Anker M, Stading M, Hermansson A M
SIK-The Swedish Institute for Food and Biotechnology, P.O. Box 5401, SE-402 29 Göteborg, Sweden.
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.
这项工作聚焦于用甘油（G）和山梨醇（S）增塑的乳清分离蛋白（WPI）薄膜的老化。薄膜由pH值为7的加热水溶液浇铸而成，并在23摄氏度和50%相对湿度（RH）下干燥16小时。它们在气候室（23摄氏度，50%RH）中储存120天，并定期测量薄膜性能。WPI/G薄膜的水分含量（MC）从22%（2天）降至15%（45天），此后一直保持在15%（直至120天）。这影响了机械性能，导致断裂应力增加（从2.7兆帕增至8.3兆帕），断裂应变降低（从33%降至4%），玻璃化转变温度（T(g)）升高（从-56摄氏度升至-45摄氏度）。然而，阻隔性能未受影响，水蒸气透过率恒定，薄膜厚度均匀。WPI/S薄膜的MC约为9%，保持恒定，薄膜性能无变化。
