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.

Donald Winston Tufts. / "July 28, 1960." Issued also as a thesis, M.I.T. Dept. of Electrical Engineering, May 25, 1960. / Bibliography: p.48. / Army Signal Corps Contract DA36-039-sc-78108. Dept. of the Army Task 3-99-20-001 and Project 3-99-00-000.

The use of multi angle laser light scattering on-line to size exclusion chromatography, analytical ultracentrifugation and viscosity measurements for the determination of molecular weights and conformations of polysaccharide systems is described. The use of several independent techniques for the characterization of polysaccharide systems was found to be essential due to the polydisperse nature of the materials. These techniques were used to investigate the changes in molecular size and conformation of guar gum due to irradiation. Molecular weights and viscosities were found to decrease significantly with increasing radiation dose. Conformational studies on the resulting series of homologous samples confirmed the random coil-like conformation of guar gum. Investigations on BSNdextran complexes, obtained by dry-heating at different molar ratios showed that complex formation (most likely by a Maillard-type reaction) only took place when a low molecular weight dextran fraction was used. The highest molecular weight complexes were obtained when the BSA ratio was high, suggesting that some form of association between individual complexes and/or BSA had taken place.

The work described in this thesis addresses two classes of mixed biopolymer systems: (a) starches and sodium caseinate ; (b) gelling seaweed polysaccharides (x-carrageenan - both with and without locust bean gum - agar and alginate) and proteins (gelatin and blood plasma proteins). The viscosity and swelling volume of a 1% potato starch paste in distilled, deionised water is markedly reduced in the presence of caseinate. Similar effects were seen with simple electrolytes suggesting that this occurs as a consequence of a non-specific ionic strength effect. In contrast a 4% maize starch paste in distilled, deionized water undergoes a viscosity and swelling volume increase in the presence of caseinate. However, when pasted in a 0.1M, pH 7.0 phosphate buffer caseinate addition has little effect on the viscosity of the fresh paste and at high concentrations appears to prevent retrogradation on ageing. It is suggested that in buffer caseinate prevents the leaching of starch polysaccharides from the swollen granule and therefore maintains amylose in the granular phase. This is attributable to the high ionic strength of the solvent, allowing caseinate and the starch polysaccharides to phase separate. In water the unfavourable entropy, change due to the uneven distribution of the counter-ions, prevents phase separation and results in an interpenetrating network. Studies on the large deformation stress relaxation behaviour and melting points of 2% carrageenan, 0.5% carrageenan/0.5% locust bean gum (LBG) and 2% agar gels in a variety of solvent media indicate that the inclusions of 0-20% gelatin and 0-5% bovine serum albumin (BSA) give different results depending on both protein and polysaccharide. The main points of this study show that agar/gelatin mixed gel undergoes a distinct phase inversion at 4-7% gelatin levels, which is not seen with the carrageenan gels containing gelatin. Even when 20% gelatin is incorporated into a 2% carrageenan gel the melting point of the gel is unaltered from that of carrageenan alone. In the presence of high levels of BSA the carrageenan/LBG gel undergoes a marked increase in melting point. Investigations using locust bean gums of variable protein content suggests a possible (LBG)protein-BSA interaction since the melting point increases with the LBG protein content. It is shown that carrageenan/LBG gels have clear regions when formed by autoclaving in the presence of blood plasma. This supports the idea of an association between the protein in the insoluble husk and the blood plasma proteins. The interaction mixtures of BSA with sodium alginate at the interface and in bulk solution have been studied through the techniques of microelectrophoresis and ultracentrifugation respectively, to further elucidate the association between denatured proteins above their isoelectric point and anionic polysaccharides. Both techniques clearly show that the macromolecules can associate electrostatically at pH's above the pI of the protein.

