Moisture Adsorption by Grain Protein Films

Journal of Food Science, 2000

The effects of whey protein hydrolysis on film water vapor permeability (WVP) and solubility at 3 plasticizer levels were studied. Little or no significant difference (p Ͼ Ͼ Ͼ Ͼ Ͼ 0.05) appeared for film WVP between unhydrolyzed whey protein isolate (WPI), 5.5% degree of hydrolysis (DH) WPI and 10% DH WPI films at comparable plasticizer contents. However, increase in glycerol (gly) content significantly increased film WVP. Thus, reduction in WPI molecular weight (MW) through hydrolysis may be a better approach to improving film flexibility than addition of plasticizer. Both 5.5% and 10% DH WPI had significantly different (p Յ Յ Յ Յ Յ 0.05) film solubility compared to unhydrolyzed WPI. Soluble Protein (SP) and total soluble matter (TSM) of hydrolyzed WPI films were much higher than for unhydrolyzed WPI films.

Journal of Agricultural and Food Chemistry, 1993

Soy protein isolate (SPI) and wheat gluten (WG) films can be cast from appropriate solvent systems. Such films can find use as edible or nonedible food packaging materials. The effect of pH of WG and SPI film-forming solutions on film formation, tensile strength (TS), percentage elongation at break (E), and water vapor permeability (WVP) was investigated. WG films formed within pH 2-4 and 9-13, whereas SPI films formed within pH 1-3 and 6-12. Film formation was inhibited by poor protein dispersion around the isoelectric pH region of SPI (pH 4.5) and WG (pH 7.6). SPI films prepared from pH 6 to 11 had significantly (P < 0.05) higher TS, higher E, and lower WVP than films from pH 1 to 3. WG films produced under alkaline conditions had significantly (P < 0.05) higher TS than films processed under acidic conditions.

Journal of Agricultural and Food Chemistry, 2001

Plasticized whey-protein and whey-protein emulsion films were produced using sorbitol and glycerol as plasticizers and butterfat and candelilla wax as lipids. Protein, plasticizer, and lipid ratios were optimized to obtain acceptable free-standing flexible films. Water solubility (20°C, 24 h) and moisture sorption isotherms (0.18-0.90 a w , 25°C) of the films were determined. The experimental moisture sorption isotherm values were fitted using the Guggenheim-Anderson-DeBoer (GAB) model. Solubility and equilibrium moisture contents (EMC) of the films were influenced by plasticizer and lipid incorporation. EMCs of all films increased rapidly at a w g 0.65. Incorporation of lipids reduced solubilities and EMCs of sorbitol-and glycerol-plasticized films. The effects of plasticizer and lipid type on GAB constants were also determined.

International Dairy Journal, 2010

This study deals with the effect of whey protein isolate (WPI) and glycerol (GLY) used as a plasticizer on some physical properties of cast whey protein isolate (WPI) films. Films were prepared from heated (80 C for 30 min) aqueous solutions of WPI at 7, 8, 9 and 10% (w/w), GLY (40%, w/w, of WPI) and WPI at 8% (w/w), GLY (30, 40, and 60%, w/w, of WPI). For all types of films, water vapour permeability for four relative humidity differentials (30-100%, 30-84%, 30-75%, and 30-53%), surface and thermal properties were measured. Varying the proportion of WPI and GLY in edible films had some effect on water vapour permeability, wetting and thermal properties of WPI films. A cumulative effect of both glycerol and protein content was observed on the water vapour permeability increase. Indeed film barrier properties are much better for the lowest WPI (7%) and GLY (40%) contents. GLY increases the degradation temperature and favours film surface wettability whereas protein content did not affects thermal properties of films.

Innovative Food Science & Emerging Technologies, 2010

This study was conducted to determine the effect of both soy protein and glycerol contents on physico-chemical properties of soy protein isolate-based edible (SPI) films. The aim of this study was to better understand the influence of SPI and GLY contents on the behavior of the physico-chemical properties of soy protein isolate-based films. Films were casted from heated (70°C for 20 min) alkaline (pH 10) aqueous solutions of SPI at 6, 7, 8, and 9 (w/w %), glycerol (50%, w/w, of SPI) and SPI at 7 (w/w %), glycerol (40, 60, 70 %, w/w of SPI). Water vapor permeability (WVP), was measured at 25°C and for four different relative humidities (30-100%, 30-84%, 30-75%, 30-53%). Surface properties and differential scanning calorimetry were also measured. Varying the proportion of SPI and GLY had an effect on water vapor permeability, wetting and thermal properties of SPI films. A synergistic effect of glycerol and protein was observed on the water vapor permeability. Glycerol and RH gradient strongly enhance the moisture absorption rates and permeability of SPI based films. SPI content weakly increases the WVP and does not modify the surface properties. The temperature of denaturation of soy protein decreases glycerol content except for the higher concentration whereas it increases with protein ratio. Industrial relevance: This topic of research aims to control mass transfers within composite foods or betweenfoods and surrounding media (for instance the headspace in packagings). The targeted applications from this work deals with the food product coating or the coating of paper-based packaging for limiting both the loss of water and flavors by cheese based products. This will allow to maintain the weight of the cheese during "ripening" and commercialization, and also to prevent (off-) flavour dissemination from very odorant cheese as produced in France and Poland.

