Effects of Storage Temperature and Water Activity on the Degradation of Carotenoids Contained in Microencapsulated Chili Extract

The aim of this work was to evaluate the effects of storage temperature and water activity on degradation of carotenoids contained in microencapsulates of non-aqueous extracts from chili (NAEC). Total carotenoids content and adsorption isotherms of microencapsulated NAEC in a 1:1 weight ratio with gum Arabic-maltodextrin DE 20 (GA 50%–MD50%) were determined at 25, 35, and 40°C. The isotherms were fitted using the Guggenheim-Anderson-de-Boer model and their enthalpies and entropies, both differential and integral, were estimated by the Clausius-Clapeyron method. The minimum integral entropy was considered as the point of maximum stability at which water less readily participates in degradation reactions. Zones of minimum integral entropy were found between 7.56–8.30, 6.10–6.95, and 5.15–6.04 kg H₂O/100 kg dried solids, corresponding to water activity (a_w) of 0.210–0.239, 0.238–0.277, and 0.262–0.313 at 25, 35, and 40°C, respectively. Total carotenoids content (CT) degraded over time, but degradation of carotenoids was lower in microcapsules stored at 25°C than those stored at 35 or 40°C. The morphology of microcapsules was altered at a_w > 0.6, including swelling of the polysaccharide matrix was presented, and possible subsequent dissolution of the wall material, which indicates a high rate of carotenoid degradation. When microencapsulated NAEC were storage between 0.2–0.6 of water activity, the highest glass transition temperatures were achieved. In this range, the wall materials of the microcapsules suffer less microstructural modifications, associated with the minimum level of degradation of carotenoids. Sometimes, in this water activity range, the zones of minimal entropy were observed.     

Moisture Sorption Isotherms,Thermodynamic Properties,and Glass Transition of Pears and Apples

Moisture sorption isotherms of apples and pears were determined at 30, 45, and 60°C and water activity (a _w ) range of 0.04–0.83 using a standard static gravimetric method. The sorption isotherms of both fruits decreased with increasing temperature and exhibited type III behavior according to Brunauer–Emmett–Teller (BET) classification. The moisture desorption data fitted well with the Peleg model (0.997 ≤ r ≤ 0.999, 0.009 ≤ SE ≤ 0.071, and 4.840 ≤ p ≤ 13.779).

The glass transition temperature (T _g ) of both fruits decreased linearly with the increase in water activity (a _w ). The variation in glass transition temperature versus water activity (T _g  ～ a _w ) and glass transition temperature versus solid fraction of pears and apples (T _g  ～ W _s ) were adequately predicted by Khalloufi et al.'s model (0.998 ≤ r ≤ 0.999 and 0.007 ≤ SE ≤ 4.088) and the Gordon and Taylor model (0.879 ≤ r ≤ 0.979 and 9.798 ≤ SE ≤ 18.507). The thermal transition and desorption isotherms data were used to establish state diagrams of pear and apple and evaluate suitable fruits storage conditions.     

Characteristics,Stability, and Release of Peanut Sprout Extracts in Powdered Microcapsules by Spray Drying

This study was carried out to investigate the characteristics of powdered microcapsules from peanut sprout extracts prepared by spray drying. The microcapsules were made from medium-chain triglyceride (MCT) as primary coating material and whey protein concentrate (WPC) or maltodextrin (MD) as selected secondary coating materials. The microcapsule studies conducted were microphotograph, scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR), particle size, moisture contents, sorption, zeta potential, storage stability, and in-vitro study. The surface of microcapsules coated with WPC were rough and smooth, and particle size ranged from 2.86 to 8.59 µm. An FT-IR study revealed that absorption bands at 1,537 and 1,657 cm^?1 of microcapsules can be attributed to the protein amide I and II bands of WPC overlapped by the conjugated C?C. The moisture content was 1.33% in the microcapsules coated with WPC. The moisture sorption increased until 18% at the 90% RH. The yield of peanut sprout extracts from microcapsules was 89.01%. In the in-vitro study, the microcapsules released 2.48 and 6.01% at pH 2.0 and 4.0, respectively, in simulated-gastric fluid, and 61.07 and 89.24% at pH 6.0 and 8.0, respectively, in simulated-intestinal fluid. The preservation rate of the microcapsules dropped down to 60.43% from 89.01% during six months of storage. The stability of peanut sprout extracts in the microcapsules was over 80% at 4 and 20°C during 10-day storage. The zeta-potential of microcapsules was stable with ?30 mV. Based on the data obtained from the present study, the powdered peanut-sprout-extract microcapsules coated with WPC exhibited high stability during storage. Therefore, the powdered microcapsules by spray drying may be useful as a functional ingredient.     

