Author: R&D Team, CUIGUAI Flavoring Published by: Guangdong Unique Flavor Co., Ltd. Last Updated:  Oct 28, 2026 WhatsApp & Telegram: +86 189 2926 7983 Email: info@cuiguai.com   Fondant and icing look like the simplest products a bakery or confectionery factory makes and behave like the most delicate. A sugar syrup is cooked, cooled, agitated and flavoured, and a cake, doughnut or cookie is coated with the result. Nothing about that description suggests difficulty. In practice, the addition of a flavour, a colour, an acid or a preservative to a sugar system at the wrong point, in the wrong format or at the wrong dose will change the rheology of that system permanently, and the failure shows up in ways that are expensive and very visible to the consumer: a fondant that sets with a gritty surface, an icing that slides off the top of a bun, a glaze that never dries, a cookie that goes soft in the bag, or a colour that fades from a bright red to a dull pink in three weeks on the shelf.   Consistency, in the confectionery and bakery sense, is a single idea wearing many hats. It means viscosity at the point of application, so the icing flows but does not run. It means texture and crystal structure, so the fondant is smooth rather than grainy or crumbly. It means adhesion and film formation, so the coating grips the product and dries to a stable surface. It means colour and flavour stability through the shelf life. And it means batch-to-batch reproducibility, so that the product produced on Tuesday matches the product produced on Thursday. Flavouring decisions sit at the centre of every one of those requirements, which is why the questions our technical team receives from bakeries most often concern fondant and icing rather than the more glamorous parts of the range. Guangdong Unique Flavor Co., Ltd. supplies flavour systems to bakery, confectionery and beverage manufacturers in more than forty countries, and this article collects what we have learned about the interaction between flavour chemistry and sugar rheology. It covers why fondant and icing are unforgiving systems, the five consistency faults that appear most often in production, how to select a flavour format deliberately, how to dose it correctly, and which production and storage controls actually determine whether a flavoured fondant performs on the line and on the shelf.

Why Fondant and Icing Are Unforgiving Flavour Systems

A fondant is a supersaturated sugar solution in which a large proportion of the sugar has been deliberately crystallised under controlled conditions, so that the final material is a dense suspension of very fine sucrose crystals in a saturated syrup. An icing is a related system, usually built on icing sugar or a cooked syrup, often with added fat, milk solids, protein or aeration, and it sets either by drying, by fat crystallisation, by protein gelation or by a combination of all three. Both are dominated by the same underlying variables: sugar concentration, water content and water activity, fat content and crystalline state, and the presence of any dissolved or dispersed material that is not sugar.

The Sugar-Water-Fat Balance

The consistency of any sugar-based coating is governed first by the ratio of sugar to water and second by the amount of fat and solids dispersed in the continuous phase. Cooking a syrup to a higher solids level produces a more viscous, faster-setting fondant; lowering the solids produces a softer, slower-setting one. Introduction of fat changes the system from a simple solution into an emulsion, and an emulsion behaves differently: viscosity depends on droplet size distribution, on the emulsifier system and on the temperature history of the mix. Anything added to the system that dissolves in the aqueous phase will raise the dissolved-solids content and therefore viscosity; anything that dissolves in the fat phase will lower the solids content of the fat and soften it.   This is the first reason flavouring is risky. A flavour is not a neutral passenger. Alcohol-based extracts, glycerol-containing carriers, propylene glycol solutions, invert sugar syrups and salt-containing emulsion flavours all contribute dissolved solids or water to the continuous phase. That contribution is measurable and it changes the boiling point, the set point and the final texture even when the flavour impact itself is modest. A formulator who thinks only about the aroma compound and ignores the carrier has already lost control of the batch.   The second reason is that the fondant or icing is frequently the last unit operation in the factory before packaging, so there is no subsequent process step that can correct a defect. If a dough is over-hydrated it can be re-sheared on the divider; if a filling is too soft it can be re-chilled. But a fondant that has been flavoured and is spreading on a line is already committed. The window for adjustment is measured in minutes, which is why the correct approach is specification and prevention rather than correction.

