Comparing liquid homogeneous and multilayer phantoms for human body implantable antennas

We compare the performance of a ultrawideband implantable antenna when immersed in a liquid homogeneous phantom and in a multilayer phantom. The goal is to assess how good the simple liquid phantom is to represent the real body over a broad bandwidth. We evaluate not only the frequency-domain parameters – input reflection (s11) and transmission coefficients (s21) – but also the performance of the antenna in the time domain – pulse fidelity and window containing 90% of the pulse energy. The results show a good resemblance between both phantom results, suggesting that liquid homogeneous phantoms may be enough to test the performance of this type of antennas and potentially simplify the measurement setup.info:eu-repo/semantics/acceptedVersio

Products and Applications of Biopolymers

It is interesting to consider that biopolymers are by no means new to this world. It is only because of our fascination with petrochemical products that these wonderful materials have been neglected for so long. Today we face a different challenge. Environmental pressure is pushing away from synthetic or petro-chemically derived products, while economic factors are pulling back from often more expensive "green" options. This book presents two aspects of biopolymers; potential products and some applications of biopolymers covering the current relevance of biopolymers

Utilization Of Electrospun Nanofibers Containing Gelatin Or Gelatin-cellulose Acetate For Preventing Syneresis In Tomato Ketchup

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2014Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2014Nanoteknoloji, nano düzeyde yürütülen bilim, mühendislik ve teknolojiler olarak tanımlanabilir. Nanoteknoloji uygulamaları şu ana kadar çok etkileşimde olmayan birçok mühendisliği biraraya getirmiştir. Diğer alanlardaki çok çeşitli uygulamaları yanında, nanobilim gıda ve gıda ile ilişkili ürünlerde de kullanılmaya başlamıştır. Bu uygulamaların kaynağından gıdaların makroskopik ölçekteki özelliklerinin mikroskopik yapısından kaynaklanması ve bunun reoloji gibi diğer özellikleri etkilemesi gelmektedir. Diğer alanlara kıyasla nanoteknolojinin gıdalarda uygulamaları sınırlı kalmıştır. Bunun başlıca nedenleri arasında gıdaların etiketlenmesi ve tüketici sağlığı konusunda bazı endişelerin bulunması sayılabilir. Nanoteknoloji ile atomik düzeyde tasarım yapılabiliyor olması çığır açarak standart operasyon koşullarını etkilemektedir. Gıda ve tarım alanındaki uygulamaları diğer uygulamalara nispeten yenidir. Yine de, özellikle son iki yıl içinde, bu yeni teknolojinin gıdalarda nasıl kullanılıp avantaj sağlanabileceği ile ilgili çalışmalar yapılmaktadır. Nanoteknoloji uygulamalarında kullanılan nanoyapılar üçe ayrılmaktadır: nanopartiküller, nanotüpler ve nanolifler. Nanolifler çapı 100 nm civarındaki lifler olarak tanımlanmaktadır. Nanolifler, özellikle organik nanolifler, tek boyutlu nanomateryallerin ilginç bir bileşenidir. Nanolif elde etmek için çeşitli teknikler kullanılmaktadır. Elektrodöndürme yöntemi ile, elektrostatik kuvvetlerle polimer çözeltisinden veya eriyiğinden ince çaplı (mikrometreden nanometreye kadar) ve yüzey alanı geniş lifler elde edilmektedir. Elektrodöndürme işlemini etkileyen faktörler arasında besleme çözeltisinin özellikleri (konsantrasyon, viskozite, elektriksel iletkenlik, yüzey gerilimi ve dielektrik özellikler), işlem parametreleri (elektriksel alan kuvveti, besleme hızı ve toplayıcı plaka mesafesi) ve nem ve sıcaklık gibi çevresel faktörler bulunmaktadır. Domates ketçabı, konsantre, püre veya domates salçasından veya domatesten soğuk veya sıcak ekstraksiyon işlemi ile üretilen baharatlı ve heterojen bir gıda ürünüdür. Domates salçası ve domates ketçabı sulu ortamda çözünmeyen maddelerin büyük konsantrasyonda bulunduğu dispersiyonlardır. Ketçap viskozitesini, yapısında doğal olarak bulunan pektik maddeler oluşturur. Bu ürünün reolojik özellikleri hazırlık, depolama, işleme ve taşıma sırasında önemlidir. Ketçap yapısal olarak ikiye ayrılabilir: kıvamlı şurup ve domates lifi. Bu iki kısmın oranı ve şurubun karakteristikleri, ketçabın kıvamını etkilemektedir. Ketçabın yapısı veya kıvamı, sıvı kısmın viskozitesine ve mevcut bulunan çözünmeyen domates lifinin miktarına bağlıdır. Viskozite, ketçabın işlenmesi sırasında ekonomik olarak da önemli bir parametredir. Çünkü ürün verimini ve kalitesini