Thermal Activation of Mendable Epoxy through Inclusion of Microcapsules and Imidazole Complexes

Epoxy resin was encapsulated in poly(urea–formaldehyde) microcapsules using an in situ dispersion polymerization technique. The efficiency of Ni and Cu–imidazole complexes as latent hardeners was compared to that of 2-methylimidazole. Calorimetric studies revealed higher reactivity of the nickel complex toward oxirane functionalities. Both the complexes could effectively cure the epoxy released from within the microcapsules in the event of damage followed by thermal treatment. The curing could be effected at lower temperature (T_onset = 145°C) using [Ni(2-Me-ImidH)₄Cl]Cl as compared to [Cu(2-Me-ImidH)₄Cl]Cl (T_onset = 152°C). A healing efficiency of 100 ± 2% could be achieved at 30% microcapsule loading, irrespective of the type of metal complex used.     

Spray drying of folic acid within nano-emulsions: Optimization by Taguchi approach

Research over recent decades has shown that inadequate folate concentrations may contribute to some disorders. Cereal flours have been a primary candidate for fortification by folic acid as they are consumed by most of the people but the main obstacle is destruction of this vitamin by the process and environmental deteriorating factors. So, it can be nano-encapsulated for protection and efficient delivery. Our main goal was to find the optimum conditions in spray drying of pectin–whey protein concentrate (WPC) double emulsions containing folic acid. Five independent variables including pectin and WPC content, dispersed phase content, pH, and surfactant type of span and polyglycerol polyricinoleate (PGPR) were considered along with water activity (a_w) and bulk density as the main responses. The experiment design was performed by Taguchi approach and 16 treatments were determined. The grand average of a_w and bulk density for folic acid powders was approximately 0.371 and 343?kg/m³, respectively. The main effect analysis with Taguchi technique revealed that pectin content was the most important factor affecting a_w (39.5%), and WPC had the minimum influence (6%). In terms of bulk density, it was found that the most important parameter was WPC (29.6%) and the minimum influence was related to surfactant system (8.1%). Finally, optimum conditions were determined as 0.5% pectin, 4.0% WPC, 10% dispersed phase, and pH 8, with a PGPR micro-emulsion, which resulted in a_w?=?0.229, and 1.5% pectin, 8.0% WPC, 10% dispersed phase, and pH 9, with a PGPR nano-emulsion, which resulted in density?=?245.45?kg/m³ for folic acid powders.     

Water Sorption,Glass Transition,and Microstructures of Refractance Window– and Freeze-Dried Mango (Philippine “Carabao” Var.) Powder

Water sorption isotherms, glass transition, and microstructures of Refractance Window (RW)– and freeze-dried Philippine “Carabao” mango powders were investigated. Water sorption isotherms were developed by the isopiestic method, while thermal transition of the powders, at various water activities (a _w  = 0.11–0.86), was determined using differential scanning calorimetry (DSC). The sorption isotherms of RW- and freeze-dried (FD) mango powders exhibited a type III sigmoidal curve, showing higher and lower adsorption capacities above and below 0.5 a _w , respectively. A significant difference (p < 0.05) in water content of RW- and freeze-dried mango powders for equivalent water activities was obtained above 0.5 a _w . The onset glass transition temperature (T _gi ) of RW- and freeze-dried mango powder solids decreased as the water content increased. There were no significant differences (p ≥ 0.05) in T _gi of RW- and freeze-dried mango powder solids at constant water activities, except for a _w  = 0.86. Microscopic examination of mango powders indicated that freeze-dried mango powders exhibited greater surface area and porosity in comparison to RW-dried mango powders.     

