Shelf Life Extension of Toasted Groundnuts through the Application of Cassava Starch and Soy Protein-Based Edible Coating

The use of cassava starch and soy protein concentrate edible coatings containing 20% glycerol in extending the shelf life of toasted groundnut during ambient (27 ± 1°C) storage for 14 days was studied. Chemical indices of oxidative rancidity and sensory parameters were evaluated using standard procedures. Moisture uptake, peroxide and thiobarbituric acid values of uncoated groundnuts were higher than 100% cassava starch coated groundnuts while toasted groundnuts coated with 50:50 (cassava starch:soy protein concentrate) had the lowest values. Toasted groundnuts coated with 50:50 (Cassava starch:soy protein concentrate) film had higher colour, taste, texture and overall acceptability scores than toasted groundnuts coated with 100% cassava starch film and control. The use of 50:50 (cassava starch:soy protein concentrate) edible coatings on toasted groundnut extended the shelf life of toasted groundnuts for 14 days compared to uncoated toasted groundnuts which developed objectionable taste after second day of storage at ambient (27 ± 1°C) condition.     

MOISTURE SORPTION CHARACTERISTICS of STARCH GELS. PART II: THERMODYNAMIC PROPERTIES

A thermodynamic approach was used to interpret the experimental adsorption and desorption isotherm data for potato starch gel. Calculation of the thermodynamic properties (differential enthalpy, integral enthalpy, differential entropy and integral entropy) provides an understanding of the properties of water and energy requirements associated with the sorption behavior. Isosteric heats (differential enthalpies) were calculated through direct use of moisture isotherms by applying the Clausius‐Clapeyron equation. the differential enthalpy and entropy decreased with increasing moisture content and were adequately characterized by an exponential model. A plot of differential heat versus entropy satisfied the enthalpy‐entropy compensation theory. the spreading pressure increased with increasing water activity, and decreased with increasing temperature. the net integral enthalpy increased with moisture content to a maximum value (around the monolayer moisture content) and then decreased. In a reverse manner, the net integral entropy decreased with moisture content to a minimum value and then increased.     

Moisture sorption isotherms and thermodynamic properties of walnut kernels

The moisture sorption isotherm data of walnut kernels stored in a chamber, the relative humidity (r.h.) of which is regulated by atomizing humidifier, were determined at three different temperatures (25, 35 and 45 °C) and r.h. ranging from 10% to 90%. Eight models, namely the GAB, BET, Henderson, Iglesias and Chirife, Oswin, Peleg, Smith and Caurie equations, were fitted to the sorption data. Several statistical tests were adopted as the criteria to evaluate the fitting performance of the models. Of the models tested, the Peleg model gave the best fit to experimental data. The surface area of a monolayer was calculated. The BET equation was applied to the monolayer moisture content and the corresponding a_w values at which a monolayer forms are presented. The experimental data were also used to determine the thermodynamic functions such as isosteric heat of sorption, sorption entropy, spreading pressure, net integral enthalpy and entropy. The sorption isosteric heats for walnut kernels were determined by the application of the Clausius-Clapeyron equation to sorption isotherms obtained from the best-fitting equation. Isosteric heats decreased with increase in moisture content and approached the latent heat of pure water. Adsorption entropy increased with increasing moisture content, and then it decreased sharply with increase in moisture content. The spreading pressures (adsorption and desorption) increased with increasing water activity. Net integral enthalpy of adsorption increased slightly with moisture content to a maximum value. Thereafter, it remained constant. Net integral entropy of adsorption was negative in value and it decreased with increase in moisture content to a minimum value, and then increased slightly with increase in moisture content.     

Thermo-mechanical properties of egg albumen–cassava starch composite films containing sunflower-oil droplets as influenced by moisture content

The effect of moisture content on the thermo-mechanical and structural properties of egg albumen–cassava starch composite films containing sunflower oil droplets was studied using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Composite films were prepared by cold gelation, dried in a moisture controlled incubator (83.5%RH) at 25 °C for 8 days and aged at different relative humidity at room temperature (21 ± 1 °C) for 7 days to obtain composite films with moisture contents of 4%, 7%, 11%, 17% and 46% (dry weight basis). In DMA thermograms the magnitude of G′ and G″ increased with increasing temperature in high-moisture samples, decreased and then again gradually increased for intermediate-moisture samples, and decreased in low moisture samples. DSC thermograms indicated two distinct peaks (at 49–53 °C and 79.8 to 132.4 °C) which were attributed to phase transitions and protein denaturation. SEM images indicated that the microstructure of the composite matrix changed with moisture content and heating temperature. Our study confirms that moisture content plays a key role in the thermo-mechanical properties and microstructure of egg albumen–cassava starch composite films containing sunflower oil.     

