Enhanced Functionalities of Whey Proteins Treated with Supercritical Carbon Dioxide

Schematic of the supercritical CO₂ system.

Appearance of powders (5g) of A) unprocessed whey protein isolate (WPI); B) WPI processed with CO₂ at 65°C and 10MPa; C) WPI processed with CO₂ at 65°C and 30MPa; D) WPI processed with N₂ at 65°C and 10MPa; E) unprocessed whey protein concentrate (WPC); F) WPC processed with CO₂ at 65°C and 10MPa; and G) WPC processed with CO₂ at 65°C and 30MPa.

Scanning electron microscopy images for powders of A) unprocessed whey protein isolate (WPI); B) WPI processed with supercritical (sc)CO₂ at 65°C and 10MPa; C) WPI processed with scCO₂ at 65°C and 30MPa; D) WPI processed with N₂ at 65°C and 10MPa; E) unprocessed whey protein concentrate (WPC); F) WPC processed with scCO₂ at 65°C and 10MPa; and G) WPC processed with scCO₂ at 65°C and 30MPa. Scale bar = 100μm.

Storage modulus of 9.4% (wt/vol) whey protein isolate (WPI) solutions (pH 3.35) processed with supercritical CO₂ or N₂ and unprocessed during (A) heating from 20 to 90°C at 1°C/min and holding at 90°C for 3h and (B) during cooling from 90 to 20°C at 1°C/min. Data are averages from 3 tests.

Phase angle of 9.4% (wt/vol) whey protein isolate (WPI) solutions (pH 3.35) processed with supercritical CO₂ or N₂ and unprocessed during holding at 90°C for 3h after heating from 20 to 90°C at 1°C/min. Data are averages from 3 tests.

Mechanical spectra of 9.4% (wt/vol) whey protein isolate (WPI) solutions (pH 3.35) processed with supercritical CO₂ or N₂ and unprocessed after cooling to 20°C. Data are averages from 3 tests and error bars are 95% confidence intervals. G′ = storage modulus; G″ = loss modulus.

Storage modulus (G′) of 9.4% (wt/vol) whey protein isolate (WPI) solutions (pH 3.35) constituted from powders processed with supercritical CO₂ or N₂ and that unprocessed during (A) heating from 20 to 90°C at 1°C/min and holding at 90°C for 3h and (B) cooling from 90 to 20°C at 1°C/min. Data are averages from 3 tests.

Phase angle of 9.4% (wt/vol) whey protein isolate (WPI) solutions (pH 3.35) constituted from powders processed with supercritical CO₂ or N₂ and that unprocessed during holding at 90°C for 3h after heating from 20 to 90°C at 1°C/min. Data are averages from 3 tests.

Salting-out of whey protein isolate (WPI) samples at pH 3.35 by different concentrations of ammonium sulfate. The remaining soluble protein concentrations are normalized to that at 0 M ammonium sulfate.

Storage modulus (G′) of 9.4% (wt/vol) whey protein concentrate (WPC) solutions (pH 3.35) constituted from powders processed with supercritical CO₂ and that unprocessed during (A) heating from 20 to 90°C at 1°C/min and holding at 90°C for 3h and (B) cooling from 90 to 20°C at 1°C/min. Data are averages from 3 tests.

Phase angle of 9.4% (wt/vol) whey protein concentrate (WPC) solutions (pH 3.35) constituted from powders processed with supercritical CO₂ and unprocessed during holding at 90°C for 3h after heating from 20 to 90°C at 1°C/min. Data are averages from 3 tests.