Yrjö Roos
University College Cork, Food and Nutritional Sciences, Faculty Member
Abstract The present study investigated structural relaxations of spray dried emulsions with trehalose-maltodextrin (M100), trehalose-maltodextrin (M250), and trehalose-WPI mixtures as wall materials at different aw and wall materials... more
Abstract The present study investigated structural relaxations of spray dried emulsions with trehalose-maltodextrin (M100), trehalose-maltodextrin (M250), and trehalose-WPI mixtures as wall materials at different aw and wall materials properties on carotenoids degradation. The exponential decrease in structural relaxation times (τ) above the Tg was described using strength of the solids (S). S generally decreased with increasing aw and was affected by the wall materials with carbohydrate-carbohydrate mixtures exhibiting higher S and lower carotenoids degradation rates. Non-Arrhenian temperature dependence of carotenoids degradation was attributed to increased S due to collapse above the Tg. Carotenoids degradation was not only described by S but also by layer-by-layer (LBL) interfacial structure. Single layer and LBL systems with the same wall materials had corresponding S but carotenoids degradation was slower in LBL systems. The use of S allows stability and quality control of food materials during processing and storage, and to estimate degradation of encapsulated bioactives.
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The objective of the present study was to investigate flocculation in layer-by-layer (LBL) emulsion systems with high total solids content and deflocculation at various pH conditions, and the effects of whey protein isolate (WPI)... more
The objective of the present study was to investigate flocculation in layer-by-layer (LBL) emulsion systems with high total solids content and deflocculation at various pH conditions, and the effects of whey protein isolate (WPI) concentration and total solids content on the stability of LBL emulsions. WPI (1.96% (1WPI) or 10.71% (10WPI), w/w in water) was prepared in water and high-pressure homogenized with sunflower oil (10%, w/w, of total emulsion). Gum Arabic (0.15%, w/w, in total emulsion) was added to assemble electrostatically on WPI at oil particle interfaces at pH3.5 using aqueous citric acid (10% w/w) forming LBL emulsion. The ζ-potential measurements showed charge reversal upon addition of gum Arabic solution into single layer (SL) emulsion confirming the formation of LBL interface. Trehalose:maltodextrin mixture (1:1, w/w, total emulsion, 28.57% (28) or 57.14% (57), w/w, in water) was used in the continuous phase. The high total solids content of the system results in depletion flocculation of the particles leading to bridging flocculation without coalescence as deflocculation into individual particles occurred with increasing pH from pH3.5 to pH6.5 in 10WPI systems. Deflocculation was evident in 10WPI-28 and 10WPI-57 as found from a decreased ζ-average diameter and visually under microscope. Coalescence was observed in 1WPI systems. Viscosity of the systems was significantly (P<0.05) increased with higher total solids content. Accelerated destabilization test showed that systems at higher WPI and total solids contents exhibited the highest stability against creaming. Deflocculation in LBL systems can be controlled by pH while high solids in the aqueous phase provide stability against creaming.
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Abstract Objectives of the present study were to spray dry high total solids content single layer (SL) and layer-by-layer (LBL) emulsions, and to compare the ability of the SL and LBL powders in preventing the loss of carotenoids upon... more
Abstract Objectives of the present study were to spray dry high total solids content single layer (SL) and layer-by-layer (LBL) emulsions, and to compare the ability of the SL and LBL powders in preventing the loss of carotenoids upon storage in the vicinity of the glass transition temperature (T g ). Carotenoids stability in humidified spray dried (HSD), non-humidified freeze-dried (NHFD), and humidified freeze-dried (HFD) systems were determined as well. The loss of carotenoids followed first order loss kinetics. An initial rapid followed by a second slower first order loss kinetics was observed in the non-humidified spray dried (NHSD) systems. Storage of systems above the T g delayed carotenoids losses based on the rate constants. The loss of carotenoids in LBL systems was more heat sensitive as the activation energies were generally higher. Activation energy decreased above T g indicating that the loss of carotenoids became less temperature dependent. The application of LBL interface structure reduced the rate of carotenoids losses and can be applied to prevent loss of oil soluble bioactives in formulated materials.
