GAB Model Research Articles

Biocompounds recovery from purple corn cob by-product: extraction kinetics, thermal and physicochemical stability of liquid and powdered anthocyanin-rich extract

This study evaluated the thermal degradation kinetics of total monomeric anthocyanins (TMA) from in-natura purple corn cob and the recovery of bioactive compounds from their by-products. The TMA and antioxidant capacity (AC) extraction kinetics were evaluated by conventional (CE) and ultrasound-assisted extraction (UAE, 25°C, 40kHz, 32W/L) methods. The stability of liquid and powdered extract by using maltodextrin (M) [M(2%)] and corn starch (C) [M(1.5%) + C(0.5%)], was evaluated. Thermal degradation kinetics (65-90°C) showed that TMA are relatively stable at high temperatures, with a half-life of 5.3h at 90°C and an activation energy of 949.2J·mol-1. The TMA and AC extraction kinetics from corn cob by-product, described by the Peleg model, showed that the UAE had the highest extraction rate (<k1) and equilibrium yield (<k2), reducing CE times by up to 58% and 67%, for TMA and AC respectively. Furthermore, the stability of this extract was greater at pH ≤ 3, decreasing at neutral and alkaline pH. On the other hand, the water adsorption isotherms modeled by GAB model showed that the powder [M(1.5%) + C(0.5%)] had greater stability (Xm = 5.97g/100g d.m.) compared to the powder [M(2%)] (Xm = 3.71g/100g d.m.). Additionally, significant differences were observed between treatments in terms of color density, polymeric color, and % tannin contribution, where the powder [M(1.5%) + C(0.5%)] demonstrated greater stability. These results highlight the effectiveness of the UAE method for recovering TMA and AC from purple corn cob by-products and the importance of storage conditions and pH in the stability of anthocyanin-rich extracts and powders with potential applications in food and non-food industries.

Vitamin B Complex Encapsulation in Bacterial Nanocellulose: A Novel System for Heat and Chemical Stabilization in Food Products

Bacterial nanocellulose has been commonly used as a gelling or stabilizing agent in the food industry and as an excipient in pharmacology. However, due to its physical and chemical properties, such as its high degradation temperature and the ease with which it can interact with other molecules, bacterial nanocellulose has been established as a material with great potential for the protection of bioactive compounds. This research shows the capacity of bacterial nanocellulose to establish interactions with B vitamins (B1, B2, B3 and B12) through different sorption isotherms, mainly by means of the BET, GAB and TSS models. First, the degradation of the vitamin B complex, which mostly occurs upon heating, is minimized in the presence of BNC, herein proposed as a thermal stabilizer. Secondly, BNC is shown to bind to micronutrients and act as dietary fiber. BNC acts as a thickening and water-binding agent. The effects of BNC are determined to occur as an encapsulation system that facilitates affinity adsorption in mono- and multilayers. Finally, bacterial nanocellulose was used as an encapsulating agent for the vitamin B complex by spray drying. It is demonstrated that BNC is a very successful new nanomaterial for encapsulation, with a high level of adsorption, and for the protection of hydro-soluble vitamins. BNC has shown great potential to adsorb vitamins B1, B2, B3 and B12 owing to their hydroxyl groups, which are responsible for its water or vitamin sorption. Due to the features of bacterial nanocellulose, it is possible to use it as a raw material in the food industry to protect micronutrients during the thermal process.

