) to characterize the chemical structural changes that occurred at the specific mass loss percentages. The results obtained from characterization analyses indicated that the three coals differ in chemical composition and thus were expected to behave differently during pyrolysis. The coal samples consist of different amounts of macerals and minerals according to X-ray Fluorescence (XRF) and X-ray Diffraction (XRD) analyses. The Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT) results indicated that some of the functional groups within the coal samples evolved with the increase in temperature. The highly caking coal (TSH) exhibited the highest aromaticity and ring condensation. The surface areas were determined by CO2 adsorption and an increase in surface area was observed with an increase in temperature. The surface area of the GG and TSH coal-derived char samples decreased at some stage, which is an indication of thermoplastic behaviour and subsequent swelling of the coal samples. Scanning electron microscopy (SEM) images confirm the plastic stage of caking coals at specific temperatures and volatile matter release via the multiple bubble mechanism. All these results are given and discussed extensively in this dissertation. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2015

Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009.

Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009.

Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009.

Mozzarella cheese production has been gaining market share due in part to increasing market for pizza and ready to eat food items. Anti-caking agents are utilized in the production of shredded cheese for reducing clumping and increasing the appearance of separate cheese shreds. Six anti-caking agents were applied to low moisture part skim Mozzarella cheese and examined for effects on three major functional properties of Mozzarella cheese; meltability, stretchability, and free oil formation. Meltability determination utilizing a fabricated UW Meltmeter resulted in no significant differences between untreated samples (control) and samples treated with anti-caking agents containing cellulose, potato starch or mixtures including dextrose. Stretchability measurements taken using a modified helical viscometry procedure also resulted in no significant differences between control and treated samples. Significant differences were found when comparing free oil percentages obtained from varying treatments of anti-caking agents. A mixture of potato starch and cellulose resulted in the lowest level of free oil among all samples tested. Because potato starch treated samples performed equally to cellulose treated samples in both meltability and stretchability testing, anti-caking agents containing potato starch could be considered as an alternative to cellulose-based anti-caking agents. In addition, the use of potato starch alone and in conjunction with powdered cellulose has been shown to be more effective for free oil control. By treating with potato starch, functional properties of shredded Mozzarella cheese have been positively altered in a way which may increase acceptability by consumers. / Master of Science

The effects of starch-based anti-caking agents on the browning of Mozzarella cheese were evaluated in this experiment. Six commercially available anti-caking agent treatments were examined and color measurements indicated that the starch-based anti-caking agents produced a baked cheese with a greater degree of browning than the samples treated with cellulose based anti-caking agents or no treatment (control). The cellulose-based treatments and the control also had a significantly greater moisture loss than the potato starch-based treatments. A negative correlation between percent moisture loss and the amount of browning was found (R2=0.51). The average surface temperature was at least 16 °C higher for the treatments containing potato starch than for the cellulose-based treatments. A significant relationship between average surface temperature and browning was also found (R2=0.67). These relationships suggest that the starch-based treatments impeded moisture loss, which decreased the amount of evaporative cooling. An increase in surface temperature resulted from the decrease in the amount of evaporative cooling and thus the Maillard reaction was accelerated leading to increased browning. The effects of the starch source were examined using starches from corn, rice and wheat. These starches were compared to commercially available potato starch and cellulose anti-caking agents. All starch sources were found to produce a greater degree of browning on the cheese sample compared to the cellulose treatment and control. Four adjuncts treatments, including dimethypolysiloxane, lactic acid, partially hydrogenated sunflower oil, and a combination of the dimethylpolysiloxane and sunflower oil were added to cheese treated with potato starch to determine if a reduction in the degree of browning could be achieved. No differences in browning between the potato starch treatment and those with added adjuncts were found. / Master of Science