The fitting of various models to water sorption isotherms of tea stored in a chamber under controlled temperature and humidity

The moisture sorption characteristics of tea stored in a chamber regulated by an atomizing humidification system were investigated at 25, 35 and 45 °C for water activity ranging from 0.1 to 0.9. The sorption isotherms of tea were typical type II sigmoidal curves according to BET classification. In both adsorption and desorption, an increase in temperature resulted in lower equilibrium moisture contents at corresponding values of water activity. The sorption isotherms exhibited hysteresis over the whole water activity range. GAB, BET, Henderson, Iglesias and Chirife, Oswin, Peleg, Smith and Caurie models were applied for analysing the experimental data. Nonlinear regression analysis was used for the determination of the parameters in the equations. Estimated parameters and fitting ability for sorption models were evaluated. The Peleg model was found to be the most suitable for describing the relationship between equilibrium moisture content and water activity for the whole range of temperatures and relative humidities studied. The surface area of monolayer was calculated. The BET equation was solved for the monolayer moisture content and the corresponding a_w values at which monolayer forms were presented. Sorption isotherm data were used to determine the thermodynamic functions such as isosteric heat of sorption, sorption entropy, spreading pressure, net integral enthalpy and entropy. The Clausius-Clapeyron equation was used to evaluate the isosteric heats of sorption. The isosteric heats of sorption and sorption entropy decreased with increasing moisture content. The heat of desorption was little higher than that of adsorption at low moisture content. The enthalpy-entropy compensation theory could be successfully applied to water sorption by tea. This theory showed that the moisture sorption of tea was governed by enthalpy-controlled mechanisms. The spreading pressure increased with increase in water activity and decreased with increasing temperature. The net integral enthalpy decreased with moisture content while the net integral entropy increased.     

Development and characterization of cassava starch and soy protein concentrate based edible films

The sensory attributes, mechanical, water vapour permeability (WVP) and solubility properties of cassava starch and soy protein concentrate (SPC)‐based edible films of varying levels of glycerol were studied. Addition of SPC and glycerol up to 30% and 20%, respectively, reduced stickiness and improved colour and appearance of the films. Tensile strength (TS), elastic modulus (EM) and elongation at break (EAB) of films increased, while film solubility (FS) and WVP decreased with SPC and glycerol up to 50% and 20% level, respectively, ranging from 20.33 to 26.94 MPa (TS), 41.33 to 72.76 MPa (EM), 7.90 to 12.28 MPa (EAB), 15.07 to 31.90% (FS) and 2.62 to 4.13 g H₂O mm m^?2 day kPa (WVP). The TS, EAB and WVP were higher for the biofilms than for low‐density polyethylene and cellophane films.     

Physicochemical,thermal and sorption properties of nutritionally differentiated flours and starches

The aims of this work were to analyze physicochemical and thermal properties of ahipa and cassava flours and starches and to determine their water sorption isotherms and thermodynamic properties. Both flours are naturally gluten-free products, obtained by relatively simple procedures (grating or slicing). Ahipa flour gelatinized at lower temperature than cassava, indicating a better aptitude for cooking. Gelatinization temperatures of flours were higher than those of their starches. Water holding capacity of ahipa flours was significantly higher than those of cassava, leading the slicing process the highest values. Sorption isotherms were determined at 10, 20 and 30 °C. Experimental data were satisfactorily fitted using different mathematical models. Thermodynamic parameters associated with water adsorption process were calculated from GAB model, as well as the monolayer water content. All samples could be considered as products with an acceptable stability.     