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Mechanical properties of food are important to their behavior in four areas—processing, storage, distribution, and consumption. Several compositional factors and processing parameters affect mechanical properties of foods. The overall... more
Mechanical properties of food are important to their behavior in four areas—processing, storage, distribution, and consumption. Several compositional factors and processing parameters affect mechanical properties of foods. The overall mechanical properties may be defined by cell structure, typical of vegetables and fruits. It may also result from the physical state, flow properties, or porosity. The focus in this chapter is on the mechanical properties related to phase transitions that occur in the nonequilibrium state of non-fat food solids and their time dependent characteristics. Changes in mechanical properties have been observed to occur as a function of temperature, water activity, and water content. Studies have suggested that temperature, diluents content, and time have equal effect on the modulus that can be superimposed with any of the variables. The effects of stiffness, mechanical properties, and crystallinity are discussed in the chapter. The mechanical properties of frozen food materials are affected by high temperature (T8) in the maximally freeze concentrated state. The main cause for changes in mechanical properties of frozen foods is probably related to ice melting.
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In this study, zein protein isolate (ZPI) and chickpea protein concentrate (CPC) ingredients were used to formulate five plant-based cheese alternatives. Ingredient ratios based on protein contributions of 0:100, 25:75, 50:50, 75:25 and... more
In this study, zein protein isolate (ZPI) and chickpea protein concentrate (CPC) ingredients were used to formulate five plant-based cheese alternatives. Ingredient ratios based on protein contributions of 0:100, 25:75, 50:50, 75:25 and 100:0 from ZPI and CPC, respectively, were used. Formulations were developed at pH ~4.5, with a moisture target of 59%. Shea butter was used to target 15% fat, while tapioca starch was added to target the same carbohydrate content for all samples. Microstructural analysis showed differences among samples, with samples containing ZPI displaying a protein-rich layer surrounding the fat globules. Schreiber meltability and dynamic low amplitude oscillatory shear rheological analyses showed that increasing the proportion of ZPI was associated with increasing meltability and greater ability to flow at high temperatures. In addition, the sample containing only CPC showed the highest adhesiveness, springiness and cohesiveness values from the texture profile ...
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ABSTRACT Collapse phenomena in food systems are important because they affect food dehydration characteristics and deterioration during the storage of foods at intermediate and low water contents. These phenomena often include stickiness... more
ABSTRACT Collapse phenomena in food systems are important because they affect food dehydration characteristics and deterioration during the storage of foods at intermediate and low water contents. These phenomena often include stickiness and fl ow properties of particles in dehydration and manufacturing of powders; collapse in freeze drying; and stickiness, caking, and loss of structure during the storage of dehydrated materials. Collapse phenomena result from a change in stiffness and fl ow properties as a result of the glass transition of food solids. Diffusion, reaction rates, and component crystallization can be affected signifi cantly by the glass transition and the consequent changes in food structure. The glass transition and structural properties of low - water food systems can be described by state diagrams that include information on water plasticization and frozen - state properties, as well as saturation of dissolved components. Food composition can be manipulated to control collapse phenomena in dehydration and storage of low - water food systems.
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Stickiness in the production of food powders can cause low yield, operational problems of equipment, powder-handling problems and fire hazards. It may result from the appearance of attractive forces between particles including static... more
Stickiness in the production of food powders can cause low yield, operational problems of equipment, powder-handling problems and fire hazards. It may result from the appearance of attractive forces between particles including static electricity. Stickiness in food systems often appears when the surface viscosity of amorphous particle components decreases and particles adhere. Increasing adhesion forces between particles causing stickiness and caking depends on the material properties, storage and processing conditions. Stickiness is a serious problem in spray drying of sugar-rich and fat-rich products, such as milk and juice. Solids composition affects structure formation and changes of foods during processing and storage. Powders containing high sugar contents show high adhesion of powder particles with increasing temperatures and water contents as a result of surface plasticization and the formation of liquid bridges. The stickiness of milk powders resulted from liquid flow of am...