Orientadores: Florencia Cecilia Menegalli, Maria Isabel Rodrigues / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-24T08:01:10Z (GMT). No. of bitstreams: 1 Vissotto_FernandaZaratini_D.pdf: 6786611 bytes, checksum: dffef14262649a8cbe2a7daad1cf4d46 (MD5) Previous issue date: 2014 / Resumo: Os achocolatados em pó são formulados com a mistura de cacau, açúcar, maltodextrina e aromas, podendo conter derivados lácteos. Para se obter uma adequada reconstituição em líquidos, os achocolatados são submetidos aos processos de lecitinação (adição de um agente tensoativo: lecitina de soja) e aglomeração com vapor. Um dos objetivos desse estudo foi o de avaliar os efeitos das variáveis do processo de aglomeração com vapor (pressão do vapor, temperatura do secador rotativo, vazão de sólidos da alimentação e frequência de rotação do secador) sobre as características físicas e físico-químicas de achocolatados em pó. A aglomeração com vapor levou a um aumento do diâmetro médio de partículas, sendo mais pronunciado no produto formulado com o açúcar moído. O processo foi responsável pelo escurecimento e redução da umidade dos achocolatados, além da diminuição dos tempos de molhabilidade. Adicionalmente foi caracterizada a morfologia dos grânulos de achocolatado, obtidos em diferentes condições operacionais do aglomerador (máxima, média e mínima), utilizando os descritores de tamanho e forma. Os resultados mostraram que não existe diferença entre os descritores de forma e quanto aos descritores de tamanho verificou-se diferença entre as condições de processo para grânulos maiores que 600 ?m. Concluiu-se que os grânulos de achocolatado aglomerados apresentaram formato alongado. Foram também determinadas as transições de fase e as temperaturas de transição vítrea (Tg) de achocolatados em pó e dos seus principais constituintes. Durante a aglomeração com vapor a alta temperatura levou o açúcar moído a uma condição acima da sua Tg, passando a ser esse componente um veículo para a granulação. A Tg da maltodextrina é pequena em atividades de água elevadas (Tg= - 4,9 °C; Aa= 0,843), o que também a torna um veículo para o processo de aglomeração. No cacau em pó alcalino foi observada a fusão da manteiga de cacau (aparecimento das formas polimórficas ?v e ?). Para o achocolatado lecitinado verificou-se que a Tg aumenta com o incremento da atividade de água do meio, portanto para esse tipo de produto a água, ao ser adsorvida, não consegue interagir com o material, não sendo verificado o efeito plasticizante. Para o achocolatado aglomerado com vapor verificou-se que a Tg diminuiu com o aumento da atividade de água do meio (efeito plasticizante). A evolução do caking dos constituintes dos achocolatados mostrou que o cacau em pó apresentou baixa higroscopicidade (pequeno aumento do ângulo de repouso com o tempo), pequena formação de aglomerados e a ausência do caking. A medida da força de compressão dos agregados formados mostrou que a sacarose formou pontes mais rígidas entre as partículas que a maltodextrina. Foi também monitorada a estabilidade de achocolatados em pó lecitinados e aglomerados com vapor, estocados a 25 e 35 °C, numa umidade relativa de 84%, buscando-se simular um clima quente e úmido (região norte do Brasil). Ao longo do tempo, verificou-se aumento do ângulo de repouso e escurecimento dos produtos. O achocolatado lecitinado mostrou-se mais susceptível ao empedramento que o aglomerado, com a formação de grumos a partir do 63° dia de armazenamento / Abstract: Cocoa beverage powders consist of a mixture of cocoa, sugar, maltodextrin, flavors, and may contain dairy products. To obtain products with adequate reconstitution in liquids, the cocoa beverage powders are subjected to the processes of lecithination (addition of the surfactant soy lecithin) and steam agglomeration. One objective of this study was to evaluate the effects of the main variables of the steam agglomeration process (vapor pressure, temperature of rotary dryer, solid feed rate and dryer rotation frequency) on the physical and physicochemical characteristics of cocoa beverage powders. The steam agglomeration led to an increased average particle diameter, being more pronounced in the product formulated with granulated sugar. The process was responsible for powder darkening, reduction of the product¿s moisture and decrease in the wettability. Additionally, the morphology of the cocoa beverage powder granules was characterized in different operating conditions of the steam agglomerator (maximum, average and minimum) using the descriptors of size and shape. There were no differences between the shape descriptors and as to the size descriptors there were differences in the process conditions studied for the granules of size above 600 ?m. It was observed that the steam agglomerated cocoa beverage granules had a more elongated shape. It was also determined phase transitions and the glass transition temperature (Tg) of cocoa beverage powders and the main constituents of these products. During the steam agglomeration, the high temperature led the granulate sugar to a condition above its Tg, making this ingredient a granulation vehicle. The Tg of maltodextrin is small at higher water activities (Tg = - 4.9 °C, aw = 0.843), which makes this ingredient a vehicle for the agglomeration process. For the alkaline cocoa powder the phase transition observed is the melting of the cocoa butter with the appearance of polymorphic forms ? and ?v. For the lecithinated cocoa beverage powder, it was verified that the Tg increases with the increasing of the water activity, which leads to the conclusion that for this type of product the adsorbed water cannot interact with the material, and the plasticizing effect is not noted. For the steam agglomerated cocoa beverage powder it was observed that the Tg decreases with increasing water activity (plasticizing effect). The evolution of the caking for the constituents of cocoa beverage powders showed that the cocoa powder had low hygroscopicity (small increase of the repose angle with time), little formation of granules and the absence of caking. The measurement of the compression strength of the aggregates showed that sucrose formed bridges more rigid between the particles than maltodextrin. Stability of lecithinated and steam agglomerated cocoa beverage powders stored at 25 and 35 °C, in a relative humidity of 84%,was also monitored, in order to simulate hot and humid climates (like northern Brazil). Overtime, it was observed increase of the repose angles and products darkening. The lecithinated cocoa beverage powder was more susceptible to caking than the steam agglomerated product, with the formation of lumps from the 63th day of storage / Doutorado / Engenharia de Alimentos / Doutora em Engenharia de Alimentos

