Why a wall is needed at all
Many valuable ingredients are unstable in the open — fish oils oxidise, flavours evaporate, some actives react with the matrix around them. A wall separates the sensitive core from its environment and can be engineered to release the contents at a chosen point. Gelatin is well suited to this because it forms films readily and its charge can be manipulated.
Complex coacervation exploits opposite charges
The most common gelatin route pairs it with an oppositely charged polymer, typically at a pH where the two attract. The pair separates from solution and deposits around dispersed core droplets, forming a wall that is then hardened. Because the mechanism is charge-driven, pH and ionic strength control the process almost entirely.
Spray drying is simpler and coarser
Where the requirement is protection rather than precise triggered release, spray drying gelatin around an emulsified core is faster and cheaper. The resulting particles are less uniform and the wall less controlled, but for many flavour and oil applications the performance is entirely adequate and the process fits existing plant.
Wall thickness trades payload against protection
A thicker wall protects better and releases more slowly, but carries less core per unit weight. That trade-off is the central formulation decision and should be settled against the shelf life and release profile the product actually requires, rather than optimised for either extreme in isolation.
Hardening determines robustness
The deposited wall is soft and must be hardened to survive drying, handling and incorporation. The hardening chemistry chosen has regulatory and labelling consequences that vary by market and application. It is worth establishing what is acceptable in the destination markets before selecting the route rather than after.
Test release in the finished matrix
Capsules behave differently in a dry powder blend, a beverage and a baked product. Release testing has to be done in the matrix the capsules will live in, across the intended shelf life. Data generated in water tells you the wall works; it does not tell you the product will.
Capsules behave differently in a dry powder blend, a beverage and a baked product. Release testing has to be done in the matrix the capsules will live in, across the intended shelf life. Data generated in water tells you the wall works; it does not tell you the product will.