Transactions of the ASAE, 1991

Published methods for production of homogeneous edible films from com and wheat proteins were adapted. Barrier and mechanical properties of the edible films were evaluated with procedures commonly used on polymeric films. Mechanical property data included thickness, elongation, tensile strength, tear strength, and burst strength measurements. Barrier property data included water vapor, oxygen, and carbon dioxide gas transmission rate measurements. Homogeneous com and wheat protein films were found to have low tensile strengths, far less than cellophane. Com films were brittle while wheat films were elastic in comparison to cellophane. All three types of film had low permeabilities for dry gases but relatively high water vapor permeabilities. KEYWORDS. Corn, Wheat, Edible films. Barrier properties. Mechanical properties. Physical properties.

Texturized soy proteins (TSP) have been used for many years as a substitute of animal protein. In recent times, TSP was used as a functional ingredient in several food applications; its process involves a drying step. The water adsorption isotherms of TSP were determined using the static method of saturated salt solutions at 10, 20, 30 and 40 °C. The experimental data were fitted to Oswin, Halsey, BET, GAB, Peleg and Darcy Watt models. The equilibrium moisture content at water activities up to 0.9 decreased as the temperature was increased from 20 to 40 °C. At higher water activities, the moisture content showed an inverse behavior, resulting a crossover of the isotherms. The GAB and Peleg equation showed the best fit for the experimental curves. The total heat of sorption of TSP increased with decreased moisture content.

Journal of Agricultural and Food Chemistry, 1996

Edible films were prepared from solutions of soy protein with calcium salts and glucono-delta-lactone (GDL). Calcium salts cross-linking interactions with soy-protein isolate (SPI) could result in the formation of films with rigid three-dimensional structure. GDL contributed to the formation of a homogeneous film structure due to increased protein--solvent attraction. Tensile strength (TS) of calcium sulfate treated SPI film (8.6 MPa) was higher than the TS of calcium chloride treated SPI films (6.4 MPa) and the control SPI film (5.5 MPa). Puncture strength (PS) of calcium sulfate treated SPI film (9.8 MPa) was higher than the PS of calcium chloride treated SPI films (8.5 MPa) and the control SPI film (5.9 MPa). SPI film formulated with GDL had larger elongation at break (39.4%) than that of SPI control film (18.2%). Calcium salts and GDL-treated SPI films had lower water-vapor permeability than the SPI control film.

2009

The influence of drying conditions (air temperature and relative humidity) on mechanical properties, solubility in water, and color of two kinds of soy protein isolate film: a commercial one (CSPI) and other obtained under laboratory conditions (LSPI) were evaluated using the response surface methodology (RSM). Soy protein films were prepared by casting using glycerol as plasticizer. The films were dried in a chamber with air circulation under controlled conditions of relative humidity (24%, 30%, 45%, 60%, 66%) and air temperature (34, 40, 55, 70, 76°C). It was verified that mechanical properties of films made from LSPI and CSPI are influenced in a very different way by the drying conditions due to a diverse initial protein conformation in both materials, as was revealed by DSC and SDS-Page studies. The solubility of the LSPI film was affected by temperature and relative humidity, being lowest ($50%) for films obtained at high RH and temperatures ranging from 45 to 76°C. For CSPI films, in contrast, solubility did not depend on the drying process and it remained relatively constant ($40%). The optimal drying conditions determined by RSM were: 70°C and 30% RH for CSPI films and 60°C and 60% RH for LSPI films. Dried under these conditions, CSPI films presented a higher tensile strength, lower elongation at break, lower solubility and better water and oxygen permeability than LSPI ones.

Journal of Food Engineering, 2008

The effect of protein, sorbitol, beeswax and potassium sorbate concentrations in whey protein films on their ultimate tensile strength, Young's modulus, elongation and transparency was investigated using mixture response surface methods. Protein, sorbitol and potassium sorbate were important factors influencing ultimate tensile strength, Young's modulus and elongation. Beeswax did not have an impact on ultimate tensile strength and Young's modulus, and it had little effect on elongation. On the other hand, it was the primary factor affecting the transparency of the films. Mixture proportions of protein = 0.58, sorbitol = 0.38, beeswax = 0 and potassium sorbate = 0.04 would yield an edible film with transparency P89%, ultimate tensile strength P4 MPa, elongation P40% and Young's modulus 6190 MPa.