Influence of Poly(L-lactic acid) Molecular Weight on the Encapsulation Efficiency of Urea in Microcapsule Using a Simple Solvent Evaporation Technique

Poly(L-lactic acid) microencapsulated urea was prepared in water-in-oil-in-water (W₁/O/W₂) system by the solvent evaporation technique. The influence of poly(L-lactic acid) molecular weight on the percent loading, encapsulation efficiency, and the microcapsule morphology was studied using poly(L-lactic acid) having different number average molecular weights (M_n). Using the higher M_n, the smoother shell with complete encapsulation microcapsules was formed. Moreover, the percent loading and encapsulation efficiency of urea also increased with the poly(L-lactic acid) molecular weight. At 80,000 g/mol of poly(L-lactic acid), the obtained microcapsule gave the highest both percent loading (32%) and encapsulation efficiency (56%). The urea control release study of the prepared microcapsules was implemented by in vitro testing. The encapsulated urea was gradually released from the microcapsules, approximately 53, 29, and 22% of poly(L-lactic acid) at 3,000, 30,000, and 80,000 g/mol, respectively, for a month. These results presented the possibility of the prepared poly(L-lactic acid) microcapsules-encapsulated urea for urea control release that could be utilized in agricultural applications.     

Sorption Isotherms and Drying Characteristics of Tomato Peel Isolated from Tomato Pomace

Tomato peel was separated from pomace by sedimentation and dried in cabinet and fluidized-bed dryer at 50–70°C using 4–12 kg/m²tray load. The drying of tomato peel took place under the falling rate period and the drying behavior was well described by Page's model with coefficient of determination greater than 0.99 and standard error of 0.003–0.016. A fluidized-bed dryer was much more efficient than a cabinet dryer to dry tomato peel. The moisture adsorption isotherms of tomato peel were obtained by equilibrating above saturated salt solutions of known a _w (0.113–0.92) at 20–60°C. The data were analyzed using fifteen sorption models based on coefficient of determination, standard error, and residual plots. Modified Henderson was the best model for tomato peel with coefficient of determination >0.99, standard error <0.210, and a scattered residual plot. The net isostearic heat of sorption, estimated using the Clausius-Clapeyron equation, was 0.74–23.23 kJ/mol at 2.0–2.5% moisture content (dry basis).     

On the Efficacy of Ru/Al2O3 Catalyst for Steam Reforming of Ethylene Glycol

This work describes hydrogen (H₂) production via steam reforming of ethylene glycol (EG) over a supported ruthenium catalyst. EG is chosen as a model compound for the alcohols contained in the aqueous phase of bio-oil. Using a fixed-bed reactor, experimental runs are carried out over Ru/Al₂O₃ at various temperatures (350–500°C), ratios of the mass of the catalyst (W) to the molar flow rate (F_O) of EG at the inlet (W/F_O = 0.37 ? 2.38 g h/mol), and feed concentrations (22.3–53.4 wt.% EG in water). The role of Ru in conversion of EG, production of H₂, and product distribution of the carbonaceous species is studied. Reaction pathways previously described in the literature are used to elucidate our results.     

Utilization of paper mill sludge for removal of cationic textile dyes from aqueous solutions

ABSTRACT

The present study is concerned usage of paper mill sludge (PMS) as an effective adsorbent to remove the two cationic character dyes (Basic Blue 3 [BB3] and Basic Yellow 28 [BY28]) from aqueous solutions. The surface morphology and some characteristics of PMS were determined by Fouirer Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Brunauer Emmett Teller (BET). The parameters affecting the process – temperature (10–55°C), adsorbent dose (0.5–10 g/l), initial pH (2–10 pH), initial concentration (50–250 mg/l) and contact time (0–24 h) – were examined in the batch adsorption experiments. Maximum adsorption capacities (q_max) of two dyes at 1 g/l dose and pH value of 7 were also calculated as 89.35 and 79.81, respectively. Adsorption phenomena of BB3 and BY28 cationic dyes onto PMS is controlled by pseudo-second-order model. Thereafter, equilibrium experimental data were applied to Langmuir, Freundlich and Dubinin–Redushkevich (D-R) isotherms, and Langmuir isotherm is the best represent the equilibrium adsorption process for both dyes. The processes occurred by physical adsorption because of calculated activation values (E_a) of BB3 and BY28 dyes were 19.43 and 9.35 kJ/mol, respectively. In addition, based on thermodynamic calculations such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°), the results clearly demonstrated that the adsorption process were of exothermic and spontaneous nature for both dyes. At the light of obtained findings, it can be stated that PMS can be used effectively in removal of cationic dyes from textile wastewaters and is an alternative to commercial adsorbents due to its low-cost and abundance in the paper industries.     

