Summary

Storage caking, powder floating, clumping during preparation, and residue at the bottom of a cup are usually not caused by the poor solubility of a single ingredient. These problems more often result from the combined effects of particle size distribution, moisture uptake and moisture migration, particle surface wettability, hydrocolloid hydration rate, and premixing methods.

To address these issues, it is first necessary to distinguish storage-stage caking from reconstitution-stage abnormalities, and then examine particle size, fine-particle content, moisture content, water activity, bulk density, ingredient compatibility, and addition procedures according to the specific symptoms. Simply reducing particle size or increasing the amount of an anticaking agent may temporarily improve one parameter while increasing the risks of moisture uptake, segregation, floating, or agglomeration.

What Are Food Powder Caking and Reconstitution Abnormalities?

Food Powder Caking

Food powder caking is the process in which originally free-flowing particles form stable agglomerates through liquid bridges, solid bridges, surface softening, electrostatic attraction, or mechanical compaction.

Mild caking can usually be reversed by kneading or vibration. Hard lumps often indicate that particle surfaces have absorbed moisture, partially dissolved, softened, or recrystallized. Even after sieving, such powders may cake again.

Reconstitution of Instant Powders

Reconstitution of instant powders refers to the wetting, sinking, dispersion, dissolution, or hydration that occurs after a powder comes into contact with a liquid.

For soluble ingredients such as sugars, salts, and organic acids, dissolution rate is the main consideration. For hydrocolloids, proteins, dietary fibers, and some plant powders, it is more appropriate to evaluate wetting, dispersion, hydration, and the time required to reach the target viscosity.

Therefore, the presence of lumps in a prepared beverage does not necessarily indicate insufficient ingredient solubility. A powder may appear to “dissolve slowly” because it has not been wetted, has not sunk into the liquid, or has formed a rapidly hydrated outer layer that encloses dry powder inside.

Application Scenarios and Core Performance Requirements

This article focuses on instant powdered beverage systems intended for direct preparation with water, including:

• Fruit-flavored powdered beverages;
• Electrolyte drink powders;
• Vitamin and mineral premixes;
• Coffee-, tea-, and cocoa-flavored beverage powders;
• Plant extract-based beverage powders;
• Protein and dietary fiber beverage powders.

These formulations commonly contain sugars or sugar alcohols, acidulants, sweeteners, flavors, colorants, mineral salts, vitamins, thickeners, emulsifiers, and carrier materials. The addition levels, particle sizes, densities, surface properties, and hygroscopic behavior of these ingredients may differ significantly.

A dry blend suitable for commercial production generally needs to meet four requirements:

1. Maintain flowability during storage and conveying;
2. Keep low-dose ingredients uniformly distributed;
3. Wet, sink, and disperse rapidly during preparation;
4. Avoid visible lumps, sediment, or localized viscosity abnormalities after reconstitution.

First Distinguish Caking, Floating, Agglomeration, and True Solubility Limitations

Different abnormalities correspond to different causes. Identifying the stage at which the problem occurs before changing ingredient specifications can prevent inappropriate adjustments.

Functions and Risks of Different Ingredients in Dry Blends

The stability of a dry blend depends on how different ingredients work together, rather than on whether a single additive is simply “soluble” or “anticaking.”

How Particle Size Affects Flowability, Segregation, and Reconstitution

Smaller Particles Do Not Necessarily Reconstitute More Easily

Reducing particle size increases the contact area between the powder and water and may accelerate the dissolution of some soluble ingredients. However, excessively fine particles may also cause:

• A larger specific surface area and faster short-term moisture uptake;
• Stronger interparticle forces and greater powder cohesiveness;
• Reduced flowability, leading to bridging or wall adhesion in hoppers;
• Greater air entrapment, causing fine particles to float on the water surface;
• Excessively rapid localized dissolution, creating highly concentrated viscous layers;
• Rapid hydration of hydrocolloid surfaces, preventing water from entering the interior of agglomerates.

