Flavour perception of food and beverages is a complex multisensory experience involving the gustatory, olfactory, trigeminal, auditory and visual senses. Thus, investigations into multimodal flavour perception require a multidisciplinary design of experiments approach. This research has focussed on beer flavour perception and the fundamental interactions between the main flavour components - sweetness, bitterness (from hop acids), alcohol content and carbonation level. A model beer was developed using representative ingredients which could be manipulated to systematically vary the concentration of the main flavour components in beer and was used in the following experiments. Using a full factorial design, the physical effect of ethanol, C02 and hop acid addition was determined by headspace analysis and in-nose expired breath (in-vivo) measurements. Results from headspace and in-vivo methods differed and highlighted the importance of in-vivo measures when correlating to sensory experience. Ethanol and C02 significantly increased volatile partitioning during model beverage consumption. The effects of ethanol and C02 appeared to be independent and therefore additive, which could account for up to 86% increase in volatile partitioning. This would increase volatile delivery to the olfactory bulb and thus potentially enhance aroma and flavour perception. This was investigated using quantitative descriptive analysis. Results showed that C02 significantly impacted all discriminating attributes, either directly or as a result of complex interactions with other design factors. C02 suppressed the sweetness of dextrose and interacted with hop acids to modify bitterness and tingly perception. Ethanol was the main driver of complexity of flavour and enhanced sweet perception. In a first study of its kind, the impact of C02 on gustatory perception was further investigated using functional magnetic resonance imaging (fMRI) to understand cortical response. In addition, classification of subjects into PROP taster status groups and thermal taster status groups was carried out. Groups were tested for their sensitivity to oral stimuli using sensory techniques and for the first time, cortical response to taste and C02 was investigated between groups using fMRI techniques and behavioural data. There was no correlation between PROP taster status and thermal taster status. PROP taster status groups varied in their cortical response to stimuli with PROP super-tasters showing significantly higher cortical activation to samples than PROP non-tasters. The mechanism for thermal taster status is not currently known but thermal tasters were found to have higher cortical activation in response to the samples. The difference in cortical activation between thermal taster groups was supported by behavioural data as thermal tasters least preferred, but were more able to discriminate the high C02 sample than thermal non-tasters. This research has provided in-depth study into the importance of flavour components in beer. It advances the limited data available on the effects of C02 on sensory perception in a carbonated beverage, providing sound data for the successful development of products with reduced ethanol or C02 levels. The use of functional magnetic resonance imaging has revealed for the first time that oral C02 significantly increases activation in the somatosensory cortex. However, C02 seemed to have a limited impact on activation strength in 'taste' areas, such as the anterior insula. Research comparing data from PROP taster status groups and thermal taster status groups has given insight into the possible mechanisms accounting for differences in oral intensity of stimuli.

Drying is an old traditional method of removing liquid from inside material, suchas wood, food, paper, ceramics, building materials, textiles, granular products, pharmaceutical and electronic devices. The kinetics of this liquid removal depends on the material properties of the solid phase as well as on cellular structure. The aim of this project is to understand the effect of complex interaction of heat, moisture and shrinkage to create a detailed mathematical modelling to quantify the drying of a food product and tropical fruits in particular, which typically have high water content. To this purpose, in first part of the thesis, an initial simple coupled diffusion model with Fickian moisture transfer and Fourier heat transfer by Wang and Brenann [122] has been extended. A one-dimensional model is applied with the effect of shrinkage for a prediction of moisture and temperature distribution during drying. Constant physical and thermal properties are used relevant to tropical fruits. A numerical solution technique, based on the method of lines, is used with local finite difference methods approximation to the drying. The results match well with published food drying simulation studies and the anticipated final state of shrinkage in particular. To obtain a detailed understanding of simultaneous heat and liquid transfer during drying of fruits, the internal structure has to be modelled. In fruit tissue, intercellular space existing within a highly complicated network of gaseous channels can be considered as a porous medium. Guided by this, an extended model of drying, incorporating the heterogeneous properties of the tissues and their cellular structure, is recognized and simplified to represent the physical model. In this model, a distinction is made between the different classes of water present in the material (free water, bound water and water vapour) and the conversion between them. Evaluation is applied to the range of one-dimensional structures of increasing complexity: the first is an isothermal model without consideration of heat effects; the remaining have heat effects but differ in the correlated spatial arrangement of micro and macro pores. All results are given as drying curves and phase distributions during drying.