Dehumidifier-Assisted Drying Characteristics of Nutrient Enriched Gellan and Agar Gels

The characteristics of moisture removal and selected physical properties during the dehumidifier-assisted drying of model food gel systems like agar and gellan gels were studied. The effect of gel forming ingredients/nutrients like FeSO₄ (0.05%), whey protein concentrate (WPC; 5%), and flaxseed powder (FSP; 5%) were investigated with an overall intention of developing a delivery system for nutrients as a convenience food. Gellan and agar gels were prepared at concentrations of 1, 2, and 3% (w/w) and subjected to drying at a low temperature of 40°C in a dehumidifier-assisted dryer up to 12 h. The different quality parameters that were determined included the extent of shrinkage, moisture content, textural parameters, and the diffusion coefficient. Agar gels possessed higher moisture ratios compared to corresponding gellan samples. The diffusion coefficients for agar and gellan gels were 0.83 × 10^?7 ? 2.38 × 10^?7 m²s^?1. The gellan gels were much harder than their corresponding agar gels. The addition of WPC, FeSO₄, and FSP increased the textural indices like fracture force, fracture strain, fracture energy, and total energy for 50% compression for all the gels. Gellan and agar gels showed volume shrinkage; the lowest shrinkages were with WPC added gels followed by the FSP and FeSO₄ incorporated samples. Dehumidifier-assisted dried food gels can serve as a delivery system for nutrients.     

Macromolecular sorbent materials for urea capture

Three types of chitosan–glutaraldehyde (Chi–Glu) crosslinked copolymer materials were prepared at various Chi–Glu weight ratios (i.e., 1 : 0.0835, 1 : 0.334, and 1 : 0.585) and variable reaction times. The corresponding Chi–Glu copolymer materials were imbibed in CuSO₄ solution to yield impregnated materials in the form of copolymer/Cu(II) complexes. The copolymer materials were characterized using FTIR spectroscopy and thermogravimetry analysis. Urea sorption isotherms were obtained in aqueous solution at 295 K and pH 7 with pristine chitosan, Chi–Glu copolymers (i.e., 1 : 0.0835 and 1 : 0.585), and the corresponding Chi–Glu/Cu(II) complexes. The concentration of unbound urea was monitored indirectly using a colorimetric method with p‐dimethylaminobenzaldehyde. The equilibrium adsorption data were analyzed using the Sips isotherm model. The uptake of urea with pristine chitosan was 4.7% w/w, whereas Chi–Glu copolymers display increased sorption (Q_m = 10.6–17.1% w/w) with increasing glutaraldehyde content. Urea sorption is further enhanced (Q_m = 16.3–26.4% w/w) for copolymer Chi–Glu/Cu(II) complexes. The preparation of Chi–Glu copolymers at various conditions illustrates that the sorption capacity and molecular recognition of urea can be systematically tuned via crosslinking and the formation of copolymer/Cu(II) complexes, and these results are related to a previously reported study (Shimizu and Fujishige, J. Biomed. Mater. Res. 1983, 17, 597). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Microencapsulation of Kaffir Lime Oil and Its Functional Properties

