Gordon-Taylor Model Research Articles

Glass transition and state diagram for freeze-dried Lentinus edodes mushroom

Glass transitions of freeze-dried Lentinus edodes mushroom were determined using differential scanning calorimetry (DSC) as a function of water contents. Freeze-dried L. edodes containing unfreezable and freezable water were examined to explore the state diagram of L. edodes. The state diagram included the freezing curve, glass transition line, and ultimate maximal-freeze-concentration condition. The freezing curve and the glass transition line were fitted according to Clausius-Clapeyron model and Gordon-Taylor model, respectively. The ultimate maximal-freeze-concentration conditions were calculated as solid content of 0.81g solid/g (w.b.) with the characteristic glass transition temperature (Tg′) being −53.2°C, and characteristic temperature of end point of freezing (Tm′)u being −33.4°C. The other characteristic glass transition temperature Tg″ was −42.4°C. The state diagram of Lentinus edodes can be used in determining the storage stability as a function of temperature and water content, and optimizing drying and freezing processes.

Glass Transition Temperature of Saccharide Aqueous Solutions Estimated with the Free Volume/Percolation Model.

The glass transition temperature of trehalose, sucrose, glucose, and fructose aqueous solutions has been predicted as a function of the water content by using the free volume/percolation model (FVPM). This model only requires the molar volume of water in the liquid and supercooled regimes, the molar volumes of the hypothetical pure liquid sugars at temperatures below their pure glass transition temperatures, and the molar volumes of the mixtures at the glass transition temperature. The model is simplified by assuming that the excess thermal expansion coefficient is negligible for saccharide-water mixtures, and this ideal FVPM becomes identical to the Gordon-Taylor model. It was found that the behavior of the water molar volume in trehalose-water mixtures at low temperatures can be obtained by assuming that the FVPM holds for this mixture. The temperature dependence of the water molar volume in the supercooled region of interest seems to be compatible with the recent hypothesis on the existence of two structure of liquid water, being the high density liquid water the state of water in the sugar solutions. The idealized FVPM describes the measured glass transition temperature of sucrose, glucose, and fructose aqueous solutions, with much better accuracy than both the Gordon-Taylor model based on an empirical kGT constant dependent on the saccharide glass transition temperature and the Couchman-Karasz model using experimental heat capacity changes of the components at the glass transition temperature. Thus, FVPM seems to be an excellent tool to predict the glass transition temperature of other aqueous saccharides and polyols solutions by resorting to volumetric information easily available.

Plasticization of amorphous polystyrene by volatile organic compounds

The plasticizing effect of 4 model volatile compounds (n-hexane, toluene, p-xylene, and ethylbenzene), able to be sorbed on polystyrene (PS) was studied. A large weight fraction range was investigated (up to 0.35) using differential scanning calorimetry. Mathematical modeling, using Fox, Kelly-Bueche, Chow and Gordon-Taylor models, was performed to model the behavior of the glass transition temperature of PS after VOC sorption. A strong plasticization of PS was evidenced by a significant reduction in the glass transition temperature of the binary mixtures (T gm). Among the four studied molecules, the linear one, n-hexane, displayed a better plasticizing efficiency than the aromatic ones, which lay in the same range. Indeed, a 15 % (w w−1) n-hexane content in PS decreased the T gm by 84 K. The Gordon-Taylor model was the best model to fit the experimental data for all the volatile organic compounds tested.

Effect of vacuum spray drying on the physicochemical properties, water sorption and glass transition phenomenon of orange juice powder

Vacuum spray drying is a new technique used to produce concentrated orange juice powder using maltodextrin as a drying agent. The dryer was developed for the low-temperature (40–50 °C) drying powderization of liquefied food using superheated steam (200 °C) as a heating medium. The physicochemical properties of orange juice powder with four different combinations of juice solids: maltodextrin solids at 60:40, 50:50, 40:60, and 30:70 were determined. The moisture content, hygroscopicity, water activity, particle size, particle morphology, color characteristics, rehydration and ascorbic acid retention were significantly affected by the maltodextrin concentration and drying conditions. Water sorption and the glass transition temperature of orange juice powder conditioned at various water activities were also evaluated. The obtained data were well fitted to both BET and GAB models. A strong plasticizing effect of water on Tg was able to predicted by the Gordon–Taylor model, where Tg was greatly reduced by the increasing moisture content of the powder.