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The objective of the present study was to investigate flocculation in layer-by-layer (LBL) emulsion systems with high total solids content and deflocculation at various pH conditions, and the effects of whey protein isolate (WPI)... more
The objective of the present study was to investigate flocculation in layer-by-layer (LBL) emulsion systems with high total solids content and deflocculation at various pH conditions, and the effects of whey protein isolate (WPI) concentration and total solids content on the stability of LBL emulsions. WPI (1.96% (1WPI) or 10.71% (10WPI), w/w in water) was prepared in water and high-pressure homogenized with sunflower oil (10%, w/w, of total emulsion). Gum Arabic (0.15%, w/w, in total emulsion) was added to assemble electrostatically on WPI at oil particle interfaces at pH3.5 using aqueous citric acid (10% w/w) forming LBL emulsion. The ζ-potential measurements showed charge reversal upon addition of gum Arabic solution into single layer (SL) emulsion confirming the formation of LBL interface. Trehalose:maltodextrin mixture (1:1, w/w, total emulsion, 28.57% (28) or 57.14% (57), w/w, in water) was used in the continuous phase. The high total solids content of the system results in de...
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Freezing of biological materials is commonly carried out to delay biochemical and chemical changes resulting in loss of activity. However, the physicochemical background of freezing is not well understood. Freeze-drying is generally aimed... more
Freezing of biological materials is commonly carried out to delay biochemical and chemical changes resulting in loss of activity. However, the physicochemical background of freezing is not well understood. Freeze-drying is generally aimed at preserving biological materials and bioactive components for long periods of time without the need for frozen storage. Freeze-drying relies on proper freezing and process control based on an understanding of the frozen state properties of biological materials. Such properties relate to unfrozen water and its distribution across carbohydrates, proteins and other components. Here, novel methods for deriving accurate protein hydration levels and unfrozen water content are discussed. The role of water and carbohydrate distribution in preserving the viability of micro-organisms in freezing and freeze-drying is also discussed, as this is a significant factor affecting the success of freezing and freeze-drying processes in the production of starter cultures and the preservation of probiotic bacteria.
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A number of food components are sensitive to deteriorative reactions, such as nonenzymatic browning and oxidation, during food storage. Food components, i.e., carbohydrates, lipids, proteins and water undergo changes due to the... more
A number of food components are sensitive to deteriorative reactions, such as nonenzymatic browning and oxidation, during food storage. Food components, i.e., carbohydrates, lipids, proteins and water undergo changes due to the surrounding atmosphere, the presence of minor components and catalysts, and variations in local reactant concentrations resulting from changes in temperature, water migration, and the state of the components. Bioactive proteins and peptides may participate in nonenzymatic browning and oxidation reactions. Oil-soluble bioactive components, for example carotenoids, need protection against oxidation. Water content, and often the physical state of components as well as food structure, may have a significant impact on bioactive stability during food manufacturing and storage.
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Abstract Although the glass transition properties and encapsulation efficiency of various biopolymers have been documented, no attempts have been made to relate the α-relaxation behavior, molecular structure and stability of an... more
Abstract Although the glass transition properties and encapsulation efficiency of various biopolymers have been documented, no attempts have been made to relate the α-relaxation behavior, molecular structure and stability of an encapsulation system above the glass transition. In this work, the efficiency of whey protein (W), maltodextrin (M) and their combination (MW) to encapsulate α-mangostin was assessed through the monitoring of the changes in the mechanical property and molecular structure around the glass transition using dynamic-mechanical analysis and Fourier transform infrared spectroscopy, respectively. A dramatic decrease in the storage modulus was observed in the non-encapsulation system (NE). Addition of W and M increased the temperature difference (Tstorage − Tα), resulting in a decrease in the α-mangostin degradation rate during storage. Carbonyl group (C–H) vibration of reducing sugars became smaller when W was added, while the spectra of the M and MW systems exhibited sharp peaks. This confirmed better encapsulation with W than with M.