Therefore, further grinding does not necessarily solve slow dissolution. For rapidly hydrating hydrocolloids and some protein powders, excessive fineness may increase agglomeration.

Coarse Particles Can Also Create New Problems

When composition and surface condition are similar, larger particles have a lower external surface area per unit mass, may absorb moisture more slowly in the short term, and are generally easier to keep free-flowing.

However, excessively coarse particles may cause:

• Longer dissolution or hydration times;
• Segregation from fine particles during transportation;
• Localized high concentrations at the bottom of a cup;
• Noticeable grittiness;
• Difficulty in uniformly distributing low-dose ingredients.

Particle Size Distribution Is More Important Than Average Particle Size

Two ingredients with the same average particle size may still behave differently in terms of flowability, mixing, and reconstitution.

In addition to D50, specification review should include:

• D10, D50, and D90;
• Proportions of ultrafine and coarse particles;
• Oversize and undersize fractions;
• Whether agglomerated particles readily break apart;
• Particle shape, porosity, and surface structure;
• Whether the sample is sieved or deagglomerated before testing.

When the test method is consistent, the following parameter may be used to assist in comparing particle size distribution span:

Particle size distribution span = (D90 − D10) ÷ D50

This parameter should only be used to compare similar ingredients or batches produced under comparable processing conditions. It cannot independently predict flowability or segregation risk without considering particle density, shape, surface condition, and degree of agglomeration.

How Moisture Migration and Hygroscopicity Cause Caking

Moisture Content and Water Activity Are Not Interchangeable

Moisture content represents the total amount of water in a sample. Water activity reflects the thermodynamic state of water in the system and can help indicate the direction of moisture migration between different ingredients.

In a blend, moisture may migrate from ingredients with higher water activity to those with lower water activity. Therefore, the fact that each ingredient individually meets its specification does not guarantee that localized moisture uptake or adhesion will not occur after blending.

Spray-dried flavors, plant extracts, hydrocolloids, sugars, salts, and organic acids may establish a new moisture equilibrium after mixing. The moisture behavior of the final formulation cannot be fully predicted from data on individual ingredients alone.

Liquid Bridges, Solid Bridges, and Surface Softening

During the early stage of moisture uptake, small amounts of water on particle surfaces may form liquid bridges that bind adjacent particles.

If soluble sugars, salts, or organic acids are present on the surface, localized moisture may also partially dissolve the particles. When ambient humidity decreases, the dissolved material recrystallizes, gradually converting liquid bridges into stronger solid bridges.

For powders containing amorphous sugars, spray-dried carriers, or some plant extracts, absorbed moisture may also lower the glass transition temperature, causing previously rigid particle surfaces to soften, become sticky, and undergo structural collapse.

This type of caking generally cannot be solved simply by increasing the amount of an anticaking agent.

Temperature Changes Increase Moisture-Uptake Risk

The following conditions may cause localized condensation inside the package or on powder surfaces:

• Materials from cold storage are moved directly into a warm, humid production area;
• Packages are opened before the materials reach temperature equilibrium;
• Warm powders are packaged before adequate cooling;
• Repeated temperature cycling occurs during storage or transportation;
• Opened materials remain exposed to high humidity for extended periods;
• Packaging seals or moisture-barrier performance are inadequate.

Recording only the average warehouse humidity is not sufficient. The actual exposure time during package opening, mixing, temporary storage, and packaging should also be considered.

How to Design Premixing, Agglomeration, and Addition Procedures

Use Stepwise Premixing for Low-Dose Ingredients

High-intensity sweeteners, colorants, vitamins, and concentrated flavors should not be added directly to a large quantity of bulk powder.

A more stable approach is to carry out an initial dilution with a small amount of carrier, followed by stepwise increases in the blend ratio. At each stage, the volume, particle size, and density of the premix should be as close as possible to those of the material used in the next mixing stage.

