Abstract:

Low-cost film without oil permeation was prepared from corn gluten meal instead of zein by stretching method.
Using tensile strength as the response, the optimal processing parameters was determined by response surface methodology
as follows: ethanol concentration, 84.5%; temperature, 62 ℃; and pH, 7.7. Under these conditions, the maximum tensile
strength of the film of 20.77 MPa was obtained. It was shown that film thickness had no significant influence on tensile
strength, elongation at break, percentage dissolution or thermostability. However, there was a positive correlation between
film thickness and either oil permeation coefficient or transmittance. At a film thickness of 0.021 mm, the minimum oil
permeation coefficient of 0.018 9 (g·mm)/(m 2·d) and the maximum transmittance of 82.33% were achieved, whereas oil
permeation coefficient was maximum, 0.159 8 (g·mm)/(m2·d), and transmittance was minimum, 65.53%, when the film
thickness was 0.101 mm. The scanning electron microscopy (SEM) results showed that the surface of all prepared films
was smooth without obvious particles, bubbles or bumps. However , there were linear stripes on the surface of the films.
The irregular linear stripes turned into an oval with a large diameter, sparse when the tension was increased. Stretching
action obstructed protein aggregating on the surface of the films, which had a positive effect on the formation of stable
and compact films.

Key words: corn gluten meal, stretching method, tensile strength, oil permeation coefficient