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Maltodextrins are used to improve dehydration and storage stability of food solids. The main problem during storage is crystallization of amorphous sugars and resultant changes in sorbed water. Crystallization is delayed by the addition... more
Maltodextrins are used to improve dehydration and storage stability of food solids. The main problem during storage is crystallization of amorphous sugars and resultant changes in sorbed water. Crystallization is delayed by the addition of high molecular weight components. The rate of crystallization is related to molecular mobility, including effects of various molecular species and impurities in amorphous systems. The objective of the present study was to determine effects of maltodextrins on crystallization of lactose in freeze-dried lactose-maltodextrin systems. Maltodextrins were of high dextrose equivalent (DE) of 23-27 and low DE of 9-12. Freeze-dried amorphous solids of lactose and lactose-maltodextrins were prepared from solutions containing 20% total solids. The ratios of lactose and maltodextrins were 90:10, 80:20, and 70:30 (w/w). Crystallization was followed from changes in sorbed water during storage over saturated salt solutions over the range 54.5% to 76.1% relative ...
Properties of high protein systems containing whey protein isolate (WPI) or milk protein concentrate (MPC-80) with glucose-fructose (1:1) syrup, WPI or MPC-80 with glucose-fructose syrup and sunflower oil during storage at 20, 40, and... more
Properties of high protein systems containing whey protein isolate (WPI) or milk protein concentrate (MPC-80) with glucose-fructose (1:1) syrup, WPI or MPC-80 with glucose-fructose syrup and sunflower oil during storage at 20, 40, and 60°C for 16, 15, 14 weeks, respectively, were investigated. The most significant changes in appearance (at 40 and 60°C) and mechanical properties occurred in WPI with glucose-fructose syrup, and WPI with glucose-fructose syrup and sunflower oil (at all temperatures) systems. WPI and MPC-80 retained sunflower oil in the protein structure more strongly with increasing storage temperature up to 60°C.
Effects of thermal treatments of protein-oil systems on their thermal and mechanical properties were investigated to study protein-oil interactions in concentrated systems. Whey protein isolate (WPI) and milk protein concentrate (MPC)... more
Effects of thermal treatments of protein-oil systems on their thermal and mechanical properties were investigated to study protein-oil interactions in concentrated systems. Whey protein isolate (WPI) and milk protein concentrate (MPC) were used with sunflower oil (SO) or hydrogenated palm kernel oil (HPKO). Prehydrated proteins and oil (7:3) were emulsified (8:2 water:solids) and spray dried. The materials were heated at varying times at 60, 105, and 130°C and analyzed for mechanical properties using dynamic mechanical analysis (DMA). Reconstituted materials in water (1:9) were analyzed for viscosity, pH of coagulation, particle size, and thermal properties using differential scanning calorimetry (DSC). DMA data of all systems showed thermal treatment independent oil melting and possible flow of oil to particle surfaces upon heating. Heat treatment at 130°C resulted in decreased viscosity for MPC-oil systems, but the viscosity of WPI-oil systems was constant at 5 mPa s. Increased te...
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The pivotal role of water in understanding the phase transitions of the various components of food is discussed in this chapter. The presence of water in all foods affects food processing especially, in palatability and stability of food... more
The pivotal role of water in understanding the phase transitions of the various components of food is discussed in this chapter. The presence of water in all foods affects food processing especially, in palatability and stability of food and its microbial content. The phase behavior of pure water is quite different from the properties of water in solutions, such as freezing temperature depression and elevation of boiling temperature. Sorption behavior and plasticization are the two characteristics of water that have an impact on the stability and physical state of food. Sorption behavior of water in foods is regulated by external vapor pressure and temperature. The plasticization of water and its influence on the other crystalline and amorphous material in food are also discussed in the chapter, since these substances can depress freezing point or elevate boiling temperatures. The chapter also highlights the impact of plasticization of water on food solids, provides details with illustrations on freeze concentration and ice formation, and effects of frozen storage food items on the nutrient quality.