Deterioration of flavour quality during processing and storage is often brought about by oxidative processes. These typically involve oxygen or an active form of oxygen in effecting transformation of a wide range of volatile and non-volatile compounds, including key quality chemicals, flavour precursors and antioxidants. To investigate the nature of the chemical and biochemical change within vegetables and herbs, unblanched frozen parsley was selected as a suitable tissue. The chemical status of parsley during technological processing was determined using novel analytical protocols (SNCV A/SNCNV A) implemented as part of a unified strategy for the quantitative analysis of volatile and non-volatile species. The analysis utilized a single stabilized solution produced from plant tissue, under a regime which minimized isolation stress and artifact formation. On frozen storage (-10OC) the principal volatiles of parsley, myrcene, beta-phellandrene and menthatriene were extensively degraded to non-volatile products at differential rates. p-Cymenene and the tentatively assigned menthatriene diepoxide were formed as minor volatile oxidation products. Myristicin remained largely unchanged. Under similar frozen storage, chlorophyll 'a' displayed significant degradation with only minor amounts of chlorophyllide 'a', pheophytin 'a' and 13[superscript]2 hydroxychlorophyll 'a' formed. Ascorbic acid was extensively degraded in timescales preceding monoterpene and chlorophyll loss. Thermal blanching of parsley extensively prevented the degradation of the monoterpenes, suggesting that endogenous enzymes were responsible for the changes. Elimination of oxygen, in the absence of blanching, prevented volatile loss, confirming the requirement for oxygen. The hypothesis that peroxidase can operate in a co oxidative couple with the flavonoid, apigenin-7-glucoside and hydrogen peroxide, as proposed by Yamauchi (1985), was investigated to establish its potential role in the degradation of terpenoids and chlorophyll. In model experiments, using horseradish peroxidase, menthatriene and chlorophyll showed extensive degradation only when all components of the couple were present. In addition the requirement for oxygen was also established. Naringenin and umbelliferone have been shown to behave similarly to apigenin, as co-substrates for peroxidase. Lycopene, with some structural similarity to menthatriene, was also susceptible to co-oxidation. Polyphenol oxidase, proposed to operate in a similar fashion to peroxidase with mono- and di-phenols as substrates (Montedoro et al. 1995), in model experiments did not cause the degradation of chlorophyll. The co-oxidative role of lipoxygenase in parsley is believed to be of minor significance, however, it is likely to be responsible for the production of low levels of hexanal observed during thawing of frozen parsley. From this thesis it is concluded that the aroma and colour quality loss in frozen unblanched parsley probably results from the oxidative degradation of the unsaturated monoterpenes and chlorophyll 'a' respectively via an oxidative cascade initiated by the action of peroxidase.

Lipase 3 is a fungal lipase produced industrially for use as a dough-conditioning enzyme in bread making. Mutants of Lipase 3 were designed to improve enzyme specific activity and to prevent N-linked glycosylation, which was found to cause a drop in activity on industrial-scale production. These were based on three-dimensional model structures of Lipase 3 in `open' and `closed' conformational states derived from crystallographic data of fungal lipases sharing high sequence homology. Lipase variants were expressed and secreted by Pichiapastoris yeast and purified by anionexchange chromatography, which allowed the separation of two active isoforms. Analysis of the `glycosylation' mutants by SDS-PAGE and MALDI-TOF mass spectrometry implied that mutation of N-linked glycosylation sites prevented attachment of oligosaccharide groups to these sites. Mutants were characterised by measurement of specific activities with soluble and emulsified substrates and determination of kinetic constants with emulsified substrate. None of the `activity' mutants showed improved activity over wild type, and the significant drop in activity with emulsified substrate on mutation of a `lid' tryptophan residue indicated that this residue was required for interaction with long-chain triacylglycerol substrates. Specific activities and kinetic constants measured for the ‘glycosylation' mutants did not differ significantly from those of the wild type enzyme. Sigmoidal kinetic curves were observed for lipases expressed in Pichia pastoris and Aspergillus niger with emulsified substrate. Co-operativity was measured using the Hill plot and found to be positive. The possibility of a kinetic mechanism, rather than an allosteric mechanism (involving interactions between ligand binding sites), for cooperativity is discussed.

