Powder Processing Technology Guide (Milling, Granulation & Tableting) | Principles, Equipment & Quality Control

"I want to create a supplement." "I want to sell a health food product in powder stick form." — When you start thinking along these lines, powder processing technology becomes essential. The processing technology required differs depending on the final product form — tablets, capsules, granules, or sticks. This article compiles the foundational knowledge of powder processing needed for OEM manufacturing.

Milling is the fundamental powder processing technology that uses mechanical force to reduce solid raw materials into fine particles. In the food industry, it serves various purposes including raw material pre-processing, product particle size adjustment, and improving solubility by increasing surface area. The milling method is selected based on target particle size and raw material characteristics.

Hammer Mill (Impact Mill)

This method uses high-speed rotating hammers (impact elements) to pulverize raw materials through impact. By changing the screen, it can handle everything from coarse to fine milling, making it the most commonly used mill in food processing. Its simple structure and high throughput (tens of kg to several tons/hour) make it widely used for coarse to medium milling of dry materials with low to medium hardness such as grains, dried herbs, spices, and sugar. However, it is not suitable for raw materials with high oil content (nuts, cacao nibs, etc.) as heat generation can turn them into paste. Temperature rises during milling may also degrade quality, so cooling jackets should be considered.

Jet Mill (Air-Flow Mill)

This technology uses high-velocity airstreams (sonic to supersonic speeds) generated by compressed air or nitrogen gas to make particles collide with each other, producing sub-micron to tens-of-μm ultra-fine powders. Since there are no mechanical moving parts in the milling chamber, the risk of metal contamination is low, making it suitable for pharmaceutical and supplement raw material milling. Classification-rotor-integrated models that perform milling and classification simultaneously are mainstream, enabling precise control of average particle sizes from 1–20 μm. The increased specific surface area from fine milling is also applied to improve bioavailability of poorly soluble functional ingredients (curcumin, coenzyme Q10, etc.). High energy consumption is a drawback, but for high-value-added products, the cost is justified.

Pin Mill (Impact/Shear Mill)

This method passes raw material between pins (protrusions) arranged on a rotating disc and a fixed disc, pulverizing through impact and shear. Milling fineness ranges from 20–500 μm, finer than what hammer mills can achieve. It is used for powdered sugar processing, finishing milling of powdered seasonings, and medium-to-fine milling of herbs. Although throughput is lower than hammer mills, it offers the advantage of producing uniform powders with a sharper particle size distribution.

Ball Mill (Media-Agitated Mill)

This method pulverizes raw materials through the rotation and collision of ceramic balls (milling media) inside a cylindrical vessel. It can also handle wet milling and is used for chocolate refining (fine milling of cacao mass) and finessing paste-type seasonings. Milling fineness is 5–50 μm. While the long processing time (several hours to more than ten hours) is a drawback, it produces uniform, fine particles. In addition to conventional rotating drum types, more efficient bead mills (using 0.1–2 mm micro beads) are also gaining popularity in the food industry.

• Coarse milling (500 μm–5 mm): Hammer mill, cutter mill
• Medium milling (50–500 μm): Pin mill, hammer mill (fine screen)
• Fine milling (1–50 μm): Jet mill, bead mill, ball mill

Granulation is a technology that processes fine powder raw materials into appropriately sized granules using a binder (binding agent). Granulation significantly improves powder flowability, compressibility, solubility, and weighing accuracy, enhancing the efficiency and quality of downstream processes such as tableting and capsule filling. In the food industry, the following three methods are primarily used.

Fluid Bed Granulation

This technology suspends (fluidizes) powder raw materials using hot air blown from below while spraying binder solution from above to agglomerate and bind particles together. The greatest advantage is that granulation and drying can be performed simultaneously in a single unit. The resulting granules are porous, offering excellent solubility and dispersibility in water, making this method widely used for granulating instant beverages, powdered soups, and health foods. Particle size can be controlled in the range of 100–1,000 μm, with spray rate, airflow, and binder concentration as key parameters. Common binders include HPC (hydroxypropyl cellulose), PVP (polyvinylpyrrolidone), and dextrin solutions, as well as food-grade natural binders (gum arabic, pullulan, etc.). Fluid bed granulators come in Wurster type (bottom spray) and top-spray type configurations, with the Wurster type chosen when coating is also required.