Study of moisture sorption thermodynamic in canola oilseed and drying energy requirement considerations

AbstractThe objective of this study is to derive the thermodynamic characteristics from sorption isotherm data for canola. The semi‐gravimetric method was utilized at three different temperatures (25, 40, and 55°C) and seven air relative humidity levels within the range of 11%–90%. The observed data indicated that the equilibrium moisture content of the sample decreased as the temperature increased. The “GAB and BET” models were applied to fit the empirical data, which demonstrated a Type III isotherm, and the monolayer water content was subsequently determined using these models. Thermodynamic properties such as “isosteric heat,” “net isosteric heat,” “differential entropy,” “net integral entropy,” and “net integral enthalpy” were determined from isothermal sorption curves. The results show that as moisture content increases, both the sorption isosteric heat and the differential entropy of sorption decrease. This indicates that at higher moisture levels, the energy required for additional moisture adsorption and the changes in entropy are reduced. Similarly, the net isosteric heat of sorption and the net integral enthalpy of sorption also decrease with increasing moisture content, consistent with the observed reductions in isosteric heat and differential entropy. The specific absorption surface area for each temperature was determined by calculating the monolayer moisture content using both the “GAB and BET models.” The net integral entropy had an increasing trend in the range of 4%–4.5% (db%), while it decreased in the range of 4.5%–6.8% of moisture content. In addition, the spreading pressure at three levels of temperature was reported. Finally, an empirical relation was employed to illustrate the cumulative energy requirement for drying versus moisture content. The results indicated that at low moisture content levels, the drying process required significantly higher energy.Practical applicationsMoisture sorption isotherms are essential for understanding the interaction between water and food ingredients. This knowledge is vital for improving food processing methods such as drying, mixing, cooling, and storage. In industry, isotherms can help determine the best drying method to maintain food quality, identify the optimal mixing conditions to ensure consistency, establish cooling protocols to prevent spoilage, and set storage guidelines to extend shelf life. In addition, understanding thermodynamic properties is crucial for regulating moisture absorption and release, achieving the desired food texture, managing surface characteristics, and calculating the energy needed for effective dehydration processes.

Identification of water transitions using a combination of moisture sorption characteristics and dielectric properties of different parts of jasmine rice (Oryza sativa).

In this work, water transition points (first transition: monolayer-multilayer water; and second transition: multilayer-free and solvent water) of different parts of jasmine rice including white rice, brown rice and bran were identified through the integration of sorption isotherm and dielectric properties data. Desorption isotherm data were fitted to four established models to select the optimal model for describing the sorption behaviors. Then, dielectric properties such as dielectric constant (ε') and dielectric loss factor (ε″) were measured across various moisture content levels within the frequency range of 200-20 000 MHz. A type III isotherm was observed for all samples and the Peleg model was the best fit with the experimental data. Monolayer moisture content of the samples, estimated using the GAB model, ranged from 3.25% to 4.17% dry basis. For dielectric properties, frequency and moisture dependencies were evident for all sample types. Moreover, the sorption isotherm models effectively described the relationship between water activity (aw) and dielectric properties as reflected by their goodness of fit, and their strong correlation through principal component analysis and Pearson's correlation results. The first water transition occurs at aw values of 0.11, 0.12, and 0.22, while the second transition appears at aw values of 0.9, 0.9 and 0.75-0.85 for white rice, brown rice and bran, respectively. This knowledge will be useful for food processors, providing insights into the optimization of food processing and storage conditions to extend food products' shelf life. © 2024 Society of Chemical Industry.

Drying kinetics and water adsorption properties of jalapeño pepper seeds (Capsicum annuum L.): A study aiming at their recovery and integral exploitation

Drying kinetics (DK) and water adsorption isotherms (WAI) of Jalapeño pepper seeds (JPS) were evaluated and modeled at different temperatures. The proximate composition, flavonoid content (FC), and total phenolic compounds (TPC) of JPS were determined. Furthermore, JPS oil was extracted and characterized. Five mathematical models were tested to describe the JPS drying kinetics at five temperatures (40–80 °C) as well as the effective diffusion coefficient (Deff) and activation energy (Ea) were calculated. The WAI of the JPS was determined at nine temperatures (8–72 °C) and five mathematical models were fitted to JPS adsorption data. Thermodynamic properties were also estimated. The JPS presented TPC (30.9 mg GAE/g), FC (17.4 mg catechin equivalents/g), fibers (54.8 g/100 d.b.), lipids (22.2 g/100 d.b.), and proteins (15.5 g/100 d.b.). The study on drying kinetics pointed out that the Weibull model best fitted to drying kinetics data, Deff increased directly to temperature, and the Ea = 30.302 kJ/mol. The GAB model presented good accuracy in describing the WAIs that were classified as BET Type II. The net isosteric heat of adsorption and differential entropy decreased with increasing EMC. Enthalpy-entropy compensation theory was corroborated and characterized the adsorption of JPS as enthalpy-driven and spontaneous.