Le mottage ou l’agglomération non désirée des cristaux déliquescents est un phénomène récurrent dans l’industrie, notamment au cours du transport et du stockage. Les variations des conditions environnantes sont fréquemment responsables de la dégradation de ce type de poudres. En particulier, les fluctuations de l’humidité ambiante conduisent à la formation d’une solution saturée par déliquescence du solide puis à la formation de ponts solides par évaporation de l’eau. Dans cette étude, on se concentre sur le chlorure de sodium. L’équilibre avec la vapeur d’eau et les cinétiques de prise et perte en eau sont analysés et reliés au comportement mécanique macroscopique des cristaux. Le contact avec des cristaux de différente nature tels que le sucrose met en évidence le phénomène de déliquescence mutuelle. Le modèle des solutions régulières appliqué aux systèmes ternaires comportant du NaCl, du sucrose et de l’eau permet de mieux comprendre la chute de déliquescence. La présence des molécules d’eau à la surface des cristaux et la condensation capillaire à faible humidité relative provoque la déliquescence de NaCl et du sucrose simultanément. L’évaporation de l’eau et la recristallisation des cristaux à partir de la solution ainsi formée sont inhibées, en particulier à la composition solide du point eutonique. Le comportement singulier à cette composition qui s’apparente à celui d’un corps pur montre une recristallisation partielle du mélange "eutonique" associée à la formation d’une phase amorphe dans les conditions de l’expérimentation. Afin d’éviter le renforcement au mottage, l’étude de différents agents anti-mottants révèle l’efficacité du stéarate de magnésium. / Caking or undesired agglomeration of deliquescent crystals is a recurrent phenomenon in industry, especially during transportation and storage. The variation of environmental conditions is often pointed out as a cause of the degradation of this kind of powders. More precisely, the fluctuations of ambient humidity lead to the formation of a saturated solution by deliquescence followed by the formation of solid bridges when water evaporates. Sodium chloride is chosen as a model substance in this study. The equilibrium with water vapor and the kinetics of water uptake and loss are analyzed and related to the mechanical macroscopic behavior of crystals. The contact with crystals of different nature such as sucrose highlights the phenomenon of mutual deliquescence. The model of regular solutions applied to ternary systems containing NaCl, sucrose and water allows a better understanding of deliquescence lowering. The presence of water molecules and capillary condensation at low relative humidity lead to the deliquescence of NaCl and sucrose simultaneously. Water evaporation and recrystallization of solid from such solution is compromised, especially at the solid composition of the “eutonic point”. The singular behavior at this composition which resembles to the one of a pure substance shows a partial recrystallization of the “eutonic” mixture and the formation of an amorphous phase under the experimental conditions applied. In order to avoid caking reinforcement, the study of differentanti-caking agents reveals the efficiency of magnesium stearate.