Effects of Pressure Level and Time Treatment of High Hydrostatic Pressure (HHP) on Inulin Gelation and Properties of Obtained Hydrogels

The aim of this study was the evaluation of the influence of different HHP levels (150 and 300 MPa) and time treatment (5, 10, 20 min) on the gelation and properties of hydrogels with different inulin concentration (15, 20, 25 g/100 g). High-pressure treatment, in tested ranges, induces inulin gels and allows obtaining gel structures even at a lowest tested inulin content (i.e., 15 g/100 g). Selecting the pressure parameters, it is possible to modify the characteristics of the created hydrogels. The use of higher pressure (i.e., 300 MPa) allows to increase the stability of the hydrogels and change their structure to more compressed, which results in higher yield stress, lower spreadability, harder and more adhesive structure. For example, increasing the inulin gelling induction pressure (concentration 20 g/100 g) from 150 to 300 MPa with a time treatment of 10 min resulted in an increase in yield stress from 38.1 to 711.7 Pa, spreadability force from 0.59 to 4.59 N, firmness from 0.11 to 1.46 N, and adhesiveness from −0.06 to −0.65 N. Extending the time treatment of HHP increases this effect, but mainly when higher pressure and a higher concentration of inulin are being used. For example, extension of time treatment at 300 MPa pressure from 5 to 20 min resulted in an increase in yield stress from 774.8 to 1273.8 Pa, spreadability force from 6.28 to 8.43 N, firmness from 1.87 to 2.98 N, and adhesiveness from −0.94 to −1.27 N. The obtained results indicate the possibility of using HHP to create inulin hydrogels tailored to the characteristics in a specific food product.