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This chapter deals with the effects of various changes in the physical state on reaction kinetics and the rates of deteriorative changes in foods. Food deterioration results due to various factors, such as structural transformation,... more
This chapter deals with the effects of various changes in the physical state on reaction kinetics and the rates of deteriorative changes in foods. Food deterioration results due to various factors, such as structural transformation, chemical changes, or microbial growth. The rate of deterioration changes are related to water content and water activity. A number of changes occur in zero or in the first order of kinetics. The first order reaction show that the change in concentration occurs exponentially with time. In the second order of kinetics, it is observed that the rate of reaction may be dependent on the nature of reaction and the reactant concentrations. Changes and deterioration are also temperature dependent. The Arrhenius equation is the most important relationship used to model temperature dependence of various physicochemical and chemical properties of food. Labuza and Riboh list ten reasons as the primary causes of nonlinearities in Arrhenius plots of reaction rates in food. Levine and Slade have indicated that the importance of the glass transition of maximally freeze concentrated solute matrix on the rate of deterioration changes in frozen food. It is evident that the stability of frozen food is related to the physical state of the unfrozen solute matrix. Food storage below a certain range of temperature will increase the shelf life of food, while the quick decrease in viscosity and increase of diffusivity, which occurs above a certain range of temperature, brings about a dilution of food solutes, and causes increased reaction rates.
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Mechanical properties of food are important to their behavior in four areas—processing, storage, distribution, and consumption. Several compositional factors and processing parameters affect mechanical properties of foods. The overall... more
Mechanical properties of food are important to their behavior in four areas—processing, storage, distribution, and consumption. Several compositional factors and processing parameters affect mechanical properties of foods. The overall mechanical properties may be defined by cell structure, typical of vegetables and fruits. It may also result from the physical state, flow properties, or porosity. The focus in this chapter is on the mechanical properties related to phase transitions that occur in the nonequilibrium state of non-fat food solids and their time dependent characteristics. Changes in mechanical properties have been observed to occur as a function of temperature, water activity, and water content. Studies have suggested that temperature, diluents content, and time have equal effect on the modulus that can be superimposed with any of the variables. The effects of stiffness, mechanical properties, and crystallinity are discussed in the chapter. The mechanical properties of frozen food materials are affected by high temperature (T8) in the maximally freeze concentrated state. The main cause for changes in mechanical properties of frozen foods is probably related to ice melting.
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This chapter describes various aspects of time-dependent changes that are related to phase transitions and which may occur and govern quality changes during processing and storage of foods. Such foods include several lowmoisture foods,... more
This chapter describes various aspects of time-dependent changes that are related to phase transitions and which may occur and govern quality changes during processing and storage of foods. Such foods include several lowmoisture foods, confectioneries, various cereal products, and frozen foods. In addition, structural transitions during dehydration or agglomeration can be described as a phase transitions-related phenomena. Glass formation through dehydration, freezing, or freeze-drying is discussed in the chapter. The noncrystalline or amorphous states are analyzed under the collapse phenomena, where methods, such as stickiness and caking, which are seen not merely as an aging process but also as transitional changes affected by temperature. The effects of temperature and water are seen in the crystallization kinetics in food. The chapter concludes with the retrogradation of starches and the staling of bread.
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This chapter explains the physical state and stability of food material and its molecular mobility through its various physical transitional phases. These changes are viewed through the impact of temperature on the properties of food... more
This chapter explains the physical state and stability of food material and its molecular mobility through its various physical transitional phases. These changes are viewed through the impact of temperature on the properties of food within and through the transitional phases. Application of crystallization methods, such as nucleation and crystal growth in understanding the impact on frozen foods and during the manufacturing process of salts sugars, or fats, and retention of the homogeneity of the food components transitional phases are described in the chapter. Derivatives and application of homogenous, heterogeneous, and secondary nucleation are explained as well. The chapter explains the characteristics of amorphous and polymeric materials through an understanding of the mechanics of cooling and super cooling. Young's modulus and Shear's modulus are used to evaluate the elasticity of materials and its impact on tensile stress, strain, and viscosity. In addition to assessing the influence of temperature on various transitional phases of the glassy state in amorphous substances, the chapter also provides a backdrop for glass transition theories, such as the free volume theory, kinetic theory, and thermodynamics.