This approach can reduce:

• Small-dose weighing errors;
• Excessive localized concentrations;
• Color or flavor spots;
• Re-segregation after mixing;
• Composition variation among individual packages.

Longer mixing time cannot replace stepwise premixing. In some systems, prolonged mixing may cause ingredients with different particle sizes or densities to segregate again.

Predisperse Rapidly Hydrating Hydrocolloids with a Carrier

When hydrophilic hydrocolloids such as xanthan gum and guar gum come into direct contact with water, the particle surface may rapidly form a viscous hydrated layer. This layer prevents the dry powder inside from continuing to contact water, resulting in fisheyes that are wet outside and dry inside.

Common improvement methods include:

• Premixing thoroughly with sugar, sugar alcohol, or maltodextrin;
• Reducing the instantaneous local concentration of the hydrocolloid;
• Controlling the addition rate and avoiding concentrated dumping onto the liquid surface;
• Adding the powder gradually after a stable vortex has formed;
• Using easy-dispersing grades produced through agglomeration or surface treatment;
• Adjusting shear intensity and hydration time according to the available equipment.

The evaluation endpoint for hydrocolloid ingredients should not be stated only as “complete dissolution.” It should specify no visible lumps, achievement of the target viscosity, or completion of the specified hydration time.

Improve Wetting and Sinking Through Agglomeration

Agglomeration or granulation converts large quantities of fine particles into larger particles with a certain degree of porosity. Water can enter the particle interior and displace trapped air, thereby improving wetting, sinking, and disintegration.

This method is suitable for:

• Instant beverage powders with a high proportion of fines;
• Plant powders or protein powders that tend to float;
• Composite powders containing hydrocolloids or flavor carriers;
• Production lines with strict dust-control requirements.

Particle strength must be balanced. Excessively strong particles may disintegrate slowly, while excessively weak particles may generate fines again during transportation and packaging.

Anticaking Agents Address Only Part of the Problem

Food-grade anticaking agents may improve flowability by separating particles, adsorbing localized moisture, reducing contact area, or modifying surface friction. The specific mechanism depends on the material.

Anticaking agents are more suitable for addressing mild moisture uptake and reduced flowability caused by particle contact. The following problems should not be addressed primarily by increasing the anticaking agent level:

• Packaging leakage or inadequate moisture-barrier performance;
• Abnormal initial moisture content of the ingredient;
• Severe temperature cycling and condensation;
• Surface softening of amorphous powders;
• Localized reactions between acidulants and alkaline salts;
• Severe compaction caused by stacking pressure;
• Segregation caused by differences in particle size and density.

For specific anticaking agents, suitability for the target market, food category, and intended use must also be verified.

How Material Compatibility Affects Reconstitution

Acidulants and Alkaline Mineral Salts

When organic acids coexist with alkaline ingredients such as carbonates and bicarbonates, trace amounts of moisture may trigger localized reactions, resulting in gas release, powder expansion, flavor changes, or caking.

These formulations require particular attention to:

• Ingredient moisture content;
• Package-opening and mixing environment;
• Contact time;
• Packaging moisture barrier;
• Whether coating, separate granulation, or delayed blending is required.

Mineral Salts with Hydrocolloids or Proteins

Multivalent ions such as calcium and magnesium may alter the hydration, aggregation, or precipitation behavior of certain hydrocolloids and proteins.

A mineral salt that dissolves in pure water may not behave in the same way when added to a complete formulation containing acidulants, hydrocolloids, and proteins. Application testing should use the target pH, solids concentration, and actual ionic level rather than only a single-salt solution.

Spray-Dried Flavors in High-Acid Systems

The carrier type, surface oil content, encapsulation integrity, and particle structure of spray-dried flavors affect moisture uptake, flowability, floating, and flavor release.

