De Boer Model Research Articles

Physical Properties of Selected Fruit Fibre and Pomace in the Context of Their Sustainable Use for Food Applications

Pomace, a waste product, generates a huge problem in the fruit and vegetable industry. Numerous studies prove that pomace and fibre are valuable sources of many nutrients. Due to their properties, their popularity is growing in many industries. Water vapour isotherms and kinetics were determined for selected fruit fibre and pomace. The activity and water content, colour, apparent and bulk density, and material structure were also investigated. In addition, the thermal stability of the tested fibres and pomace was examined. Fibre and pomace from chokeberries, apples and currants were used in the research. The determined kinetic curves proved that apple fibre absorbed more water vapour. The isotherms were found to have a shape characteristic of type III sorption isotherms. The Guggenheim–Anderson–de Boer model (GAB) described experimental data for sorption isotherms well (taking an RMS value of less than 10% as a good fit of the model to the sorption data). Thermogravimetric analysis showed good thermal stability, and all analysed fruit fibre and pomace showed similar behaviour in the three main stages of weight loss. The results suggest that the analysed waste materials can be used for different applications, including flour replacements for food products or filling materials in edible packaging films.

Evaluation of surface structure, water sorption properties, water plasticizing effect, and color stability of dried chrysanthemums

The storage stability of two varieties of chrysanthemum (Chrysanthemum morifolium Ramat. cv. HSGJ and C. morifolium Ramat. cv. JSHJ)was evaluated in this study through an analysis of their water binding behavior. This involved examining the surface structure of the powdered dried chrysanthemums, studying the water sorption characteristics, and quantifying the water plasticizing effect. In comparison to JSHJ, powdered HSGJ had a smaller particle size and more hydrophilic groups on its surface. Additionally, it exhibited significantly higher characteristic values of adsorbed water, excluding the number of adsorbed monolayers (Nam). The sorption of water by the powdered chrysanthemums conformed to a type II isotherm. The Guggenheim–Anderson–deBoer (GAB) model was trustworthy for predicting water sorption within the range of aw from 0.112 to 0.907 and temperatures between 20 and 40 °C. The exothermic interactions between water molecules and the primary sorption sites of the powdered samples became more powerful when the temperature decreased. Powdered chrysanthemums can be preserved at 30 °C if the humidity is below 0.0852 g/g for HSGJ and 0.0766 g/g (d.b) for JSHJ. The color changes of powdered samples were not significantly affected when stored in a glassy state. This study is significant for identifying the drying endpoint, predicting shelf life, and choosing suitable packaging materials for dried chrysanthemums.

Osmotic Dehydration Model for Sweet Potato Varieties in Sugar Beet Molasses Using the Peleg Model and Fitting Absorption Data Using the Guggenheim-Anderson-de Boer Model.

This study investigates the applicability of the Peleg model to the osmotic dehydration of various sweet potato variety samples in sugar beet molasses, addressing a notable gap in the existing literature. The osmotic dehydration was performed using an 80% sugar beet molasses solution at temperatures of 20 °C, 35 °C, and 50 °C for periods of 1, 3, and 5 h. The sample-to-solution ratio was 1:5. The objectives encompassed evaluating the Peleg equation's suitability for modeling mass transfer during osmotic dehydration and determining equilibrium water and solid contents at various temperatures. With its modified equation, the Peleg model accurately described water loss and solid gain dynamics during osmotic treatment, as evidenced by a high coefficient of determination value (r2) ranging from 0.990 to 1.000. Analysis of Peleg constants revealed temperature and concentration dependencies, aligning with previous observations. The Guggenheim, Anderson, and de Boer (GAB) model was employed to characterize sorption isotherms, yielding coefficients comparable to prior studies. Effective moisture diffusivity and activation energy calculations further elucidated the drying kinetics, with effective moisture diffusivity values ranging from 1.85 × 10-8 to 4.83 × 10-8 m2/s and activation energy between 7.096 and 16.652 kJ/mol. These findings contribute to understanding the complex kinetics of osmotic dehydration and provide insights into the modeling and optimization of dehydration processes for sweet potato samples, with implications for food processing and preservation methodologies.

