Oxygen permeability coefficients (OP), water vapor permeability coefficients (WVP), ethylene permeability coefficients (EP), tensile strength (TS) and percent elongation (%E) at break values were determined for chitosan films plasticized with glycerin at two concentrations (0.25 and 0.50 mL/g chitosan). Film samples were tested after 0, 2, 4, 8 and 12 wk of storage. After an initial drop in permeability during the first 2 wk of storage, mean OP (4.6 ϫ 10 Ϫ5 cc/m⅐day⅐atm) and mean EP (2.3 ϫ 10 Ϫ4 cc⅐/m⅐day⅐atm) remained constant while mean WVP (2.2 ϫ 10 Ϫ1 g/m⅐day⅐atm) decreased with respect to storage time. TS values (15-30 MPa) decreased and %E values (25%-45%) increased with respect to storage time. The stability of OP and EP values with storage was not expected, while the change in mechanical properties was as expected.

The effects of acid (acetic, formic, lactic, propionic) concentrations, plasticizer concentrations, and storage time (up to 9 wk) on mechanical properties, water vapor permeability, and oxygen permeability of solution-cast chitosan films were determined. Measured water vapor permeability coefficients ranged from 5.35 to 13.20 ϫ 10 -1 g/m·day·atm. Oxygen permeated coefficients ranged from 0.08 to 31.67 ϫ 10 -3 cc O 2 / m·day·atm. Neither property was affected by storage time. Tensile strength (6.85-31.88 Mpa) also was not time dependent, but elongation (14-70%) decreased with storage time. Lactic acid solutions produced the lowest oxygen permeability values, formic acid the highest. Films formed with 7.5% lactic acid solutions had uniquely high values for elongation at break.

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/m 2 /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.

An inexpensive zein-lipid mixture was isolated from yellow dent, dry-milled corn. Grease permeation through zein isolate applied to brown Kraft paper was found to be independent of loading levels at zein isolate levels above 30 mg/16 in.(2). The data shows that water vapor transmission rates depended on the amount of coating applied. Triacylglycerols were the most abundant lipid in milled corn but were absent in the zein isolate (perhaps due to hydrolysis by lipases). Zein from the paper was hydrolyzed enzymatically and the hydrolysis monitored by SDS-capillary electrophoresis. At an E:S ratio of 1:100 no further increase in the hydrolysate peak occurred after 10 and 30 min for alpha-chymotrypsin and pancreatin 8 x; however, zein and lipid were still present 1 h after hydrolysis by pancreatin 1 x.