A Comprehensive Review of Food Hydrogels: Principles, Formation Mechanisms, Microstructure, and Its Applications

Abstract

Food hydrogels are effective materials of great interest to scientists because they are safe and beneficial to the environment. Hydrogels are widely used in the food industry due to their three-dimensional crosslinked networks. They have also attracted a considerable amount of attention because they can be used in many different ways in the food industry, for example, as fat replacers, target delivery vehicles, encapsulating agents, etc. Gels-particularly proteins and polysaccharides-have attracted the attention of food scientists due to their excellent biocompatibility, biodegradability, nutritional properties, and edibility. Thus, this review is focused on the nutritional importance, microstructure, mechanical characteristics, and food hydrogel applications of gels. This review also focuses on the structural configuration of hydrogels, which implies future potential applications in the food industry. The findings of this review confirm the application of different plant- and animal-based polysaccharide and protein sources as gelling agents. Gel network structure is improved by incorporating polysaccharides for encapsulation of bioactive compounds. Different hydrogel-based formulations are widely used for the encapsulation of bioactive compounds, food texture perception, risk monitoring, and food packaging applications.

Keywords: bioactive compounds; food applications; hydrogels; mechanical strength; microstructure.

Figure 2

Different factors affecting the formation of food hydrogels.

Figure 4

Mechanism of polysaccharide and protein gel formation. Crosslinking of chitosan (A); composite hydroxypropyl methyl cellulose-sodium alginate hydrogels (B); gelation process of chemically crosslinked protein hydrogels (C). (A,B) are reprinted with permission from He et al. [89] (Copyright © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany) and Hu et al. [90] (Copyright © 2018 Springer Nature B.V., Dordrecht, The Netherlands), respectively, whereas (C) is reprinted from Hanson et al. [91] and is an open-access article (Copyright © 2020 by authors) distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license. HPMC, hydroxypropyl methyl cellulose; CaCl₂, calcium chloride; CS, chitosan.

Figure 4

Mechanism of polysaccharide and protein gel formation. Crosslinking of chitosan (A); composite hydroxypropyl methyl cellulose-sodium alginate hydrogels (B); gelation process of chemically crosslinked protein hydrogels (C). (A,B) are reprinted with permission from He et al. [89] (Copyright © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany) and Hu et al. [90] (Copyright © 2018 Springer Nature B.V., Dordrecht, The Netherlands), respectively, whereas (C) is reprinted from Hanson et al. [91] and is an open-access article (Copyright © 2020 by authors) distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license. HPMC, hydroxypropyl methyl cellulose; CaCl₂, calcium chloride; CS, chitosan.

Figure 1

Different types of plant- and animal-based ingredients as gelling agents in the food industry. Figure 1 is reprinted with permission from Munir et al. [15] (Copyright © 2022 by authors).

Figure 3

Different junction zones in polysaccharide gels: (A) connecting points, (B) extended junction zone resembling a block, (C) model of crosslinks in alginate and pectin gels based on an egg-box structure, (D) the region of the double-helix junction, and (E) junction zone for the aggregation of polysaccharide chains. Figure 3 is reprinted with permission from Nazir et al. [8] (Copyright © 2017 Elsevier Ltd., Amsterdam, The Netherlands).

Figure 5

The linear viscoelasticity of low-modulus materials extracted from the fluctuation spectrum using particle-tracking microrheology. (A) The probe particle’s trajectory is calculated; (B) the spectrum of average fluctuations is computed as a function of time (t′); and (C) mechanical spectrum in the linear viscoelastic region (LVER). Figure 5 is reprinted with permission from Nazir et al. [8] (Copyright © 2017 Elsevier Ltd., Amsterdam, The Netherlands).

Figure 6

Illustration of a biopolymer-based delivery system for the encapsulation of bioactive compounds. Figure 6 is reprinted with permission from McClements [128] (Copyright © 2016 Elsevier B.V., Amsterdam, The Netherlands).