Proteins as agricultural polymers for packaging production

Advantages, types, formation, and properties of agricultural packaging materials based on proteins, with examples, are reviewed in detail. Proteins have long and empirically been used to make biodegradable, renewable, and edible packaging materials. Numerous cereal and vegetable proteins (such as corn zein, wheat gluten, and soy proteins) and animal proteins (such as milk proteins, collagen, gelatin, keratin, and myofibrillar proteins) are commonly used to form agricultural packaging materials. Two technological processes have been investigated to make materials based on proteins: the "wet (or solvent) process" based on dispersion or solubilization of proteins in a solvent medium, and the "dry process" based on the thermoplastic properties of proteins under low water content conditions. The macroscopic properties (including solubility in water, mechanical properties, and barrier properties) of agricultural packaging materials based on proteins are dependent mainly on the structure of the macromolecular three-dimensional network and on interactions between proteins, plasticizers, and cross-linking agents.