State diagram for freeze-dried mango: Freezing curve, glass transition line and maximal-freeze-concentration condition

Freeze-dried mango powders containing unfreezable and freezable water were measured to explore the state diagram of mango. The state diagram was composed of the freezing curve, glass transition line, and ultimate maximal-freeze-concentration condition. Freezing points and glass transition temperatures were determined using differential scanning calorimetry (DSC) as a function of water contents. The freezing curve was fitted according to Clausius–Clapeyron model and adjusted with unfreezable water, and glass transition line was fitted to the Gordon–Taylor model. The ultimate maximal-freeze-concentration conditions were calculated as Xw′ (characteristic water content, i.e. unfreezable water content)=0.16gwater/g sample (w.b.) with the characteristic temperature as Tg′ (characteristic glass transition)=−54.6°C and (Tm′)u (characteristic end point of freezing)=−33.0°C. The state diagram of freeze-dried mango is useful for determining the stability during storage and selecting the optimum processing conditions.

Effect of air humidity on traditional Chinese medicine extract of spray drying process and prediction of its powder stability

In order to solve the adhesion and the softening problems of traditional Chinese medicine extract during spray drying, a new method of adding dehumidified air into spray drying process was proposed, and the storage stability conditions of extract powder could be predicted. Kouyanqing extract was taken as model drug to investigate on the wet air (RH = 70%) and dry air conditions of spray drying. Under the dry air condition, the influence of the spray drying result with different air compression ratio and the spray-dried powder properties (extract powder recovery rate, adhesion percentage, water content, angle of repose, compression ratio, particle size and distribution) with 100, 110, 120, 130, 140 °C inlet temperature were studied. The hygroscopic investigation and Tg value with different moisture content of ideal powder were determined. The water activity-equilibrium moisture content (aw-EMC) and the equilibrium moisture content-Tg (EMC-Tg) relationships were fitted by GAB equation and Gordon-Taylor model respectively, and the state diagram of kouyanqing powder was obtained to guide the rational storage conditions. The study found that in the condition of dry air, the extract powder water content decreased with the increase of air compression ratio and the spray drying effect with air compression ratio of 100% was the best performance; in the condition of wet air, the extract powder with high water content and low yield, and the value were 4.26% and 16.73 °C, while, in the dry air condition the values were 2.43% and 24.86 °C with the same other instru- ment parameters. From the analysis of kouyanqing powder state diagram, in order to keep the stability, the critical water content of 3.42% and the critical water content of 0.188. As the water decreased Tg value of extract powder is the major problem of causing adhesion and softening during spray drying, it is meaningful to aid dehumidified air during the process.

Determination of glass transition temperatures during cooling and heating of low-moisture amorphous sugar mixtures

Glass transition temperatures (Tg) of amorphous sugar samples, prepared from 0% to 14% (wb) moisture content, were determined during both cooling and heating using differential scanning calorimetry (DSC). The DSC protocol used involved heating, cooling, and reheating the sugar samples, where Tg was obtained during both cooling and reheating steps. The Gordon-Taylor equation modeled the water plasticization effect, where the Tg of anhydrous solids and constant (k) values were determined simultaneously. No significant difference was found between the cooling and heating glass transition temperature values, with both values significantly influenced by sugar composition (p<0.05). No significant effect of sugar composition was observed for the k values, resulting in discrepancies displayed by the Gordon-Taylor model for solid mass fractions below 0.84. Thus, k values should be estimated from measured Tg data at low solid mass fractions rather than extrapolated from high solid mass fractions, for prediction of Tg curve at high moisture contents.

Thermal characteristics and state diagram of extruded instant artificial rice

Instant artificial rice was developed by extrusion method using corn flour, glycerol monostearate (GSM), and glucomannan and guar gum. Moisture sorption isotherm and thermal characteristics of the artificial rice with glucomannan and guar gum were measured and modeled to develop different regions of a state diagram. The freezing point, glass transition, and solids-melting were measured and modeled by Chen’s model, modified Gordon–Taylor model, and Flory–Huggins model, respectively. The ultimate maximal-freeze-concentration conditions were found as (Tm′)u (i.e., annealed end glass transition temperature for the sample with moisture 0.40g/g sample) equal to −8.3°C and (Tg‴)u (i.e., annealed onset glass transition temperature for the sample with moisture 0.40g/g sample) equal to −8.4°C, and the characteristic solids content, Xs′ as 0.76g/g sample (i.e., un-freezable water, Xw′ equal to 0.24g/g sample). Similarly the characteristic glass transition temperature, Tgiv (i.e., intersection of vertical line passing through Tm′ and glass transition line above Xs′) was estimated as 29.8°C.

