Boer Equation Research Articles

Thermodynamic water adsorption analysis of biodegradable films based on corn starch-chitosan added with triblock copolymers

Adding triblock copolymers to hydrophilic films is an option to improve the functional properties and water resistance under high equilibrium relative humidity (RHeq) environments. Sorption isotherms of corn starch-chitosan based films added with triblock copolymers (L64 and P123) measured at 4, 20, and 36 °C were fitted using the Guggenheim-Anderson-De Boer equation. Thermodynamic analysis allowed allocating the minimum integral entropy value between 0.09 and 0.50 of water activity. The compensation enthalpy-entropy showed that the entropy driven the process at low water activities (0.10–∼0.33) and the enthalpy driven the water sorption at high water activities (∼0.33–∼0.90).

Assessment of the performance of Cromarty's equation to predict seed equilibrium moisture content during drying

For conventional seed (gene)banking of orthodox seeds, it is essential to effectively dry the seeds and maintain a low moisture content (MC). Cromarty's equation describes the MC and relative humidity (RH) relationship of drying seeds, based on their oil content, and can be used to predict the MC seeds would reach when dried to equilibrium in a controlled environment (RH, temperature). However, the equilibrium MC-RH relationship ('isotherm') varies not only between seeds of different species and depending on temperature, but also on whether seeds are losing (desorbing) or gaining (adsorbing) moisture. The reliability of Cromarty's equation in predicting the equilibrium MC for drying different seed species was examined and compared with the Guggenheim-Anderson-De Boer (GAB) equation, to model both desorption and adsorption data. Cromarty's equation provided a good fit to the desorption data for oilseed rape and barley (R 2 = 0.98). For yellow mustard, seed MC was overestimated and for lupin, wheat, buckwheat and pea, the MC equilibria predicted by Cromarty's equation were closer to the adsorption data. Overall, the GAB equation provided a better fit of the data. While Cromarty's equation is a useful tool for estimating the MC of seeds under a given environment, it should be used with caution in critical situations.

Influence of plant proteins blend or polydextrose on freeze-dried açaí (Euterpe oleracea) sorption isotherms and thermal properties

The influence of polydextrose or plant proteins blend, as a drying aid in freeze-dried açaí pulp, was evaluated regarding stability by vapor sorption isotherms at 20 °C in a water activity range of 0.1–0.95, obtained by vapor sorption analyzer and by saturated salt solutions, and the enthalpic properties were obtained by differential scanning calorimetry.The experimental isotherms data presented a good fit to the Peleg and Guggenheim-Anderson-de Boer (GAB) equations, açaí powder with polydextrose presented a Brunauer-Emmett-Teller (BET) type III, while the açaí powder without and with a plant proteins blend, type II. The freeze-dried açaí powders showed two endothermic peaks between −15 °C and 10 °C, probably related to linoleic and oleic fatty acids fusion. Fusion enthalpies of these peaks were lower when a carrier agent was used, which could be explained by a lower lipids content (25.0 J/g and 3.5 J/g for powder without the carrier and 12.0 J/g and 1.5 J/g for powder with plant proteins blend). The glass transition temperatures were between 49 °C and 58 °C, depending on the water activity, for powder without carriers and from 45 °C to 54 °C for the one with proteins.

Physical origin of adsorption heat and its significance in the isotherm equation

Adsorption heat is a cornerstone concept underpinning almost all the existing theoretical isotherms for porous media. Yet, it remains elusive what this concept stands for and what are the physical sources for it. Here, a rigorous thermodynamic formulation is derived for the adsorption process with the aid of the law of mass action, leading to an expression of adsorption heat as the external chemical potential difference between two adjacent adsorbate layers. The interaction between adsorbent and adsorbates like van der Waals is theoretically identified as the intermolecular source for the change of adsorption heat. Thereby, adsorption heat is formulated as a spatially varied function of the distance to adsorbent surfaces. This adsorption heat function facilitates the establishment of a two-parameter sorption isotherm equation. The equation can be theoretically converted to two widely used adsorption isotherm equations, namely Brunauer–Emmet–Teller (BET) and Guggenheim-Anderson-de Boer (GAB) equations, and shows excellent performance in capturing experimental isotherm data of a wide array of materials. The comparative analysis demonstrates that the derived two-parameter isotherm equation outperforms the two-parameter BET equation and the three-parameter GAB equation in most cases. Such performance verifies the generality of the derived isotherm equation, thus further confirming the validity of the derived formulation of adsorption heat.