etkiler. Bu nedenle ketçaba, şurup kısmının viskozitesini arttıracak, daha kıvamlı bir ürün oluşturacak ve sineresisi azaltacak kıvam vericiler ilave edilmektedir. Serum ayrılması veya sineresis, geleneksel olarak işlenen domates ürünlerinde rastlanan önemli bir problemdir. Hem ürün kalitesini hem de tüketici beğenisini olumsuz etkilemektedir. Bunun için kullanılan hidrokolloidler, hem viskoziteyi arttırır hem de serum ayrılmasını azaltır. Hidrokolloidler, suda disperse olduklarında kıvamlı dispersiyonlar veya jel oluşturan yapılarıyla karakterize edilen uzun zincirli polimerlerden (polisakkaritler ve proteinler) meydana gelmiş heterojen yapıya sahip maddelerdir. Çok sayıda hidroksil gruplarının bulunması, bu maddelerin su moleküllerine bağlanmasını arttırarak hidrofilik olmalarını sağlamaktadır. Bunların oluşturdukları dispersiyonlar, gerçek çözelti ve süspansiyon arasında, kolloid özelliği göstermektedir. Bu nedenlerden dolayı bu maddeler “hidrofilik kolloidler” veya “hidrokolloidler” olarak adlandırılmaktadır. Jelatin, kolajenden elde edilen ve özellikleri kolajene benzeyen doğal bir biyopolimerdir. Jelatin ucuz olması bakımından da özel bir öneme sahiptir. Çeşitli işlemlerden geçirilerek veya diğer polimerlerle karıştırılarak jelatinden nanolif elde edilebilmektedir. Selüloz asetat, sülfirik asit varlığında selülozun asetik anhidrit ve asetik asitle reaksiyonu sonucunda elde edilen selülozun asetatıdır. Asetik asit, selüloz asetat için mükemmel bir çözeltidir. Selüloz asetat birçok uygulamada kullanılmaktadır. Bu tez çalışmasında elektodöndürme yöntemiyle elde edilen jelatin ve jelatin-selüloz asetat nanolifleri ketçapta sineresis önlemek için kullanılmıştır. Besleme çözeltisi olarak kullanılan jelatin çözeltilerinin konsantrasyonu arttıkça elektriksel iletkenlikleri de artmıştır. Buna karşın, yüzey gerilim değerleri azalmıştır. %7’lik jelatin çözeltisinden nanolif elde edilememiştir. Bunu nedeni ortamda yetersiz madde olması ve buna bağlı olarak yüzey geriliminin fazla ve viskozitesnin düşük olmasıdır. SEM fotoğraflarından %20’lik jelatin çözeltisinden nanolif elde edilebildiği görülmüştür. Buna ilaveten bu konsantrasyonda bütün etkili parametreler değiştirilse bile nanolif elde edilebildiği belirlenmiştir. Elde edilen nanolifler, uygulanan voltaj arttıkça daha düzgün yapıda, boncuksuz ve homojen olmuşlardır. Jelatin ve jelatin-selüloz asetat içeren nanoliflerin bulunduğu dispersiyonların zeta potansiyelleri ölçülmüştür. Sonuçlara göre, jelatin-selüloz asetat nanolifleri dispersiyonda daha stabildirler. Nanolif içeren dispersiyonların difüzyon katsayıları karşılaştırıldığında jelatin-selüloz asetatlı örneğin difüzyon kabiliyetinin daha fazla olduğu belirlenmiştir. Laboratuvarda hazırlanan ketçaplara % 0,25 ve % 0,5 oranında jelatin nanolifi, %0,5 oranında jelatin-selüloz asetat nanolifi ilave edilmiştir. Bu örnekler iki farklı sıcaklıkta (4 ve 25 oC’de) bir ay depolanmıştır. Örneklerde her hafta sineresis ve reoloji ölçümü yapılmıştır. Sonuçlara göre, en az sineresis görülen örnek jelatin-selüloz asetat nanolif içeren örnektir. Sineresisin, düşük sıcaklıkta yüksek sıcaklığa göre daha az belirlenmiştir. Reolojik ölçüm sonuçlarına göre, nanolif içermeyen ketçap örneklerinin n değerlerinin büyük olduğu belirlenmiştir. Ancak bütün örneklerin n değerleri 1’den küçük olduğu için hepsi psödoplastiktir. Nanolif ilavesi ketçap örneklerinin kıvam indekslerinde artışa neden olmuştur. En yüksek artış, jelatin-selüloz asetat içeren örneklerde görülmüştür. Bu çalışmada, ketçap örneklerinin sineresisi ve kıvamlarının, nanolif ilavesiyle değiştiği tespit edilmiştir. Az miktarda bir nanolif ilavesinin ketçap örneklerinin kıvamını arttırıp sineresis azalttığı belirlenmiştir. En iyi sonuç jelatin-selüloz asetat içeren ve düşük sıcaklıkta depolanan örneklerde tespit edilmiştir. Nanoliflerin ketçaplarda sineresisi önleyici ve kıvam arttırıcı olarak kullanılabileceği sonucu gıda endüstrisi bakımından önemli bir bulgudur.Nanotechnology is science, engineering, and technology conducted at the nanoscale. Nanotechnology applications located in the center of various engineering branches, it also brings many scientists together doesn’t interact so far. In addition to applications in general areas, nanoscience is also inspiring science in the fields of food and food related products. It roots from the concepts that this technology provides a sound framework for developing an understanding of