Measurement and Comparison of Glass Transition and Sticky Point Temperatures of Distillers Dried Grains with Solubles (DDGS) with Varying Condensed Distillers Solubles (CDS) and Drying Temperature Levels

ABSTRACTDistillers dried grains with solubles (DDGS) is the main coproduct of the U.S. fuel ethanol industry and has significantly impacted the livestock feed markets in recent years. Particle agglomeration and subsequent flowability problems during storage and transport are often a hindrance, a nuisance, and expensive. This paper aims at characterizing the glass transition (Tg) and sticky point (Ts) temperatures of DDGS samples prepared with varying condensed distillers solubles (CDS) levels (10, 15, and 20%, wb), drying temperatures (100, 200, and 300°C), and moisture contents (0, 10, and 20%, db), and it discusses implications on DDGS flowability behavior. Distillers wet grains were combined with specified levels of CDS and dried in a convection‐style laboratory oven to produce DDGS. Subsequently, predetermined amounts of water were added to the DDGS to achieve desired moisture content levels. To determine Tg (°C), a differential scanning calorimeter was used, whereas Ts (°C) was determined through a novel technique with a rheometer. Results indicated high correlations between observed Ts and observed Tg (R2 = 0.87) data for DDGS samples. Also, the empirical model for predicted Tg = f (drying temperature, CDS level, and moisture content) based on the Gordon–Taylor model showed favorable R2 (0.74). Stickiness of DDGS increased with an increase in moisture content, indicating flow problems resulting from moisture. It was found that drying temperatures and CDS levels each had significant effects on Tg and Ts as well.

Water Adsorption and Glass Transition of Spray-Dried Soy Sauce Powders Using Maltodextrins as Carrier

Moisture adsorption isotherm and glass transition temperature of various spray-dried soy sauce powders containing different types and concentrations of maltodextrins were studied and compared. Maltodextrins of dextrose equivalent (DE) = 5, DE = 10 and DE = 15, respectively, with concentrations of 20 or 40 % (w/v) were used as carrier agents. The equilibrium moisture content was reduced with increased maltodextrin concentration, whereas it was not apparently influenced by the value of maltodextrin DE. Both the Brunauer–Emmett–Teller (BET) and Guggenheim–Anderson–de Boer (GAB) models could be applied to simulate the moisture adsorption behaviour of the soy sauce powders. The monolayer moisture content of the powders was determined by fitting experimental data to the BET/GAB models with a w up to 0.53, although both models could fit satisfactorily with the experimental data to a higher water activity level. The glass transition temperatures (T g) of the powders equilibrated under various water activities were determined using a differential scanning calorimeter. Increasing moisture adsorption of the soy sauce powders resulted in a T g reduction, and the experimental T g values fitted the Gordon–Taylor model well. The BET and Gordon–Taylor models were applied together to predict the critical moisture contents (i.e. 0.0464–0.0777 g water/g dry matter) and water activities (i.e. 0.032–0.241), above which the soy sauce powders become vulnerable to degradation and changes in their physicochemical properties.

The Effects of Moisture on Physical Properties of Spray-Dried Egg Powder

The aim of this study was to evaluate the effect of moisture on the glass transition temperature (T g ), flow properties, color, and morphology of spray-dried powdered egg. Powdered egg was stored under environments with different relative humidities at 25°C and the moisture sorption isotherm was determined. The Guggenhiem-Anderson-de Boer (GAB) model fitted the isotherm data well. A differential scanning calorimeter was used to determine the T g of samples with different water activities. The T g data were satisfactorily correlated by the Gordon-Taylor model. The results showed that the glass transition temperature of powdered egg decreased with increasing water activity. The changes in flowability based on the Carr index (CI) and cohesiveness based on the Hausner ratio (HR) with water activity were defined. At low water activity values, the powder had poor flowability and high cohesiveness. These flow properties were also supported with scanning electron microscope (SEM) images.

Determination of critical storage conditions of coffee oil microcapsules by coupling water sorption isotherms and glass transition temperature

SummaryCoffee oil microcapsules were produced by spray‐drying using as encapsulating agents gum Arabic, whey protein isolate (WPI) and mixtures of maltodextrin (MD) and WPI, at three different proportions (3:1, 1:1 and 1:3). Sorption isotherms were determined by the gravimetric method, and the glass transition temperature (Tg) was measured by differential scanning calorimetry. Microcapsules produced with gum Arabic showed the highest water adsorption and underwent a stronger water plasticising effect. At the highest water activity (0.843), this sample had a Tg value of −18.3 °C, while those produced with WPI at higher proportions showed values around 25 and 30 °C. The good fit of experimental data by Guggenheim‐Anderson‐de Boer and Gordon–Taylor models allowed the determination of the critical storage conditions, at which powders are not susceptible to deteriorative physical changes. The samples produced with 1:1 and 1:3 of MD/WPI were the most stable ones, showing critical water activity values of 0.890 and 0.938, respectively.

