Читать книгу Sustainable Food Packaging Technology - Группа авторов - Страница 29

Soy protein (SP) is an inexpensive renewable resource, sustainable, abundant, and functional, constituted by different globulins with mainly polar amino acids including acidic and basic amino acids and nonpolar amino acids fractions such as 2S, 7S, 11S, and 15S. The major components of SP are β‐conglycinin (7S, nearly 35%) and glycinin (11S, nearly 52%) [136]. The protein with higher 11S fractions produces stronger films with lower water uptake than those richer in 7S, which is attributed to the presence of different sets of amino acids in 7S and 11S fractions [137]. Likewise, different chemical treatments and plasticizers have been explored to improve the intrinsic brittleness and low water resistance of SP‐based films. Among them, glycerol, ethylene glycol, and propylene glycol have been found to outperform 1,3‐propanediol. Glycerol and water can significantly increase the flexibility of films made of SP, but greatly decrease the tensile strength [138].