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.

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.

Four batches of pasteurized process cheese were prepared from the same Cheddar cheese by cooking to 82C in the presence of sodium citrate, disodium phosphate, tetrasodium pyrophosphate or sodium aluminum phosphate. Each batch contained the same moisture (40.6%) and emulsifying salt concentration (2.5%). The process cheese was sampled for microstructural and rheological examination after 0, 5, 10, 20 and 40 min in the cooker at 82C. Even though each emulsifying salt affected the physical properties of the process cheese differently, the cheese generally became firmer, stiffer, more elastic and less meltable as cooking time increased from 0 to 40 min. These changes were accompanied by a decrease in the dimension of fat masses and an increase in the degree of emulsification as evidenced by scanning electron microscopy and transmission electron microscopy. The degree of emulsification (fineness of fat particles) seemed directly related to firmness, poor meltability, toughness, breaking force, apparent stiffness modulus, degree of elasticity , apparent ultimate stress and inversely related to hysteresis and apparent ultimate strain. Tetrasodium pyrophosphate produced the most rapid emulsification of the fat in the cheese and sodium aluminum phosphate the slowest. The effect of the other salts was intermediate. The softest most meltable cheese was poorly emulsified while the firmest most sliceable was well emulsified. Sodium citrate and tetrasodium pyrophosphate crystals remained undissolved in the cheese after 40 min in the cooker while sodium aluminum phosphate crystals were still undissolved after 10 min. There was a close statistical relationship among several of the rheological measurements viz. meltability and firmness, toughness and breaking force, and meltability and breaking force. Future rheological studies on process cheese should not require all of the above measurements. An increase in the fineness of the fat emulsion as determined by scanning electron microscopy was generally accompanied by increased firmness, poorer meltability and increased toughness.

The prime object of the work undertaken in the present study has been done with the view of determining whether or not the quality and yield of brick cheese may be improved by pasteurizing the milk from which the cheese is made. An effort should be made to put brick cheese-making on a more scientific basis and at the same time produce cheese of better and more uniform quality. Since milk, containing large numbers of undesirable microorganisms thus causing objectionable flavors and odors in dairy products, is frequently delivered to cheese factories to be processed, pasteurization seems to be one way of attacking the problem to accomplish the desirable results. In a measure it gives the cheesemaker a better opportunity to encourage the growth of the more desirable organisms by inoculating them into he milk after it is pasteurized and cooled down, and it also gives him a better opportunity to check the growth of the undesirable ones since most of them are killed at pasteurization temperature. It is essential to have the proper types of organisms present in the processing and ripening of the cheese; since closely associated with bacterial reproduction, there is always some form of decomposition and these products of decomposition give the cheese its flavor and odor. Is is a mistake to think that milk can be produced under unsanitary conditions and that is can be purified by heating. Pasteurization cannot atone for filth. This point should be strongly emphasized. To be made into rick cheese, milk should be clean, sweet, and free from objectionable flavors and odors and should be produced under the most sanitary conditions possible.

The effects of mechanical desinewing on yield, proximate analyses and connective tissue content of pork and beef have been examined and it's influence on the appearance and palatability of cooked salami was evaluated. Mechanical desinewing removed approximately half of the connective tissue and reduced the tendency for formation of gelatin pockets in cooked salami. Yields from the desinewer ranged from 71 to 87 percent, however, cooking yield defined as cooked weight divided by uncooked weight from the desinewed salami were 6 to 7 percent higher than from the nondesinewed salami. For both the beef and pork there was no significant increase in the protein percentage. The moisture content increased by an average of 2.17 percent while the fat content decreased by an average of 2.39 percent. The taste panel evaluation indicated that tenderness and texture of desinewed salami were significantly improved over that of the nondesinewed salami.

Pasteurized skim milk was acidified using glucono-δ-lactone (GDL) at 10, 20, 30, and 40°C or with 1.2% freeze-dried yogurt starter culture at 40°C. Milk coagulation was followed by measuring turbidity, curd firmness, particle size, and casein micelle microstructural changes using transmission electron microscopy . The pH of milk was gradually lowered during acidification with GDL or starter culture. Acidification rate showed greater influence on turbidity change at 10°C than at 20, 30, or 40°C. Average casein micelle size increased with decreasing temperature. The patterns of average micelle size versus pH were not affected by temperature. No great variation of average micelle size was observed above pH 5.2. Below pH 5.0 the size increased exponentially as the milk gelled. Acidification rate did not influence average micelle size at 10°C. Acidification rate, types of acidifying agents, and temperature had no effect on the Formagraph gelation pH and the rate at which curd firmness developed. Casein micelles became less compact and less distinct with decreasing temperature before acidification. As pH was lowered, protein was dissociated from and then reassociated with casein micelles. Acidification rate had no effect on microstructure change of casein micelles at 10°C.