This thesis investigates how hydrocolloids can be incorporated into pet food meat products to provide novel applications. The possible applications that have been investigated for hydrocolloids are satiety and the production of more sustainable meat products. The research was carried out to improve canned pet food and the processes used to manufacture the product. The main section of the thesis looks at incorporating alginate and pectin solution into a food product which then becomes a gel in a low pH environment. The gel produced in the stomach should produce a satiety effect within the pet. Hydrocolloids used in other studies have been shown to induce satiety in humans. The gel was tested in vitro with a positive result which showed good gelation; however, when tested in vivo, no reduction in food intake was seen. These results may indicate that satiety has different trigger mechanisms in dogs compared to humans. More research is needed to understand whether dogs have the same hormonal responses to satiety as humans. The second application was the use of agar and methylcellulose (MC) to produce a thermally stable gel. The incorporation of this gel structure into a wet meat product would allow the level of meat to be reduced and additional powders to be used as a nutrient component instead. A thermally stable gel also enables the pet food to be processed more efficiently. The gel allows the meat chunks to be cut at high temperatures; therefore, no cooling step is needed in production. Agar and MC produce a strong thermally stable gel at both high and low temperatures. There is evidence that an interpenetrating network is formed in which the molecular ordering and aggregation of the individual polymers appears to be affected by the presence of the second polymer. The use of hydrocolloids for new applications in meat will transform and improve the quality of these products in the future.

Five diagrams in pocket.

Call number: LD2668 .T4 1986 H866 / Master of Science / Apparel, Textiles, and Interior Design

Submitted in fulfillment of the academic requirements of the degree of Master of Applied Sciences in Chemistry, Durban University of Technology, Chemistry Department, Durban, South Africa, 2016. / Cellulose is a sustainable, abundant biopolymer derived from a variety of living species such as plants, animals, bacteria and some amoebas. An attractive source of cellulose for industrial uses is agricultural waste, as this use does not jeopardize food supplies and improves the local rural economy. Sugarcane bagasse (SCB) is one of the main biomass wastes from sugar production and represents 30–40 wt % of sugar production waste. In 2008, South Africa produced on average 22 million tons of sugar cane each season from 14 sugar mill supply areas which resulted in 7,9 million tons of “waste” bagasse. In this study cellulose nanocrystals were prepared from soda pulped sugarcane bagasse by acid hydrolysis followed by separation using centrifugation, ultrasonication and dialysis. Transmission Electron Microscopy (TEM) images showed nanocrystals of approximately 300 nm in length and 20 nm in width. Thermogravimetric Analysis and Differential Thermogravimetry (TGA and DTG) profiles of FD CNC, MCC and Pulped bagasse all had characteristic onset and decomposition temperatures indicating a change in the structure after chemical treatments. Particle size distribution measurements corroborated with the TEM and FE - SEM results and showed that the majority of the nanocrystals were in the 100 – 300 nm range. Attenuated Total Reflectance – Fourier Transform Infra Red (ATR - FTIR) analysis showed functional group changes as the amorphous regions of the polymer were removed revealing the ordered crystalline portions. These were further confirmed by an increase in the Lateral Orientation Index (LOI) of the samples as the nanocrystals were isolated. X - Ray Diffraction (XRD) Crystallinity Index (CrI) calculations showed a steady increase in the crystallinity of the materials from pulped bagasse to MCC to FD CNC. / M