Model-based investigation of water adsorption in Achira (Canna edulis K.) biscuits

The water adsorption properties of Achira biscuits were investigated using a mathematical model-based strategy to understand the relationship between water activity and moisture content due to the fact that it is highly relevant for its storage. For this purpose, the water adsorption isotherms of commercial Achira biscuits were firstly experimentally determined by the dynamic dew point (DDI) method at 25, 35, and 45 °C and ATR–FTIR spectroscopy was used to detect the functional groups. Secondly, the Guggenheim-Anderson-de Boer (GAB) equation, 4 empirical models (Smith, Oswin, Peleg and DLP), and 5 machine-learning techniques (Regression trees, Random Forest, k-Nearest Neighbors, Artificial Neural Networks and Support Vector Machine) were used to model the isotherms. The fundamentals of water adsorption were analyzed via GAB model parameters, adsorption surface area, spreading pressure, effective pore size, and thermodynamic properties, such as enthalpy-entropy and Gibbs free energy. The experimental results reflected a type III water isotherm and a moderate temperature effect. The GAB model quantified the effect of temperature on the adsorption properties, which reflected a lower degree of hygroscopicity at high temperatures. The Support Vector Machine Learning model provided the best mathematical description of the water adsorption isotherms considering the temperature effect (MRE<3% and R2adj>99%).

S-shaped adsorption isotherms modeled by the Frumkin–Fowler–Guggenheim and Hill–de Boer equations

S-shaped adsorption isotherms modeled by the Frumkin–Fowler–Guggenheim and Hill–de Boer equations

Study on water absorption and dielectric response of epoxy resin impregnated paper bushing

AbstractEpoxy‐impregnated paper transformer bushings are prone to water absorption due to the presence of water‐attracting moieties in the cellulose chemical structure and epoxy resin, leading to moisture‐induced insulation defects. To understand the mechanism of moisture's impact on epoxy‐impregnated paper, this study developed a testing platform that integrated moisture diffusion, adsorption, and dielectric properties of insulating materials. Insulation specimens made of epoxy resin and epoxy‐impregnated paper were prepared and their water diffusion characteristics were investigated using the Fick diffusion model and the Langmuir model, respectively. The Guggenheim–Anderson–de Boer equation was used to examine the vacuum vapour adsorption characteristics of the materials, providing a theoretical foundation for examining the form of water present within them. The dielectric response of materials with varying moisture levels was then tested to study the effect of water on the dielectric spectrum curve. Using the Extended Derivative Method, the characteristic frequency reflecting the water content of the epoxy‐impregnated paper was extracted. The results demonstrate that 0.01‐Hz characteristic frequency provides superior accuracy for moisture assessment in epoxy resins compared to 50 Hz, and extracting and fitting the relaxation peak characteristic frequency in epoxy‐impregnated paper moisture evaluation yields higher accuracy than using tan δ at the power frequency.

The role of natural hybrid nanobentonite/nanocellulose in enhancing the water resistance properties of the biodegradable thermoplastic starch

Abstract This study focuses on investigating the effect of hybrid nanofillers on the hydration characteristics and soil biodegradability of the thermoplastic corn starch (TPCS) hybrid nanofiller biocomposite (TPCS-HB) films. The data were benchmarked with that of the pure TPCS and TPCS single nanofiller biocomposite (TPCS-SB) as control films. The water absorption properties of TPCS, TPCS-SB, and TPCS-HB films were analyzed and fitted with the standard Guggenheim–Anderson–de Boer equation to study the water activity of the films. Besides, the water permeability test, water vapor permeability, and soil biodegradability of the films were also studied and correlated with the films’ surface morphology. The results indicated that the TPCS-HB films possess excellent hydration resistance and comparable biodegradable rate with the TPCS-SB films. The optimal water resistance properties were achieved when the optimal ratio of nanobentonite/nanocellulose (4:1) was incorporated into the TPCS matrix. The outcomes of this study provide an innovative idea and new insights that, by using natural and hybrid nanofillers, the hydrophobicity of the TPCS films could be enhanced. TPCS-HB films show great potential to be developed into a fully green biodegradable TPCS biocomposite film, especially for single-use plastic applications.

