No abstract

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.

A method was developed by which films could be prepared from commercial isolated soy protein (ISP). ISP was treated -with alkali (ATISP) to alter film orooerties. Water vaoor oermeabilitv (WVP). oxygen 'permeability (G,Pj, tensile strength'(TSj, percent &ngatidn (%E), and appearanceof ISP and ATISP were compared. Alkali-treatment had no effect on WVP. 0,P. and TS. gave hieher %E. and improved film appearance. Films properties 'were alsoY compared at pH 6, 8, 10, and 12. In general, pH 6 gave higher WVP and OzP and lower TS and %E; while higher pH gave lower WVP and OaP and higher TS and %E. ATISP films could not be produced at pH 6. Film appearance generally improved with increased pH.

Factors affecting barrier properties [oxygen permeability (OP) and water vapor permeability (WVP)] and mechanical properties [tensile strength (TS) and elongation (E)] were investigated for methyl ccllulose (MC) and hydroxypropyl cellulose (HPC) films. OP, WVP and TS of MC and HPC films increased as the molecular weight (MW) of the cellulose increased. E of MC films increased as MW increased, but E of HPC films was highest for the intermediate MW of 370,000. OP, WVP and TS of MC films were not a function of thickness, but E slowly increased as film thickness increased. OP and WVP of HPC films were not relatable to film thickness, but TS and E of HPC films slowly increased as film thickness increased. TS decreased and E increased for both film types as concentration of plasticizers was increased. Plasticizers enhanced or retarded OP and WVP of cellulosebased films, depending on their concentrations.