M. Anker et al., MECHANICAL-PROPERTIES, WATER-VAPOR PERMEABILITY, AND MOISTURE CONTENTS OF BETA-LACTOGLOBULIN AND WHEY-PROTEIN FILMS USING MULTIVARIATE-ANALYSIS, Journal of agricultural and food chemistry, 46(5), 1998, pp. 1820-1829
Mechanical and barrier properties of beta-lactoglobulin (beta-Lg) and
whey protein isolate (WPI) films were studied using sorbitol(S) as a p
lasticizer. The films were cast from heated aqueous solutions and drie
d in a climate chamber at 23 degrees C and 50% relative humidity for 1
6 h. The multivariate analysis used has proved to be a valuable tool f
or evaluating and quantifying the influences of the variables in the s
pecified experimental domain. Two identical factorial designs were app
lied to evaluate the influence of the concentration of beta-Lg and WPI
, the concentration of S, and the pH. The two materials, beta-Lg and W
PI, show similar results, which can be attributed to the dominating pr
otein beta-lactoglobulin. At pH 9, Young's modulus and stress at break
are not affected when the concentration of beta-Lg, WPI, or S varies.
At pH 7 and 8, Young's modulus and stress at break increase when the
concentration of beta-Lg and WPI increases, and they decrease when the
concentration of S increases. Strain at break increases when pH incre
ases from 7 to 9, a more pronounced effect being observed for the WPI
films. Water vapor permeability (WVP) decreases and increases for pH 7
and 9, respectively, as the concentration of beta-Lg and WPI increase
s. This contrast in behavior at different pH values is probably due to
a structural difference that occurs above pH 8. Moisture content and
WVP increase when S increases. Here a clear distinction can be observe
d between the two film materials: the beta-Lg films show higher values
for both moisture content and WVP measurements.