High-Shear Granulation

This method uses an impeller (mixing blade) and chopper (breaking blade) inside a sealed vessel to vigorously agitate powder raw materials while adding binder liquid. Compared to fluid bed granulation, it produces denser and harder granules, making it well suited for preparing granules for tableting. Granulation time is short at 5–15 minutes, and batch throughput is large (tens to hundreds of kg), offering excellent production efficiency. However, a separate drying step is required afterward, using fluid bed dryers or tray dryers downstream. The key quality parameters are impeller speed (100–500 rpm), chopper speed (1,000–3,000 rpm), binder volume, and addition rate. Preventing over-granulation (granules becoming too large) is important, and advanced manufacturers have introduced endpoint control through power consumption or torque monitoring.

Extrusion Granulation

This method uses a screw or roller to push a moistened powder mixture through a die (a plate with holes), producing cylindrical granules of uniform diameter. The granule diameter is determined by the die hole size, typically selected within the range of 0.5–3 mm. After extrusion, the granules can be processed through a marumerizer (spheronizer) to form spherical granules. The stable production of uniformly shaped and sized granules makes this method suitable for supplement granules and pellet-type seasonings. Twin-screw extruders can perform kneading and extrusion simultaneously, achieving uniform mixing and granulation in a single step.

Tableting is the technology of compressing powder or granules inside a die (punch and die set) to produce tablets. It is widely applied in the food industry, including supplements, ramune (tablet candy), and solidified powdered stock.

Direct Compression

This method directly compresses raw material powder in a tablet press without going through a granulation step. The process is simple, manufacturing costs are low, and since no heat or moisture is applied, it is suitable for heat-sensitive ingredients (vitamin C, probiotics, etc.). However, the raw material must have sufficient flowability (uniform die filling) and compressibility, which limits the usable materials. Direct compression excipients include microcrystalline cellulose (MCC), lactose, mannitol, and dicalcium phosphate, and it is not uncommon for excipients to comprise 50–80% of the formulation. When the active ingredient ratio is high, direct compression becomes difficult, and wet granulation tableting is chosen instead. Lubricants (magnesium stearate, calcium stearate: 0.5–1.5% addition) prevent sticking to the punch and die surfaces.

Wet Granulation Tableting

This is the most widely adopted tableting method, where raw materials are granulated with a binder before tableting. Granulation improves the flowability and compressibility of the powder, enabling compatibility with a wide range of raw materials. The process consists of six steps: mixing → granulation → drying → sizing → mixing (lubricant addition) → tableting. While the process is longer compared to direct compression, it yields products with an excellent balance of tablet hardness, disintegration, and weight uniformity. The high-shear or fluid bed granulators described earlier are used for the granulation step.

Types and Specifications of Tablet Presses

Rotary tablet presses are the mainstream for food and supplement manufacturing. Multiple punch-and-die sets (station count: 8–60+) arranged on a rotating turret continuously produce tablets, achieving production speeds of thousands to tens of thousands of tablets per minute. Typical tablet diameters range from 6–25 mm, and weights from 100–2,000 mg. Compression force is set within 5–100 kN — higher pressure yields harder tablets, but excessive pressure causes capping (delamination of the tablet top) and lamination (layered cracking).

Tablet Quality Evaluation Items

• Hardness: Mechanical strength of the tablet, measured with a hardness tester. For supplement tablets, 40–100 N (Newtons) is a typical standard. Sufficient hardness to prevent breakage during transport must be balanced with disintegration in the oral cavity.
• Friability: Mass loss percentage after rotating tablets in a drum. 1% or less is the passing criterion, improved through surface coating and optimization of tableting conditions.
• Disintegration: Disintegration time measured in water. For supplement tablets, disintegration within 30–60 minutes is a typical standard. Slow disintegration affects active ingredient absorption, so it is controlled by the amount of disintegrants (croscarmellose sodium, crospovidone, etc.).
• Weight Variation: Variation in individual tablet weights, with a standard of ±5% or less from the average weight (for tablets weighing 300 mg or more).

Capsule filling is the technology of filling capsule shells with powder, granular, or liquid contents to create finished products. Along with tableting, it is a major dosage form for supplements and health foods, offering excellent taste and odor masking, ingredient stability, and precise volume control.

Hard Capsules

Hard capsules consist of a two-piece body and cap and are primarily used for filling powders and granules. While gelatin (porcine or bovine derived) has traditionally been the mainstream shell material, demand for HPMC (hydroxypropyl methylcellulose) plant-based capsules has surged in recent years. HPMC capsules enable vegetarian/vegan compatibility and Halal certification. Compared to gelatin capsules, their lower moisture content (4–6%) provides better stability for hygroscopic contents. Capsule sizes range from 000 (largest, approximately 1,600 mg fill capacity) to 5 (smallest, approximately 60 mg), with size 0 (approximately 500 mg) and size 1 (approximately 400 mg) being the most common for supplements.