the interactions and assembly behavior of food components into microstructure, which influence food structure, rheology and functional properties at the macroscopic scale. Comparing to other areas, applications of nanotechnology in foods has been limited. The main reasons for the late incorporation of food into the nanotechnology sector are issues associated with the possible labeling of the food products and consumer-health aspects. The ability to design at atomic level nanotechnology creating a new world and deeply affects standardized operating procedures. Their applications to the agriculture and food sector are relatively recent compared with their use in other areas. Nevertheless, in the last two years, the world has entered into the search for ways to take advantage of this technology in the food industry. Nanostructures used in nanotechnology applications divided into three groups including nanoparticles, nanotubes and nanofibers. Nanofibers are defined as fibers with diameters on the order of 100 nanometers. Nanofibers especially organic nanofibers constitute a particularly interesting and versatile class of one dimensional nanomaterial. There are some different techniques to produce nanofiber. Electrospinning, a spinning technique, is a unique approach using electrostatic forces to produce fine fibers from polymer solutions or melts and the fibers thus produced have a thinner diameter (from nanometer to micrometer) and a larger surface area than those obtained from conventional spinning processes. Some properties related to solution (e.g., concentration, viscosity, electrical conductivity, surface tension, and dielectric properties), governing variables (e.g. electrical field strength, fluid flow rate, and distance to the collector plate) and ambient parameters such as humidity and temperature, can affect electrospinning process. Tomato ketchup is a heterogeneous, spiced product, produced basically from either cold or hot extracted tomatoes; or directly from concentrates, purees or tomato paste. Many foods of commercial importance, such as tomato paste and tomato ketchup, are concentrated dispersions of insoluble matter in aqueous media. Tomato ketchup obtains its viscosity from naturally occurring pectic substances in fruits. Their rheological behavior is important during handling, storage, processing and transport of concentrated suspensions in industry. Ketchup consists of two parts: a thick syrup and tomato fiber. The proportion of these two components and the characteristics of the syrup are the principal factors that determine the consistency of ketchup. The thickness or body of ketchup is largely determined by the viscosity of the liquid and the proportion of insoluble tomato fiber present. Viscosity has economic implications for tomato ketchup processors because it largely determines processing yields and product quality. For this reason, different thickeners are used to increase the viscosity of the syrup, yielding more consistent products and minimizing the phenomenon of syneresis. Serum separation or syneresis is one of the most important problems in conventionally processed tomato products and it affects both product quality and hence consumer acceptability negatively. Hydrocolloids increased the viscosity and reduced the serum loss of tomato ketchups. Hydrocolloids are a heterogeneous group of long chain polymers (polysaccharides and proteins) characterized by their property of forming viscous dispersions and/or gels when dispersed in water. Presence of a large number of hydroxyl (-OH) groups markedly increases their affinity for binding water molecules rendering them hydrophilic compounds. Further, they produce a dispersion, which is intermediate between a true solution and a suspension, and exhibits the properties of a colloid. Considering these properties, they are aptly termed as ‘hydrophilic colloids’ or ‘hydrocolloids’. Gelatin is a natural biopolymer made from collagens and has biological features as the collagens. It is an aqueous polymer. Gelatin does have a significant value that it is a low price biopolymer. By some post treatment method or combine with another polymer, gelatin can be used alone or as a blend component to prepare nanofiber. Cellulose acetate is important ester of cellulose, which can be obtained by reaction of cellulose with acetic anhydride and acetic acid in the presence of sulfuric acid. Acetic acid is in usually an