How Flavour Format Changes Rheology

Every flavour format delivers a different package of chemistry alongside the aroma. An oil-soluble flavour is a solution of aroma compounds in a vegetable oil, a medium-chain triglyceride or a similar carrier, and it introduces fat and no water. A water-soluble liquid flavour is usually a solution or suspension of aroma materials in water, ethanol, propylene glycol or glycerol, and it introduces either water or a strongly hygroscopic solvent. A flavour emulsion is an oil-in-water or water-in-oil system stabilised by gum arabic, modified starch or a similar hydrocolloid, and it introduces both water and a polysaccharide that will itself thicken the system. A spray-dried or encapsulated powder introduces a carrier matrix, typically a starch, maltodextrin, gum or protein wall material, which behaves as an insoluble solid in the fondant and can contribute a slight opacity or a fine grittiness at high dosage. Because each of those formats interacts differently with the sugar-water-fat balance, the practical rule is that the flavour format should be selected together with the fondant formulation rather than afterwards. The choice of format is a functional decision about water, fat, solids and surfactant load, and only secondly a decision about aroma profile. The same is true of colour: a water-based colour in an oil-based coating will bead and mottle, while an oil-dispersed colour in a water-based glaze will streak. There is a direct parallel with baked goods, where the choice between a heat-stable and a heat-labile flavour format determines whether the flavour survives the oven at all, a distinction we examined in our guide to selecting flavours that survive the bake.

The Five Consistency Faults That Matter Most

In bakery and confectionery plants the complaints that reach the technical department about flavoured fondant and icing cluster into five recurring faults. Each has a specific mechanism, a specific set of contributing factors and a specific remedy. Diagnosing the fault correctly before adjusting the recipe is the difference between solving a problem and creating a second one.

Gritty, Grainy or Crumbly Texture

Grittiness is a crystallisation fault. Fondant texture depends on the size of the sucrose crystals formed during the beating and cooling stage. When crystals are small and uniform the fondant is smooth and plastic; when crystals are large, irregular or agglomerated the fondant feels grainy on the tongue and breaks rather than flows. Several flavouring-related factors push crystal size upward. Seeding by foreign particles, including undissolved powder flavour carriers, fine sugar dust from an unsealed bag and mineral particulates, provides nucleation sites that grow into detectable crystals. Adding water or an aqueous flavour after the fondant has been cooled dilutes the saturated syrup at the surface of existing crystals, allowing them to grow. Adding an acid or an acidic flavour that hydrolyses sucrose to glucose and fructose alters the sugar composition and the solubility balance, so the crystals that form are no longer the fine, uniform sucrose crystals the process was designed to create.   The remedies are consistent. Disperse powdered flavours fully in a small portion of the syrup or in a compatible oil before addition and screen the dispersion where the dose is high. Add aqueous phases to the syrup stage rather than to the finished fondant so that the water is removed by cooking and does not remain free in the system. Where an acid-flavoured fondant is required, use a pH-stable acidulant system and cook to a slightly higher solids level to compensate for the inversion that will occur, and validate the texture at the end of shelf life rather than on the day of production.

Unexpected Thinning and Runoff

Runoff, sagging and edge build-up on enrobed or glazed products are viscosity faults. An icing that is too thin will not hold a film on a vertical surface, will pool at the base of the product and will leave a translucent, patchy coat where it has run. Several flavouring decisions lower viscosity. Adding a liquid flavour that contains water or ethanol dilutes the continuous phase directly. Adding a fat-based flavour to an icing whose structure depends on a fat crystal network will soften or partially melt that network, particularly if the carrier oil has a low melting point. Adding a hygroscopic solvent such as glycerol or propylene glycol increases free volume in the aqueous phase and reduces the effective solids concentration. The correction is to rebalance the recipe to account for what the flavour contributes. Raise the cooked solids level to restore the target viscosity, reduce the water contributed from other ingredients, choose a flavour carried in a higher-melting fat where the icing structure is fat-based, or accept a small increase in a hydrocolloid stabiliser to restore the yield stress of the film. What must not be done is to solve a thinning problem by adding more powdered sugar at the mixing bowl, because that introduces air and dust, changes the crystal population, and produces a fondant that will set with a different texture from the validated specification.