This paper describes the effects of spray drying temperature and wall materials on functional properties of kaffir lime oil microcapsules. The effects of spray drying were studied at inlet air temperatures at 160, 180, and 200°C. Two coating materials (konjac glucomannan and gum arabic) were employed in this study. The results indicate that kaffir lime oil had antibacterial activity against all tested pathogens and was able to inhibit Vibrio cholerae comparable to a standard antibiotic. The combination of konjac glucomannan and gum arabic (KGM+GA) can enhance the yield and retention of total oil in the microcapsules more than using konjac glucomannan alone as a wall material. Increasing inlet air temperature resulted in a decrease of antibacterial activity and amount of bioactive volatile compounds. Physical and chemical properties of the microcapsules did not differ significantly (p > 0.05) in terms of process yield, a _w , moisture content, efficiency in retention of total, surface and inner oil, water solubility index, and color except at inlet air temperature of 200°C. However, it was found that the kaffir lime oil microcapsules from KGM+GA produced at inlet temperature of 180°C had the best functional properties in terms of antibacterial activity and efficiency of retention of total encapsulated oil.     

Effect of an Orifice on Collection Efficiency and Wall Loss of a Slit Virtual Impactor

The effect of an orifice on the collection efficiency and wall loss of a slit virtual impactor was investigated both numerically and experimentally. The ratios of the collection nozzle width (W_c ), distance between acceleration nozzle and collection nozzle (S), length of acceleration nozzle (T), inlet width (D), and nozzle span (l) to the acceleration nozzle width (W_a ) were fixed at W_c /W_a = 1.4, S/W_a = 1.5, T/W_a = 1.1, D/W_a = 6, and l/W_a = 10, respectively. The minor-to-total flow ratio was set to 0.1 in laminar flow regime. The collection efficiency and wall loss of the slit virtual impactor were found to be characterized by the square root of the Stokes number. For the slit virtual impactor without an orifice, the square root of the Stokes number corresponding to the cut-off diameter was determined to be (Stk₅₀)^1/2 = 0.77 and the maximum wall loss at the collection nozzle reached 30% or 40%. When an orifice having the same width as the acceleration nozzle was placed upstream of the acceleration nozzle at a distance of 20W_a , the value of (Stk₅₀)^1/2 decreased to 0.68 and the wall loss at the collection nozzle decreased below 5%.

Copyright 2014 American Association for Aerosol Research     

Rheological properties of the blends of polychloroprene with poly[ethylene(vinyl acetate)]

Blends of poly[ethylene(vinylacetate)] (EVAc-45; 45% VAc content) and polychloroprene (CR) have been studied with respect to capillary and dynamic flow. It is found that EVAc-45, CR, and their blends are shear thinning (pseudoplastic) in nature. Though shear viscosity (η_a) and dynamic out-of-phase viscosity (η′_E) obeys power law, dynamic elongational viscosity (η′_E) does not follow it due to the synchronization of molecular vibration with the applied frequency at around 11 Hz. Both η_a and η′_E of the blends show positive deviation with respect to their additive values. The relative positive deviation (RPD) in shear flow increases with increasing temperature and shear rate. In the case of dynamic flow, RPD increases with increasing temperature but exhibits a decreasing trend with increasing frequency. RPD can be fitted well into a fifth-order equation with a weight fraction of CR (W_CR) in EVAc-45—CR blends. From rheological point of view, this relative positive deviation indicates blend compatibility between EVAc-45 and CR. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1759–1765, 1997     

Preparation and characterization of paraffin microcapsules for energy-saving applications

A series of microencapsulated phase-change materials (PCMs) with styrene–divinyl benzene shells composed of an n-octadecane (OD or C₁₈)–n-hexadecane (HD or C₁₆) mixture as the core were synthesized by an emulsion polymerization method. The effects of the core/shell ratio (C/S) and surfactant concentration (C_surf) on the thermal properties and encapsulation ratios of the PCMs were investigated. The chemical structures and morphological properties of the microcapsules were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy analysis, respectively. The characteristic peaks of the paraffin mixtures and shell material located in the FTIR spectrum of the microencapsulated PCMs proved that the encapsulation of the PCM mixture was performed successfully. The thermal properties of the paraffin microcapsules were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis. DSC analysis demonstrated that the microcapsules containing the maximum amount of paraffin mixture (C/S = 2:1) and the minimum C_surf (45 mmol/L) had the highest latent heat value of 88 kJ/kg and a latent heat of temperature of 21.06°C. Moreover, the maximum encapsulation ratio of the paraffin mixture was found to be 56.77%. With respect to the analysis results, the encapsulated binary mixture, which consisted of OD–HD with a poly(styrene-co-divinyl benzene) shell, is a promising material for thermal energy storage applications operating at low temperatures, such as in the thermal control of indoor temperatures and air-conditioning applications in buildings for desirable thermal comfort and energy conservation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47874.     