The influence of polydextrose on freeze-dried unripe acerola (Malpighia emarginata DC.) by the concept of a state diagram

Unripe acerola powders obtained from freeze-drying without (AV) and with polydextrose (AP) were characterized by using differential scanning calorimetry (DSC) and vapor sorption isotherms at (25, 35, and 45) °C in water activity ( a w ) range of 0.10–0.90. State diagrams built from DSC results, such as the glass transition ( T g ) and freezing ( T m ) points, were compared with those of the sorption isotherms. The Gordon-Taylor equation presented a good fit for T g , in which the solids glass transition increased and the k parameter decreased in the presence of polydextrose. The isotherms obtained were Brunauer-Emmet-Teller (BET) type III, and the Guggenheim-Anderson-de Boer (GAB) equation fitted to the experimental data showed slightly higher monolayer water content for AP, and not affected by temperature. Although there was a divergence in the stability when comparing the criteria of a w and T g , polydextrose increased the a w and T g of freeze-dried unripe acerola and conferred a stabler powder. • The stability criterion between water activity and glass transition was studied. • State diagrams of unripe acerola with polydextrose were built. • Polydextrose used as a drying aid increased the glass transition temperature. • Sorption isotherms of unripe acerola powders were BET Type III.

Effect of Temperature and Humidity on the Water and Dioxygen Transport Properties of Polybutylene Succinate/Graphene Nanoplatelets Nanocomposite Films.

Nanocomposite films of polybutylene succinate (PBS)/graphene nanoplatelets (GnP) with a GnP content ranging from 0 to 1.35 wt.% were prepared by melt processing. The morphology of both the neat PBS and PBS/GnP nanocomposites were investigated and revealed no significant impact of GnP on the crystalline microstructure. Moisture sorption at 10 °C, 25 °C, and 40 °C were analyzed and modeled using the Guggenheim, Andersen, and De Boer (GAB) equation and Zimm-Lundberg theory, allowing for a phenomenological analysis at the molecular scale. An understanding of the transport sorption properties was proposed by the determination of the molar heat of sorption (ΔHs), and the activation energy of the diffusion (Ed) of water in the matrix since both solubility and diffusion are thermo-activable properties. Both ΔHs and Ed showed a good correlation with the water clustering theory at high water activity. Water and dioxygen permeabilities ( and ) were determined as a function of temperature and water activity. and decreased with the addition of a small amount of GnP, regardless of the studied temperature. Moreover, the evolution of as a function of water activity was driven by the solubility process, whereas at a given water activity, was driven by the diffusion process. Activation energies of the permeability (Ep) of water and dioxygen showed a dependency on the nature of the permeant molecule. Finally, from the ΔHs, Ed, and Ep obtained values, the reduction in water permeability with the addition of a low content of GnP was attributed mainly to a tortuosity effect without diffusive interfaces rather than a significant change in the transport property mechanism.

KETERTELUSURAN DALAM RANTAI PASOK MAKANAN BEKU DI CV SAKANA INDO PRIMA

Developing a traceability system in the frozen food supply chain at CV Sakana Indo Prima. Frozen food in its processing has potential hazards that affect the quality and safety of food along the supply chain of frozen food products. These hazards include microbiological, physical, and chemical hazards that foodstuffs can experience during the production process to the hands of the final consumer. The development of this traceability system is divided into three stages. The first stage, namely by mapping and assessing supply chain performance, is carried out by identifying indicators of each level of SCM performance, calculating normalization values based on the initial value of KPIs using the norm de boer equation or formula, and calculating the final value of supply chain performance. The second stage is to carry out quality assurance by implementing the Hazard Analysis Critical Control Points (HACCP) system. Hazard analysis, hazard category determination, and critical control points and control measures. Determination of hazard categories as well as determination of essential points of control and control measures.