Moisture sorption phenomena of lactose anomers and evaluation of morphological stability

The importance of knowing the phenomenon of moisture sorption and the microstructural evolution in lactose anomers, lies in being able to establish its applicability. Thus, the moisture sorption phenomenon of four types of lactose anomers (C-βL, S-βL, F-αL and C-αL∙H2O) was studied, constructing adsorption isotherms at three storage temperatures (15, 25 and 35 °C), and fitting the experimental data with four mathematical models (BET, GAB, Peleg and Caurie). The analysis of the adsorption isotherm data, showed that: (i) β-lactose anomers adsorb less moisture than α-lactose anomers. (ii) In β-lactose anomers, purity influences stability, keeping a broad range of water activities. (iii) Increasing the storage temperature reduces the water activity range in which the anomers are stable. (iv) Based on the R2 parameter at 15 °C the best fit was achieved by employing the GAB model for the four lactose isomers, Specifically, the R2 values were as follows: C-βL = 0.993, S-βL = 0.996, F-αL = 0.905, and C-αL∙H2O = 0.98. The morphological evolution of lactose particles studied by scanning electron microscopy (SEM) showed particles of irregular morphology in the α-lactose anomers. Commercial β-lactose anomer presented particles with irregular morphology and few with curved morphology, suggesting the presence α-lactose as contamination. The synthesized β-lactose anomer presented mostly curved particles, indicating its high purity. In β-lactose anomers, mutarotation into α-lactose was observed with increasing storage temperature.

Impact of sugar reduction on the glass transition temperature and sorption isotherm of freeze-dried tomato powder

The objective of this work was to improve the drying of tomato juices after identifying the main parameters that are responsible for sticking during drying. Glass transition temperature (Tg) which is one of the key parameter, depends on the juice composition, mainly sugar. In order to reduce sugar, centrifugation was applied to the juices. Tg was determined by differential scanning calorimetry (DSC) for freeze-dried tomato juice and tomato pellet conditioned at various water activity (aw) (0.1–0.5). The glass transition curve showed that Tg decreased with increasing of the moisture. Comparison of powders obtained by juice and pellet from centrifugation shows that the Tg of freeze-dried pellets is higher than that of juice at equal aw values. Adsorption isotherms of freeze-dried tomato juice and pellet were determined at 25 °C and a relative humidity (RH) of 0–98% using a dynamic technique. The data obtained were fitted to GAB model that best fitted the experimental data. The equilibrium moisture content (X) value of the freeze-dried pellets are lower and had the same value of 8% dry mass. X is lower because the pellet powders are less hygroscopic than tomato juice powders because of the reduction of soluble compounds by centrifugation, notably sugars. Reducing the product sugar content by centrifugation enables to raise Tg without using carriers and obtain less hygroscopic powders, which is advantageous for product storage.

Moisture Sorption Studies using the GAB Model of a Beef Based Dambun Nama (A Ground Meat Product) Stored over a Period of Six Months

