Food microgels are a new form of generating texture and stability in a range of products, of creating new delivery systems for flavour and nutraceuticals. It is one of the ways of creating new sensory experiences too. The microgel generally is distinct from the nanogel.
Microgels are soft porous colloidal particles that are conventionally made from cross-linked polymers (Dickinson, 2015). In terms of their physical properties, they show swelling behaviour, possess structural stability and respond to various stimuli. Because of these properties they are very effective for controlling different types of rheology and emulsification.
Food microgels can be made in a few different ways, but the basic idea is always the same: first form a bulk gel, then break it down into tiny gel particles. Here’s a step-by-step overview of common methods:
1. Pre-Gelation Step
First, you prepare a bulk hydrogel using a food-grade polymer or protein.
Typical ingredients include:
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Proteins like whey protein, casein, gelatin, soy protein.
You form a gel by:
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Heating and cooling (e.g., for gelatin or whey protein).
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Changing pH (e.g., to gel certain polysaccharides).
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Adding calcium ions (e.g., alginate crosslinking with calcium).
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Enzymatic cross-linking (e.g., with transglutaminase).
2. Size Reduction Step
Once you have a gel, you need to break it into small particles:
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High-shear homogenization: Using a high-speed blender or homogenizer to chop the gel into micro- or nano-sized pieces.
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Microfluidization: Forcing the gel through tiny channels at very high pressure to break it down finely.
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Ultrasonication: Using sound waves to shatter the gel into smaller fragments.
The goal is to create stable, dispersed, soft microgel particles.
3. Stabilization Step
Sometimes the microgels need stabilization to prevent them from aggregating:
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Adjusting pH to optimize charge repulsion between particles.
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Adding stabilizing agents like a small amount of salt or polysaccharides.
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Controlling temperature and concentration carefully.
Visual analogy:
Imagine you make a block of Jello, then blend it into tiny, smooth spheres suspended in water — that’s basically a simple microgel!
Variations:
Depending on what you want:
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You can tune their size (nano- vs. micro-scale).
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You can load them up with flavours, vitamins, or bioactives.
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You can make them harder or softer depending on cross-link density.
Analysis
The microstructure of microgels can be examined using confocal scanning laser microscopy alongside optical.
Properties
Microgels have been cooked to understand how they perform. If the microgel contains lipid particulates then these can be released as the gel breaks down during cooking. The evidence for this in such model cooking systems, is that the aqueous phase of such a gel becomes slightly cloudy. Nonetheless, these microgels are relatively heat-stable because the particle size remains relatively stable and ‘monomodal’ throughout the cooking process (Wang et al., 2019).
Sensory Impact
Microgels are capable of creating an appealing perception of ‘creaminess’ in sauces and dips. One of the reasons is that through modification of texture it exploits the value of rapid enzymatic oral breakdown in the mouth (Dickinson, 2015).
Starch microgels are now used as fat replacers in dressings and sauces.
References
Dickinson, E. (2015). Microgels—An alternative colloidal ingredient for stabilization of food emulsions. Trends in Food Science & Technology, 43(2), pp. 178-188 (Article).
Wang, M., Doi, T., & McClements, D. J. (2019). Encapsulation and controlled release of hydrophobic flavors using biopolymer-based microgel delivery systems: Sustained release of garlic flavor during simulated cooking. Food Research International, 119, 6-14. .
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