A batch of capsules can look perfect when it enters the warehouse and still cause trouble a few weeks later. On the capsule filling line, shells may crack during separation. Another batch may feel soft, deform in the hopper, hoặc dính vào nhau. Production may blame the viên nang phụ, QA may suspect the shell supplier, and procurement may wonder whether the packaging material is inadequate.
Very often, the real issue is moisture balance.
Hard capsule shells exchange water with the surrounding air, các điền vào công thức, and the headspace inside their package. For gelatin shells in particular, losing too much moisture reduces flexibility and increases capsule brittleness; gaining too much moisture can cause softening, swelling, Và sticky capsules. HPMC and pullulan behave differently, but they are not completely independent of humidity either. USP recognizes gelatin, hypromellose, and pullulan hard shells as water-containing polymer systems, while USP guidance separately treats water content, hoạt động của nước, and packaging moisture transmission as important pharmaceutical quality khái niệm.
This article focuses on hard two-piece capsules that become soft, not the separate dosage form commonly called a viên nang mềm.
Khi capsules become brittle, start by looking for moisture loss. Hard gelatin capsules commonly contain about 13–16% water under suitable conditions. Research indicates that when their water content falls below the normal operating range—because of low relative humidity, very dry or hygroscopic fills, or moisture migration—the shell progressively loses flexibility and can fracture more easily. Ngược lại, excessive water uptake can plasticize gelatin, making shells softer and potentially sticky.
For production and QA teams, four points matter most:
Below is a quick summary of common environmental factors and their effects on capsules:
| Condition | Capsule Shell Effect | Fill/Powder Effect | Preventive Action |
| Too Dry (Low RH) | Capsules lose water and become giòn; may crack or shatter | Fine powders may adhere to shell due to static; hygroscopic fill can draw moisture from shell | Raise humidity (use humidifiers); seal supply rooms; use less-absorbent capsule (HPMC) |
| Too Humid (High RH) | Capsules absorb moisture, soften or swell; may become flaccid or sticky | Powders clump; oils may swell capsules | Use dehumidifiers; employ high-barrier packaging; add desiccants |
| Moisture Migration | Water moves between shell and content until equilibrium; Có thể khô đi shell or ướt it depending on fill | Active ingredients can degrade or clump | Match shell and fill moisture; equilibrate capsules in controlled RH before filling |
| Packaging Issues | Leaks or poor seals let humidity in/out, causing unpredictable shell moisture | Contamination or moisture ingress from environment | Use hermetic packaging (Mụn nước Alu-Alu, túi giấy bạc); ensure proper seals; include desiccants |
| Temperature Extremes | High heat softens gelatin (∼30–32 °C melting point), promotes cross-linking; very low temp can condense moisture | Heat can accelerate degradation of fill; freezing can damage some APIs | Store in recommended 15–25 °C (Gelatin); avoid hot spots and sunlight |
The practical goal is therefore not “keep capsules dry.” It is to maintain the validated balance between capsule moisture content, độ ẩm tương đối, hoạt động của nước, xây dựng, Bao bì, và điều kiện bảo quản.
A hard capsule shell is not an inert plastic container. Gelatin, HPMC, and pullulan are hydrophilic polymer systems, and water interacts with their structure. USP monographs for all three hard-shell types explicitly include water as part of the shell composition.
For gelatin, water also contributes to flexibility. Under commonly cited conditions of roughly 15–25°C and 30–65% RH, hard gelatin shells typically contain about 13–16% water. Research reviewing capsule performance reports that falling below this normal range causes gradual loss of flexibility, while excess water makes the shell softer and stickier.
That is why capsule humidity cannot be judged from room RH alone. The system is continuously moving toward an equilibrium involving the surrounding air, vỏ viên nang, xây dựng, and package headspace.
USP also distinguishes Hàm lượng nước từ hoạt động của nước (aw). Total moisture tells you how much water is present, while water activity helps describe how much of that water is available to participate in physical, hóa chất, or microbiological processes. For a hygroscopic powder inside a capsule, this distinction is useful because two materials with similar total moisture may still have different tendencies to exchange water.
A simplified moisture-migration model looks like this:
The key point is that water can move in both directions. A package may slow moisture from entering from outside, while water is still redistributing between the shell and the fill inside the sealed package. Studies of viên nang gelatin cứng have demonstrated exactly this shell-to-fill moisture transfer.
The most common mechanism is excessive moisture loss from the shell.
Thấp độ ẩm tương đối creates a moisture gradient between the shell and its surroundings. As gelatin loses water, it becomes less flexible and less able to absorb mechanical stress. Classic research found a strong relationship between gelatin capsule brittleness and RH, while later studies have repeatedly confirmed that mechanical behavior changes as shell moisture decreases.