Effects of low-temperature microwave treatment of wheat germ.

Wheat germ has a great potential byproduct in food formulations for its outstanding nutritional value. To allow valorization, there is a need to inactivate endogenous enzymes such as lipases to avoid lipid oxidation. In the present study, the effects of microwaves on enzyme activity, as well as on functional and physical properties of wheat germ, were evaluated. Microwave treatments were performed at 50, 60 and 70 °C for 5-20 min. Lipase activity was severely affected at 60 and 70 °C in contrast to lipoxygenase. Microwave treatment did not cause changes in germ moisture content or color parameters. No significant changes were observed in equilibrium moisture content when comparing the adsorption and desorption processes of raw and microwave-treated wheat germ. The best model to describe sorption process was the Guggenheim-Anderson-De Boer equation. According to the dielectric properties of raw wheat germ, it could be considered as transparent to energy (ε' < 1.87 and ε'' < 0.35). Thermal analysis of proteins showed a low denaturation degree (below 35% to raw material). In addition, some functional properties were enhanced such as oil retention capacity. Conformational changes as a result of microwave treatment were associated with the slight decline observed on the monolayer moisture content. Microwave treatments of wheat germ at 60 and 70 °C were effective for lipase inactivation. Physical properties did not change drastically after the treatments. Microwave-treated wheat germ could be a good source of high-protein ingredient in food product development. © 2021 Society of Chemical Industry.

The Study of Bound Water Status and Pore Size Distribution of Chinese Fir and Poplar Cell Wall by Low-Field NMR

With the increasing shortage of timber resources and the advancement of environmental protection projects, many artificial fast-growing forests are planted and used as raw materials in China. There are significant differences in the properties of natural forest wood and artificial fast-growing forest wood, and the properties of wood mainly depend on the change in the status of bound water in the cell wall. In this study, the fiber saturation point (FSP) and pore size distributions within the cell wall of six species of fast-growing forest wood were studied by low-temperature nuclear magnetic resonance (NMR) technology. The effects of species, growth rings, and extractives on the FSP and pore structure were analyzed. The water vapor sorption experiments were performed, and the adsorption isotherms of the samples were fitted through the Guggenheim-Anderson-de Boer (GAB) equation. According to the least-square regression of the adsorption isotherms and combined with the low-temperature NMR experiments, the content and proportion of the different types of bound water were analyzed. The results showed that the average FSP of each Chinese fir was about 40% and that of each poplar was about 35%. There is about a 10% difference between the FSP measured by NMR technology and the adsorption bound water content obtained by adsorption isothermal. The pore size distribution results show that in all samples, the proportion of pores larger than 10.5 nm is very low, about 10%; the proportion of 1.92-10.5 nm pores is about 30%; and the proportion of pores smaller than 1.92nm is more than 50%. This work will be helpful to the study of the wood moisture status and provide reference data for wood modification.