Roasting is an important processing step for developing cocoa flavor, color, and aroma. Cocoa beans contain polyphenolic compounds, which can be desirable antioxidants. Oxygen Radical Absorbance Capacity (ORAC) values can be used as an indicator of health benefits of antioxidants in foods. ORAC values measure total antioxidant capacity of different foods by measuring antioxidant scavenging activity against peroxyl radical induced by 2,2’-azobis (2-amidinopropane) dihydrochloride (AAPH). This measurement of total antioxidant capacity gives a complete assessment during which the inhibition time and inhibition degree are measured as the reaction comes to a completion. ORAC values were determined as Trolox Equivalents (TE). Cocoa beans were also measured for antioxidants using Total Phenolics assay and DPPH assay and measured as gallic acid equivalents (GAE). Cocoa beans from the Ivory Coast were roasted at varying times (10-40 minutes) and temperatures (100ºC -190ºC). It was determined that cocoa beans from the Ivory Coast, roasted at 130ºC for 30 minutes resulted in an ORAC value of 522,789 μmol (micromoles) TE/g, GAE value of 2.46 mg/L as determined by Total Phenolics, and GAE value of 1.48 mg/L as determined by DPPH assay. The analyzed values tended to decrease at the highest temperatures and times of roasting. Cocoa beans from different countries were roasted at 130ºC for 30 minutes and antioxidants were analyzed. It was determined that Dominican Republic and Ecuador had the highest TE values (487,913 and 463958 μmol (micromoles) TE/g respectively). GAE differed and Total Phenolic assay found Haiti had the highest GAE (3.26 mg/L) and DPPH assay found Ivory Coast and Dominican Republic had the highest (0.623 and 0.610 mg/L respectively). If an acceptable flavor, color, and aroma of cocoa can be developed at a roasting temperature closer to 130ºC than to 160ºC, then a greater antioxidant content should occur in dry cocoa powder.

Applesauce prepared for the US military is processed as MRE (meals-ready-to-eat) in several forms including Type VI - Applesauce with raspberry puree, and Type VII - Carbohydrate enriched applesauce. Production of MRE applesauce starts with commercially prepared and thermally processed applesauce that is further processed by a military contractor. The further processing includes adjusting pH, ºBrix, and ascorbic acid level, packaging into pouches, and again thermally processing. Both types of the MRE applesauce are very much liked by troops, but under stress storage applesauce darkens and its consumption is drastically reduced. The overall goal of this project was to identify additives to be used during further processing in order to slow darkening when exposed to elevated temperatures during shipping and storage. The specific objective was to determine whether different types of ascorbic acid, calcium salts, or addition of chelators can reduce deterioration under stress storage. Applesauce (AS), applesauce with raspberry puree (RPAS), MRE AS (Type VII) and MRE RPAS (Type VI) for all experiments were provided by Sopakco, Bennettsville S.C. The research was carried out in three phases. From the Phase 1, we learned that Type VII and Type VI darkened at faster rates at the beginning of the storage, but the effects of storage at 50°C for more than 2 weeks overcame any differences caused by further processing. Phase 2 helped us determine the formulations for the processing on the industrial scale. The formulations were: 0.15% L-ascorbic-acid (AA), and 0.15% AA with 300 ppm EDTA for both AS and RPAS, with 0.83% calcium lactate gluconate (CLG) for AS, and 0.15% ascorbyl-palmitate for RPAS. The results from the Phase 3 indicated that AS with addition of CLG and RPAS with total of 0.18% AA had the least total color change. In all samples, accumulation of HMF was related to amount of ascorbic acid with exception of samples with Pal which had the lowest HMF content. Our results indicate that current MRE Types VI and VII may have better stability at stress storage if the level of AA is limited to 0.18% and 0.83% CLG is added to the AS formulation.