Sodium Alginate and Chitosan as Components Modifying the Properties of Inulin Hydrogels

Abstract

The aim of the study was to investigate the influence of addition of sodium alginate (SA) and chitosan (CH) on the properties of inulin hydrogels. Inulin hydrogels (20 g/100 g) containing various additions (0.0, 0.1, 0.3, and 0.5 g/100 g) of SA and CH were produced. The hydrogels’ properties were assessed based on the volumetric gel index, microstructure, yield stress, texture, stability, and color parameters. According to the findings, the inclusion of these polysaccharides had no influence on the gelation ability of the inulin solution. The physical properties of the hydrogels containing SA or CH differed from hydrogels containing only inulin (INU). The obtained microstructural pictures revealed that the addition of SA and CH resulted in the formation of hydrogels with a more compact, smooth, and cohesive structure. Consequently, they had higher yield stress, strength, and spreadability values than INU hydrogels. The addition of chitosan in comparison with sodium alginate also had a greater effect in strengthening the structure of hydrogels, especially at the level of 0.5 g/100 g. For example, the addition of this amount of SA increased the yield stress on average from 195.0 Pa (INU) to 493.6 Pa, while the addition of CH increased it to 745.3 Pa. In the case of the strength parameter, the addition of SA increased the force from 0.24 N (INU) to 0.42 N and the addition of CH increased it to 1.29 N. In the case of spreadability this increase was from 2.89 N * s (INU) to 3.44 N * s (SA) and to 6.16 N * s (CH). Chitosan also caused an increase in the stability of inulin hydrogels, whereas such an effect was not observed with the addition of sodium alginate. The gels with the addition of SA and CH also had significantly different values of color parameters. Inulin–alginate hydrogels were characterized by higher values of the color parameter a *, lower values of the color parameter b *, and in most concentrations higher values of the color parameter L * compared to inulin–chitosan hydrogels. Based on the collected data, it can therefore be concluded that through the addition of sodium alginate and chitosan, there is a possibility to modify the properties of inulin hydrogels and, consequently, to better adapt them to the characteristics of the pro-health food products in which they will be used.

A Comparative Evaluation of the Structural and Biomechanical Properties of Food-Grade Biopolymers as Potential Hydrogel Building Blocks

“…It can be also observed that GG, KG, and PS are more transparent than the other biopolymers (although PS has a higher a* and b* parameter—more yellow tones). The color parameters of inulin hydrogels are in accordance with the available literature [ 19 , 54 ]. Novel edible composite films made of whey protein isolate and zein also showed similar values of the color parameters to those of the pea protein (PP) and wheat protein (WP) samples.…”

“…The high physical stability of PP, GG, KG, INU, and PS might be due to the formation of a network that acted as a stabilizing structure when the samples were subjected to the centrifugal force during the test. Florowska et al, (2022) [ 19 ] in their studies on inulin hydrogels with the addition of sodium alginate and chitosan, also reported the high physical stability of inulin hydrogels. Furthermore, the hydrogel’s water-holding capacity is related to its physical stability [ 69 ].…”

“…When the gel structure is not formed, VGI equals zero, and when the sample is completely gelled, VGI equals 100%. VGI is calculated based on the following equation [ 19 ]: where V G —volume of the formulated gel, V T —total volume of the sample. The reported values represent the averages of three replicates.…”

“…These biopolymers are proteins and polysaccharides with different biomechanical and functional properties [ 16 ]. Natural biopolymers are typically obtained from natural resources such as animals (e.g., gelatin [ 17 ], whey protein [ 18 ], chitosan [ 19 ]), plants (e.g., soy protein [ 20 ], pea proteins [ 21 ], inulin [ 22 ], cellulose [ 23 ]), microorganisms (e.g., gellan gum [ 24 ], curdlan [ 25 ]), and algae (e.g., carrageenan [ 26 ], agarose [ 27 ]) via bioprocessing and chemical modification. Furthermore, because of the high reactivity of their functional groups, these biopolymers can be modified to meet the demands of various specific functions (mechanical properties, solubility, gel structure, etc.)…”

Plant Polysaccharides in Engineered Pharmaceutical Gels

“…Inulin Branched fructosyl units Typically, inulin properties highly depend on their degree of polymerization [29,30] Pectin Rich in carboxylate units (methyl esters)…”