Comparison of flavor powders should not be based solely on flavor content. It should also examine:

• Moisture uptake after package opening;
• Degree of caking after storage;
• Surface oil and tackiness;
• Floating and turbidity after preparation;
• Flavor release and retention.

Key Parameters and Their Application Significance

Parameters are only comparable when test conditions are consistent. Data generated using different instruments, dispersion methods, water temperatures, stirring speeds, and endpoint definitions should not be compared directly.

How to Establish Comparable Reconstitution Tests

Statements such as “dissolves quickly” or “disperses well” are difficult to use for supplier or batch comparisons without standardized test conditions.

At a minimum, sample testing should record the following information.

Powder-to-Liquid Ratio

Specify the sample mass and water volume. Changes in concentration directly affect local viscosity, dissolution equilibrium, and hydration rate.

Water Temperature

Cold water, room-temperature water, and hot water may produce completely different preparation results. The exact temperature should be recorded rather than stating only “room temperature.”

Addition Method

The following methods should be distinguished:

• Added all at once;
• Added gradually;
• Added into a vortex;
• Predispersed with part of the carrier;
• Powder added to water or water added to powder.

Mixing Conditions

Record the type of mixer, rotational speed, mixing time, and container size. Results from magnetic stirring, high-shear dispersion, and manual spoon stirring cannot be compared directly.

Endpoint Definition

Select a clear endpoint according to the ingredient type, such as:

• No powder floating;
• No visible lumps;
• No crystalline residue at the bottom;
• Target viscosity reached;
• No obvious sedimentation or phase separation after standing.

Observation After Standing

Some systems appear normal immediately after mixing but later develop sedimentation, flocculation, or continued viscosity increase. A standardized standing time should be specified before further observation.

Sample Validation and Batch Control

Stage 1: Individual Ingredient Testing

First confirm the powder characteristics of the ingredient itself:

• Appearance, odor, and color;
• Moisture content and water activity;
• Particle size distribution;
• Loose bulk density and tapped density;
• Flowability and compaction tendency;
• Wetting, dispersion, and reconstitution behavior.

Stage 2: Testing in the Actual Formulation

Normal performance of a single ingredient does not guarantee stability after formulation. Formulation testing should use the actual addition ratio and examine:

• Different addition sequences;
• Different premix ratios;
• Different mixing times;
• Uniformity of samples taken from the top, middle, and bottom;
• Target water temperature and actual preparation method;
• pH, viscosity, sedimentation, and sensory changes after reconstitution.

Stage 3: Comparison Before and After Storage

Storage testing should not only observe whether caking occurs. It should also compare reconstitution performance before and after storage:

• Changes in particle size and agglomerates;
• Changes in flowability;
• Wetting and dispersion time;
• Powder adhesion to the package interior;
• Changes in aroma, color, and mouthfeel;
• Short-term moisture uptake after opening.

Stage 4: Production Scale-Up Validation

Results from a laboratory beaker do not fully represent commercial production. Scale-up validation should examine:

• Mixer fill level;
• Addition position and timing;
• Holding time between mixing and packaging;
• Segregation during conveying and discharge;
• Packaging-machine feeding stability;
• Dust and equipment wall adhesion during continuous production;
• Sampling differences between the beginning, middle, and end of production.

Why Changes in Ingredient Specifications Alter Dry-Blend Performance

The same chemical name, primary composition, or assay does not guarantee identical powder application performance.

Different suppliers or batches may vary in:

• Drying and milling methods;
• Proportions of fine and coarse particles;
• Particle porosity and surface roughness;
• Hydration state or crystalline form;
• Carrier and surface treatment;
• Bulk density;
• Initial moisture content and moisture uptake rate;
• Packaging method.

When replacing an ingredient, comparing only assay, purity, or unit price may overlook effects on blend uniformity, packaging-line feeding, and preparation speed.

Specification review should normally include:

1. Particle size distribution and test method;
2. Moisture content, water activity, or hygroscopic behavior;
3. Bulk density and flowability;
4. Premixing or granulation method;
5. Powder condition after storage and transportation;
6. Reconstitution results under conditions matching the target formulation.