excellent solvent for cellulose acetates with degree of acetyl substitution (DS) greater than 0.8. According to its processing, cellulose acetate can be utilized for various applications. In this study it was investigated using gelatin and gelatin-cellulose acetate nanofibers obtained by electrospinning technique to prevent syneresis in tomato ketchup. First process factors affecting the morphology and diameter of gelatin and gelatin-cellulose acetate nanofibers was investigated. The electrical conductivity of gelatin solutions increased with gelatin concentration. In contrast electrical conductivity results, surface tensions decreased with gelatin concentration. In this study, the gelatin solution at low concentration of 7% did not produce nanofibers, due to insufficient entanglements and high surface tension. Instead, the mixtures of drops and some fibrous structures were seen, and this is due to the viscosity of the solution being too low to generate continuous fibers. SEM images revealed that nanofibers could be obtained from the gelatin solution at 20%. In addition, nanofiber formations under all electrospinning process conditions can be obtained at that concentration, meaning the amount of gelatin in the solution at 20% was enough to form nanofibers. It should also be noted that nanofibers became less branching, without bead and more homogenous as applied voltage increased. The zeta potential values of dispersions with electrospun nanofibers from the gelatin solution at 20% , were higher than values for dispersions with electrospun nanofibers from the gelatin solution at 7%. However the zeta potential of dispersions with electrospun nanofibers from the gelatin-cellulose acetate solution was the highest one, 20.78 mV. For keeping a suspension in a stable or in a dispersed state the zeta potential values should be above +25 mV or below -25mV. Accordingly the closer value to the +25 mV belonged to the sample obtained from gelatin-cellulose acetate, meaning these nanofibers may suspend in a dispersed state longer comparing to the other nanofiber samples. The diffusion coefficient value of dispersion containing electrospun nanofibers from the gelatin solution at 20% was higher than the sample containing nanofibers from the gelatin solution at 7%. However the diffusion coefficient of dispersions with electrospun nanofibers from the gelatin-cellulose acetate solution was the highest one. Accordingly, higher diffusion coefficient means higher mobility of the polymer in the suspension. It was determined that the sample obtained from gelatin-cellulose acetate, had the highest diffusion coefficient (1.81 &#956;m2/s), and probably the highest mobility comparing to the other electrospun samples. After preparing the ketchup samples, different two concentrations of gelatin nanofiber (0.25% and 0.5%) and gelatin- cellulose acetate nanofiber (0.5%) added to ketchup samples and stored at different two temperatures (4°C and 25°C) for one month. After each week the syneresis and rheological measurements were done. The results showed that the ketchup samples including gelatin-cellulose acetate nanofiber provided the least amount of syneresis. Moreover, syneresis values of all samples that kept at 4°C were less than samples with the same concentration nanofiber that stored at 25°C. According to the rheological characterizations n values of ketchup samples without any nanofiber was the highest, however the n value of all samples was n<1, which means all samples are pseudoplastic. In addition, according to the rheological measurements it was obvious that the addition of electrospun nanofibers led to a dramatic increase in the consistency index of the tomato ketchups. It is well known that the higher the total solids the better will be the quality of the end product. The highest amount of consistency index was for ketchup samples with gelatin cellulose acetate electrospun nanofiber. In this study syneresis and consistency are factors that affected by adding electrospun nanofiber to ketchup samples. Little amount of electrospun nanofiber increase the consistency and, as a result, decrease the syneresis of tomato ketchup samples. According to the comparisons it was concluded that ketchup samples including gelatin-cellulose acetate nanofiber are more stable at 4oC. This study provided valuable information about the potential application of nanofibers as thickener in tomato ketchup.Yüksek LisansM.Sc