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This chapter deals with the physical states of food, and the factors likely to influence phase transition behavior of the main components of foods, like carbohydrates, lipids, proteins, and water. The main component of food is normally... more
This chapter deals with the physical states of food, and the factors likely to influence phase transition behavior of the main components of foods, like carbohydrates, lipids, proteins, and water. The main component of food is normally carbohydrates, although it generally exists in combined forms. The main methods that can be used to predict the physical state of food items and factors related to their phases of transition are also mentioned in the chapter. Carbohydrates exist in crystalline form in sugars and starches. Several factors affect and alter their physical state. Sugars are often used as cyropreservatives, and substantially, alter the freezing points of the item. The chapter explains the solubility changes and differential melting points of different sugars and sugar based alcohols, and discusses the transitional factors of both crystalline and amorphous types of sugars. It discusses the mixtures of sugars in foods, the state transition of different natives, and the classification and properties of starches as A-, B-, C-, and V-type starches. The final products in view are the large number of raw materials that make each blend original.
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Water in dairy products is a nonnutrient component, which, however, is the principal responsible determinant of important physicochemical properties and stability of dairy foods. Water, for example, is the main solvent of water-soluble... more
Water in dairy products is a nonnutrient component, which, however, is the principal responsible determinant of important physicochemical properties and stability of dairy foods. Water, for example, is the main solvent of water-soluble components, such as lactose, proteins, and minerals, as well as water-soluble vitamins. Moreover, water has a crucial role in defining the physicochemical properties of dairy products, including viscosity, emulsion structure, and thermal properties, and it contributes to most processing requirements in the manufacture of dairy products. In addition, water has a key role in controlling microbial growth, product shelf life, palatability, and overall quality. One important property of water is its equilibrium relative vapor pressure or water activity. Water activity is a useful measure of water availability for the growth of various microorganisms and physicochemical stability of low-moisture dairy products. Water is also a plasticizer and it may control changes in the physical state, molecular mobility, and shelf life of low-moisture and frozen dairy products.
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Encapsulation protects ingredients (core material) by entrapping them inside a protective layer (4, 6). Encapsulation is a common phenomenon during spray
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ABSTRACT The physical state of materials is often defined by their thermodynamic properties and equilibrium. Simple one-component systems may exist as crystalline solids, liquids or gases, and these equilibrium states are controlled by... more
ABSTRACT The physical state of materials is often defined by their thermodynamic properties and equilibrium. Simple one-component systems may exist as crystalline solids, liquids or gases, and these equilibrium states are controlled by pressure and temperature. In most food and other biological systems, water content is high and the physical state of water often defines whether the systems are frozen or liquid. In food materials science and characterization of food systems, it is essential to understand the physical state of food solids and their interactions with water. Equilibrium states are not typical of foods, and food systems need to be understood as nonequilibrium systems with time-dependent characteristics.
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Research Interests: Chemistry, Water, ARTIC SEA ICE MELTING, Phase Transitions, Pharmaceutical industry, and 12 moreDifferential scanning calorimetry, Glass Transition, Thermal Analysis, Glass Transition Temperature, Dehydration, Collapse, Freeze Drying, Reaction Mechanism, Amorphous Ice, Lyophilisation, Thermal Analysis and Calorimetry, and ice crystals
Stickiness correlates with changes in mechanical α-relaxation properties and often results from glass transition and plasticisation of amorphous food components. In this study, milk solids with maltodextrins with different dextrose... more
Stickiness correlates with changes in mechanical α-relaxation properties and often results from glass transition and plasticisation of amorphous food components. In this study, milk solids with maltodextrins with different dextrose equivalents (DE9 and DE17) were analysed for glass transition (T(g) ), α-relaxation (T(α) ) and sticky point (SPT) temperatures using differential scanning calorimetry, dynamic mechanical analysis and a sticky point test respectively. At the same maltodextrin contents, T(g) and T(α) were lower for milk solids with the higher-DE maltodextrin. Increasing maltodextrin contents gave T(g) , T(α) and SPT at higher temperatures, and the magnitudes of α-relaxations with high maltodextrin (DE9 and DE17) contents were less pronounced. Stickiness was governed by glass transition and affected by skim milk/maltodextrin composition. Stickiness was reduced with increasing maltodextrin content as a result of maltodextrin miscibility with skim milk solids, particularly lactose, which changed the relaxation behaviour above the glass transition. The mixes of milk solids with low-DE maltodextrin may show improved dehydration characteristics and powder stability resulting from increased T(g) , T(α) and SPT.