Energy requirements and production cost of the spray drying process of cheese whey

The influence of spray drying conditions on the energy required, production cost, and physicochemical characteristics of cheese whey was researched. The factors investigated were the inlet air temperature (180–220°C), outlet air temperature (80–100°C), and silica and maltodextrin (DE-10) as additives at 2 and 5% (w/w), respectively. Analysis of variance revealed that the inlet and outlet air temperatures, and the addition of additives had significant effects (p?T_inlet of 180°C, T_outlet of 80°C, and the addition of 5% additive material. Under these conditions, 0.2165?kg/h of dried product was obtained, with a moisture content of 2.08% and water activity of 0.125, and the product cost was $17.06?kg with an energy consumption of 2.0490?kW?·?h/kg of dry product.     

Characterization of nanosized silica size standards

Nanosized silica size standards produced with a sol–gel synthesis process were evaluated for particle size, effective density, and refractive index in this study. Particle size and effective density measurements were conducted following protocol from the National Institute of Advanced Industrial Science and Technology (AIST) in Japan. Particle sizes were measured via electrical mobility analysis using a differential mobility analyzer (DMA) at sheath flow rates (Q_sh) of 3.0 and 6.0 L/min and a constant aerosol flow rate (Q_a) of 0.3 L/min. The measured mean and mode diameters agreed well with the labeled sizes in the size range 40–200 nm, with differences ranging from 0.03% to 0.8%, well within the labeled expanded uncertainties (95% confidence intervals) of 1.8%–2.2%. The coefficient of variation (CV) of the size distribution was 0.012–0.027 for 40–200 nm. Particle sizes measured for 20 nm and 30 nm standards showed size differences with respect to the certified sizes of 1.7% and 8.3% at Q_sh = 6.0 L/min, but the size distributions were narrow, with CV = 0.047–0.064. The average effective density for the range 40–200 nm measured with an aerosol particle mass analyzer (APM) was 1.9 g/cm³. The real component of the refractive index measured with an optical particle counter (OPC) was 1.41 at a wavelength of 633 nm. All properties (size, effective density, and refractive index) were stable and could be measured with good repeatability. From these evaluations, it was found that the nanosized silica size standards have good characteristics for use as size standards and constitute a feasible alternative to PSL particles.

© 2017 American Association for Aerosol Research     

PREPARATION AND THERMAL EXPANSION OF FE2-xYxW3O12 POWDER BY CITRATE SOL-GEL PROCESS

Fe_2-xY_xW₃O₁₂ powder has been synthesized by the citrate sol-gel process. A model was proposed to calculate the concentration of species in a citric solution. The calculated results could provide valuable information for determining the optimal molar ratio of cation to citric acid and pH value of solution for Fe_2-xY_xW₃O₁₂ preparation. The predicted parameters derived from this model are in good agreement with the experimental results. The prepared gel and the Fe_2-xY_xW₃O₁₂ powder were characterized by X-ray diffraction (XRD) and differential thermal analysis-thermogravimetry (DTA-TG). The results show that it is very difficult to obtain pure Fe₂W₃O₁₂ powder by the citrate sol-gel process in the temperature range 500°–1000°C, however, Y₂W₃O₁₂ can easily be prepared even at 500°C. Y₂W₃O₁₂ annealed at 1000°C for 10 h is favorable for absorbing moisture in air to form Y₂W₃O₁₂·3.3H₂O. The thermal expansion coefficients of Y₂W₃O₁₂·3.3H₂O are: α_a = ? 8.01 × 10^?6°C^?1, α_b = ? 2.51 × 10^?7°C^?1, and α_c = ? 5.55 × 10^?6°C^?1 in 473–1173 K.