Water adsorption isotherms of Dambun Nama, a ground beef product, were determined over a storage period of six months, at an average ambient temperature of 33.8oC and an accelerated temperature of 50oC, using the static gravimetric method. The study was aimed at establishing the moisture sorption profile of a traditional meat product Dambun Nama common in Northern Nigeria, produced from beef and stored over a period of six months. The sample was produced using a standardized method; it was sterilized, packaged in six airtight glass containers and stored at ambient temperature as the sample stock for the analyses over a period of six months. Data was generated from the sorption studies based on the isopiestic transfer method using concentrated sulphuric acid solutions. The isotherms are generally shaped like the type 4 isotherms for food products. Between 33.8oC and 50oC adsorption, the monolayer moisture content ranged from 0.036 to 0.048 gH2O/g solids, and between 0.037 to 0.049 gH2O/g solids for desorption. There was a general increase in the GAB constants K and C. The correlation coefficient (R) values obtained for adsorption ranged from 0.941 to 0.959, and for desorption, the values ranged from 0.940 to 0.957, indicating that the GAB model was suitable in describing the moisture sorption profile of Dambun Nama within the prescribed water activity ranges and storage period.

Desorption properties of taioba (Xanthosoma taioba E.G. Gonç.) leaves: A non-conventional edible plant

This study aimed to determine the desorption isotherms and the thermodynamic properties of taioba leaves. For this, gravimetric-static method was used to determine the equilibrium moisture content (EMC) and water activity of taioba leaves at nine storage and drying temperatures (5–80 °C). The proximate composition was also determined. The Clausius-Clapeyron and Gibb's-Helmholtz equations were used to determine the net isosteric heat of desorption and differential entropy, respectively. The enthalpy-entropy compensation theory was also investigated. The relationship between water activity and equilibrium moisture content was best described by GAB model (Radj2 ≥0.987; χ2.105≤3.126; RMSE≤0.006) for the whole range of relative moistures and temperatures. The sigmoid-shaped type II was predominant at all temperatures. The net isosteric heat of desorption decreased from 8907.62 to 1120.15 J/mol as the moisture content increased. The linear relationship between enthalpy and entropy endorsed the enthalpy-entropy compensation mechanism in which TB > Thm, thus, an enthalpy-driven process. The free Gibbs energy was less than zero spontaneous (ΔGBstorage = −728.79 J/mol and ΔGBdrying = −1217.20 J/mol), indicating that water desorption is spontaneous. The spreading pressure varied from 0.001 to 0.05 J/m2 for all temperatures studied. The water surface area tended to decrease with increasing temperature, ranging from 185.71 to 251.97 m2/g. Therefore, this study provided an understanding of the water desorption properties of taioba leaves, contributing to the development of storage and drying practices.

State diagrams of green peas (Pisum sativum L.) powders with different maltodextrin additions.

The purpose of this study was to examine the effect of maltodextrin addition on the physical stability of powdered green peas. The evaluation of the physical state of the material was based on the equilibrium water content of the monolayer (Xm) and the glass transition temperatures of the powders at room temperature (Tg) and in the frozen state (Tg'). Graphical sorption characteristic at 25°C was determined using static-gravimetric method while capacity of the monolayer values was calculated from the mathematical GAB model. Differential scanning calorimetry was carried out in order to determine glass transition lines and freezing curves which combine together were used to plot state diagrams. Relationship between Tg and solid content were shown by using Gordon-Taylor model. Freezing data were modeled employing the Clausius-Clapeyron equation and its development-Chen model. Sorption isotherms showed sigmoidal shape characteristic for high-molecular weight materials. Monolayer moisture content varied between 0.047 and 0.106 g water/g solids. The glass transition temperature of anhydrous green peas increased in from 89.9 to 175.6°C while Tg' value changed from -43.4 to -26.6°C to as a result of 75% polysaccharide addition. The ultimate maximum-freeze-concentration conditions of the powders were observed in range from 0.783 to 0.814 g solids/g sample. Monolayer capacity, Tg and Tg' values increased with increasing maltodextrin amount in the sample which indicates that the addition of starch hydrolysate has a beneficial effect on the stability of powders stored frozen and at room temperature.