ADSORPTION CHARACTERISTICS OF FUNCTIONAL SOY PROTEIN PRODUCTS

The moisture adsorption characteristics of three commercial functional soy protein products (two isolates and one concentrate) in the temperature range of 10 to 40C were studied. The temperature showed significant effect on both the change of moisture content during adsorption and equilibrium moisture content. The rate of moisture adsorption of a soy protein isolate at water activity of 0.84 increased, but its equilibrium moisture content decreased with the increase of temperature. The suitability of Peleg and GAB equations for modeling the change of moisture content during adsorption and adsorption isotherms was respectively examined, and the constants in both equations were determined. In the temperature range of 10C to 40C, the relative errors of predicted change in moisture content at water activity of 0.84 and predicted isotherms of a soy protein isolates were ranged from 1.36% to 4.85% and 2.80% to 3.63%, respectively. The two equations can be used to predict the change in moisture content during adsorption and isotherms of functional soy protein products at different temperatures with satisfactory accuracy.     

Water barrier and physical properties of starch/decolorized hsian-tsao leaf gum films: Impact of surfactant lamination

The moisture barrier and physical properties of bilayer films prepared by lamination of starch/decolorized hsian-tsao leaf gum (dHG) and surfactant layers were investigated. It was found that the water vapor permeability (WVP) of tapioca starch/dHG film (1.31 × 10^?10 g/m s Pa) pronouncedly decreased by the aid of a surfactant layer lamination (1.36–5.25 × 10^?12 g/m s Pa). The WVP of bilayer film increased with increasing the concentration of starch/dHG in the surfactant layer, but was not significantly influenced when it was thickened. The sorption isotherms of both monolayer and bilayer films made from starch/dHG showed typical behavior of water-vapor-sensitive hydrophilic biopolymers. However, the equilibrium moisture content of the monolayer film was significantly higher than that of bilayer films when water activity (a_w) reaches 0.33. Both the tensile and puncture force of starch/dHG films did not vary significantly by laminating a surfactant layer, indicating the mechanical strength of surfactant layer is relatively weak, and this surfactant layer mainly served as a barrier for moisture. When compared to emulsion-based starch/dHG films with surfactant, the surfactant laminated starch/dHG films showed higher water barrier property, mechanical strength, and transparency.     

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

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

Antimicrobial,rheological, and physicochemical properties of sago starch films filled with nanorod-rich zinc oxide

The effects of zinc oxide nanorod incorporation on the flow properties of sago starch solution and antimicrobial, sorption isotherm, water vapor permeability, and UV transmission of sago starch films were investigated. The nanorod-rich ZnO (ZnO-N) was homogenized by sonication and incorporated into sago starch solutions at different concentrations (e.g. 1%, 2%, 3%, and 5% w/w dried starch). Introduction of low concentration ZnO-N to starch solutions significantly increased the viscosity of the solution and significantly decreased the permeability of the films to water vapor by less than one third. Solubility, moisture content, and monolayer water content of the films were decreased, whereas contact angle was increased with higher ZnO-N concentration. ZnO-N starch films had 0% UV transmittance and were able to absorb more than 80% of Near Infrared spectra. ZnO-N sago starch films exhibited excellent antimicrobial activity against Staphylococcus aureus. These properties suggest that ZnO nanorod has the potential as a filler in starch-based films for use as active packaging materials in the pharmaceutical and food industries.     

Moisture sorption characteristics of dried acid casein from buffalo skim milk

Adsorption and desorption isotherms of dried acid casein prepared from buffalo skim milk were determined at 25°, 35° and 45 °C over a water activity range of 0.11-0.97 using static moisture gain/loss from test samples. Both the adsorption and desorption isotherms exhibited sigmoid shape corresponding to type II, typical to many foods. There was generally a negative temperature effect on equilibrium moisture content. The effect of temperature was, however, statistically not significant over the temperature range of 25-45 °C. Of the seven sorption models tested for fitting the sorption data, the GAB model gave the best fit at all the three temperatures. The temperature dependence of GAB parameters has been determined in the form of Clausius-Clapeyron equation. The calculated values of monolayer moisture content from BET isotherm equation have been found to be lower than the corresponding values found by using GAB equation. However, in both cases the monolayer moisture was higher in desorption than the adsorption and deceased with increase in temperature. The net isosteric heat of sorption decreased exponentially with increasing moisture content and approached a constant value of 0.331 kJ/mol at moisture content 28 g/100 g (d.b.). The moisture sorption hysteresis observed at 25°, 35° and 45 C was statistically significant. The extent of hysteresis was negligible in monolayer moisture content region, occurred predominantly in the water activity range 0.35-0.60 and decreased at higher water activities. Total hysteresis energy was evaluated from the sorption data using Everett and Whitton plot. The effect of increase in temperature was to decrease the amount of hysteresis.     