Ogi is a fermented food made from maize, sorghum or millet which serves as complementary food for infants and breakfast for adults in Nigeria, West Africa. This study characterized the microbial diversity of maize and sorghum grains and ogi produced by their natural fermentation in an attempt to understand the roles of the key microbial species and the impact of the population dynamics and selected species on changes in nutritional composition and aroma notes of ogi during fermentation. A combined approach of culture dependent and culture independent methods of analysis was applied to investigate the microbial community of grains and ogi from two different sources. Microbial diversity and viable populations varied with the source of the grain. Bacterial and fungal genera identified with the partial 16S rRNA and 26S rRNA sequence analysis respectively in maize and sorghum were Bacillus, Enterobacter, Micrococcus, Kytococcus, Pantoea, Staphylococcus, Amycolatopsis, Methanoculleus, Aspergillus, Penicillium, Eupenicillium, Acremonium, Schizosaccharomyces, Meyerozyma, Hyphopichia, and Pichia in maize grains; Enterococcus, Enterobacter, Pantoea, Bifidobacterium, Aspergillus, Cladosporum, and Penicillium in maize ogi; Enterococcus, Enterobacter, Pantoea, Aeribacillus, Cyanobacterium, Acinetobacter, Fusarium and Trametes in sorghum grains; and Pediococcus, Lactobacillus, Enterococcus, Bacillus, Cladosporum and Penicillium in sorghum ogi. Similar species were observed in both sources of maize while those of sorghum differed slightly. Predominant microbes included species of Enterobacteriaceae and moulds. Acetic acid bacteria were not identified as part of the diverse community. Following the predominance of moulds during the natural fermentation, preliminary screening was performed by PCR using specific biosynthetic gene primers to test whether they are the mycotoxin producing species. None of the genes tested were detected by PCR thus they may not be the toxin producing species. Starch, non-starch polysaccharide (NSP), phytate and phenolic compounds were determined in the grains and respective ogi to ascertain the levels of these nutritionally important components in the naturally fermented ogi and the impact of the varying microbial populations on the fate of these compounds during fermentation. In the grains, the average starch and NSP contents in each case were 80.35 g/100g and 9.40g/100g in maize and 93.12 g/100g and 8.14 g/100g in sorghum. Out of the total in grain the average percentage recovery of starch and NSP respectively in the ogi showed 63% and 42% in maize and 58% and 27% in sorghum. Maize showed good starch and fibre (NSP) retention than sorghum after fermentation. To further understand the types and levels of polymers in NSP hydrolysis in ogi fermentation, HPLC analysis of the hydrolysed extract was performed. Glucose was entirely present in maize and sorghum ogi which represents the beta-D-glucans while arabinose and xylose (in maize only), mostly lost with the pomace, signify the arabinoxylans. Overall variations in the microbial populations of sorghum seemed causal to the difference in starch and NSP recoveries. Phytate was assessed based on release of total phosphorus in the samples by enzymatic and chemical methods. Recovery of phytate in the naturally fermented ogi ranged from 18-25% in maize and 40-48% in sorghum suggesting greater phytase activity and more nutrient bioavailability in maize ogi than in the sorghum. Greater activity in maize reflects the presence of phytate hydrolysing species such as Aspergillus in the grain. Total phenolic content (TPC) was assessed by Folin-Ciocalteu colorimetric method after direct extraction of samples by saponification. TPC in the original grains ranged from 410–437 mg GAE/100g in maize and 221–247 mg GAE/100g in sorghum. Due to the nutritional significance, the amount of phenolics that are either freely soluble or are covalently bound to the food matrix were assessed. Soluble phenolics in ogi ranged from 16-38% in maize and 32-49% in sorghum based on the total soluble fraction in the original grain. In all cases loss of soluble phenolics with the waste waters accounted for 12-25% and 31-39% with the pomace. Only the LAB population seemed to correlate with the release of phenolics in the natural fermentation. Given the higher value of soluble phenolics, naturally fermented sorghum ogi appeared to have higher antioxidant potential than the maize ogi. Furthermore an attempt was made to ascertain whether the use of selected microbes would improve the antioxidant properties and aroma of ogi while minimizing the incidence of pathogens due to chance inoculation. Thus the impact of selected LAB (Pediococcus pentosaceus) and fungi (T. hirsuta and A. zeae previously shown to have phytase activity) on changes in phytate, phenolics and aroma of ogi was assessed following a parallel experiment to the previous study but using autoclaved grains. Five fermentation treatments of the pure and co-cultures were investigated. Cell populations in all culture fermentations varied and reached the average maximum of log 6-9 cfu/ml. Changes in the distribution of bound and soluble phenolics were observed showing esterase activity. Leaching of phenolics was evident in all cases but was higher in the sorghum fermentations. Higher levels of soluble phenolics were recovered in pure culture fermented ogi using T. hirsuta or P. pentosaceus than in the natural fermentation having 76% and 45% of the original soluble fraction in maize and sorghum respectively. This suggests greater antioxidant potentials than the naturally fermented ogi. Pure culture fermentations using T. hirsuta and co-culture of P. pentosaceus with A. zeae reduced phytate by 97% and 96% in maize and sorghum ogi respectively showing greater phytase activity and more nutrient bioavailabilty in the ogi than in the natural fermentation. The aroma profile of ogi was analysed by solid-phase microextraction and gas chromatography-mass spectrophotometry (SPME GC-MS). Ethyl acetate, butyl acetate and ethyl hexanoate were observed as the key active aroma components in ogi. The ester, methyl thiobutanoate was found to be unique to the naturally fermented ogi suggesting that it may have been generated by species other than the selected starter organisms. Overall in both natural and starter culture fermentations, maize ogi showed high relative abundance of volatile components suggesting good substrate compatibility and utilization during fermentation. Thus compounds with high threshold values may be significant in the aroma notes of maize ogi. P. pentosaceus and T. hirsuta in pure and in co-culture fermentations produced ogi with aroma notes mostly related to the naturally fermented product. In conclusion the diversity and levels of the initial microflora and the structural composition of grain could be major factors contributing to the nutritional compositional changes in ogi fermentation.