Impact of maltodextrin, egg white protein addition and microwave-assisted foam mat drying on drying kinetics, microstructures, physicochemical and quality attributes of jackfruit juice powder

This study aimed to analyze the effect of maltodextrin and egg white protein addition on the physicochemical, functional, microstructures, and drying characteristics of microwave-assisted foam mat-dried (MFD) jackfruit juice powders. A microwave intensity of 1 W/g was employed to obtain optimal yield and high quality of the powders. The concentration of maltodextrin influenced the drying rate of the jackfruit juice powders, with higher concentrations resulting in a faster drying rate. The data obtained from Microwave-assisted foam mat drying of the jackfruit juice powder data were best fitted by the Page and Logarithmic kinetic models. The moisture content of the jackfruit powders ranged from 1.323 ± 0.75 g/100 g (w.b.) to 1.712 ± 0.72 g/100 g (w.b.). Powders produced at higher maltodextrin/egg white protein ratios exhibited superior flowability, lower cohesiveness, smoother and smaller particle sizes, but degraded color quality. The maltodextrin concentration significantly influences the antioxidant properties of the powders. The water sorption of jackfruit juice powder was determined, and the findings showed a good fit with the Guggenheim–Anderson–de Boer (GAB) model.

Effect of Heat Treatment on Hygroscopicity of Chinese Fir (Cunninghamia lanceolata [Lamb.] Hook.) Wood

Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) is a widely planted species of plantation forest in China, and heat treatment can improve its dimensional stability defects and improve its performance. The wood samples were heat-treated at various temperatures (160, 180, 200, and 220 °C) for 2 h. To clarify the effect of heat treatment on wood hygroscopicity, the equilibrium moisture content (EMC) was measured, the moisture adsorption and desorption rates were determined, the hygroscopic hysteresis was examined, and the Guggenheim, Anderson, and de Boer (GAB) model was fitted to the experimental data. The moisture absorption isotherms of all samples belonged to the Type II adsorption isotherm, but the shape of the desorption isotherm was more linear for heat-treated wood samples, especially when the heat treatment temperature was higher. According to the results analyzed with ANOVA, there were significant differences in equilibrium moisture content between the control samples and the heat-treated samples under the conditions of 30%, 60%, and 95% relative humidity (RH, p < 0.05), and the results of multiple comparisons were similar. The decrease in hygroscopicity was more pronounced in wood treated at higher temperatures. The EMC of the 160–220 °C heat-treated samples of the control samples was 14.00%, 22.37%, 28.95%, and 39.63% lower than that of the control sample at 95% RH. Under low RH conditions (30%), water is taken up mainly via monolayer sorption, and multilayer sorption gradually predominates over monolayer sorption with the increase in RH. The dynamic vapor sorption (DVS) analysis indicated that the heat-treated wood revealed an increase in isotherm hysteresis, which was due to the change in cell wall chemical components and microstructure caused by heat treatment. In addition, the effective specific surface area of wood samples decreased significantly after heat treatment, and the change trend was similar to that of equilibrium moisture content.

Properties, Structure, and Acceptability of Innovative Legume-Based Biscuits with Alternative Sweeteners.

The effects of legume incorporation and sweetener substitution on the quality characteristics of innovative biscuits were investigated. The wheat flour was substituted with chickpea and lentil flour at ratios ranging from 0 to 30% legume to whole-meal dicoccum wheat flour. The sugar was substituted by oligofructose at 50 and 100% levels. The quality characteristics, including physicochemical properties (moisture content, water activity, and color), sorption characteristics, structural and textural properties, and sensory properties, were significantly affected by the substitutions. Sorption phenomena were excellently described by the Guggenheim, Anderson, and de Boer (GAB) model, while its parameters were affected by substitutions. Scanning electron microscopy revealed a porous structure with starch granules embedded within the protein matrix, showing restricted gelatinization and keeping largely their form. The incorporation of legume flour increased the biscuit density, hardness, and spread ratio and decreased the color of the products. Furthermore, principal component analysis (PCA) analysis of instrumental and sensory characteristics showed that texture and sweetness were the key quality characteristics for product acceptance. It was found that highly acceptable legume-based biscuits with alternative sweeteners can be produced, with 50% oligofructose substitution and legume flour incorporation (chickpea or lentil) up to 30%.

