Water sorption-induced crystallization, structural relaxations and strength analysis of relaxation times in amorphous lactose/whey protein systems

Water sorption-induced crystallization, α-relaxations and relaxation times of freeze-dried lactose/whey protein isolate (WPI) systems were studied using dynamic dewpoint isotherms (DDI) method and dielectric analysis (DEA), respectively. The fractional water sorption behavior of lactose/WPI mixtures shown at aw ≤ 0.44 and the critical aw for water sorption-related crystallization (aw(cr)) of lactose were strongly affected by protein content based on DDI data. DEA results showed that the α-relaxation temperatures of amorphous lactose at various relaxation times were affected by the presence of water and WPI. The α-relaxation-derived strength parameter (S) of amorphous lactose decreased with aw up to 0.44 aw but the presence of WPI increased S. The linear relationship for aw(cr) and S for lactose/WPI mixtures was also established with R2 > 0.98. Therefore, DDI offers another structural investigation of water sorption-related crystallization as governed by aw(cr), and S may be used to describe real time effects of structural relaxations in noncrystalline multicomponent solids

Structural strength analysis of partially crystalline trehalose

Strength concept, which is based on the Williams-Landel-Ferry (WLF) model, was developed using mixed structured powders containing amorphous and crystalline components. At the present study, semi crystalline trehalose powders with various (100:0; 80:20; 60:40; 40:60; 20:80) amorphous to crystalline ratios were analyzed. Amorphous components were prepared from water solution by freeze-drying. Strength analysis, which included water sorption, differential scanning calorimetry, dynamic mechanical analysis and microscopy, was applied. The results indicated that water content significantly decreases glass transition (similar to 100 degrees C) and alpha-relaxation temperatures (similar to 90 degrees C) as well as structural strength parameter (similar to 10 degrees C), while, the effect of crystalline component is less pronounced. This study can be used in processing and characterization of various partially crystalline food products including nutritional formulations and infant formulas

Influence of pre-crystallisation and water plasticization on flow properties of lactose/WPI solids systems

This study investigated the influence of pre-crystallisation and water plasticization on flow properties of lactose/whey protein isolate (WPI) solids systems. Powder characteristics of lactose/WPI mixtures with different amounts of a.-lactose monohydrate (1.01%, 11.18%, 29.20%, and 46.84%, w/w) were studied. Dairy powders with higher amounts of crystalline lactose showed larger tapped bulk density and particle density. Morphological characteristic study indicated that dairy solids with higher crystallinity had less rounded shape and rougher surface. Increasing protein content or crystalline lactose content could decrease the molecular mobility of dairy solids. Flow function tests indicated that dairy solid with 11.18% crystallinity was more easy-flowing than lactose/WPI mixtures with 1.01%, 29.20% and 46.84% crystallinity at 0% and 44% relative humidity (RH) storage conditions. Furthermore, dairy solids with higher amount of crystalline lactose showed better resistance to develop cohesive at high RH storage conditions. The friction angle of dairy solid with 1.01% crystallinity increased with increasing water content, while friction angles of lactose/WPI mixtures with higher crystallinity decreased with increasing water content

Flavor release from spray-dried amorphous matrix: Effect of lactose content and water plasticization

peer-reviewedGlass-forming carbohydrates are widely used as matrix for encapsulation of nutrients and bioactive compounds. In this study, encapsulation systems with lactose/whey protein isolate (WPI) mixtures (4:1, 1:1, and 1:4), or WPI as wall materials and ethyl butyrate as core material were prepared by spray drying. The effects of lactose content and water plasticization on encapsulation efficiency and flavor release were investigated. Wall material consisting of lactose/WPI (4:1) mixture had significantly (P<0.05) higher encapsulation efficiency. The flavor retention in powders did not have significant decrease with equilibration at 0.33 aw, while it was dramatically decreased at 0.54 aw and 0.65 aw as a result of lactose crystallisation. Mechanical property study showed that the molecular mobility and free volume of encapsulation systems with higher lactose content increased more significantly with increasing water content, which accelerated the diffusion of flavor molecules. Those results may use in the assessment of protection and release characteristics of flavor components in formulated systems

Physical and mechanical properties of lactose/WPI mixtures: Effect of pre-crystallisation

peer-reviewedThis study investigated the physical and mechanical properties of spray-dried lactose/whey protein isolate (WPI) (4:1) mixtures with different contents of α-lactose monohydrate (1.0%, 11.2%, 29.2%, and 46.8%, w/w). Particle size of samples with 11.2%, 29.2%, and 46.8% crystallinity was significantly (P < 0.05) larger compared with the sample with 1.0% crystallinity. The presence of less than 46.8% crystalline lactose in lactose/WPI mixtures had only a minor effect on water sorption behaviour at aw 0.11–0.44, whereas samples with higher crystallinity had higher stable water content after showing lactose crystallisation. Moreover, samples with lower crystallinity showed higher initial sorption rates. Increasing the amount of crystalline lactose had no significant influence on the glass transition temperature and the initial crystallisation temperatures at aw 0.11–0.44. Furthermore, dairy powders with higher crystallinity had higher stiffness and water plasticisation showed a stronger effect on the structural relaxation of dairy powders with lower crystallinity.Food Institutional Research Measure (FIRM) of the Department of Agriculture, Food and Marine, Irelan