Modified GAB model of sorption on banana: spreading pressure and Gibbs free energy

Modified GAB model of sorption on banana: spreading pressure and Gibbs free energy

Effects of maltodextrin on water adsorption and thermodynamic properties of Codonopsis Radix spray-dried powder

This study aims to reveal the effects of maltodextrin(MD) on the water adsorption and thermodynamic properties of Codonopsis Radix(DS) spray-dried powder by determining the moisture and energy changes of the powder in the process of moisture absorption. The static weighing method was used to obtain the isothermal water adsorption data of the spray-dried powder in 6 saturated salt solutions(KAc, MgCl_2·6H_2O, K_2CO_3, NaBr, NaCl, and KCl) at 3 temperatures(25, 35, and 45 ℃). Six models were used for fitting of the water adsorption process, and the most suitable model was selected based on the model performance. Furthermore, the corresponding net equivalent adsorption heat and differential entropy were calculated, and the adsorption entropy change was integrated. The linear relationship between net equivalent adsorption heat and differential entropy was drawn based on the entropy-enthalpy complementarity theory. The results showed that the water adsorption properties of DS and DS-MD spray-dried powder followed the type Ⅲ isotherm and was well fitted by the GAB model. The monolayer water content M_0 decreased with the increase in temperature. At the same temperature, the M_0 of DS spray-dried powder decreased after the addition of MD. The net equivalent adsorption heat and differential entropy of DS and DS-MD spray-dried powder decreased with the increase in water content, which presented a linear relationship. The addition of MD decreased the water activity corresponding to the lowest integral adsorption entropy of the powder, and the system became more stable. The results indicated that the spray-dried powder became more stable after the addition of MD.

Water desorption isotherms and thermodynamic properties of Ora-pro-nóbis (Pereskia aculeata Miller)

Desorption isotherms of ora-pro-nóbis leaves were determined at storage (5 °C, 10 °C, 20 °C, 30 °C, and 40 °C) and drying (40 °C, 50 °C, 60 °C, 70 °C, and 80 °C) temperatures by the gravimetric static method using saturated saline solutions to obtain relative humidities ranging from 5.20% to 98.48%. The net isosteric heat of desorption and thermodynamic properties such as differential enthalpy, differential entropy, and Gibbs free energy were also estimated. The GAB model presented the best parameters of fitting and the lowest Akaike and Bayesian information criteria values. The desorption isotherm patterns presented a sigmoid shape and were categorized as BET Type II sigmoid shape. The monolayer moisture content was estimated in 0.06 kg of water/kg of dry matter using the GAB model, and it remained constant at all temperatures. The leaves presented an optimal water activity equal to 0.35 at storage temperatures. The net isosteric heat of desorption decreased with increasing Xeq, and differential entropy increased with rising equilibrium moisture content (Xeq > 0.07). The enthalpy-entropy compensation was evaluated, and the desorption process is revealed to be entropy-driven and non-spontaneous.

Characterization, mathematical modeling of moisture sorption isotherms and bioactive compounds of Andean root flours

Andean roots can be used as an alternative to gluten-free food. The objective of this study was to enhance the technological and nutritional properties of Andean root flours to promote their industrial applicability. The water content and activity of the flour were lower than those required to prevent mold growth. The bulk density of the flour was comparable to that of wheat flour. The flour of Ipomoea batatas (L.) Lam. exhibited the lowest water absorption capacity of the tested samples. However, both this flour and Tropaeolum tuberosum Ruiz & Pavón showed a higher fat absorption capacity. The samples exhibited type-II isotherms, indicating that the flours were highly hygroscopic. The Guggenheim, Anderson, and de Boer GAB model showed a higher coefficient of determination in mathematical modeling. The chroma of T. tuberosum Ruiz & Pavón flour was higher than the other samples, which was related to total carotenoids and lycopene. Furthermore, I. batatas (L.) Lam. exhibited the highest phenol value.

Sorption Isotherms and Thermodynamic Characteristics of Gelatin Powder Extracted from Whitefish Skin: Mathematical Modeling Approach.