Chapter 34 - Biocompatibility of nanocellulose: Emerging biomedical applications

Nanocellulose already proved to be a highly relevant material for biomedical applications, ensued by its outstanding mechanical properties and, more importantly, its biocompatibility. Nevertheless, despite their previous intensive research, a notable number of emerging applications are still being developed. Interestingly, this drive is not solely based on the nanocellulose features, but also heavily dependent on sustainability. The three core nanocelluloses encompass cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and bacterial nanocellulose (BNC). All these different types of nanocellulose display highly interesting biomedical properties per se, after modification and when used in composite formulations. Novel applications that use nanocellulose includewell-known areas, namely, wound dressings, implants, indwelling medical devices, scaffolds, and novel printed scaffolds. Their cytotoxicity and biocompatibility using recent methodologies are thoroughly analyzed to reinforce their near future applicability. By analyzing the pristine core nanocellulose, none display cytotoxicity. However, CNF has the highest potential to fail long-term biocompatibility since it tends to trigger inflammation. On the other hand, neverdried BNC displays a remarkable biocompatibility. Despite this, all nanocelluloses clearly represent a flag bearer of future superior biomaterials, being elite materials in the urgent replacement of our petrochemical dependence

Index to NASA Tech Briefs, 1972

Abstracts of 1972 NASA Tech Briefs are presented. Four indexes are included: subject, personal author, originating center, and Tech Brief number

Mechanical properties of short doughs and their corresponding biscuits

The mechanical properties of short doughs of various composition were determined in small amplitude oscillatory experiments and in uniaxial compression. Regardless of composition, the linear region was very limited; beyond that, pronounced yielding and flow occurred. Conductimetry was also used to evaluate the effect of fat type and fat content on dough structure. Short doughs showed large differences in mechanical spectra, conductivity and apparent biaxial extensional viscosity, according to fat and sucrose contents, fat type and mixing time. It is concluded that short doughs are bicontinuous systems; reducing the fat content or changing the rheological properties of the fat relative to those of the non-fat phase results in fat-dispersed systems. The rheological properties of the non-fat phase are largely determined by intact flour particles present in a concentrated sucrose syrup. Sucrose delays, if not inhibits, gluten development through its effect on solvent quality and facilitates formation of a non-fat continuous phase via its effect on solvent quantity. Mixing promotes formation of a continuous fat phase.Mechanical properties of short-dough biscuits of various composition were determined in three-point bending tests. Increasing fat content or omitting sucrose from the recipe decreased the modulus and the fracture stress of the biscuits. The effect of fat content, however, was dependent on fat type. Temperature during dough preparation, dough water content and temperature during bending tests affected the mechanical properties of biscuits to an extent which depended on fat content. Diffusion of Sudan III into the biscuits indicated that low-fat biscuits are fat-dispersed systems and high-fat biscuits are bicontinuous. Differential scanning calorimetry showed that, irrespective of composition, starch gelatinisation was slight, if not absent, presumably due to the limited water content coupled with the low baking temperature. Under certain storage conditions, biscuits are in a glassy state. Upon water uptake, the matrix undergoes a glass-rubber transition. It is concluded that the mechanical properties of biscuits are mainly determined by air volume fraction, fat continuity, size of inhomogeneities, and physical state of the non-fat phase

Redesign of collagen casings for high quality performance using food grade polysaccharides