Fully automatic capsule filling machines that handle capsule separation → filling → sealing offer excellent production efficiency, with speeds of 25,000–200,000 capsules per hour. Filling mechanisms include auger (screw) type, tamping pin type, and dosing disc type, selected based on powder flowability and filling precision requirements. A fill weight accuracy of ±3% is the standard control criterion.

Soft Capsules (Softgels)

Soft capsules enclose liquid or paste-form contents in a gelatin or starch-based shell. The main manufacturing method is the rotary die process (continuous forming, filling, and sealing using rotating dies), which offers high flexibility in capsule size and shape. They are ideal for encapsulating oil-soluble ingredients such as omega-3 fatty acids (DHA/EPA), vitamin E, coenzyme Q10, and garlic oil. Contents are typically oil-based suspensions or solutions, with fill volumes generally ranging from 100–1,200 mg.

Soft capsule shells are composed of three components: gelatin, plasticizer (glycerin), and water, with shell thickness of 0.5–1.0 mm. In recent years, starch-based and carrageenan-based plant-derived soft capsules have been developed, but manufacturing constraints are greater compared to gelatin, and the number of capable manufacturers is limited.

Quality Control for Capsule Filling

• Fill Weight Uniformity: The content weight of individual capsules is measured with a precision balance, and deviation from the mean is controlled. The standard is ±5% (quality specifications of Japan's Health and Nutritional Food Association).
• Disintegration Testing: Hard capsules should disintegrate within 30 minutes in water at 37°C. Soft capsules should disintegrate within 60 minutes. Cross-linking reactions during storage may reduce the disintegration rate of gelatin capsules.
• Visual Inspection: Deformation, cracks, leaks, color unevenness, and foreign matter contamination are checked by visual or camera inspection. Fully automatic sorting machines for weight-based sorting are also used.
• Seal Strength (hard capsules): Strength of band seals or locking mechanisms is verified to prevent capsule separation during transport and storage.

Throughout the entire powder processing workflow, a system for quantitatively evaluating and managing powder characteristics and product quality is essential. Below are the major quality control items, measurement methods, and control criteria.

Particle Size Distribution Measurement and Management

Particle size distribution is the most fundamental quality indicator, affecting solubility, flowability, appearance, and mouthfeel of powdered products. The most widely used measurement method is laser diffraction/scattering, capable of high-precision measurement in the range of 0.1–3,000 μm. Representative indicators include D10 (10th percentile diameter), D50 (median diameter), and D90 (90th percentile diameter), with the span value ((D90−D10)/D50) used to evaluate distribution breadth. A smaller span value indicates a more uniform particle size distribution, contributing to product quality consistency. Sieve analysis using JIS-standard sieves is also widely adopted in quality control for simple management of larger particles.

Moisture Content Management

Moisture content affects shelf stability, flowability, and suitability for tableting and filling. Measurements are performed using halogen moisture analyzers (rapid measurement: 3–10 minutes) or Karl Fischer titration (high-precision measurement). Typical control standards are 3–6% for powdered seasonings and 2–5% for supplement raw materials. Moisture control is particularly critical for granulated products — high moisture content causes sticking (adhesion to punches) during tableting, while excessively low moisture causes capping (layered delamination).

Flowability Evaluation

Powder flowability significantly affects the quality of tableting and capsule filling. Poor flowability leads to fill weight variability and product defects, so verify that the OEM manufacturer conducts appropriate flowability testing.

Dissolution Testing (for Supplements)

For supplement tablets and capsules, the quality essence is that active ingredients dissolve and are absorbed appropriately in the body. Dissolution testing per the Japanese Pharmacopoeia (paddle method, rotating basket method) evaluates the dissolution rate and pattern in specified media. The general standard is that 75% or more of the active ingredient dissolves within 45–60 minutes in dissolution test fluid at 37°C. While disintegration alone is sometimes used for control, dissolution testing is considered desirable for Foods with Function Claims (a Japanese regulatory category).

Microbiological Control

Powder processing operations carry a risk of microbial growth due to dust dispersion and adhesion to equipment surfaces. The granulation step is particularly high-risk because water is added, meaning wet granules before drying are in a state conducive to microbial growth. Standard shipping criteria include a total viable count of 3,000 CFU/g or less and coliform-negative. Regular CIP (Clean-in-Place) and SIP (Steam-in-Place) of equipment, along with environmental monitoring (airborne bacteria, settling bacteria measurements) for manufacturing environment control, are essential.

