Soft matter strategies for controlling food texture: formation of hydrogel particles by biopolymer complex coacervation

Abstract

Soft matter physics principles can be used to address important problems in the food industry. Starch granules are widely used in foods to create desirable textural attributes, but high levels of digestible starch may pose a risk of diabetes. Consequently, there is a need to find healthier replacements for starch granules. The objective of this research was to create hydrogel particles from protein and dietary fiber with similar dimensions and functional attributes as starch granules. Hydrogel particles were formed by mixing gelatin (0.5 wt%) with pectin (0 to 0.2 wt%) at pH values above the isoelectric point of the gelatin (pH 9, 30 °C). When the pH was adjusted to pH 5, the biopolymer mixture spontaneously formed micron-sized particles due to electrostatic attraction of cationic gelatin with anionic pectin through complex coacervation. Differential interference contrast (DIC) microscopy showed that the hydrogel particles were translucent and spheroid, and that their dimensions were determined by pectin concentration. At 0.01 wt% pectin, hydrogel particles with similar dimensions to swollen starch granules (D3,2 ≈ 23 µm) were formed. The resulting hydrogel suspensions had similar appearances to starch pastes and could be made to have similar textural attributes (yield stress and shear viscosity) by adjusting the effective hydrogel particle concentration. These hydrogel particles may therefore be used to improve the texture of reduced-calorie foods and thereby help tackle obesity and diabetes.

Microgels formed by electrostatic complexation of gelatin and OSA starch: Potential fat or starch mimetics

“…In this case, the dense viscoelastic polymer-rich phase is referred to as the coacervate phase (de Kruif et al, 2004;Schmitt & Turgeon, 2011;Turgeon, Schmitt, & Sanchez, 2007). In our previous work, we showed that micron-sized hydrogel microspheres could be formed by electrostatic complexation of gelatin and pectin, and that these particles had potential for use as texture-modifiers to replace fat droplets or starch granules (Wu et al, 2014). The texture-modifying abilities of electrostatic complexes have also been reported in earlier studies (Laneuville, Paquin, & Turgeon, 2000Schmitt & Turgeon, 2011).…”

“…2). The type A gelatin has an isoelectric point (pI) around pH 7 to 9, which explains the positive charges on the gelatin molecules at pH 3 to 7 observed in this study (Djagny et al, 2001;Wu et al, 2014). The charge on the gelatin molecules decreases as the pH increases due to conversion of eNH þ 3 groups to eNH 2 groups (reduced positive charge) and of eCOOH groups to eCOO À groups (increased negative charge).…”

“…Instead, the samples were kept stirring at 300 rpm at room temperature (25 C) for 48 h until the particles could be observed by microscopy or measured by light scattering, which is different from previous studies with other biopolymers (Devi, Hazarika, Deka, & Kakati, 2012;Wu et al, 2014). This phenomenon may be related to changes in the conformation or association of the gelatin molecules during storage, e.g., there Fig.…”

“…Development of fat and carbohydrate mimetics using healthier ingredients (such as proteins and dietary fibers) has therefore become of major concern to food scientists (Akoh & Min, 2008). Our previous work has shown the potential of using hydrogel particles formed by electrostatic complexation to create fat droplet or starch granule mimetics (Wu, Degner, & McClements, 2014). Hydrogel particles based on electrostatic complexation may also be utilized to develop effective delivery systems to encapsulate, protect, and release active ingredients, such as flavors, colors, preservatives, vitamins, nutraceuticals, or pharmaceuticals (Devi & Kakati, 2013;Saravanan & Rao, 2010;Xiao, Liu, Zhu, Zhou, & Niu, 2014;Xiao, Yu, & Yang, 2011;Yeo, Bellas, Firestone, Langer, & Kohane, 2005).…”

Linear viscoelasticity of complex coacervates

“…The self-assembly of these materials is driven by entropy, where the initial electrostatic attraction between oppositely-charged macro-ions results in the release of small, bound counter-ions and the restructuring of water molecules [1][2][3][4]. Complex coacervates have a long history of use in the food [5][6][7][8][9][10][11][12][13] and personal care [14,15] industries, and have found increasing utility as a platform for drug and gene delivery [1][2][3][4], as well as underwater adhesives [5][6][7][8][9][10][11][12][13][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62]. Coacervation has also recently been implicated in the formation of various biological assemblies [1,[14][15][16]55,…”