For low-dose ingredients, changes in particle size and density are especially important. An ingredient may remain within the supplier’s specification while still requiring adjustment of the original mixing parameters.

Common Approaches with Limited Effectiveness

Only Extending Mixing Time

Longer mixing may improve initial uniformity, but it may also cause ingredients with different particle sizes and densities to segregate again. Effectiveness should be confirmed by sampling from multiple locations.

Only Grinding the Ingredient More Finely

Further milling may accelerate the dissolution of some ingredients, but it may also increase moisture uptake, cohesiveness, dust, floating, and hydrocolloid agglomeration.

Only Increasing the Anticaking Agent Level

If the underlying cause is package failure, moisture migration, surface softening, or an acid–base reaction, increasing the anticaking agent level is unlikely to restore long-term stability.

Relying Only on Single-Ingredient Dissolution Tests

The pH, ionic strength, hydrocolloids, and proteins in a complete formulation can alter ingredient behavior. Results from a single ingredient in pure water provide only basic information.

Comparing Only Average Particle Size

Average particle size does not indicate the proportion of fines, the proportion of coarse particles, or the distribution span. D10, D50, D90, and agglomeration condition should generally be evaluated together.

Support Available from ChemicalCell

ChemicalCell can assist in matching food additives, acidity regulators, thickeners, flavor carriers, anticaking agents, and related functional ingredients according to the powdered beverage formulation, current abnormality, preparation conditions, and packaging requirements.

During sample discussions, available particle size, moisture, packaging, premixing, or granulated specifications can be further confirmed, and different ingredients can be compared under standardized reconstitution conditions for the target application.

FAQ

Should Moisture Content or Water Activity Be Tested First for a Dry Blend?

The two parameters serve different purposes and cannot replace one another. Moisture content indicates the total amount of water in the sample, while water activity is more useful for evaluating moisture migration trends between different ingredients. Incoming-material control commonly uses moisture content as a basic parameter, while water activity is more informative when investigating localized moisture uptake or caking after ingredients are blended.

Why Does the Same Formulation Cake More Easily After Changing Suppliers?

Even when the main composition and assay are the same, ingredients may differ in particle size distribution, fine-particle content, crystalline form, carrier, bulk density, and moisture uptake rate. These differences affect particle contact, compaction, moisture migration, and packaging-line feeding. A formulation and storage validation should therefore be repeated when changing suppliers.

How Can Slow Wetting, Slow Dispersion, and True Solubility Limitations Be Distinguished?

Powder that remains on the liquid surface usually indicates a wetting or sinking problem. Lumps that are wet outside but dry inside usually indicate a dispersion or hydration problem. Only when the lumps have completely broken apart but crystals or particles still remain at the bottom should solubility, salt form, pH, water temperature, and use concentration become the primary focus.

When Should Packaging Be Adjusted Instead of Increasing the Anticaking Agent?

When caking varies significantly between packaging formats or storage locations, or when caking rapidly increases with storage time, temperature cycling, and ambient humidity, packaging moisture barrier, seal integrity, and open-package exposure time should be checked first. When hard lumps, surface recrystallization, or signs of condensation are present, increasing the anticaking agent alone usually has limited effect.

RFQ Information

When requesting a quotation for ingredients or customized premixes for instant powdered beverages, the following information may be provided:

• Product type and main formulation structure;
• Current caking, floating, agglomeration, or residue problems;
• Target particle size, moisture, or reconstitution requirements;
• Preparation water temperature, powder-to-liquid ratio, and mixing method;
• Packaging specification and expected storage conditions;
• Sample requirement and estimated purchase volume.

Comparing different particle sizes, carriers, or granulated grades under standardized application conditions can reduce misjudgments caused by different test methods and make it easier to identify a dry-blend solution suitable for commercial production.