Structural and nutritional properties of whey proteins as affected by hyperbaric pressure

Hyperbaric pressure has been shown to affect the secondary structure of whey proteins such as beta-lactoglobulin (beta-lg). There is limited research, however, regarding the optimal conditions by which pressurization of whey proteins could lead to irreversible changes in secondary structure including the reduction of intramolecular disulfide bonds. Irreversible changes in protein conformation and breakage of disulfide bonds of whey proteins induced by high pressure might result in an increase in their digestibility and a reduction of allergenicity. Hence, the overall objective was to explore the capability of hyperbaric pressure to alter irreversibly the secondary structure of whey proteins and thereby alter their allergenic and nutritional properties. The behaviour of different genetic variants of beta-lg was studied employing variable-pressure Fourier transform infrared (FTIR) spectroscopy to establish the optimum pressures needed for their denaturation. The results showed reversible effects of pressures up to 12.0 kbar on the secondary structure of three main genetic variants of beta-lg. The individual response of the genetic variants to pressure was distinguishable despite their subtle structural differences. Pressure-induced conformational changes were studied separately in bovine serum albumin, Ca++-saturated alpha-lactalbumin and Ca ++-free alpha-lactalbumin by FTIR spectroscopy. The studies revealed that the presence of Ca++ ion and the number of disulfide bonds protects the protein molecules against pressure. As whey proteins appeared to be resistant to denaturation upon single applications of high pressure up to 1200 MPa, we developed a novel pressure processing using a combination of pulse and continuous modes at lower pressures of 400 MPa which led to irreversible denaturation of whey protein structure and disulphide bond breakage. Weanling rats fed with whey protein isolates treated by this novel low pressure processing technique showed enhanced gro