Master of Science - Molecular and Cell Biology / The bacterial contamination profile of a typical commercial yeast factory was assessed by three replicate microbiological surveys. In order to detect low-level contamination in samples, this study made use of a preliminary incubation technique (24h at 37°C), which boosted bacterial counts for the identification of sources of contamination. Numbers of bacteria were quantified by standard pour- and spread-plate techniques and various selective media. Raw materials were negligible in contributing to the bacterial contamination of commercial yeast, with the exception of soda ash, used to control the pH of fermentations, which contained 2 log CFU/ ml Enterococcus and aerobic bacteria. It was found that the scale up of seed yeast biomass was the primary site for contamination with Enterococcus, which progressively increased in number as the product passed down the production line. Coliforms were present at low levels, with significant increases (P < 0.05) observed during the storage of yeast cream; extrusion of compressed yeast; and packaging of dry yeast. The environment surrounding the compressed yeast production line was identified as a potential source of airborne contamination. Although Salmonella spp. and S. aureus were not detected, L. monocytogenes was isolated from compressed and dry yeast products. In addition, Bacillus spp. commonly associated with the rope-spoilage of bread, were isolated from 67% of all dry yeast product samples. Shelf-life investigations, showed that cream and compressed yeast samples were spoiled with lengthened storage periods, and especially at higher temperatures (>10°C), whilst vacuum-packaged dry yeast remained bacteriologically stable. During shelf-life studies, isolates from spoiled cream and compressed yeast samples were predominantly Lactobacillus (up to 78%), while populations of Enterococcaceae predominated in vacuum-packaged dry yeast samples (up to 68%). The use of stainless steel surfaces, attached to processing equipment used in the manufacturing of Baker’s compressed yeast, in conjunction with SEM illustrated the accumulation of yeast and bacterial cells with early stages of biofilm formation, with time. Where populations of Gram-positive members of the lactic acid bacteria family, Lactobacillus and Enterococcaceae, were isolated in the highest proportion from processing equipment surfaces used in the manufacturing of Baker’s compressed yeast (81-100%).

O objetivo desta dissertação é realizar e comparar a aplicação da modelagem dinâmica de sistemas (MDS) e do activity based costing (ABC) para mensurar os custos em manufatura celular. Nesse sentido, foi realizada uma simulação utilizando os conceitos de MDS para obter os custos de produção de quatro produtos, em um ambiente de manufatura celular, considerando o método ABC e a comparação desses valores com a técnica de custeio tradicional ou absorção. Quanto à metodologia de pesquisa, esse trabalho é de enfoque quantitativo no qual o tipo de pesquisa é exploratório sem estabelecimento de hipóteses, porém, guiada pelos seus objetivos. Os resultados obtidos demonstram que a aplicação do ABC juntamente com a MDS é muito satisfatória quando comparada com a técnica tradicional. Finalmente, a aplicação do ABC com a MDS pode ser utilizada eficientemente como um método alternativo para custeio em manufaturas celulares. / The aim of this dissertation is to apply and to compare the modeling system dynamics (MDS) and activity based costing (ABC) to measure the costs in cellular manufacture. Taking this into account, a simulation was accomplished using the concepts of MDS to obtain the costs of production of four products, in an environment of cellular manufacture, considering ABC method and the comparison of those values with the technique of traditional costing. As for the research methodology, this dissertation is of quantitative focus in which the research type is exploratory without establishment of hypotheses, however guided by their objectives. The obtained results demonstrate that the application of ABC together with MDS it is very satisfactory when compared with the traditional technique. In conclusion, it can be observed that the application of ABC with MDS can be used efficiently as an alternative method to costing in cellular manufacture.