Glass transition and state diagram for freeze-dried Agaricus bisporus

Sorption isotherms and state diagram of freeze-dried Agaricus bisporus were developed to further investigate the connection between the two distinct criteria of food stability. Sorption isotherms of freeze-dried A. bisporus were determined by the gravimetric method and the data were modeled by GAB model. The GAB monolayer moisture content was calculated to be 6.2g/100g (d.b.). The glass transition temperature of freeze-dried A. bisporus was determined by differential scanning calorimetry. The state diagram was composed of the freezing curve and glass transition line, which were fitted according to Clausius–Clapeyron model and Gordon–Taylor model, respectively. The state diagram yielded maximally-freeze-concentrated solutes at 0.704 solids with the characteristic temperature of glass formation being −77.9°C. The state diagram and sorption isotherms of freeze-dried A. bisporus are useful in evaluating the storage stability as a function of temperature and moisture content as well as optimizing drying and freezing conditions.

Water Sorption and Glass Transition Temperature of Spray-Dried Mussel Meat Protein Hydrolysate

The water sorption behavior at 25°C and glass transition temperature (T g ) of mussel meat protein hydrolysate powder without and with maltodextrin 10 DE or gum arabic at 15 and 30% (w/w) were studied in this work. The sorption isotherms were determined by the gravimetric method, and the glass transition temperature was obtained by differential scanning calorimetry (DSC) after powder conditioning at various water activities. Sorption isotherms data were well fitted by a modified Brunauer-Emmett-Teller (BET) model. Powder without additives showed the highest water adsorption followed by those produced with 15 and 30% of carrier agent, respectively. The Gordon-Taylor model was able to predict the effect of water on the glass transition temperature. At 25°C, the critical water content that ensured the glassy state of the mussel hydrolysate powder during storage increased from 0.05 to 0.12 g water/g product and the critical water activity increased from 0.24 to 0.60 when the concentration of carrier agents was increased to 30%.

Determination of moisture content in relation to thermal behaviour and plasticization of Eudragit RLPO

Coalescence of polymer particles on thermal treatment plays an important role in effective control of drug release from these matrix systems. The water content of the polymer may influence coalescence since it is well established that sorbed water may act as a plasticizer, or cause other changes in mechanical properties. However, these effects depend on the amount and type (plasticizing/nonplasticizing) of water present. The purpose of this study was to determine the accuracy of different methods used to determine moisture content of a polymer (Eudragit RLPO) and to determine the types water present. The polymer powder was stored at various relative humidities (33, 56, 75, 94%). Four water determination methods, [weight loss on drying, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Karl Fischer titration (KFT)] were utilized to determine moisture content. DSC was used to study the thermal behaviour of moist and dry samples. The Gordon-Taylor equation was used to calculate the amount of plasticizing water. Scanning electron microscopy was employed to examine the morphology of the polymer particles after thermal analyses. It is concluded that KFT accurately determines the total water content but that the thermal methods underestimate total water content. However KFT does not indicate the type of water present. The Gordon-Taylor model suggests that only about 25% of the water in the polymer containing 10% water was acting as a plasticizer. Complementary methods should be used to measure the water content of pharmaceutical polymers.

Glass transition phenomenon on shrinkage of papaya during convective drying

A differential scanning calorimeter was used to determine the Tg of papaya pieces equilibrated with several water activities. Thermograms revealed the existence of two Tg. The first, which presented lower value, is due to the matrix formed by sugar and water. The second one, less visible and less plasticized by water, probably corresponds to macromolecules. The data of Tg were satisfactory correlated by the Gordon–Taylor model. A convective tray dryer was used for the drying experiments, which were carried out at air temperatures of 40°C and 70°C and air velocity of 1.0m/s. The shrinkage behavior was accomplished by total area and apparent volume alterations along drying. Samples were photographed during process, and their length and lateral areas were measured using the ImageJ® software. As result, the effect of air temperature on shrinkage was significant and the highest temperature (70°C) induced higher extent of shrinkage values. At this condition, papaya sample was in a rubbery state, characterized by great matrix mobility, and remained so until the end of process, since product temperature (Tp) was above the Tg along the process. At lower temperature (40°C), shrinkage stopped at a critical value of moisture content (0.21g/g, wet basis), which coincided with the point in which the Tg was close to Tp.