Process modeling and simulation of Gmelina arborea (GmW) and Mansonia altissima (MaW) wood drying

This study simulate the process modeling of drying characteristics of Gmelina arborea (GmW) and Mansonia altissima (MaW) wood under the influence of various process variables such as drying time, drying temperature, and airflow velocity. GmW and MaW moisture desorption isotherms, kinetics, and thermodynamics were also studied. Five (5) thin-layer and desorption isotherm drying models were used to model the moisture ratio and water activity data from the process. According to the anatomical analysis, the GmW sample has an average lumen size of 147.44 m, indicating a high moisture content. The results showed that the Guggenheim, Anderson, and de Boer (GAB) model with the lowest sum of squared error value (0.046) demonstrated the best-fit to the experimental desorption data for GmW samples and the Henderson-P model for MaW samples, while the Demir et al. model emerged as the best kinetics model fit for describing the moisture desorption isotherm and thin-layer drying kinetics. GmW effective diffusivity (Deff) values ranged from 3.671 × 10−8 to 5.378 × 10−8 m2/s and MaW effective diffusivity (Deff) values ranged from 2.923 × 10−8 to 4.678 × 10−8 m2/s. GmW and MaW activation energies were 252.702 kJ/mol and 313.604 kJ/mol, respectively. The thermodynamic studies revealed that the heat and mass transfer coefficients varied linearly with temperature, as the change in enthalpy (ΔH) and change in entropy (ΔS) decreased while the Gibbs free energy (ΔG) increased. The results obtained from this study demonstrated that the proposed drying process modeling and simulation approach could be successfully applied to investigate the wood drying phenomena. The information can be used to reduce the drying costs and improve the wood quality.

Sorption properties of paper treated with silane-modified starch

Sorption properties of paper products are important when applying paper as the packaging material. Hydrophobicity, i.e. reduced affinity of paper surface to liquid water, is of particular importance from the point of view of the direct impact on packed goods. However, hygroscopicity of the material is significant during storage of goods. The analysis of changes in the hygroscopic properties of paper products induced by the treatment with silane modified starch was presented. The results on the hygroscopicity of treated paper were related to the previously published results on the hydrophobicity. The discrete values of equilibrium moisture content allowed constructing adsorption and desorption isotherms. The three-parameter Guggenheim, Anderson, and De Boer (GAB) model, the four-parameter Generalized D’Arcy and Watt (GDW), and Yanniotis and Blahovec (Y-B) sorption isotherm models were used to quantify the hygroscopic properties for all options of untreated and modified paper samples. The effectiveness of silanes for improving hygroscopic properties was determined and compared to their impact on hydrophobicity of the studied materials. It was found that 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane was the only silane improving hydrophobic and hygroscopic properties. The analysis of the applied models of sorption isotherms depicted that the GAB model was not valid for describing water sorption isotherms in the case of the tested materials, while the GDW and Y-B models provided a much more realistic description of water sorption mechanisms. The evaluation of the results of fitting the GDW model indicated that water molecules bonding to the primary sites was the dominating mechanism of sorption.

Moisture Sorption Isotherms and Thermodynamic Properties of Biodegradable Polymers for Application in Food Packaging Industry.

This work aims to evaluate the influence of two starch-based materials (B16 and B20) on the moisture sorption isotherms, determined at 30, 40, and 50 °C, where B16 contains 5% (w/w) more starch than B20. Thermodynamic functions (differential enthalpy (∆Hdif), differential entropy (∆Sdif), integral enthalpy (Δhint), integral entropy (ΔSint), free Gibbs energy (∆G), and spreading pressure (φ)) were used to understand the water-binding behaviors and the energy requirements to remove the moisture content from the surface of these materials. The moisture sorption isotherms exhibited type III behavior, and the Guggenheim-Anderson-de Boer (GAB) model was the most suitable to fit the experimental moisture adsorption data. The adsorption isotherms of microparticles were enthalpy-controlled, with isokinetic temperature values of 221.45 and 279.77 K for B16 and B20, respectively, being higher than the harmonic mean temperature (312.94 K). The values of ∆G were positive (45.274 and 44.307 kJmol-1 for B16 and B20, respectively), indicating a non-spontaneous process. The spreading pressure values increased with increasing water activity (aw) for all isotherms. Higher values of ∆Hdif and ∆Sdif obtained from B16 confirmed its higher number of sorption sites available for binding with water molecules when compared to B20, making it less suitable for application in the food packaging industry.