Hardening, Skinning and Crusting

The opposite fault is a fondant or icing that dries too fast, skins over in the holding tank, forms a leathery crust on the surface of the finished product or becomes brittle and flakes during transit. Fast skinning is almost always a water-loss phenomenon: a high-solids syrup in a warm, dry environment loses surface moisture quickly and forms a glassy layer. Flavouring contributes to it by adding solutes that accelerate the approach to the glass transition, and by adding volatile components that evaporate from the surface and let the film contract.   Protein-based icings, such as royal icing, behave differently again, because their setting depends on a protein network that is sensitive to pH, to salt and to the solvent environment. An acidic flavour added to a royal icing will slow or prevent the protein from setting, giving a coating that stays tacky indefinitely, while an alcohol-containing flavour will denature the protein prematurely and produce a lumpy, uneven film. The practical control is to match the flavour format to the setting mechanism: with a protein-set icing, use water-soluble flavours with minimal alcohol and check pH after addition; with a sugar-set glaze, control humidity and holding time so that skinning does not occur before the product is coated.

Colour and Flavour Fading

Fading is not a rheological fault but it is a consistency fault in the commercial sense, because the product no longer matches the standard the consumer recognises. Synthetic and natural colours fade at different rates and for different reasons. Anthocyanin-based natural colours are sensitive to pH, to heat, to light and to the presence of metal ions, and they will shift hue before they lose intensity. Carotenoid colours are oxidised readily in the presence of light, heat and free radicals, and their loss is often accelerated by a high-fat environment. Flavour loss follows parallel chemistry: citrus terpenes oxidise to less pleasant aldehydes and off-notes, while volatile top notes escape through the packaging film over time.   The controls that work are format and protection, not higher dosage. Encapsulated and spray-dried flavour systems that protect the aroma from oxidation and from premature volatilisation deliver both better retention and a more consistent sensory profile through the shelf life, for the reasons set out in our technical note on microencapsulation for stability and shelf life. The same principle applies to colour: buffering the system to a pH where the chosen colorant is most stable, adding an antioxidant system where the colour is oxidation-sensitive, and selecting packaging with an appropriate light and oxygen barrier will do more for colour stability than doubling the colour dosage.

Separation, Weeping and Syneresis

Weeping is the appearance of free syrup or water at the surface of a fondant or at the interface between an icing and the product it coats. It has two common causes in flavoured systems. The first is emulsion instability: a flavour emulsion added to a fondant whose aqueous phase is already saturated with sugar will have less free water available to hydrate its stabiliser, and the emulsion can break, releasing oil. The second is osmotic migration: a high-solids fondant in contact with a lower-solids filling or a moist cake crumb will draw water from the substrate, thinning at the interface and producing a wet layer.   Separation is best prevented at the formulation stage. Select emulsion flavours whose stabiliser system is tolerant of high sugar concentrations and low water activity, verify the stability of the emulsion in a bench sample of the actual fondant rather than in water, and where a high-moisture substrate is involved insert a barrier layer, such as a thin fat-based seal coat or a protein film, to limit water migration. Where syneresis has already occurred on a manufactured batch, the useful diagnostic is to check whether the free liquid is syrup, oil or water, because each points to a different root cause and a different corrective action.

Selecting the Right Flavour Format

Format selection is the single most consequential decision in flavouring a fondant or an icing, and it should be made on functional grounds before sensory ones. The table below is the framework our applications team uses when a customer describes a new product, and it holds for both natural and synthetic flavour chemistries.

Oil-Soluble Flavours

Oil-soluble flavours are the correct choice for fat-based coatings, compound chocolate-flavoured glazes, fat-based fillings and any system in which water is unwelcome. They disperse readily in a fat continuous phase, they do not introduce free water, and they typically survive the mixing and holding stages of a coating process well. Their limitations are equally clear. Because they are lipophilic, they will not disperse in a water-based glaze without a suitable emulsifier, they add fat to a recipe that may already be fat-sensitive, and their carrier oil can soften a coating whose structure depends on a hard fat network. Dosage must therefore be checked against the solid fat content of the finished coating, particularly where the coating must remain firm at summer temperatures. Where a fat-continuous glaze needs a deep cocoa character without any addition of water, a rich chocolate flavour for confectionery coatings disperses directly into the molten fat phase, rebuilds the roasted and cocoa depth that a diluted fat system loses, and leaves the texture of the coating untouched.