醇法大豆浓缩蛋白（SPC）挤压组织化的机理（Ⅰ）──利用反相色谱法研究蛋白质的吸湿过程

本研究开发了一种反相气相色谱法并将其成功地运用于测试蛋白质的吸湿等温线。结果表明：醇法大豆浓缩蛋白的单分子层吸湿量明显低于酸法大豆浓缩蛋白，且在吸湿过程中无溶胀现象。由于蛋白质聚集微粒表面的极性吸附点减少，致使醇法大豆浓缩蛋白无法获得有效的塑化作用。这是该大豆蛋白在常规挤压条件下无法实现组织化的主要原因。     

Sorption Characteristics of Soy Protein Films and their Relation to Mechanical Properties

Effects of plasticizers (glycerol, sorbitol, and 1:1 mixture of glycerol and sorbitol) on moisture sorption characteristics of hydrophilic soy protein isolate (SPI) films were investigated at three levels of plasticizer concentration (0.3, 0.5, and 0.7 g plasticizer/g SPI). The combined effects of relative humidity and plasticizer on mechanical properties of soy protein films were also examined. Moisture affinities of soy protein films were affected by hydrophilicity of plasticizer and its concentration. Under given RH conditions, films with higher glycerol ratio absorbed more moisture with higher initial adsorption rate, and films with higher plasticizer contents exhibited higher equilibrium moisture contents. Monolayer moisture contents of SPI films increased as glycerol ratio in a plasticizer mixture and plasticizer concentration increased. Plasticizer and absorbed water loosened the film synergistically, resulting in higher elongation but lower tensile strength. RH effects on mechanical properties of SPI films were varied with plasticizers and their concentration. Films of lower glycerol contents were more sensitive to RH variation as compared to the higher glycerol samples, whereas sorbitol concentration affected the RH region where a sharp decrease in TS value occurred.     

MOISTURE SORPTION STUDY ON NIGERIAN FOODS: MAIZE and SORGHUM

Adsorption-desorption behavior of maize and sorghum between a_w= 0.10–0.98 at temperatures of 20, 25 and 40C was studied. the grains exhibited type II sorption isotherm. the sorption data were analyzed using six sorption models and the coefficients of determination were between 0.6965–0.9994. the Caurie model gave the poorest fit and the Henderson model the best. Some models were better for adsorption than for desorption. the GAB and BET monolayer moisture contents were not significantly (p > 0.05) different. Monolayer values were temperature-dependent with activation energy from 1.36–10.08 MJ/mol and the maize monolayer values exhibited the highest sensitivity to temperature. Heat of sorption was obtained by applying Claussius-Clapeyron equation to the sorption isotherms at the three temperatures. the heat of sorption decreased with an increase in moisture content and an exponential equation was used to describe the relationship. the processing and storage consequences of this information were discussed.     

Effect of soybean substitution for cowpea on physical,compositional, sensory and sorption properties of<Emphasis Type="Italic"> akara</Emphasis> Ogbomoso

Akara Ogbomoso was prepared from cowpea:soybean flour mixture ratios of 100:0, 80:20, 60:40 and 40:60. Physical, compositional, sensory and sorption characteristics of the akara were evaluated. Protein and fat content increased, while carbohydrate content decreased as the soy content of the flour mixture of akara Ogbomoso increased. There were no significant differences (P<0.01) in the colour, taste, aroma and overall acceptability for either the freshly prepared akara Ogbomoso or the akara Ogbomoso stored for 10 weeks. There were significant differences (P<0.01) in crunchiness, increasing as the soy substitution increased both in the freshly prepared and stored akara Ogbomoso. The adsorption isotherms of akara Ogbomoso varied with varying levels of soy substitution and at 20, 30 and 40 °C, had sigmoid shaped, type II isotherms according to Brunauer-Emmet-Teller (BET) classification, and were affected by temperature and composition. Increased levels of soy substitution and temperature depressed the isotherms. Calculated monolayer moisture contents using BET and Guggenhein Anderson deBoer models decreased with increasing soy substitution and temperature.     