Influence of Anticaking Agents and Storage Conditions on Quality Characteristics of Spray Dried Apricot Powder: Shelf Life Prediction Studies Using Guggenheim-Anderson-de Boer (GAB) Model.

Apricot powder was developed through spray drying using gum arabic as an encapsulating material at a concentration of 19%. Inlet air temperature, feed total soluble solids (TSS), feed flow rate, and atomization speed were 190 °C, 23.0 °C, 300.05 mL/h, and 17,433 rpm, respectively. This study was therefore conducted to investigate the influence of anticaking agents (tricalcium phosphate and silicon dioxide) and storage conditions (ambient and accelerated) on physicochemical, micrometric, and thermal characteristics of spray-dried apricot powder (SDAP) packaged in aluminum laminates. Both tricalcium phosphate (TCP) and silicon dioxide (SiO2) improved the shelf life and quality of SDAP, with TCP being more effective, since a lower increase in water activity (aw), moisture content, degree of caking, hygroscopicity, and rehydration time was observed in TCP-treated samples followed by SiO2-treated samples than the control. Furthermore, flowability, glass transition temperature (Tg), and sticky-point temperature (Ts) of SDAP tended to decrease in a significant manner (p < 0.05) under both storage conditions. However, the rate of decrease was higher during accelerated storage. The water activity of treated samples under ambient conditions did not exceed 0.60 and had a total plate count within the permissible range of 40,000 CFU/g, indicating shelf stability of the powder. The predicted shelf life of powder obtained from the Guggenheim−Anderson−de Boer (GAB) model and experimental values were very similar, with TCP-treated samples having a predicted shelf life of 157 days and 77 days under ambient and accelerated storage conditions, respectively. However, the respective experimental shelf life under the same conditions was 150 and 75 days, respectively. Similarly, the predicted shelf life of SiO2-treated samples under ambient and accelerated storage was 137 and 39 days, respectively, whereas the experimental values were 148 and 47 days, respectively. In conclusion, TCP proved more effective than SiO2 at preserving shelf life by preventing moisture ingress.

Utilization of industrial hemp by-product defatted seed flour: effect of its incorporation on the properties and quality characteristics of 'tsoureki', a rich-dough baked Greek product.

A rich-dough baked Greek product named 'tsoureki' was prepared using non-gluten hemp seed flour at ratios of 0:100, 10:90, 30:70, and 50:50. The effects of hemp flour addition on the properties of 'tsoureki', including physicochemical properties (moisture content, water activity, sorption phenomena), structural properties, textural properties, total phenolic content, antioxidant activity, and sensorial characteristics, as well as the macroscopic structure and morphological characteristics, were studied. Hemp flour addition affected dough rheology, showing tan δ values < 1, a decrease in both G' and G″ values, while both flow behavior and consistency indices were also significantly affected, which might have an influence on the final baked goods. The Guggenheim-Anderson-de Boer model satisfactorily described sorption data, while both hemp addition and temperature had a significant effect. A significantly higher hardness of 11.55 N, a lower specific volume of 2.65 cm3 g-1 , and a lower porosity of 0.676 were observed at high hemp additions. The hemp flour level influenced the color of the crumb and crust, and the total color difference (ΔE) increased significantly with the increase in hemp flour. Hemp flour additions were detectable by the naked eye, with an obvious color difference between control and hemp-containing samples. Moreover, the phenolic content and antioxidant capacity were increased, as were some organoleptic characteristics, such as the bitter aftertaste. Concurrently, overall acceptability decreased significantly. Overall, the incorporation of gluten-free defatted hemp seed flour in 'tsoureki' formulations seems to be a promising alternative for improving quality of such rich-dough baked products. © 2022 Society of Chemical Industry.