Nanoparticles of γ-Sitoesterol and Ag on Clinoptilolite Zeolites

This work reports, the obtainment and stabilization of organic nanoparticles (γ-sitosterol) and Ag cations on the external area of Ca-clinoptilolite zeolite (Z17) are presented. The novelty of the present study lies in the formation and stabilization of nanoparticle organic molecules (γ-sitosterol) and inorganic cations (Ag) on the external area of Ca-clinoptilolite zeolite. The γ-sitosterol nanoparticles were obtained using Tournefortia hirsutissima and were later stabilized on the external area of Ca-clinoptilolite. The Ca-clinoptilolite-rich mineral as well as silver zeolitic minerals was characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM); elementary composition of the zeolitic mineral was determined by microanalyses (EDS) and high-resolution adsorption (HRADS) using N2 adsorption as a probe molecule. The EDS results about the exchange with Ag indicate the following sequence: Z17Ag03 &gt; Z17Ag-09 &gt; Z17Ag-06 &gt; Z17Ag-01. The XRD studies indicate that only in the sample Z17Ag-03 there is an average crystal size of nanoparticles formed of 45.387 nm as determined by Sherrer’s equation. SEM images of clinoptilolite showed the presence of crystals with irregular and poorly defined box shapes that are typical for this type of zeolites. The nanoporosity of natural zeolites was studied by N2 adsorption; external areas were estimated through the De Boer and BET equations. The specific surface area calculated by BET equation, A SB , presents the following sequence: γ-SZ17 &gt; Z17 &gt; Z17Ag09 &gt; Z17Ag03 &gt; Z17Ag01 &gt; Z17Ag06, while for the values of the external area obtained by the t method, the sequence is A ST : γ-Z17 &gt; Z17 &gt; Z17Ag03 &gt; z17Ag09 &gt; Z17Ag06 &gt; Z17Ag01. For its part, the pore size distributions tell us that the sample Z17 exhibits a sharp multimodal distribution with pore size maxima happening at 1.262, 1.933, 3.824, and 4.282 nm. Z17Ag01 exhibits a bimodal distribution with pore size maxima occurring at 5.45 and 5.533 nm. The sample Z17Ag06 exhibits a sharp bimodal distribution with pore size maxima happening at 3.666 and 7.021 nm, and the sample Z17Ag09 exhibits a sharp trimodal distribution with pore size maxima happening at 1.853, 4.275 and 5.967 nm. Antibacterial activities of the exchanged samples with Ag on the external surface area were measured as a function of exchange level against Gram-positive bacteria (P. aureoginosa, K. pneumonie, and A. baumannii) and Gram-negative bacteria (E. coli, S. saprophyticcus, S. aureus, and E. feacalis); the selectivity sequence of the clinoptilolite and antibacterial activity results are presented. Z17Ag09 clinoptilolite seemed to be a promising antibacterial material.

Improvement of Barrier Properties of Biodegradable Polybutylene Succinate/Graphene Nanoplatelets Nanocomposites Prepared by Melt Process.

Polybutylene Succinate (PBS)/Graphene nanoplatelets (GnP) nanocomposites over a range of GnP from 0 to 1.35 wt.%. were prepared by a melt process. A mixture of individual graphene nanosheets and aggregates was obtained by the addition of GnP in the PBS matrix. The presence of these fillers did not significantly modify the morphology, crystalline microstructure of the matrix or its thermal stability. However, a slight reinforcement effect of PBS was reported in the presence of GnP. The water sorption isotherm modelling with Guggenheim, Andersen and De Boer (GAB) equation and Zimm-Lundberg theory allowed a phenomenological analysis at the molecular scale. The presence of GnP did not modify the water sorption capacity of the PBS matrix. From a kinetic point of view, a decrease of the diffusion coefficient with the increasing GnP content was obtained and was attributed to a tortuosity effect. The influence of water activity was discussed over a range of 0.5 to 1 and 0 to 0.9 for water and dioxygen permeability. Improvement of the barrier properties by 38% and 35% for water and dioxygen permeability respectively were obtained.

Effect of Emulsifier Diacetyl Tartaric Acid Ester of Mono- and Diglycerides (DATEM) and Enzyme Transglutaminase on Quality Characteristics of Rice Bran Croissants

Rice bran (RB) is a good source of dietary fibre. Addition of rice bran into croissant interferes with the gluten formation of dough and hence affect the physicochemical properties of croissant. The effect of RB addition on physicochemical properties of croissant were determined by using 0%, 10% and 15% RB. Besides, additives such as emulsifiers and enzymes can be used in pastry to enhance the physicochemical properties of croissant. Diacetyl tartaric acid ester of mono-diglycerides (DATEM) and transglutaminase (TGase) were used respectively on 0%, 10% and 15% RB to investigate the effect of such additives on physicochemical properties of croissant. Increased % RB and DATEM, produced a significant decrease in specific volume, together with a significant increase in colour, hardness and chewiness. With increased % RB, TGase caused significant increase in colour, hardness and chewiness but significant decrease in specic volume. The overall moisture sorption isotherm curves of the croissant belong to the Type III isotherm, also known as Flory-Huggins Isotherm (J-shaped). The critical aw obtained from the Guggenheim-Anderson-de Boer (GAB) equation showed that the shelf life of croissants were not positively impacted by the addition of DATEM and TGase and the addition of RB did not cause any significant positive effects on quality characteristics of croissants.