Water-Soluble Liquid Flavours

Water-soluble liquids are the workhorse format for sugar glazes, doughnut icings, fondant for enrobing and beverage-adjacent applications. They are economical, easy to meter and available in a very wide range of profiles. The caution is compositional: the carrier determines behaviour. An ethanol-based flavour will evaporate from a warm syrup and can leave the aroma under-strength, and it can also flash off in a closed vessel in a way that changes the headspace in the plant. A propylene-glycol-based flavour contributes a non-sugar dissolved solid that raises viscosity and can impart a faint sweet-solvent note at high dosage. A glycerol-based flavour is strongly hygroscopic and will keep a coating tacky in humid conditions. Reading the carrier specification, not only the flavour name, is essential.

Emulsion and Dispersed Flavours

Emulsions are useful where a flavour must be distributed uniformly through a system that contains both water and fat, and where a controlled release is desirable. They are also helpful for including oil-soluble aroma chemistry in a predominantly aqueous glaze. Their practical constraints are the ones described above: the stabiliser competes for water, the emulsion needs a minimum water activity to remain intact, and an unstable emulsion produces exactly the oil-release and mottling defects that the formulator was trying to avoid. Always request an application-specific stability confirmation in a sugar system at the intended solids level.

Powder, Spray-Dried and Encapsulated Flavours

Powders are convenient, shelf-stable and easy to blend, and encapsulated powders offer the best combination of heat stability, oxidation protection and controlled release. In fondant and icing they must be handled carefully because the carrier matrix is an insoluble solid in a sugar suspension. Poorly dispersed powder creates lumps that later appear as pale specks or gritty particles, and it can also nucleate crystal growth. The correct procedure is to pre-blend the powder with a small quantity of dry icing sugar or a portion of the warm syrup, to screen it, and to add it under high shear for long enough to hydrate the carrier fully. Where the application requires both heat stability through a bake and retention through shelf life, encapsulated systems are usually the only format that satisfies both requirements.

Dosage, Water Activity and Temperature: The Practical Rules

Once the format is chosen, three variables decide whether the flavoured fondant behaves. They are the dosage basis, the water activity and pH of the finished system, and the temperature at which the flavour is added. Each is straightforward to control and each is routinely neglected.

Calculating Dosage on the Correct Basis

Flavour dosage must be expressed on a consistent basis, normally as a percentage of the finished coating or of the batch as weighed, and it must be calculated after all water loss from cooking has been accounted for. A flavour specified at one percent of the cooked fondant is a very different dose from one percent of the raw syrup, because cooking removes a substantial fraction of the water. In many plants the discrepancy between the two is the reason a product tastes weaker than the bench standard. The reliable practice is to state dosage as a percentage of the finished, cooked coating mass, to verify it by weighing the finished batch, and to check the flavour profile instrumentally or by a trained panel at the start, middle and end of the production run rather than only at the beginning. Dosage also interacts with the substrate. A coating applied to a strongly flavoured product, such as a spice cake or a fermented dough, must be dosed higher to be perceived at the same intensity, because aroma release is influenced by the headspace above the product and by the composition of the crumb. Conversely, a coating on a bland substrate will seem more intense than the same coating on a strong one. Bench trials should therefore always be performed on the actual substrate, not on a neutral carrier.

