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Water Vapor Transmission Rate (water + vapor_transmission_rate)

Distribution by Scientific Domains

Chemistry	83%

Selected Abstracts

Water Vapor Transmission Rates and Sorption Behavior of Chitosan Films

JOURNAL OF FOOD SCIENCE, Issue 7 2000
J.L. Wiles
ABSTRACT: This study measured the water vapor transmission rates (WVTR) and moisture sorption of chitosan films over a range of water vapor pressures at 25 °C. Films of a constant thickness were made using chitosan with 3 levels of deacetylation. Films were tested at test relative humidity (RH) difference between RH values of 84%, 75%, 69%, 53%, 43%, 33%, 23%, 11%, and 0 at 25 °C using ASTM F1249-90 or ASTM E 96-80. The equilibrium moisture content in the films ranged from 3.7% to 31.8% (dry basis) corresponding to 11% to 84% RH. WVTRs of films increased with increase in water vapor pressure. The mean WVTR ranged from 6.7 to 1146 (g/m2/d) over the range of water vapor pressure from 2.68 (11% RH) to 19.9 mmHg (84% RH). The percentage of deacetylation of chitosan films and the viscosity of the cast solution did not have an effect on the WVTR properties of chitosan films. [source]

ANTIMICROBIAL, PHYSICAL AND MECHANICAL PROPERTIES OF CHITOSAN-BASED FILMS INCORPORATED WITH THYME, CLOVE AND CINNAMON ESSENTIAL OILS

JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2009
M.H. HOSSEINI
ABSTRACT Chitosan-based films containing thyme, clove and cinnamon essential oils at 0.5, 1 and 1.5% v/v were prepared to examine their antibacterial, physical and mechanical properties. Scanning electron microscopy was carried out to explain structure,property relationships. Films containing thyme essential oil revealed larger inhibition zones than those containing clove and cinnamon essential oils against gram-positive and gram-negative bacteria tested. Films were more effective against gram-positive bacteria than gram-negative. Incorporating thyme and clove essential oils into chitosan-based films increased moisture content (from 17.80,28.38%), solubility in water (25.97,30.62%), water vapor transmission rate (0.00233,0.00571 g/s/m2) and elongation at break (25.31,42.70%) of films. Cinnamon-enriched films had opposite changes such as increase in tensile strength (from 12.2,21.35 MPa) and decrease in moisture content (17.80,9.36%) and solubility in water (25.9,14.21%) of films. PRACTICAL APPLICATIONS Microbial growth on food surfaces is a major cause of food spoilage. Combining antimicrobial agents such as plant essential oils directly into a food packaging polymer is a form of active packaging. These films possess the potential for improving microbial stability of foods by acting on the food surface upon contact. Because of the effect of direct addition of plant essential oils to food on sensory characteristics of packaged food, incorporation of essential oils into films may have additional applications in food packaging. [source]

Effect of Pasteurization, High-Pressure Processing, and Retorting on the Barrier Properties of Nylon 6, Nylon 6/Ethylene Vinyl Alcohol, and Nylon 6/Nanocomposites Films

JOURNAL OF FOOD SCIENCE, Issue 1 2009
L. Halim
ABSTRACT:, This study determined the impact of pasteurization, high-pressure processing (HPP), and retorting on the barrier properties of nylon 6 (N6), nylon 6/ethylene vinyl alcohol (N6/EVOH), and nylon 6/nanocomposite (N6/nano) materials. The pasteurized and high-pressure treated films were coextruded with low-density polyethylene (PE) as the heat-sealing layer. The retorted films were coextruded with polypropylene (PP). Oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of the samples were measured after pasteurization (75 °C for 30 min), HPP (800 MPa for 10 min at 70 °C), and retorting (121 °C for 30 min) treatments. These were compared with the thermal characteristics and morphologies of the samples using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Results showed that OTR of N6 and N6/Nano increased after HPP (16.9% and 39.7%), pasteurization (13.3% and 75.9%), and retorting (63.3% and 112.6%), respectively. For N6/EVOH, a decrease in OTR after HPP (53.9%) and pasteurization (44.5%) was observed. The HPP treatment increased the WVTR of N6 (21.0%), N6/EVOH (48.9%), and N6/Nano (21.2%). The WVTR of N6, N6/EVOH, and N6/Nano increased by 96.7%, 43.8%, and 40.7%, respectively, after pasteurization. The DSC analyses showed that the enthalpy and percent crystallinity increased (2.3% to 6.5%) in the N6/Nano when compared with the N6 material after each treatment. Retorting caused a decrease (3.5%) in the percent crystallinity of the polypropylene material. HPP did not cause major morphological changes to the samples. Results of the barrier studies were influenced by the crystallinity changes in the materials as seen in the XRD diffractograms. [source]