Moisture adsorption and desorption isotherms of gelatin extracted from whitefish skin powder (FSGP) at different temperatures across a wide range of water activity were determined along with their thermodynamic properties. Nine mathematical models were utilized for fitting the experimental data and simulating the adsorption and desorption behavior. The thermodynamic properties were determined and fitted to the experimental data. The results showed that Peleg and GAB models were the best fit for FSGP. The energies involved in the adsorption and desorption process of FSGP indicated a stronger dependence on equilibrium moisture content (Xe). When Xe decreased, there was a consistent trend of increasing thermodynamic properties. Both the moisture adsorption and desorption behaviors of FSGP were, therefore, non-spontaneous processes. Linear correlations between the changes in enthalpy and entropy for adsorption and desorption were observed, indicating the presence of enthalpy-entropy compensation for FSGP. For preserving FSGP quality, it should be stored with Xw ≤ 8 (gw/gdm, d.b.) at temperatures below 53 °C and an RH of 50% to avoid it becoming rubbery. These findings are crucial for providing insight into the optimal drying and storage conditions.

Chemical Properties and Moisture Sorption Isotherm of Smoke- Dried Catfish (Clarias gariepinus) and Mackerel (Trachurus trachurus) Produced with a Modified Smoking Kiln: Application of Four Models to Sorption on Data

The effectiveness of a modified smoking kiln, the smoking quality, and the moisture sorption characteristics of smoked dried catfish and mackerel were all investigated in this study. Smoked dried catfish protein, ash, fat and moisture ranged between 73.37 and 73.80 %, 5.00 and 5.40% 10.30 and 11.05% and 8.05 and 8.12% respectively and for smoked dried mackerel 70.58 and 70.67%, 5.00 and 5.94%, 12.99 and13.15%, and 6.14 and 6.37% respectively, while the moisture sorption isotherm confirmed type III BET isotherm with marked hysteresis. Smoke dried catfish and mackerel's type III isotherm is as expected given that food items high in protein have been observed to display type III forms. For the Henderson, BET, GAB, and Oswin models, the values of the root means square ranged from 2.6 to 8.7, 4.6 to 9.1, 5.9 to 12.1, and 4.1 to 13.16, respectively. The coefficients of determination for these models ranged from 0.95 to 0.99, 0.93 to 0.96, 0.83 to 0.94, and 0.91 to 0.94. For catfish and mackerel, the isosteric heats of sorption for the adsorption and desorption pathways, respectively, were 4.55 and 1.22 kJ/mol and 4.07 and 1.10 kJ/mol, respectively. With an increase in temperature from 20 to 40 oC, the apparent sorbate surface area fell for catfish from 99.38 to 85.02 m2/g solid and for mackerel from 76.01 to 66.25 m2/g solid. The smoking kiln performed the basic tasks of smoking and drying the fishes very well, with high-quality nutrients.

Hygroscopic analysis of pre-dried madder roots (Rubia tinctorum L.) using a solar dryer: Implications for safe storage conditions

Current study investigated the sorption proprieties of madder roots. Sorption isotherms were measured through a gravimetric static technique using chemical salts, to control the surroundings water activity in a range of 0.05–0.9. Sorption measurements were conducted in three temperature 20, 30, and 40 °C. Integral proprieties were evaluated through Clausius-Clapeyron equation for a constant value of spreading pressure. In this study the optimal conditions for storage of madder roots were discussed in the indicated interval of temperature. The study findings showed that the madder roots isotherms were type II and the moisture content of product increased with the increase of water activity. Peleg and GAB models showed highly performance in fitting the sorption data. Integral entropy exhibited a minimum value in the region of 6–7% db, and 0.34–0.38 for moisture content and relative humidity, respectively. These conditions were considered as the best to preserve the madder roots shelf-life.

