What Are Plant-Based Softgels and How Do They Actually Work?

Plant-based softgel capsules are soft capsules whose shell is built from polysaccharide film formers (principally carrageenan and modified starch) instead of animal-derived gelatin. Because polysaccharides gel by a different mechanism than gelatin, switching is not a drop-in substitution. As such, the sealing window, moisture equilibrium, disintegration profile, and compatibility risks all change.

The curious thing here: search for plant-based softgels online, and you will find two kinds of results. On one side, consumer articles explaining that gelatin comes from animals. On the other, technology pages from CDMOs, each describing why their own proprietary shell is the answer.

Neither tells you what actually changes in the development programme when gelatin comes out. This article covers the three film-former families in commercial use, the two process problems that decide whether a plant-based programme succeeds, and the compatibility issue that disappears along with the gelatin.

What changes when you remove gelatin from a softgel shell?

The core change is the gelation mechanism. Gelatin forms a thermoreversible gel that briefly remelts during sealing, while polysaccharide films gel through helix formation or retrogradation and do not remelt cleanly, which narrows the process window at every stage of encapsulation.

Gelatin's usefulness in rotary die encapsulation rests on that reversibility. The ribbon casts warm, sets as it meets the drum, and the two ribbons fuse under the die when heat and pressure return the contact zone to a fluid state. The seal is, in effect, a controlled local remelting.

Carrageenan gels through helix formation and cation bridging; starch gels through partial retrogradation and network entanglement. Neither offers gelatin's tolerance for imprecise process settings, and, as such, the practical consequence is that plant-based shells are far less forgiving of encapsulation parameter drift. Moreover, development shifts from formulation screening alone to formulation and process screening in parallel.

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Which film formers are used in plant-based softgel shells?

Three material families dominate: carrageenan, modified starch, and (with important caveats) HPMC. Almost every commercial plant-based shell is a blend rather than a single polymer, because no one of these forms a workable capsule film on its own.

Carrageenan: the closest functional analogue to gelatin

Carrageenan is a sulfated galactan extracted from red seaweed, and it is the only common plant film former that gels thermally and reversibly, which is why it maps most closely onto gelatin's behaviour. Catalent's Vegicaps shell is carrageenan-derived, and carrageenan systems have run at commercial scale since the late 1990s.

The main formulation lever is the isoform. Kappa-carrageenan gives firm, brittle gels; iota gives softer, more elastic ones. Patent work on non-gelatin films shows blends of the two produce stronger films than either alone, with peak strength around a 50/50 ratio. Carrageenan systems also need cations (typically potassium or calcium) to set, which makes the ionic content of the gel mass a critical material attribute in a way it never is for gelatin.

The practical drawback is gel mass handling. Kappa-heavy compositions set at high temperature and build viscosity sharply on cooling, so an underheated section of transfer line will gel in place. Holding and transport temperatures need tighter control than a gelatin process demands.

Modified starch: structural bulk, but never on its own

Modified starch, most commonly hydroxypropyl starch from corn, tapioca or pea, provides the structural backbone of the shell but cannot form a capsule film alone, because it lacks both gel strength and elasticity. Hydroxypropylation gives a more stable gel mass at high mixing temperatures and better post-manufacture shell stability, at the cost of higher gel viscosity. Roquette's Lycagel range is built on hydroxypropyl pea starch, with the Flex grade shipping plasticizer-free so the formulator selects the polyol system.

Because starch alone will not work, commercial starch systems always carry a secondary gelling agent (among them, carrageenan, gellan or another hydrocolloid) as a film-forming aid. IFF's SeaGel is the clearest example: predominantly modified starch with under 10% carrageenan doing the network-forming work. Elasticity comes from the plasticizer, usually sorbitol-based, rather than from the polymer backbone, which makesplasticizer selection more consequential here than in gelatin systems.

The trade-off is format range: starch-heavy blends produce weaker gel films that struggle with large capsule sizes and complex fills. If your target is a 20-minim oval with a viscous suspension fill, expect a harder programme than the supplier literature suggests.

Is HPMC used in plant-based softgel capsules?

Rarely, and not in the way most search results imply. HPMC dominates the plant-based hard capsule market, but it gels on heating rather than cooling (the wrong direction for ribbon casting), and HPMC softgel films require a co-gelling agent to function at all.

The favourable comparisons are real, but they are about two-piece capsules. HPMC hard shells carry 3–8% moisture against gelatin's 13–16%, which makes them genuinely attractive for hygroscopic actives, and they hold mechanical integrity across a wider humidity range. None of that transfers directly to a rotary die process. When a source compares "HPMC capsules" favourably to gelatin, check which dosage form it means. Usually it is the hard capsule.

Why do plant-based softgel seals fail?

Plant-based seals fail because polysaccharide films fuse through interpenetration of two partially set networks rather than through remelting, giving a narrower process window with less margin for ribbon thickness variation, wedge temperature drift or die roll misalignment.

Seal quality is the dominant defect driver in gelatin softgels, and it becomes more dominant without gelatin. Two symptoms tend to appear together in a poorly optimised system: thin or incomplete seals showing up as early leakers, and reduced machine output as operators slow the die to compensate. Published accounts of unoptimised plant-based systems describe fill capacities dropping below 70% and encapsulation speeds falling to around 2 RPM. Treat those numbers as a diagnostic; if a plant-based trial is running at a fraction of gelatin throughput, the film former ratio is a more likely root cause than the machine.

