Aging of whey protein films and the effect on mechanical and barrier properties

J Agric Food Chem. 2001 Feb;49(2):989-95. doi: 10.1021/jf000730q.


This work focuses on the aging of whey protein isolate (WPI) films plasticized with glycerol (G) and sorbitol (S). The films were cast from heated aqueous solutions at pH 7 and dried at 23 degrees C and 50% relative humidity (RH) for 16 h. They were stored in a climate room (23 degrees C, 50% RH) for 120 days, and the film properties were measured at regular intervals. The moisture content (MC) of the WPI/G films decreased from 22% (2 days) to 15% (45 days) and was thereafter constant at 15% (up to 120 days). This affected the mechanical properties and caused an increased stress at break (from 2.7 to 8.3 MPa), a decreased strain at break (from 33 to 4%), and an increased glass transition temperature (T(g)) (from -56 to -45 degrees C). The barrier properties were, however, unaffected, with constant water vapor permeability and a uniform film thickness. The MC of the WPI/S films was constant at approximately 9%, which gave no change in film properties.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Glycerol / chemistry
  • Hot Temperature
  • Hydrogen-Ion Concentration
  • Milk Proteins / chemistry*
  • Sorbitol / chemistry
  • Thermodynamics
  • Time Factors
  • Whey Proteins


  • Milk Proteins
  • Whey Proteins
  • Sorbitol
  • Glycerol