Effect of high pressure processing on rheological and structural properties of milk-gelatin mixtures

There is an increasing demand to tailor the functional properties of mixed biopolymer systems that find application in dairy food products. The effect of static high pressure processing (HPP), up to 600MPa for 15min at room temperature, on milk-gelatin mixtures with different solid concentrations (5%, 10%, 15% and 20% w/w milk solid and 0.6% w/w gelatin) was investigated. The viscosity remarkably increased in mixtures prepared with high milk solid concentration (15% and 20% w/w) following HPP at 300MPa, whereas HPP at 600MPa caused a decline in viscosity. This was due to ruptured aggregates and phase separation as confirmed by confocal laser scanning microscopy. Molecular bonding of the milk-gelatin mixtures due to HPP was shown by Fourier-transform infrared spectra, particularly within the regions of 1610-1690 and 1480-1575cm-1, which reflect the vibrational bands of amide I and amide II, respectively.