This argues for bringing seal thickness into development testing earlier than you would for a gelatin product. Cross-sectioning capsules from encapsulation trials and measuring seal dimensions gives a quantitative parameter to optimise against, rather than waiting for leakers to appear on stability.

Are plant-based softgels more humidity-stable than gelatin?

At storage extremes, yes, but the improvement is a shift in equilibrium point and failure mode, not immunity. In accelerated storage testing, modified starch and iota-carrageenan capsules filled with mineral oil remained structurally intact with only shell softening, while gelatin controls under the same conditions fused together and lost structural integrity.Polysaccharide shells still exchange water and plasticizer with the fill and the environment, so the migration mechanisms behind late-stage leakage still apply. Plasticizer migration deserves at least the scrutiny it gets in gelatin systems, and arguably more, since the plant shell depends more heavily on the plasticizer for its flexibility.

Disintegration also runs slower. Roquette's comparative work put starch-based capsules at not more than 10 minutes against under 5 minutes for gelatin, comfortably within pharmacopeial limits, but worth knowing before you set a specification.

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Do plant-based softgels avoid crosslinking?

Yes. Crosslinking is an aldehyde reaction with the lysine and arginine residues in gelatin's protein backbone; polysaccharides have no amine groups, so the pathway does not exist and the associated dissolution slowdown does not occur.This is the clearest technical argument for plant-based shells, and it has nothing to do with dietary claims. In gelatin systems, aldehydes from fill excipients, degradation products or packaging form a pellicle that slows dissolution and inflates variability. As covered in our crosslinking webinar recap, it remains one of the most persistent stability problems in softgel development, and USP <1094> now provides Tier 1 and Tier 2 dissolution approaches specifically for handling it.

Removing that pathway does not make the shell inert. Starch and carrageenan systems bring their own interactions: cation competition between fill components and the carrageenan network, pH sensitivity, and physical incompatibilities showing up as shell softening or embrittlement. You trade one compatibility profile for another. The plant-based one is simply easier to predict.

Which products are best suited to a plant-based softgel shell?

Three fill categories make technical sense rather than purely commercial sense: high-melting-point and semi-solid fills, fills containing aldehyde-forming components, and higher-pH fills.

High-melting-point fills are the strongest case. Gelatin films have a sealing limit of roughly 38–42°C, which rules out fills that are solid or highly viscous at room temperature. Catalent's OptiShell platform, a polysaccharide shell paired with hot-fill processing, extends this to around 70°C, opening semi-solid matrices and lipid systems that gelatin cannot encapsulate at all.

Aldehyde-bearing fills follow from the crosslinking argument above. And higher-pH fills tolerate carrageenan shells better than gelatin, which narrows the usable pH band considerably.

Conversely, a straightforward fish oil or vitamin D fill in a standard oblong gains nothing technically from a plant-based shell. There, the driver is label claim, and the development cost should be weighed accordingly.

How should a plant-based softgel development programme be structured?

The film former ratio, plasticizer system, cation content and encapsulation parameters form one coupled problem, so they need screening together on capsules rather than sequentially on films.

The recurring mistake is treating the shell as a drop-in and discovering the process consequences at scale-up. The underlying logic is the same structured, risk-based approach we apply to gelatin shell development, but with a narrower process window and considerably less published precedent to lean on. Where in-house experience with polysaccharide systems is limited, our independent softgel development consulting can help define the screening design before machine time gets spent.

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FAQs: Plant-based softgel development

• Can existing softgel equipment run plant-based shells?

  Generally, yes. plant-based shells run on standard rotary die encapsulation lines, but the parameter set is not transferable. Gel mass holding and transfer temperatures, ribbon casting conditions and wedge settings all need re-establishing, and carrageenan-heavy compositions in particular demand tighter thermal control throughout the transfer path to avoid setting in place

• Do plant-based softgels disintegrate more slowly than gelatin softgels?

  Modestly, yes. Comparative work has put starch-based capsules at not more than 10 minutes against under 5 minutes for gelatin equivalents. Both sit within pharmacopeial requirements, but the difference matters when setting release specifications or comparing against an existing gelatin product.

• Are plant-based softgels suitable for vegan, halal and kosher labelling?

  Polysaccharide shells contain no animal-derived material, which supports vegan, vegetarian, halal-aligned and kosher-aligned positioning. The specific certification still depends on every other component—plasticizers, colourants, opacifiers and the fill itself—so the shell alone does not deliver the claim.

• What are the main development challenges with plant-based softgels?

  Seal integrity is the dominant one, because polysaccharide films fuse through network interpenetration rather than remelting. Beyond that: gel mass viscosity and temperature control, limits on large capsule formats with starch-heavy blends, plasticizer migration, and slower disintegration all need building into the development plan from the start.

• Who supplies plant-based softgel raw materials and shell systems?

  Raw material premixes come from suppliers including Roquette, whose Lycagel range is based on hydroxypropyl pea starch, and IFF, whose SeaGel system pairs modified starch with a small proportion of carrageenan. On the manufacturing side, Catalent offers carrageenan-based Vegicaps and the polysaccharide OptiShell platform. Each proprietary system carries its own IP position and supply arrangement, worth understanding before committing a programme to one.