There is demand from the food industry for novel savoury seasonings based on low-cost food ingredients, sourced from within the EU. A nucleotide and protein rich spray dried powder which was derived from a Fusarium venenatum fermenter waste stream and food-grade Alphitobius diaperinus with potential as a savoury flavour enhancer was evaluated. Enzymatic digestion of these two raw materials as a source of flavour precursors was evaluated. Serial enzyme combinations, enzyme dosages, sequence of enzyme application, pH, temperature and length of digestion for the liberation of amino acids and nucleotides were optimised for the liberation of taste active compounds. For amino acids, free glutamine (GLN) and glutamic acid (GLU) could be enhanced using a combination of peptidases on both raw materials. Digesting a spray dried powder derived from the fermenter waste stream of Fusarium venenatum with exopeptidase (1% Flavourzyme TM), resulted in an improved yield of GLN (from 0.1 mg/g to 28.9 mg/g powder) and GLU (from 1.71 mg/g to 5.98 mg/g powder). For milled Alphitobius diaperinus, mixed use of exopeptidase (1% Flavourzyme TM) and endopeptidase (2% Alcalase 1.4-fold increased yield of GLU (17.5 mg/g powder) and 1.7-fold increased yield of GLN (1.2 mg/g) as best production was obtained. For nucleotides, digestions of the waste stream with a yeast lytic enzyme (YL-TLTM) followed by a nuclease (RP-1GTM) resulted in the highest 5’-guanosine monophosphate (GMP) and 5’-adenosine monophosphate (AMP) production. Specifically, a 2% and 0.05% treatment by YL-TLTM and RP-1GTM respectively was shown to be optimal, followed by a 0.05% DeamizymeTM treatment for the conversion of AMP to 5’-Inosinic acid (IMP) of 38 mg/g. For the solid digestion of Alphitobius diaperinus, being treated with a nuclease tretment (2% RP-1GTM) followed by a 0.2% DeamizymeTM treatment for the conversion of AMP to IMP, resulted in the highest GMP yield, a 3.5-fold increased (2.6mg/g), and 7.8-fold increased IMP (4.7mg/g) production.