Development of state diagram of bovine gelatin by measuring thermal characteristics using differential scanning calorimetry (DSC) and cooling curve method

A state diagram of bovine gelatin was developed by measuring the freezing curve, glass transition, unfolding, solids-melting lines, and ultimate maximum-freeze-concentration conditions. The freezing point decreased with the increase of solids; whereas glass transition, unfolding, and solids-melting decreased with the decrease of solids up to solids content 0.84 g/g gelatin and then remained constant. The freezing point, glass transition and solids-melting were modeled by Chen's model based on the Clausius-Clapeyron equation, modified Gordon-Taylor model, and Flory's equation, respectively. The ultimate maximum-freeze-concentration conditions were found as ( T ′ m ) u equal to −11.9 °C and ( T ‴ g ) u equal to −14.9 °C, and the characteristic solids content, X ′ s as 0.80 g/g sample (i.e. un-freezable water, X ′ w = 0.20), respectively. Similarly the value of T g i v (i.e. intersection of vertical line passing through T ′ m and glass transition line) was estimated as 34 °C.

Glass-transition behaviour of plasticized starch biopolymer system – A modified Gordon–Taylor approach

Two plasticizers namely, glycerol and xylitol, based on their similar molecular size (˜6.3 Å) but different molecular weights (Glycerol-92; Xylitol-152) were selected for studying the glass-transition behaviour (rubber like behaviour) in multi-plasticized starch biopolymer with about 70% amylopectin structure. In the calorimetry measurements, glass-transition temperatures (onset temperature for bulk viscous flow) of plasticized samples were higher than non-plasticized samples at low water activities, thus showing typical antiplasticization behaviour. However, when plasticizer concentration was increased up to 15% and 20% wt, all plasticized samples showed significant reduction in glass-transition temperature. We used a modified Gordon–Taylor model to understand the competitive plasticization of glycerol and xylitol in presence of water, and suggest that competitive plasticization exists and occurs at a threshold amount of matrix free water content, due to strong three-way interactions: starch–plasticizer, plasticizer–plasticizer/water and starch–water. This competitive interaction is significant in determining the onset temperature for viscous flow behaviour; at higher matrix water content, the Gordon–Taylor constant was relatively unaffected by the plasticizer amount, and water was the dominant plasticizer. A new interaction parameter that separates the starch–plasticizer interaction in a starch–plasticizer–water system is also discussed.

Competitive plasticization in ternary plasticized starch biopolymer system

Two plasticizers namely, glycerol and xylitol, based on their similar molecular diameter (∼ 6.3 Å) but different molecular weights (glycerol-92; xylitol-152) were selected were selected for studying the plasticization of starch biopolymer containing 70% amylopectin structure via glass transition measurements carried over a wide range of water activity. A standard calorimetry was used to determine the onset temperature of polymeric viscous flow. For both glycerol and xylitol, typical antiplasticization was evident at low plasticizer concentrations, whereas at higher concentration, there was significant reduction in glass transition temperature. Water activity isotherms showed that equilibrium moisture content of the starch biopolymer (no plasticizer) steadily increases up to 11%, however, for plasticized biopolymer, the moisture content was nearly double than that of biopolymer. We used a modified Gordon-Taylor model, using a new interaction parameter, to understand the competitive plasticization of glycerol and xylitol in presence of water, and determined 8 wt % water as a threshold amount of matrix water for strong three-way interactions: starch-plasticizer, plasticizer-plasticizer/water and starch-water. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

State diagram of dates: Glass transition, freezing curve and maximal-freeze-concentration condition

The state diagram of Deglet Nour dates was developed using freezing curve, glass transition line, and maximal-freeze-concentration condition. Freezing points and glass transition temperature were measured by differential scanning calorimetry (DSC) as a function of water content. Freezing points were fitted to the Clausius–Clapeyron equation adjusted with un-freezable water, and glass transition was fitted to the Gordon–Taylor model. Glass transition decreased with a decrease in solids content, confirming the plasticizing effect of water on date solids. Freezing point data indicated the temperature when ice formed and dates would be most stable in terms of its deterioration if it can be stored below its glass transition. Maximum-freeze-concentration conditions was found as X s ′ (characteristic solids content) = 0.78 g/g sample, with the characteristic temperature as T g ′ (characteristics glass transition) = −48 °C and T m ′ (characteristic end point of freezing) = −38.2 °C. These characteristics indicated that 0.22 g/g sample water in date was un-freezable (i.e. bound with solids or unable to form ice). The developed state diagram can be used in determining the stability of dates during storage as a function of temperature and moisture content. Moreover, it can be used to determine optimum drying and freezing conditions.