The Effect of Protein Particle Size Reduction on the Physical Properties of CO₂‐Precipitated Casein Films

Abstract

Casein precipitated with high pressure‐CO2 (CO2CAS) has unique properties compared to commercial acid‐precipitated casein. CO2CAS is less water‐soluble and films made from it are less susceptible to high humidity environments; however, the films are also opaque and hazy. The appearance of CO2CAS films is important especially if applied as a food coating. To improve the appearance properties, the particle size of CO2CAS film plasticized with glycerol was reduced. The effect of protein particle size reduction on tensile properties, water vapor permeability (WVP), and gloss was studied using ASTM methodology. As particle size of the CO2CAS was reduced from 126 μm to 111 μm, tensile strength and modulus of the films increased, while WVP decreased. With the same particle reduction, gloss increased from 55.3 gloss units on average to 73 gloss units, but films were still hazy. With a particle size less than 86 μm, CO2CAS films were glossy and transparent, however, tensile strength decreased and WVP increased. Depending on desired application, the properties of CO2CAS films can be optimized by changing particle size.

Plasticization and moisture sensitivity of potato peel-based biopolymer films

“…As described above, it may be assumed that there is a reduction in particle size as the HPH pressure or the number of passes increase. A reduced particle size could decrease WVP due to the formation of a more difficult pathway that water molecules must cross to diffuse through the matrix (23). However, no such effect of increased pressure or pass number on the WVP of the films was observed in the present study, possibly due to the reagglomeration of small biopolymer particles during film formation (6).…”

Apple Peel‐Based Edible Film Development Using a High‐Pressure Homogenization

“…On the other hand, a drastic application of pressure may bring a marked effect on the properties of polymers like starch, affecting the quality parameters of the products made with it (Che and others 2008). A reduced particle size may increase the oxygen and water vapor barrier properties due to the creation of a longer pathway for the gases to transport through the films (Dangaran and others 2006). Therefore, reduced values of the rheological properties may lead to an increase of the edible films barrier properties.…”

“…It may be assumed that particle size is reduced with the pressure increase. A reduced particle size might result in decreasing WVP due to formation of a more tortuous pathway for water to cross through a matrix by the presence of smaller particles in it (Dangaran and others 2006). However, this possible effect of increased pressure on the WVP of the films was not observed in our study.…”

Characterization of casein and casein-silver conjugated nanoparticle containing multifunctional (pectin–sodium alginate/casein) bilayer film

“…Amongst all protein, casein based films have received tremendous attention due to their good film forming properties and oxygen barrier properties. Casein/ glycerol containing films possess good tensile and moderate barrier properties (Ghosh et al 2009;Dangaram et al 2006). However, there are some limitations to the use of casein-based edible films as a packaging material due to their poor barrier and mechanical properties.…”