Collagen film (casings) obtained from acid-swollen collagen fibres is widely used as an alternative to natural casings for sausage production. However, collagen casings possess weak properties such as low mechanical properties (tensile strength and stiffness) and thermal stability compared to natural casings. Therefore, there is a need industrially to improve these properties. The main purpose of this work was to study the effects of polysaccharides on the properties of acid-swollen collagen pastes and films as a function of collagen paste concentrations (2.5 %, 3.5 % and 4 %wt/wt). In this work, polysaccharides dispersions: cellulose fibres of different length and waxy (WS) and high amylose (HAS) maize starch granules and molecular solutions: Hydroxypropylmethylcellulose (HPMC), Methylcellulose (MC), high molecular weight (GH), low molecular weight guar gum (GM) and Carboxymethylcellulose (CMC) were blended with acid-swollen collagen paste to fabricate collagen films with improved properties such as mechanical properties (tensile strength, stiffness and flexibility) and thermal stability. The viscoelastic of the blend pastes and denaturation of collagen was studied by rheological and thermal techniques. The pure and composite films were studied by sorption, mechanical, spectroscopic, structural, and thermal techniques. The focus of the first part of this study is to investigate the effect of uncharged and negatively charged molecular solutions at comparable low-shear viscosity on the viscoelastic and thermal properties of acid-swollen collagen paste. Dynamic rheological data indicated that the addition of non-charged hydrocolloids: HPMC, MC, GH and GM increased the storage modulus (G’) and loss modulus (G’’) of the acid-swollen collagen paste. By contrast, negatively charged CMC decreased the G’ and G” of the collagen pastes. At the level of addition of non-charged solutions (HPMC, MC, GH and GM) considered in this study, the denaturation temperature of collagen as determined by DSC was not affected while negatively charged CMC increased the denaturation temperature. Composite films containing blends of collagen paste with the individual molecular solutions were formed. Films were characterised for their mechanical, thermal, sorption and structural properties. Collagen/CMC films were not tested due to the difficulty in analysing the films. The thickness of the films increased and was dependent on the collagen concentration as well as the hydrocolloid concentration in the film network. Mechanical data revealed that the addition of hydrocolloids increased the tensile strength (TS), stiffness (YM), and elongation at break (EAB) of the films. Derivatised cellulose showed higher enhancement than the guars. Consistent with the mechanical data, DSC revealed an increase in peak temperature and a decrease in enthalpy of the films with the addition of the polymers. An increase in TS, YM, and EAB and an increase in peak temperatures were dependent on the collagen concentration. XRD data of the composite film showed a reduction in the intensity of the crystalline peak of collagen. FTIR spectra of the films helped to understand the structural changes and the interaction between the collagen and hydrocolloids. The thermal degradation temperature of collagen was not affected, as evidenced by the TGA curves. Furthermore, the composite films showed lower moisture uptake than the pure collagen films. The next study focused on investigating the effect of polysaccharide dispersions, cellulose with different fibre length, waxy and high amylose maize starches at comparable dispersed phase volume on the rheological and thermal properties of acid-swollen collagen paste. The dynamic rheological measurement revealed the dominant elastic behaviour (G’ > G’’) of the blend and control pastes. Cellulose fibres, waxy and high amylose starch granules increased the storage and loss modulus, and values increased with increasing collagen content. The starches exhibited a higher value due to the high concentration used. According to the DSC data, the denaturation of collagen and enthalpy of melting was not affected by the addition of the dispersions. On the other hand, on reheating the blend pastes, the starches lowered the enthalpy of the denatured collagen. Films were made from the blend pastes and were characterised for their mechanical, thermal, sorption and structural properties. The surface of composite films appeared rough because of the protrusion of the cellulose fibres and starch granules. The thickness of the films increased with the addition of the cellulose fibres and starch granules. Values increased with increasing levels of collagen and dispersions concentration in the film-forming paste. Reinforcing collagen films with cellulose fibres increased the mechanical properties (TS, YM and EAB) of the films. The mechanical properties of collagen with starch granules films could not be tested due to the brittleness of the films. DSC data showed that cellulose fibres increased the peak temperature of the films. By contrast, starch granules decreased the peak temperature. The enthalpy of the films was significantly reduced with the addition of cellulose fibres and starch granules. Collagen with starch granules films had the lowest enthalpy values. XRD data showed a decrease in the intensity of the crystalline peak of collagen in the blend films. The thermal stability of collagen was reduced, as evidenced by the TGA data. Additionally, the water uptake of the films decreased with the addition of cellulose fibres and starch granules. For the final study, the effect of collagen pastes (2.5%, 3.5% and 4 % wt) on the pasting properties of waxy (WS), high amylose (HAS) and normal (NS) maize starches were studied using Rapid Viscous Analyser (RVA) at conventional (up to 95 °C) and high-temperature (up to 140 °C) heating modes. Results showed that collagen pastes modified the pasting properties of the starches. At conventional heating mode, high amylose did not show a noticeable pasting profile. The pasting temperature of waxy starch was unaffected by the addition of collagen paste. By contrast, the addition of collagen paste lowered the pasting temperature of normal starches. The viscosities (peak, setback, and breakdown) of NS and WS increased. The final viscosity of WS decreased while that of NS increased with the increase in collagen paste concentration. When the samples are heated to temperatures 140 °C higher, HAS showed a noticeable pasting profile. The pasting temperature of HAS decreased with increasing levels of collagen paste addition. Peak and breakdown viscosities of NS, WS, and HAS increased with increasing collagen paste levels. In contrast, setback and final viscosities reduced

