Abstract
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.
Highlights
Hydrogels are a group of polymeric materials of three dimensional cross-linked polymeric networks capable of absorbing and retaining a significant amount of aqueous solvents and biological fluids in their structures [1]
On the basis of the conducted research, it was found that the use of even the lowest from the tested pressures (150 MPa) and lasting for a shorter time (5 min) allowed us to induce the gelation process and, as a result, to create a gel structure (VGI = 100 %, Table 1)
According to the available literature data, this concentration was insufficient for other induction methods where the lowest concentration forming a gel structure (VGI = 100%) was 20 g/100 g [28,29,30]
Summary
Hydrogels are a group of polymeric materials of three dimensional cross-linked polymeric networks capable of absorbing and retaining a significant amount of aqueous solvents and biological fluids in their structures [1] They are listed as “smart structures” whose tailor-made design gives them various functional features for use in the designing, synthesis and self-assembly of novel biomaterials and drug delivery systems. HHP treatment is known to make morphological and structural changes in polysaccharides, resulting in production food with novel texture and hydrogels with different properties compared to conventional methods. The selection of process parameters depends on the type of polymer, pressure level, time of treatment and temperature. Those parameters can play an important role in determining the presence and degree of hydrogel formation as well as its properties
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