The effects of plasticizers (polyethylene glycols [PEG] 400, 1,450, 8,000 and 20,000, glycerol [G] and propylene glycol [PG]), 30% dry basis, on the physical properties of methylcellulose (MC) films were investigated. With the exception of PG, plasticizers with low molecular weights (G and PEG 400) caused the largest increase in the d101 spacing of the crystal lattice. All plasticizers significantly (α= 0.05) increased oxygen (O2P) and water vapor permeabilities (WVP) of the films as compared to that of unplasticized MC, with PEG 400 having the greatest effect on O2P and G having the greatest effect on WVP. With the exception of PG, all plasticizers decreased the tensile strength of MC films, with PEG 400 causing the largest decrease. With the exception of PG and PEG 400, all plasticizers increased percent elongation values of MC films, with PEG 1,450 having the greatest effect. Glycerol and PEG were the most effective plasticizers for MC. the higher molecular weight plasticizers do provide some plasticizing properties and may be more suitable for applications that require a lower permeability to water vapor than can be achieved with glycerol.

The water vapor (WVP) and oxygen (O2P) permeabilities of beeswax (BW), eandelUla wax (CnW), carnauba wax (CrW) and microcrystalline wax (MW), formed as freestanding films, were determined. CnW and CrW both had small values for O2P (0.29 and 0.26 g'm-l"sec-l"Pa -1 X 10 -14 , respectively), which are less than half the value for high-density polyethylene and about a decade greater than the value for polyethylene terephthalate. O2P values for BW and MW were about 6-9X greater than those of CnW and CrW. WVP of CnW was 0.18 g'm-l"sec-l"Pa -1 X 10 -12, which is about one-half the value for CrW and MW and about one-third the value for BW. The WVP of CnW was somewhat less than that of polypropylene and somewhat greater than that of high-density polyethylene. Differences in permeabilities among the wax films are attributed mainly to differences in chemical composition and crystal type as determined by X-ray diffraction.

Edible fdms composed of a water soluble, carbohydrate layer (hydroxypropyl methylcellulose) and various kinds of lipid layers were tested for resistance to water vapor permeability. Films were tested at 25°C and a relative humidity differential of 85%. Films containing solid lipids, such as beeswax, paraffin, hydrogenated palm oil or stearic acid yielded permeabilities of 0.2 g * mil * day-l * mmHg-l or less which is a smaller value than that for low density polyethylene.

An edible, lipid-cellulose ether composite film was fabricated and tested as a barrier to internal moisture migration in a bicomponent food product stored under abusive conditions of frozen storage (-6.7"C for 9 wk). The product consisted of bread and a tomato-based sauce; the film was situated at the interface of the two components. The film effectively retarded migration of moisture from the sauce to the bread during storage. As a consequence, desirable sensory properties that were related to stabilization of moisture gradients, as measured following cooking, were maintained significantly better (P < 0.05) in the presence of the film than they were in its absence.