Bio-Inspired Materials for Electrochemical Sensors

Electrochemical biosensors are a rapidly growing research area that has greatly improved its specificity, accuracy, and precision in the detection of biomolecules in contemporary literature and industry alike. Typically, these systems exist in a three-electrode conformation with a working electrode functioning as the anode, a counter electrode functioning as the cathode, and a reference electrode allowing for the control of potential in the system. The method by which these sensors work is through the sharing of electrons via redox reactions with the target molecule and the working electrode or modifications on its surface. By exploiting the function of biomaterials that participate in natural substrate-binding redox phenomena, new opportunities for detecting critical molecules in complex situations can be created. In this dissertation, three distinct electrochemical biosensors were created by mimicking natural phenomena and implementing materials that directly or indirectly participate in the corresponding reactions. First, a dopamine sensor was created via a composite of lignin-derived graphene oxide and the marine algae-derived polysaccharide kappa carrageenan. Different ratios of GO, a known electrooxidizing catalyst of dopamine, with kappa carrageenan were used to create a binder-free film for dropcasting on the working electrode. It was designed on the principle of its interactions with the nervous system when injected in rats to induce analgesia, interfering with standard dopamine behavior. The system demonstrated a linear range of 1 - 250 μmol L-1 and a limit of detection of 0.14 μmol L-1 (s/n=3). In the second chapter, a sensor for the human and animal health hazard nitrite was constructed using the transition metal sulfide NiS. Transition metal sulfides are the catalytic center for nitrite oxidation to nitrate in nitrogen fixing bacteria found in the environment. This section utilized a novel electrodeposition method for creating a binderfree layer of NiS on the surface of the glassy carbon electrode. This system demonstrated a linear range of 0.04 – 1 μM, 1 – 5.3 μM and a detection limit of 0.01 μM. For the final chapter, a novel sensor was created for the cryoprotective sugar trehalose, an indicator of bacterial contamination in meat and produce without any electrochemical assay precedent. This system utilized the interactions found between alkali earth metal ions and trehalose in which the two molecules form complexes. Magnesium phthalocyanine, which is a commercially available dye, as well as synthesized magnesium tetraphenylporphyrin and calcium tetraphenylporphyrin were implemented as drop-casted coatings on the working electrode to electrodeposit trehalose on the surface and detect its oxidation via squarewave anodic stripping voltammetry in the complex media Luria-Bertani broth. The system was also used to gauge fluctuations in E. coli in broth by autoclaving the cultures and directly testing the media containing lysed bacteria. The system demonstrated a linear range of 0.25 mM – 100 mM, with magnesium mesotetraphenylporphyrin exhibiting the highest repeatability

Self-structuring foods based on acid-sensitive gellan gum systems to impact on satiety

A novel approach that may impact on satiety, whilst meeting the demands of consumers, is the use of hydrocolloids that respond to the environment (acidic) conditions inside the human stomach by self-structuring. This thesis seeks to investigate the in vitro acid-induced gelation (“structuring”) of the mixed biopolymer systems; low-acyl and high-acyl gellan gum, and low-acyl gellan fluid gels. To explore this concept, a variety of acid structures were obtained, which were characterised by texture analysis, rheology and dynamic scanning calorimetry. The gel structures were found to rely on the pH, hydrocolloid concentration, percentage weight of each hydrocolloid used and the processing conditions used during their production. It is suggested that the use of gel alone is more than capable of providing prolonged satiety but leads to unpleasant sensations for the consumer if there is no delivery of energy to the body to compliment the sensation of satiety. Materials should be included that will modulate the energy delivery and slowly release calories over time. This research shows that the addition of co-solutes such as sugar and the measurement of their subsequent release from hydrocolloid gels could provide a first step to tackling these issues

Effect of curing conditions and harvesting stage of maturity on Ethiopian onion bulb drying properties

The study was conducted to investigate the impact of curing conditions and harvesting stageson the drying quality of onion bulbs. The onion bulbs (Bombay Red cultivar) were harvested at three harvesting stages (early, optimum, and late maturity) and cured at three different temperatures (30, 40 and 50 oC) and relative humidity (30, 50 and 70%). The results revealed that curing temperature, RH, and maturity stage had significant effects on all measuredattributesexcept total soluble solids