352
such as carboxyl and amino groups, casein films combined with other packaging
materials can also be used to protect products susceptible to oxidation (Bonnaillie
et al. 2014). Apart from these, food additives, such as flavours, antimicrobial agents,
antioxidants, vitamins, minerals and colors can also be added into these films to
provide for controlled rate and site of release (Core 2005). In addition, casein also
presents an excellent material for edible packaging due to the exceptional nutritional value (Mei and Zhao 2003). However, similar to other protein-based materials, casein possesses two major disadvantages: limited elasticity and water
sensitivity, which may limit its applications (Bonnaillie et al. 2014; Ma et al. 2015).
Whey Protein
Whey proteins are valuable by-products from the cheese industry, which have been
widely used in a variety of foods due to the superior gelling and emulsification
properties. Due to the consumer demand for high-protein foods and supplements,
whey proteins demand has been increased by the consumer awareness on its impact
of food on human health, the documented nutritional and health properties of whey
proteins (Krissansen 2007). Whey proteins contain a diverse amount of proteins
with peculiar properties. According to the protein content, it is available as whey
protein concentrate (WPC) or whey protein isolate (WPI), which ranges from 20 to
80% and>90%, respectively. They have good film forming capacity, and present as
main advantages the low barrier properties to oxygen, volatile aromas and lipids
(Ramos et al. 2012). WPC contains higher amounts of fat and lactose than WPI, and
these compounds could influence the properties of edible coatings because they
could act as discontinuities in the protein matrix of edible films and cause changes
in barrier and mechanical properties (Oses et al. 2009).
Films based on whey protein isolates (WPI) are flexible, transparent and exerts
excellent barrier function for gas, aroma compounds, and oil as compared to the
films made with polysaccharides and lipids. However, due to the presence of hydrophilic amino acids in their structure, these films have low mechanical properties and
high water vapor permeability (Umaraw and Verma 2017). Therefore, protein denaturation (physical, chemical, or enzymatic) is required for producing dense and
strong films, thus, exhibits good mechanical resistance with excellent barrier to
water vapours. Notably, when WPI is heated at low ionic strength and low pH, they
can self assemble into semi flexible amyloid-like protein nanofibrils (WPNFs)
(Loveday et al. 2012). Properties such as gelation, emulsification, foam stability,
antioxidant activity, and digestibility become remarkably modified upon the formation of WPNFs, yielding a class of high-performance biomaterials (Loveday et al.
2012; Mohammadian and Madadlou 2016). In addition, hydrophilic plasticizers are
generally added to the film-forming protein dispersion for reducing film brittleness,
thus improving flexibility, extensibility, toughness, and tear resistance (Ramos et al.
2013). Glycerol (Gly) is the most widely used plasticizer for whey protein films,
providing control of moisture transfer, respiration rate, and oxidation processes, and
prolonging shelf life (Silva et al. 2015).
F. Jhan et al.
such as carboxyl and amino groups, casein films combined with other packaging
materials can also be used to protect products susceptible to oxidation (Bonnaillie
et al. 2014). Apart from these, food additives, such as flavours, antimicrobial agents,
antioxidants, vitamins, minerals and colors can also be added into these films to
provide for controlled rate and site of release (Core 2005). In addition, casein also
presents an excellent material for edible packaging due to the exceptional nutritional value (Mei and Zhao 2003). However, similar to other protein-based materials, casein possesses two major disadvantages: limited elasticity and water
sensitivity, which may limit its applications (Bonnaillie et al. 2014; Ma et al. 2015).
Whey Protein
Whey proteins are valuable by-products from the cheese industry, which have been
widely used in a variety of foods due to the superior gelling and emulsification
properties. Due to the consumer demand for high-protein foods and supplements,
whey proteins demand has been increased by the consumer awareness on its impact
of food on human health, the documented nutritional and health properties of whey
proteins (Krissansen 2007). Whey proteins contain a diverse amount of proteins
with peculiar properties. According to the protein content, it is available as whey
protein concentrate (WPC) or whey protein isolate (WPI), which ranges from 20 to
80% and>90%, respectively. They have good film forming capacity, and present as
main advantages the low barrier properties to oxygen, volatile aromas and lipids
(Ramos et al. 2012). WPC contains higher amounts of fat and lactose than WPI, and
these compounds could influence the properties of edible coatings because they
could act as discontinuities in the protein matrix of edible films and cause changes
in barrier and mechanical properties (Oses et al. 2009).
Films based on whey protein isolates (WPI) are flexible, transparent and exerts
excellent barrier function for gas, aroma compounds, and oil as compared to the
films made with polysaccharides and lipids. However, due to the presence of hydrophilic amino acids in their structure, these films have low mechanical properties and
high water vapor permeability (Umaraw and Verma 2017). Therefore, protein denaturation (physical, chemical, or enzymatic) is required for producing dense and
strong films, thus, exhibits good mechanical resistance with excellent barrier to
water vapours. Notably, when WPI is heated at low ionic strength and low pH, they
can self assemble into semi flexible amyloid-like protein nanofibrils (WPNFs)
(Loveday et al. 2012). Properties such as gelation, emulsification, foam stability,
antioxidant activity, and digestibility become remarkably modified upon the formation of WPNFs, yielding a class of high-performance biomaterials (Loveday et al.
2012; Mohammadian and Madadlou 2016). In addition, hydrophilic plasticizers are
generally added to the film-forming protein dispersion for reducing film brittleness,
thus improving flexibility, extensibility, toughness, and tear resistance (Ramos et al.
2013). Glycerol (Gly) is the most widely used plasticizer for whey protein films,
providing control of moisture transfer, respiration rate, and oxidation processes, and
prolonging shelf life (Silva et al. 2015).
F. Jhan et al.