Mathematical modeling approach for the green synthesis of high-performance nanoporous zeolites Na-X optimized for water vapor sorption

A mathematical approach and green synthesis were employed to develop high-performance nanoporous zeolites with a high water vapor sorption capacity and to optimize the synthesis parameters using natural raw kaolin as the starting alumina-silicate material. The Box-Behnken design model with four factors was employed to elucidate the experimental matrix. The physicochemical and structural properties of the synthesized zeolite were characterized using XRD, FTIR, TG/DSC, 27Al and 29Si solid-state MSA NMR spectroscopy, Raman spectroscopy, FE-SEM, and N2 sorption isotherms. The obtained zeolite sample exhibited a BET surface area of 772.19 m2/g and a microspore volume of 0.16 cm3/g. The maximum water vapor uptake capacity at 25 °C and the highest relative pressure was determined to be 12.1137 mmol/g. The isosteric heat of adsorption and average entropy change were calculated to be − 41.340 KJ·K−1 and 115.308 J·mol−1·K−1, respectively. The resulting zeolite demonstrated excellent stability after five consecutive cycles of water vapor adsorption. The experimental data were fitted using five different isotherm and three kinetic models, and the accuracy of each model was assessed using error functions. GAB model and pseudo-first-order kinetic model exhibited the highest correlation coefficient. The nanoporous zeolite sample obtained through the surface response methodology is well-suited for industrial applications.

Potential effect of citrate nanocellulose on barrier, sorption, thermal and mechanical properties of chitosan/Arabic gum packaging film

Currently, the necessity to diminish environmental pollution caused by petroleum-based packaging plastics has encouraged interest in creating renewable and biodegradable packaging polymers. The objective of this study is the development of a green nanocomposite constructed from citrate cellulose nanospheres (CNC) that have been embedded in (CH/AG) Chitosan/Arabic gum (CNC@CH/AG) to meet the mechanical requirements. Citrate CNC was prepared using a citric acid/HCl acid mixture and it is investigated by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electron microscopy (TEM), Zeta potential, and degree of substitution. CNC@CH/AG film was investigated by FTIR, XRD, scanning electron microscope (SEM), wettability, mechanical, barrier, water vapor sorption, and thermal characteristics. CNC@CH/AG film displayed declining in water vapor permeability. The lowest water vapor permeability (WVP) value was 0.044 ± 23 × 10−3 g. mm. kPa−1. h−1. m−2 compared with control (CH/AG) was 0.129 ± 81 × 10−3 up to 3 mg CNC. For sorption properties, the CNC@CH/AG nanocomposite films are consistent with the GAB model, Smith, Henderson, and Peleg models. In comparison to CH/AG, the addition of CNC enhances all of the nanocomposites' tensile strength and Young's modulus by nearly two and three times, respectively, with a decrease in elongation percentage. The addition of CNC renders CNC@CH/AG nanocomposite films more thermally stable and the total activation energy of CNC@CH/AG nanocomposite film (−94.97 J/mol) is more than three times that CH/AG film (−34.04 J/mole).

Anthocyanin-based indicators design by polyelectrolyte complexation: A study on structural and thermodynamic properties, and application for milk freshness assessment

Non-pomace residue of grape juice powder (NPG) was used in the development of indicator films for food freshness assessment by polyelectrolyte complexation of alginate and gelatin, and alginate and chitosan. The surface topography of the films was evaluated qualitatively by the 3D plot of scanning electron microscopy images and quantitatively by mechanical profilometry, which demonstrated the formation of a heterogeneous surface. Higher NPG contents increased the average and the root mean square roughness of the films, with values of 0.450 and 0.634, respectively, for the alginate and chitosan complex with 1.0 g NPG 100 g complex−1. The diffractograms of the samples, as well as the FTIR spectra, demonstrated that NPG interacted differently with the two complexes. This behavior was evidenced in the evaluation of wettability, which was increased by the addition of NPG, as well as in the evaluation of thermodynamic properties. The water adsorption isotherms of the films were determined at 20, 30, and 40 °C. The GAB model presented the best fit for the adsorption data, which was an enthalpy-controlled process. The films demonstrated to be efficient in evaluating the freshness of whole milk samples acidified with lactic acid through the quantification of red chromatic shift as a function of pH, which proved to be a promising way to interpret the visual result of color change by digital image analysis.