Molecular imprinted polymer with dorzolamide for contact lens applications assisted by computational and experimental design

The main aim of the present study was to prepare a molecularly imprinting polymer for dorzolamide as a potential soft contact lens. A computational protocol was used for molecular imprinting polymers (MIP) and Non-molecular imprinting polymers (NIP) preparation. Physicochemical characteristics of MIP and NIP were determined by using Fourier transform infrared spectroscopy analysis (FTIR), Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC) and Brunauer–emmett–teller (BET). Release profile studies were done by using Franz™ Diffusion Cell. Five isotherm models, including Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin and Hill deboer, were investigated to study adsorption equilibrium. Kinetic parameters were evaluated using the Zero-order model, Pseudo-first order and Pseudo-second order. Results revealed that hydroxyethyl methacrylate (HEMA), methacrylic acid (MAA) and methyl methacrylate (MMA) could be considered suitable monomers to form the elastic network. The molecular imprinting technique increased the loading capacity of hydrogels. The optimized imprinted hydrogels were prepared in 1:3:2:1:34 M ratios of DZD, HEMA, MAA, MMA, and EGDMA, respectively. This molar ratio was obtained with a computational method. SEM, FTIR, DSC and BET of MIP confirmed a high degree of polymerization. The adsorption information was essentially fitted on the Hill DeBoer model (R2 = 0.9997); maximum sorption capacity was 187.8 mg/g of DZD for MIP and occurred at the weight of the polymer; 50 mg, temperature; of 25 °C and concentration of DZD solution; of 100 mg/L. maximum sorption capacity was 128.4 mg/g of DZD for NIP and occurred at the weight of the polymer; 50 mg, temperature; of 25 °C and concentration of DZD solution; of 30 mg/L. Release profile analysis showed that MIP has a superior control to release DZD, and the release mechanism fits the Peppas model (R2 = 0.9911). The molecular imprinting method had a substantial impact on loading and releasing DZD from hydrogels.

Adsorption isotherm and thermodynamic properties of microwave vacuum dried tilapia fillets

The aim of the present study was to report the drying characteristics and adsorption isotherms of Tilapia Fillets. The static weighing method was used to measure the storage temperatures (25, 35, and 45 °C) and the moisture content (0.11–0.97) and determine microwave vacuum dried adsorption characteristics and thermodynamic properties of tilapia fillet. Eight classical adsorption models were used to evaluate the nonlinear fitting of the experimental data. The results showed that the dry tilapia products type adsorption isotherm belongs to the type III isotherm curve. At a given temperature, the equilibrium moisture content increased with an increase of water activity. The Guggenheim–Anderson–de Boer model was the optimal model for describing the adsorption kinetics of dry tilapia fillet products. The characteristic thermodynamic parameters showed that the enthalpy entropy compensation theory showed that the adsorption process of dry tilapia fillet products was non-spontaneous and enthalpy driven. This study provides a scientific reference for the processing and storage stability of tilapia and other aquatic products.

Changes in the Structural Composition and Moisture-Adsorption Properties of Mechanically Rolled Bamboo Fibers.

The chemical content, mechanical capability, and dimensional stability of bamboo fibers (BFs) are all directly related to the hygroscopic behavior, which is crucial for industrial applications. To support the utilization of BFs, the structural and chemical composition of BFs with different opening times after mechanical rolling were investigated in this study, and the Guggenheim–Anderson–de Boer (GAB) model was selected to predict their moisture-adsorption properties. The results showed that the length and diameter of the fibers gradually decreased with the increase in the number of openings, and the fibers gradually separated from bundles into single fibers. It was also observed that the treated BFs exhibited different equilibrium moisture contents (EMCs). BFs with a smaller number of openings had a higher hemicellulose content and more exposed parenchyma cells on the fibers, which increased the number of water adsorption sites. As the number of openings increased, the parenchyma cells on the fibers decreased, and the lignin content increased, which reduced the number of fiber moisture-adsorption sites and decreased the EMC of the fibers.