Accelerated shelf life testing of mocatilla chip using critical moisture content approach and models of sorption Isotherms

Mocatilla is a tortilla chip made from composite flour consists of modified cassava, corn, and rice flour which is enriched by tempeh. This study aimed to estimate the shelf life of mocatilla chips when packed in polyethylene terephthalate (PET), polypropylene (PP), and aluminum foil (alufo) using the Accelerated Shelf Life Testing (ASLT) method by the critical moisture content approach. The study was conducted by determining the initial, critical, and equilibrium moisture content of the sample by thermogravimetry. Six models of moisture sorption isotherm were fitted to determine the equilibrium moisture content using six salts with relative humidity (RH) values at a range of 0.076-0.903. The result showed that the initial and critical moisture content of mocatilla chips (g H2O/g solid) was 0.0141 and 0.0532, respectively. Meanwhile the equilibrium moisture content at relative humidity 80% and temperature 30°C was 0.1471. The Guggenheim Anderson de Boer (GAB) equation was the most suitable model for describing the sorption isotherm phenomenon of mocatilla chips. Based on Labuza’s equation, the shelf life prediction of mocatilla chips (80% RH, 30°C) packed in PET, PP, and alufo was 3, 8, and 62 months, respectively.

Sorption and thermal characteristics of ancient grain pasta of various compositions

The effect of ancient grain pasta composition on its sorption properties and phase transitions was evaluated. Three pasta samples were prepared from ancient grain flours: spelt wheat, einkorn wheat, emmer wheat and quinoa, and for comparison purposes one pasta sample from durum wheat flour. Water adsorption and desorption isotherms of pasta were determined and they were fitted by the Guggenheim–Anderson–de Boer equation. The state diagrams of pasta samples were developed by measuring their freezing points, glass transition temperatures, and the maximum-freeze-concentration conditions by Differential Scanning Calorimetry. All the pasta samples exhibited sorption hysteresis with higher equilibrium water content determined for desorption. Substitution of spelt wheat flour with other ancient grain flours in pasta samples resulted in decreased glass transition temperature, freezing temperature and the end point of freezing. The amount of un-freezable water in ancient wheat flour-based pasta was significantly higher than in durum wheat pasta. The results showed that the modification of chemical composition of pasta as a result of replacing semolina with flours from ancient grains is accompanied by a change in their sorption and thermal properties.

Application of the Guggenheim, Anderson, de Boer equation to study the impact of sealing treatments on pine wood sorption characteristics

Application of the Guggenheim, Anderson, de Boer equation to study the impact of sealing treatments on pine wood sorption characteristics

Kinetic study of vitamin D2 degradation in mushroom powder to improve its applications in fortified foods

The aim of this study was to develop a value chain approach to address the need for sustainable vitamin D2 food sources. A combined process of UV-irradiation and air-drying was used to produce a Pleurotus ostreatus powder with a target amount of vitamin D2 as an ingredient for functional foods. The kinetics of vitamin D2 degradation was studied as a function of water activity (aw) in the range 0.11–0.75 at 30 °C, and temperature in the range 20–40 °C, at aw 0.32. The Guggenheim–Anderson–de Boer equation was applied to model experimental data of moisture content as a function of aw at 30 °C, and the resulting monolayer water activity was found to correspond to the aw level of 0.45. During storage under different environmental conditions, vitamin D2 degradation followed first-order kinetics. The rate constants ranged from 0.00308 to 0.0121 d−1 at aw 0.11 and 0.75 at 30 °C, respectively. The Arrhenius equation was applied to calculate the activation energy for vitamin D2 degradation at aw 0.32, which resulted 37.6 kJ/mol. The kinetics data obtained can be used as a basis to design the best formulation strategy to deliver this vitamin with functional foods.