Chitosan,alginate,CaCl2 system for membrane coat application

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2001
Lishan Wang
Abstract Water-based formulations are preferred for membrane coat application because they do not require the use of noxious solvents. A novel aqueous chitosan,alginate,CaCl2 system was evaluated as a potential formulation to produce water-insoluble membranes of biodegradable polymers. Chitosan,alginate coacervates were prepared by controlled reaction of chitosan (0.25% w/v) and sodium alginate (0.25% w/v) solutions. Coherent membranes were obtained by casting and drying the coacervates suspended in aqueous CaCl2 solutions (0.05,0.07% w/v). Increasing the calcium content did not modify membrane thickness (25,26 ,m), but reduced the water vapor transmission rate from 658 to 566 g/m2/day, and improved the tensile strength of the membranes from 9.33 to 17.13 MPa. Differential scanning calorimetry, Fourier transform infrared spectroscopy, and elemental analyses of the chitosan,alginate coacervates indicated they were stable for up to 4 weeks of storage in distilled water at ambient temperature. Membranes of the stored coacervates required less calcium to attain maximum mechanical strength. They also had higher water vapor transmission rates than corresponding films prepared from fresh coacervates. On the basis of the properties of the cast film and its storage stability, the chitosan,alginate,CaCl2 system can be considered for potential membrane coat application. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:1134,1142, 2001 [source]

Effect of ovenproof plastic films on the quality of spotted rose snapper (lutjanus guttatus) fillets during frozen storage

PACKAGING TECHNOLOGY AND SCIENCE, Issue 5 2007
José Angel Dorado-Rodelo
Abstract Spotted rose snapper (Lutjanus guttatus) fillets packed in two polymer films, polyamide 6,6 (PA66) and polyethylene terephthalate (PET), were stored at ,20°C for a period of 120 days. Films were tested for melting temperature (PA66 253,257°C and PET 252,255°C), oxygen transmission rate [PA66 51.8 ± 12.9cm3/(m2·24h·atm) and PET 152.7 ± 0.2cm3/(m2·24h·atm)] and water vapor transmission rate [PA66 17.8 ± 1.7g/(m2·24h) and PET 6.5 ± 0.2g/(m2·24h)]. Sensory analyses (firmness, flavour and appearance) were performed at 0, 30, 60, 90 and 120 days of storage after baking the fillets in the same storage bags. For raw fillets, their water-holding capacity (WHC), total aerobic counts (TAC), pH, trimethylamine (TMA) and shear-force resistance were measured at the same periods. Sensory analyses after baking showed no differences between the fillets packaged in the two films. The WHC, TAC, pH and TMA values in both products were kept within accepted limits. The fillets packed in PET showed a significant increase in firmness (shear-force resistance) during the first 60 days of storage and then a decrease at 90 days due to dehydration through the film seals. Over the same period, the fillets packed in PA66 showed no significant changes in firmness. In this study, it was demonstrated that it is possible to develop a ready-to-bake fish fillet product by using ovenproof films for packaging during storage. Copyright © 2006 John Wiley & Sons, Ltd. [source]