Sorption and thermodynamic properties of Terminalia superba Engl. & Diels and Triplochiton scleroxylon K. Schum. through the 15, 35 and 50 °C sorption isotherms

The hygroscopicity and thermodynamic properties of Terminalia superba Engl. & Diels (limba) and Triplochiton scleroxylon K. Schum. (obeche) wood were studied and the species were compared. The 15, 35 and 50 °C isotherms were plotted by applying the saturated salts method and fitted using the GAB model. The thermodynamic parameters were obtained from the isotherms through the integration method of the Clausius–Clapeyron equation. Infrared spectra were used to study possible chemical modifications in the cell wall, and X-ray diffractograms were used to analyse the crystal structure of the cell wall. Obeche had shorter crystallite length and a lower crystallinity index, giving rise to a higher number of amorphous zones and thus a higher number of sorption sites in the monolayer. As a result, the saturation moisture content in the monolayer (X _m ) is greater in obeche than in limba. In terms of the thermodynamic properties, in both species the net isosteric heat of sorption decreases as the equilibrium moisture content increases, and more energy is required in desorption than in adsorption.     

Effect of glycerol on the physicochemical properties of films based on legume protein concentrates: A comparative study

The overall goal of this research was to examine the mechanical, water vapor barrier properties and opacity of films prepared using legume protein concentrates (faba bean, pea, lupin, lentil, and soy) as a function of glycerol concentration (50, 75, or 100% [wt/wt]—relative to the protein weight). Overall, tensile strength (TS) decreased with increasing glycerol concentration, whereas tensile elongation (TE) and water vapor permeability (WVP) increased with increasing glycerol concentration. Film opacity was independent of glycerol concentration. The effect of protein‐type varied considerably depending on the functional property of the film being measured; TS was greatest with faba bean and lowest with lupin, whereas TE was highest for pea, and lowest for soy. Lentil protein films had considerably higher WVP, at the 100% glycerol concentration, as compared to the other protein concentrates. Findings from this study indicate that legume protein concentrates are capable of forming biodegradable, edible films. Overall, pea protein concentrate films showed the most promise for application in terms of strength, elongation, and moisture barrier properties.     

Rheological and calorimetric properties of corn‐, wheat‐, and cassava‐ starches and soybean protein concentrate composites

The effect of soy protein concentrate (SPC) on the rheological and calorimetric properties of corn, wheat, and cassava starches was assessed. SPC increased T_o values and decreased the ΔH of all tested starches, which could be related to lower availability of water for starch gelatinization and/or to the interactions between SPC and amorphous regions of starch granules. SPC and sugar addition modified the viscosity parameters (obtained through a rapid visco‐analyser) of starch pastes, which was attributed to an increase in solid content and to the interaction of proteins with the starch dispersed phase. Frequency sweeps were carried out with a rheometer on gels containing starch, SPC, and sucrose. SPC raised storage and loss modulus, producing more consistent starch gels. Besides, penetration tests showed that SPC steadily increased starch gel firmness. Scanning electron micrographs showed that protein concentrate produced gels with closer structures. Summarizing, the starch and SPC in the gels obtained were expected to be arranged in a two‐phase system. Results showed that it is possible to achieve different textures for starch dessert formulations.     

Influence of protein concentration on surface composition and physico-chemical properties of spray-dried milk protein concentrate powders

Surface composition, moisture sorption behaviour and glass–rubber transition temperature (T_gr) were determined for spray-dried milk protein concentrate (MPC) powders over a range of protein contents (35–86 g 100 g⁻¹). Surface characterisation of MPC powders indicated that fat and protein were preferentially located on the surface of the powder particles, whereas lactose was located predominantly in the bulk. Moisture sorption analysis at 25 °C showed that MPC35 exhibited lactose crystallisation, whereas powders with higher protein contents did not and continually absorbed moisture upon humidification up to 90% RH. The GAB equation, fitted to sorption isotherms of MPCs, gave increases in monolayer moisture value (m_m) with protein content. T_gr, measured with a rheometer, decreased significantly (P < 0.05) with increasing water content and increased with increasing protein content (P < 0.05). In conclusion, increasing protein concentration of MPCs resulted in altered surface composition and increased m_m value and T_gr values.