Water Activity, pH and Acid Tolerance

Water activity governs both microbial stability and the physical behaviour of the coating, and it determines which flavour chemistries will remain stable. Some aroma compounds, particularly certain esters and acetals, hydrolyse or rearrange in acidic, high-water-activity environments, and the resulting profile changes from a clean fruity note to a flatter, slightly solventy one. Others, including many of the components that give a fresh citrus character, are sensitive to oxidation, which is accelerated by heat, light and the presence of catalytic metal ions. Selecting an acid-stable flavour where the system is acidic, and an oxidation-protected or encapsulated format where the system is exposed to air and light, is more effective than increasing the dose.   Water activity matching between coating and substrate is equally important. A coating at a lower water activity than its substrate will draw moisture and become soft and sticky, while a coating at a higher water activity will donate moisture and dry out. Where a coating must sit on a moist cake or a filled pastry, controlling the water activity gap and adding a moisture barrier are the two levers that prevent the interface problems described earlier. Flavours with a high glycerol or propylene glycol content effectively raise the water activity and the hygroscopicity of the coating, so the carrier specification has a direct effect on the interfacial behaviour of the finished product.

Temperature at the Point of Addition

Temperature at addition determines both the loss of volatile aroma and the physical effect on the coating structure. Adding a volatile liquid flavour to a syrup that is still hot will drive off the top notes and flatten the profile, which is why a fresh strawberry flavour for glazes and fruit icings added above the recommended temperature tastes cooked and jammy rather than fresh. Adding a fat-based flavour to a coating at a temperature above the melting point of its carrier produces a uniform dispersion that will harden correctly on cooling; adding it below the melting point produces undispersed fat particles and a mottled coating.   The general rule is to follow the format recommendation. Water-soluble and emulsion flavours are normally added at the lowest temperature at which the coating is still fluid enough to mix, typically after cooling to the recommended addition window. Oil-soluble flavours are added to the molten fat phase at a temperature a few degrees above the carrier melting point. Powdered flavours are added either to the dry blend or dispersed in a warm liquid phase. In each case the mixing time after addition should be long enough to achieve uniformity but short enough to limit the loss of volatile components to the headspace of an open vessel.

Production Controls, Storage and Shelf Life

Formulation establishes the ceiling on performance; production control determines whether that ceiling is reached. Flavoured fondant and icing are sensitive to holding time, temperature, aeration and humidity, and the controls that matter most are inexpensive to implement and easy to overlook.

Mixing, Aeration and Holding Time

Fondant is a crystallisation product and its texture depends on the shear history it experiences. Holding a flavoured fondant warm in an agitated tank for hours after preparation allows the crystal population to change and the texture to drift, so batches should be sized to the production requirement and used within a defined time window. Over-agitation entrains air, which lowers the apparent density, changes the opacity of the finished coating and introduces bubble defects on the surface. Under-agitation leaves flavour and colour unevenly distributed, producing visible streaking or, in extreme cases, a product that tastes different at the edges than in the centre.   The practical controls are a defined holding temperature, a defined maximum hold time, an agitation speed that keeps the mass homogeneous without whipping air into it, and a record of how long each batch actually spends between preparation and application. Where the line runs intermittently, it is often better to prepare a fresh small batch at each start-up than to carry a large batch through a long stoppage.

Drying, Crusting and Humidity Control

The setting of a dried glaze depends on a controlled loss of surface moisture. Room temperature, relative humidity, air velocity and product dwell time all influence the outcome, and they interact. A product held in a hot, dry draught may skin before it is fully levelled, leaving a visible ridge or a dull surface. A product held in a cool, humid area will stay tacky, pick up dust and stick to the packaging. Both are humidity and airflow problems rather than flavour problems, but they present as flavour problems because the flavoured coating is the visible layer.   The controls are to maintain the coating room within a defined temperature and humidity band, to direct airflow so that it is uniform across the whole conveyor rather than concentrated at one point, and to verify the condition of the finished surface before packaging. Where a climate-controlled coating room is not available, the recipe can be adjusted toward a faster-setting system with a higher solids content and a modest reduction in the hygroscopic component of the flavour carrier.