Modeling moisture adsorption isotherms for extruded dry pet foods

Two mathematical models were used to determine the moisture adsorption isotherm curves of dry pet foods. Ten extruded commercial diets for dogs (n = 6) and cats (n = 4) were tested within 7 days of manufacture. The equilibrium moisture content of each food at 30 and 40 °C was determined by gravimetry. Six saturated saline solutions (lithium chloride, potassium acetate, sodium nitrite, magnesium chloride, sodium chloride, and potassium chloride) were prepared and used to obtain pet food samples at different water activities. Solutions were placed in airtight flasks containing food samples (without direct contact) and oven-dried to constant weight. The relationship between water activity and equilibrium moisture content was modeled by the exponential Peleg and Guggenheim–Anderson–de Boer (GAB) models. All pet foods exhibited a type II isotherm. Akaike information criterion, R2, and standard deviation values were − 29.79, 0.914, and 3.89, respectively, at 30 °C by the Peleg model; − 28.86, 0.876, and 6.36 at 40 °C by the Peleg model; − 31.17, 0.937, and 4.34 at 30 °C by the GAB model; and − 29.63, 0.888, and 7.71 at 40 °C by the GAB model. At 0.60 water activity, equilibrium moisture contents by the Peleg and GAB models were 12.04 ± 0.84 and 11.67 ± 0.78 g H2O/g dry matter, respectively, at 30 °C and 7.83 ± 1.31 and 8.09 ± 0.81 g H2O/g dry matter at 40 °C. The GAB model also allowed estimating monolayer moisture content (5.81 ± 0.81%). Both models provided similar results and may be useful for determining quality parameters for pet foods. Adsorption isotherm studies can provide practical information about the moisture ranges of pet foods, contributing to the optimization of food safety, palatability, and processing conditions.

Effect of maltodextrin weight fraction on the amorphous state and critical storage conditions of freeze‐dried juices

SummaryDiagrams relating to water activity (aw), equilibrium moisture content (Xw) and glass transition temperature (Tg) are valuable tools for predicting amorphous fruit powders' storage procedure and stability. Thus, Tg–aw–Xw diagrams were constructed to characterise the amorphous state and define the critical values of water content (Xwc) and water activity (awc) of freeze‐dried juices of strawberry, pineapple, kiwi and prickly pear prepared with maltodextrin at the dry mass fraction (WMD) of 0, 0.4 and 0.8. The Tg and sorption data were fitted with a polynomial equation and the Guggenheim–Anderson–de Boer (GAB) model respectively. A Tukey test was performed to evaluate the difference between critical values of the powders (P &lt; 0.05). The awc and Xwc increase with WMD and depend on the chemical composition of the powders. The highest critical values were found in pineapple powders, ranging from 0.174 to 0.632 and 0.029 to 0.142 dry basis (d.b.), and the lowest ones in kiwi juice powders ranging from 0.029 to 0.550 and 0.013 to 0.129 (d.b.). For WMD of 0.8, however, regardless of juice composition, stable powders in an amorphous state were obtained up to an aw of 0.52 at 25°C.

Solubility and diffusivity of six volatile compounds in ionic liquids [BMIM][Tf2N], [BMPy][Tf2N], [BMIM][TfO] and [BMPy][TfO

Diffusivity and solubility of water, methanol, ethanol, 1-butanol, acetone and p-xylene in four ionic liquids (ILs) were determined microgravimetrically by studying the absorption of the vapors (without air) in the ILs at 40 °C. The studied ILs comprised of all four possible combinations of two cations [1-butyl-3-methylimidazolium, BMIM, and 1-butyl-1-mehtylpyrrolidinium, BMPy] and two anions [bis(trifluoromethylsulfonyl)imide, Tf2N, and trifluoromethanesulfonate, TfO]; data for 24 systems are reported. Higher solubility of the vapors of protic compounds (water, methanol, ethanol and 1-butanol) was observed for the ILs containing the TfO anion while higher solubility of aprotic compounds (acetone and p-xylene) was observed for ILs containing the Tf2N anion. While ILs containing BMPy cation showed discernibly higher solubilities than those containing BMIM in for 1-butanol in TfO based ILs and p-xylene in Tf2N based ILs, limited solubility changes due to the cation exchange were observed for the remaining systems. The equilibrium dissolution was parameterized using the Margules and Guggenheim, Anderson, de Boer (GAB) models. For all compounds except water, mutual diffusivity followed the relations BMIM > BMPy and Tf2N > TfO, while for water it followed BMIM > BMPy and TfO > Tf2N. Diffusion was anomalously fast with respect to the Einstein-Stokes-Sutherland equation in all studied systems presumably due to the “cage” and “jump” mechanism. Despite the observed non-ideality of the liquid phase, mutual diffusivities were practically constant over the tested ranges of vapor activity (and concentration) for most systems while thermodynamic (self) diffusivities varied with the experimental conditions. Overall, structure-property relationships were assessed for four combinations of practically relevant constituting ions and six volatile solutes at 40 °C.