When outsourcing powder processing to an OEM manufacturer, the required equipment and quality control systems vary significantly depending on the product dosage form (powder, granule, tablet, capsule). Especially for supplement and health food manufacturing, compliance with GMP (Good Manufacturing Practice) has become a de facto requirement, so careful evaluation is needed when selecting a manufacturer.

Confirming GMP Requirements

Under Japanese law, GMP certification is not legally mandatory for manufacturing supplements (health foods). However, it is strongly recommended to select a manufacturer that holds GMP certification from the Japan Health and Nutrition Food Association or GMP certification from the Japan Institute for Health Food Standards (JIHFS). For Foods with Function Claims (a Japanese regulatory framework), manufacturing at a GMP-certified facility is effectively a requirement. GMP-certified facilities systematically implement raw material receiving tests, manufacturing process control records, product release testing, equipment qualification (IQ/OQ/PQ), change control, and deviation management.

Cost Estimates by Dosage Form

• Powder/Granule Manufacturing (milling + mixing + granulation + filling/packaging): Processing fee ¥200–800/kg (approx. $1.40–$5.50 USD/kg). Minimum lot: approximately 50–100 kg of raw material. For stick pack filling, the filling processing fee is ¥3–8/stick (approx. $0.02–$0.06 USD).
• Tablet Manufacturing (granulation + tableting + inspection + bottle filling): Processing fee ¥1–5/tablet (approx. $0.007–$0.035 USD). Minimum lot: 100,000–300,000 tablets (30–100 kg raw material). Initial tooling costs of ¥50,000–200,000 (approx. $350–$1,400 USD) apply for punch-and-die sets. Custom shapes (irregular tablets, embossed) increase tooling costs.
• Hard Capsule Manufacturing (mixing + filling + inspection + bottle filling): Processing fee ¥2–6/capsule (approx. $0.014–$0.04 USD). Minimum lot: 50,000–100,000 capsules. Unit costs differ by shell material (gelatin vs. HPMC) and size, with HPMC capsules costing 1.5–2x more than gelatin.
• Soft Capsule Manufacturing (formulation + capsule forming + filling + drying + inspection): Processing fee ¥5–15/capsule (approx. $0.035–$0.10 USD). Minimum lot: 100,000–500,000 capsules. Soft capsule equipment is large-scale and specialized, limiting the number of capable OEM manufacturers.

Initial Costs

• Formulation design and prototyping: ¥100,000–300,000 (approx. $700–$2,100 USD) (includes 3–5 prototype rounds)
• Stability testing (accelerated: 40°C/75% RH, 6 months): ¥100,000–200,000 (approx. $700–$1,400 USD)
• Nutritional analysis and microbiological testing: ¥50,000–100,000 (approx. $350–$700 USD) per product
• Tableting tooling (punch/die): ¥50,000–200,000 (approx. $350–$1,400 USD) (not needed if existing tooling is available)
• Package design and printing plates: ¥50,000–150,000 (approx. $350–$1,050 USD)

Lead Time Guidelines

From formulation design to shipment of the first production batch, 3–6 months is typical. This breaks down as: formulation design and prototyping (1–2 months), initiation of stability testing (1 month), packaging material procurement (1–2 months), and production (2–4 weeks). If filing for Foods with Function Claims (a Japanese regulatory pathway), an additional review period (60 business days) is required. Lead time is reduced for contract manufacturing of existing formulations.

Powder processing encompasses a combination of technologies spanning milling, granulation, tableting, and capsule filling. Since the required equipment and quality control systems vary significantly by product dosage form (powder, granule, tablet, capsule), the key to success is selecting an OEM manufacturer with the right technology and track record for your product concept.

This technology is ideal when you want to:

• Sell supplements (tablets, capsules, granules) under your own brand
• Commercialize health foods in powder stick or individual sachets
• Improve solubility or bioavailability through raw material milling and micronization
• Commission manufacturing of Foods with Function Claims at a GMP-certified facility in Japan

Key questions to ask OEM manufacturers:

• Do they have sufficient manufacturing experience with your desired dosage form (tablets, capsules, granules, powder)?
• Do they hold GMP certification (Japan Health and Nutrition Food Association or JIHFS)?
• Can they handle the entire process from formulation design and prototyping through to mass production?
• Do they have adequate quality evaluation systems, including flowability testing and stability testing?
• What are the minimum lot sizes and initial costs (tooling, prototyping)?

Our platform makes it easy to search and compare OEM manufacturers in Japan that offer powder processing services. Start by checking the detail pages of manufacturers that interest you and reach out for a free consultation.