Thermal gelation and hardening of whey protein beads for subsequent dehydration and encapsulation using vitrifying sugars

peer-reviewedSolid beads were developed using whey protein isolate (WPI) and sugars for controlled hardening and vitrification of wall materials. A concentrated mixture of WPI and sucrose in water, intended for use as gelling and glass-forming ingredients, respectively, was used to form liquid feeds with varying pH, viscosities, surface tensions, solids contents and compositions. Using a peristaltic pump, feeds flowed continuously through silicon tubing and formed droplets. Rapid solidification occurred when droplets were submerged in heated, stirred oil; beads were harvested for vacuum oven drying. Dispersions were characterized by viscosity and flow testing. Dried beads were characterized for porosity, hardness, diameters, and water activity, and microstructures were analyzed with microscopy. Drop-forming dispersions comprised of 40% WPI with 10% sucrose by mass possessed structure forming and shape retention qualities. Feed composition influenced characteristics of the final product more strongly than processing conditions including heating times and temperatures.University College Cor

State diagrams for improving processing and storage of foods, biological materials, and pharmaceuticals (IUPAC Technical Report)

Supplemented temperature/composition phase diagrams include the non-equilibrium glass-transition temperature (Tg) curve and equilibrium ice-melting and solubility curves. The inclusion of the non-equilibrium curve allows one to establish relationships with the time coordinate and, thus, with the dynamic behavior of systems, provided that the thermal history of such systems is known. The objective of this report is to contribute to the potential applications of supplemented state diagrams for aqueous glass-formers, in order to describe the influence of water content, nature of vitrifying agents, and temperature on the physico-chemical properties of foods and biological and pharmaceutical products. These data are helpful to develop formulations, processing strategies, or storage procedures in order to optimize the stability of food ingredients and pharmaceutical formulations. Reported experimental data on phase and state transitions for several food and pharmaceutical systems were analyzed. Some methodological aspects and the effect of phase and state transitions on the main potential chemical reactions that can alter those systems during processing and/or storage are discussed.Fil: Buera, Maria del Pilar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Químicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Químicos; ArgentinaFil: Roos, Yrjö. University College Cork; IrlandaFil: Levine, Harry. Food Polymer Science Consultancy; Estados UnidosFil: Slade, Louise. Food Polymer Science Consultancy; Estados UnidosFil: Corti, Horacio Roberto. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Reid, David S.. University of California at Davis; Estados UnidosFil: Auffret, Tony. taPrime Consulting; Reino UnidoFil: Angell, C. Austen. Arizona State University; Estados Unido

A sound approach: exploring a rapid and non-destructive ultrasonic pulse echo system for vegetable oils characterization

A rapid and non-destructive ultrasonic pulse echo system was developed for vegetable oils characterization. To understand the differences in the ultrasonic properties of the oils, physical traits, such as their viscosity and density, were related to the ultrasonic data. In turn, these physical traits were correlated with the fatty acid compositions of the oils. Eighty oil samples, including 30 extra virgin olive oil (EVOO), 15 refined olive oil, 15 pomace olive oil, 10 rapeseed oil, 5 sunflower oil and 5 peanut oil samples, were analysed for their sound properties, viscosities, densities and fatty acid compositions. It was observed that the ultrasonic velocity of EVOO decreased linearly with increase in temperature, the temperature coefficient of ultrasonic velocity in EVOO was −2.92 m·s−1·°C−1. The ultrasonic velocity of EVOO (1453 ± 2 m/s) differed significantly from those of pomace olive oil and the oils of other botanical origin, but not from the velocity of refined olive oil. Ultrasonic velocity was positively correlated with the density and negatively correlated with the viscosity of the oils. The higher density and lower viscosity of the oils were in turn related to a higher unsaturation degree of the oils. Hence, oils with a higher proportion of unsaturated fat present higher densities and lower viscosities, which resulted in higher ultrasonic velocity values. Ultrasonic measurements allow rapid, non-destructive analysis, and this first application for characterization of these oils is promising

Glass Transition and Re-Crystallization Phenomena of Frozen Materials and Their Effect on Frozen Food Quality

Noncrystalline, freeze-concentrated structures are formed during food freezing. Such freeze-concentrated food materials often exhibit crystallization and recrystallization phenomena which can be related to the state of solutes and water. State diagrams are important tools in mapping the physical state and time-dependent properties of frozen materials at various storage temperatures. Transition of simple solutions, such as sucrose, can be used to describe vitrification and ice melting in freeze-concentrated materials. A maximally freeze-concentrated material often shows glass transition at Tg′. Ice melting occurs at temperatures above Tm′ These transitions at temperatures above Tm′ can be used to estimate crystallization and recrystallization phenomena and their rates in frozen foods. Furthermore, frozen food deterioration accelerates above Tm′ and particularly as a result of temperature fluctuations during frozen food distribution and storage