Packaging and Flavour Retention

Aroma compounds migrate into, through and out of packaging films. Whether a flavour is retained through the shelf life depends on the barrier properties of the film, on the storage temperature, on the light exposure and on the interaction between individual aroma molecules and the polymer. Terpene-rich citrus flavours, in particular, are absorbed by some polyolefin films, which reduces perceived intensity over time, and they are also prone to oxidation. Where the product carries a high-value top note, the packaging specification is a flavour specification.   For high-retention products, the appropriate combination is an oxygen and moisture barrier film, a light-protective structure where the colour or flavour is light-sensitive, storage at a stable and moderate temperature, and a flavour format that protects the volatile fraction, such as an encapsulated or spray-dried system. Accelerated shelf-life testing with sensory assessment at defined intervals is the only reliable way to confirm that the combination works for the specific product, because the interaction between a given aroma profile and a given film is difficult to predict from specification sheets alone.

A Diagnostic Sequence for Consistency Faults

When a consistent product begins to fail, the order in which the causes are investigated matters. The sequence our applications team recommends is to check the incoming flavour and colour lots first, comparing the lot number, the carrier composition and the analytical certificate against the previous good production. Second, check the actual dosage against the specification, using the finished cooked mass as the basis, since an unnoticed change in the flavour carrier or in the cooking endpoint will shift the effective dose. Third, check the temperature and the point of addition against the format recommendation. Fourth, check the water activity, pH and solids content of the finished batch. Fifth, check the production environment, including room humidity, airflow and holding time.   In the great majority of cases the cause lies in the first three checks, and it is a change in the flavour delivery rather than a fault in the flavour chemistry. Where the flavour chemistry itself has changed, the correct response is not to increase the dosage but to confirm with the supplier whether the carrier, the solvent or the raw material source has changed, because a carrier change with no change in the declared aroma profile can nevertheless change the rheology of the finished fondant substantially. That is one more reason to buy flavour systems from a supplier who will tell you what is in the carrier and why.

Key Takeaways for Fondant and Icing Developers

Treat the flavour format as a formulation decision. Oil-soluble for fat-based coatings, water-soluble for sugar glazes, emulsion where both phases are present, encapsulated where the flavour must survive heat, air and a long shelf life. The carrier chemistry changes the rheology of the coating as much as the aroma changes the taste.   Account for what the flavour contributes. Water, ethanol, glycerol, propylene glycol, vegetable oil, polysaccharide stabiliser and carrier solids all alter viscosity, setting behaviour and water activity. Rebalance the recipe for the contribution rather than adding the flavour on top of an unchanged formula.   Control crystal formation. Disperse powders fully, screen them, avoid adding free water to a cooled fondant, and be cautious with acid in high-sugar systems where inversion will change the crystal population and the final texture.   Match water activity between the coating and the substrate, and insert a barrier where the gap cannot be closed. Weeping, softening and interface drying are almost always water-activity problems, and they will not be solved by changing the flavour dosage.   Validate on the real substrate and at the end of shelf life. Bench performance in a beaker is not a prediction of coating performance on a moist cake, and a product that meets specification on the day of manufacture may not meet it after twelve weeks in a warm warehouse. Combine instrumental viscosity and water-activity checks with trained sensory assessment in an accelerated protocol.   Technical Consultation / Free Sample: 📞 Phone: +86 0769 8838 0789 🌐 Website: https://www.cuiguai.cn 📧 Email: info@cuiguai.com 💬 WhatsApp & Telegram: +86 189 2926 7983  

References

U.S. Food and Drug Administration, Code of Federal Regulations Title 21, Parts 172, 182 and 184 - Food Additives Permitted for Direct Addition to Food for Human Consumption, including flavouring agents and colorants used in bakery and confectionery coatings.   European Parliament and Council, Regulation (EC) No 1334/2008 on flavourings and certain food ingredients with flavouring properties for use in and on foods, and Commission Regulation (EU) No 231/2012 on specifications for food additives.   Journal of Food Science, Journal of the Science of Food and Agriculture, and Food Hydrocolloids - peer-reviewed studies on sucrose crystallisation in fondant, glass transition and moisture migration in sugar-based coatings, and the rheological effects of hydrocolloids and polyols in confectionery glazes.   Journal of Agricultural and Food Chemistry and LWT - Food Science and Technology - peer-reviewed studies on aroma retention, encapsulation efficiency and colour stability in sugar-based confectionery systems during storage.