Sago starch is extracted from the trunk of sago palm (Metroxylon spp.), which is found throughout South East Asia. In Indonesia sago is considered an underutilised crop and moreover Iron Deficiency Anaemia (IDA) is prevalent among particularly women and children. Creation of a ready to eat product from sago, which was fortified with iron, would address issues of food security both in terms of nutrition and as a non-imported carbohydrate source. With this aim studies for the manufacture of a thermomechanical directly expanded snack product using a commercial source of sago starch were conducted. Composition and properties of sago starch were analysed and compared with rice and cassava. Sago starch differed in several aspects from the two other starches widely processed in Asia. Sago starch had large granules, had the highest amylose levels and gelatinisation temperature (76 °C). X-ray diffraction suggested an A-type packing for all samples, including the sago where literature suggest a C-type ordering. Conversion of the starches (30% moisture) and their flow were studied in a capillary rheometer. A stable extruded product was achieved, but it did not expand. Capillary rheometer data showed pseudoplastic behaviour of the moistened sago starch. With increasing temperature viscosity decreased and no impact of the presence of iron (ferrous sulphate heptahydrate 800 ppm) on the flow behaviour was found, but the inclusion of iron made the extrudates brown in colour. The losses of crystallinity were measured on the extrudates from the rheometer. Levels of order loss were predicted from the state diagram and by comparison with the DSC enthalpy changes for uncooked sago at higher moisture contents. When processed at 70 °C the samples showed more amorphous material than anticipated. When processed at 100 °C still 30% of the order remained. This indicated that shear and moisture levels are critical in the processing of the starch. Thermomechanical extrusion was carried out on a twin screw pilot scale machine (Thermo Fisher, Prism). The screw and die configuration and feed rate for the sago starch (8 kg/h) were fixed. The impact of variable processing parameters of water feed rate (16.5 to 25% wwb), screw speed (200, 300 and 400 rpm) and die temperature (120, 140 and 160 °C) on the physical and physicochemical properties of extruded sago starch were investigated. At the lower water feed rates expansion occurred as the product left the extruder to form a stable extrudate with multiple air cells, which gave a crispy texture. The specific mechanical energies needed to create the expanded product were high at 400-500Whr/kg. The properties of the extrudates were more affected by water feed rate than by alterations in screw speed or die temperature. In order to reduce discolorations, iron-fortified sago starch extrudates were made using iron and ascorbic acid (1:6 ratio). The presence of additives at low water feed rate had no detrimental impact on the extrudates. The recommended extrusion parameters for the manufacture of an extruded sago starch product would be: feed rate of 8 kg/h, screw speed of 300 rpm, die temperature at 140 °C, and water feed rate at 4 mL/min (equivalent to 16.5% wwb), and it is possible that machine settings that produce even higher SME values may allow a more expanded product. From this work it appears that an iron fortified directly expanded sago product could be manufactured. Its nutritional properties and commercial applicability would need to be ascertained.

The 21st century demand for innovation is leading towards a revolution in the way products are perceived. This will have a major impact on manufacturing technologies as current product innovation is constrained by the available manufacturing processes, which function independently. One of the most significant developments is the emergence of hybrid manufacturing technologies integrating various individual manufacturing processes. Hybrid processes utilise the advantages of the independent processes whilst minimising their weaknesses as well as extending application areas. Despite the fact that the drawbacks of the individual processes have been significantly reduced, the application of state of the art hybrid technology has always been constrained by the capabilities of their constituent processes either from technical limitations or production costs. In particular, it is virtually impossible to machine complex parts due to limited cutting tool accessibility. By contrast, additive manufacturing (AM) techniques completely solve the tool accessibility issue, but this increased flexibility and automation is achieved by compromising on part accuracy and surface quality. Furthermore, the shape and size of raw materials have to be specific for each hybrid process. More importantly, process planning methods capable of effectively utilising manufacturing resources for hybrid processes are highly limited. In this research, a hybrid process, entitled iAtractive, combining additive, subtractive and inspection processes is proposed. An experimental methodology has been designed and implemented, by which a generative reactionary process planning algorithm (GRP2A) and feature-based decision-making logic (FDL) is developed. GRP2A enables a complex part to be accurately manufactured as one complete unit in the shortest production time possible. FDL provides a number of manufacturing strategies, allowing existing parts to be reused and transformed into final parts with additional features and functionalities. A series of case studies have been manufactured from zero and existing parts, demonstrating the efficacy of the iAtractive process and the developed GRP2A and FDL, which are based on a manual process. The major contribution to knowledge is the new vision for a hybrid process, which is not constrained by the capability of the individual processes and raw material in terms of shape and size. It has been demonstrated that the hybrid process together with GRP2A and FDL provides an effective solution to flexibly and accurately manufacture complex part geometries as well as remanufacture existing parts.