Effects of maltodextrin on physicochemical properties of freeze-dried avocado powder

The effect of maltodextrin on the moisture sorption isotherm, glass transition temperature (Tg), and degree of caking of freeze-dried avocado samples at room temperature (25°C) was investigated. The incorporation of maltodextrin reduced the water sorption capacity of the powder due to its less hygroscopic nature. Parameters derived from the Guggenheim, Anderson, and de Boer (GAB) model describing the properties of absorbed water are discussed. The water absorption isotherm possessed the characteristic sigmoid-shaped type II isotherm curves and the model gave the best fit over the whole range of aw tested. The differential scanning calorimetric method was used to measure the Tg of freeze-dried avocado samples. Increasing the water content decreased the Tg, and Tg was increased with increasing maltodextrin content. Increased maltodextrin content to solid material in the freeze-dried sample was associated with less sensitivity to caking as evidenced by Tg values. In addition, increased maltodextrin content in the powders caused brighter, less yellowish, and more greenish coloration and protected color change including browning index. The antioxidant capacity was significantly decreased with increasing maltodextrin content. Thus, the effect of maltodextrin concentration on physicochemical properties was a promising way to preserve the physical property and chemical compounds in freezedried avocado powder.

Water sorption characteristics of freeze-dried bacteria in low-moisture foods

Water sorption isotherms of bacteria reflect the water activity with the change of moisture content of bacteria at a specific temperature. The temperature-dependency of water activity change can help to understand the thermal resistance of bacteria during a thermal process. Thermal resistance of bacteria in low-moisture foods may differ significantly depending on the physiological characteristics of microorganisms, including cell structure, existence of biofilms, and growth state. Previous studies demonstrated that the incremental change of aw in bacterial cells during thermal treatments resulted in changes in their thermotolerance. In this study, a pathogen associated with low-moisture foods outbreaks, Salmonella Enteritidis PT30 (in planktonic and biofilm forms), and its validated surrogate, Enterococcus faecium, were lyophilized and their water sorption isotherms (WSI) at 20, 40, and 60 °C were determined by using a vapor sorption analyzer and simulated by the Guggenheim, Anderson and De Boer model (GAB). The published thermal death times at 80 °C (D80 °C-values) of these bacteria in low-moisture environments were related with their WSI-derived aw changes. The results showed that planktonic E. faecium and biofilms of Salmonella, exhibiting higher thermal resistance compared to the planktonic cultures of Salmonella, had a smaller increase in aw when thermally treated from 20 to 60 °C in sealed test cells. The computational modeling also showed that when temperature increased from 20 to 60 °C, with an increase in relative humidity from 10% to 60%, freeze-dried planktonic E. faecium and Salmonella cells would equilibrate to their surrounding environments in 0.15 s and 0.25 s, respectively, suggesting a rapid equilibration of bacterial cells to their microenvironment. However, control of bacteria with different cell structure and growth state would require further attentions on process design adjustment because of their different water sorption characteristics.

A Case Study of Turbulent Free Jet Flows Issuing from Rectangular Slots on Process Performances and Quality of Hot-Air-Dried Apple

This study deals with the improvement in drying process performances and the quality of the final product for industrial equipment in the food industry. Designers need to optimize the design parameters of devices to create synergies between the greater energy efficiency of the process and high-quality dried products. Air impingement drying was carried out on apple cylinders at 323 K and with air velocities ranging between 30 and 60 m s−1. The studied drying process presents a particular setup of jets as they are multiple rectangular slot jets issued from triangular nozzles. The effect of four design jet parameters (slot width, nozzle-to-surface height, nozzle-to-nozzle spacing, and airflow) on the drying process performances and the quality of the final product was analyzed and optimized using response surface methodology (RSM). A minimal influence of design jet parameters on the process performances was shown, while an important impact was observed on the quality of dried apple. The slot width and the nozzle-to-nozzle spacing had a significant effect on the textural and functional properties. Predictive models were established and good agreements were found between predictive and observed values. Sorption isotherms were properly modeled by the Guggenheim–Anderson–de Boer (GAB) model.