RESUMO
A protein concentrate (PC) was obtained from Grouper fish skin and it was used to prepare films with different amounts of sorbitol and glycerol as plasticizers. The best performing films regarding resistance were then modified with various concentrations of CaCl2, CaSO4 (calcium salts), and glucono-δ-lactone (GDL) with the purpose of improving their mechanical and barrier properties. These films were characterized by determining their mechanical properties and permeability to water vapor and oxygen. Formulations with 5% (w/v) protein and 75% sorbitol and 4% (w/v) protein with a mixture of 15% glycerol and 15% sorbitol produced adequate films. Calcium salts and GDL increased the tensile fracture stress but reduced the fracture strain and decreased water vapor permeability compared with control films. The films prepared represent an attractive alternative for being used as food packaging materials.
RESUMO
Thermal, functional and nutritional properties of the main protein fractions and a protein isolate of chia seed from the state of Jalisco, Mexico, were studied by differential scanning calorimetry, gelling, foaming, water-holding capacity (WHC) and oil-holding capacity, amino acid profile, chemical score and in vitro digestibility tests. The protein isolate showed good WHC (4.06 g/g) and excellent oil-retention capacities (4.04 g/g), making it attractive as an additive in bakery products and food emulsions. It also contained high amounts of glutamic acid (123 g/kg raw protein), arginine (80.6 g/kg raw protein) and aspartic acid (61.3 g/kg raw protein). However, its essential amino acid profile showed deficiencies with respect to the 1985 standard of the FAO/WHO/UNU for pre-school children. Therefore, its use as a sole protein source is not recommended; supplementation with a lysine-rich source would be necessary, as this was the limiting amino acid.