Research Interests: Engineering, Materials Science, Chemistry, Food Science, Water, and 15 morePolysaccharides, Medicine, Differential scanning calorimetry, Viscosity, Phase transition, Solubility, Glass Transition, Food Additives, Dietary Carbohydrates, Dairy Products, Elastic Modulus, CARBOHYDRATES, Milk proteins, Transition Temperature, and Maltodextrin
ABSTRACTThe water sorption isotherms for freeze‐dried horseradish roots (Armoracia rusticana) were determined using the interval sorption technique, and the thermal behavior of dried and rehumidified products was analyzed using... more
ABSTRACTThe water sorption isotherms for freeze‐dried horseradish roots (Armoracia rusticana) were determined using the interval sorption technique, and the thermal behavior of dried and rehumidified products was analyzed using differential scanning calorimetry. The hygroscopicity of the dried material increased when the surface temperature during freeze‐drying was increased from 20°C to 60°C. Both sorption and thermal data showed that drying at high surface temperatures affected the physical structure of the material, resulting in increased water adsorption, decreased glass transition temperature, and increased unfreezeable water content. Water sorption isotherms and thermal data can be used to determine the proper drying and storage conditions for horseradish roots.
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ABSTRACT Thermal and water plasticization and glass transition of amorphous components often result in changes in physico-chemical properties of food solids including stickiness and component crystallization. The glass transition... more
ABSTRACT Thermal and water plasticization and glass transition of amorphous components often result in changes in physico-chemical properties of food solids including stickiness and component crystallization. The glass transition temperatures (Tg) of skim milk–maltodextrin solids systems were measured by differential scanning calorimetry (DSC) and a sticky point test was used to determine the sticky-point temperatures (SPT). The mechanical α-relaxation around glass transition was measured by dynamic-mechanical analysis (DMA). The Guggenheim–Anderson–deBoer (GAB) model was fitted to water sorption data and sorption isotherms were established. The glass transition and water sorption properties were dependent on the dextrose equivalent (DE) of the maltodextrin and the skim milk–maltodextrin solids system composition. Maltodextrins and lactose in skim milk solids were miscible and lactose crystallization was delayed in solids containing maltodextrins. The mechanical α-relaxation behavior was governed by the skim milk–maltodextrin solids system composition and was related to the development of stickiness. The α-relaxation at varying frequencies occurred at higher temperatures in solids with increasing maltodextrin contents and the sticky point was governed by the glass transition of the carbohydrates phase.
Research Interests: Materials Science, Chemistry, Food Science, Food Engineering, Crystallization, and 13 moreDifferential scanning calorimetry, Sorption, SPT, Glass Transition, Glass Transition Temperature, DMA, SMP, Food Sciences, Dynamic Mechanical Analysis, Skim Milk, Maltodextrin, Relaxation Time, and Dextrose Equivalent
Dielectric and mechanical α-relaxations of milk solids with varying milk protein contents were determined by dielectric (DEA) and dynamic-mechanical (DMA) analysis, respectively. The frequency dependence of α-relaxations occurring around... more
Dielectric and mechanical α-relaxations of milk solids with varying milk protein contents were determined by dielectric (DEA) and dynamic-mechanical (DMA) analysis, respectively. The frequency dependence of α-relaxations occurring around and above the glass transition was modeled by the Vogel–Fulcher–Tamman (VTF) relationship. The α-relaxations were governed by the amorphous lactose and shifted to higher temperatures when protein contents of milk solids