Trong thực tế, brittle shells may show up as:
The important diagnostic question is where the capsule breaks. If empty capsules crack before powder enters the body, investigate shell condition, kho, capsule age, environmental RH, tooling contact, and vacuum first. If cracking occurs mainly during closing, overfill, closing depth, căn chỉnh, and excessive mechanical force become more likely contributors. Jinlu’s capsule filling defect analysis makes the same distinction between shell weakness and equipment/process causes.
Usually the moisture gradient is moving in the opposite direction.
At high humidity, gelatin absorbs water. Water plasticizes the polymer, reducing hardness and stiffness. MỘT 2025 controlled study exposing gelatin and HPMC shells to 25°C/75% RH found substantial moisture-related softening in gelatin and a marked decline in its mechanical strength; HPMC retained mechanical integrity better under the same test.
On a production floor, excessive moisture can appear as soft bodies, dimensional changes, poor cap/body movement, capsules sticking to one another, feeding instability, or deformation. Earlier mechanical studies also found capsule softening became especially noticeable as RH moved above roughly 60%, although the exact response depends on shell formulation.
Temperature matters because it changes both material behavior and moisture-transfer dynamics. Sudden movement between cool and warm environments can also create local condensation risk. Vì lý do này, avoid treating RH and temperature as unrelated controls; the product experiences both simultaneously.
Yes—and this is one of the most frequently overlooked causes of gelatin capsule brittleness.
Suppose your warehouse is controlled correctly, your unopened capsules passed incoming inspection, and the empty shells run well on the machine. After filling and several weeks of storage, Tuy nhiên, the finished capsules crack easily.
The fill may be pulling water from the shell.
A well-known Journal of Pharmaceutical Sciences study investigated a highly hygroscopic drug substance filled into hard gelatin capsules. Moisture transferred from the shell into the powder, lowering shell water content enough to create a brittleness problem. The researchers used moisture sorption/desorption relationships to predict equilibrium and redesign the moisture balance.
This is why formulation teams should evaluate more than the powder’s initial loss on drying.
MỘT bột hút ẩm has an affinity for atmospheric water. If its water activity and equilibrium moisture characteristics differ strongly from those of the capsule shell, moisture migration can continue even after the capsule is sealed. USP’s water-activity framework is useful here because aw addresses the thermodynamic availability of water rather than simply measuring total water percentage.
Về mặt thực tế, QA and formulation teams should ask:
Is the fill very dry? Is it strongly hygroscopic? What is its sorption isotherm? What is its water activity? What happens after the shell and formulation reach equilibrium?
Do not assume that specifying shell moisture and powder moisture independently is enough. Finished-product stability depends on the combined system.
For empty hard gelatin capsules, pharmaceutical literature commonly cites approximately 15–25°C and 30–65% RH as a suitable working/storage window associated with the normal 13–16% shell-water range. Some commercial and industry guidance uses a slightly narrower humidity band such as 35–65% RH. These values should be treated as general technical guidance—not as a universal specification. Your capsule supplier’s approved storage instructions and certificate/specification should take priority.
Vì gelatin capsule storage, avoid prolonged exposure to very dry air, độ ẩm cao, excessive heat, direct sunlight, and repeated package opening. Keep empty capsules in their original protective packaging until they are needed, and allow sealed containers to equilibrate to the processing room before opening when there has been a significant temperature difference. These practices follow the broader USP principle that pharmaceutical storage should protect materials from moisture and excessive environmental exposure and maintain labeled storage conditions.
Đối với filled drug product, do not simply copy the empty-shell storage range onto your product label. Shelf-life conditions must be supported by stability data generated with the formulation in its intended container-closure system. Tôi Q1A(R2), as adopted by FDA, establishes stability-testing frameworks that include controlled temperature/RH conditions; those are stability-study conditions, not automatically the operating specification for every empty-capsule room.
Gelatin vs. HPMC vs. Pullulan
The comparison below summarizes peer-reviewed moisture-sorption research, USP shell definitions, ACG/Qualicaps technical specifications, and recent humidity studies. HPMC generally has lower initial moisture and greater low-RH mechanical resilience; pullulan absorbs less moisture than gelatin but still changes mechanically with moisture variation.
| Capsule shell | Typical moisture behavior | Low-humidity brittleness risk | High-humidity behavior | Practical fit |
| Gelatin | Common shell moisture around 13–16% | Highest sensitivity of the three | Can soften, swell and become sticky | Conventional pharmaceuticals and supplements where humidity is well controlled |
| HPMC | Lower shell moisture, commonly about 3–8% depending on product | Generally much more resistant | Still exchanges moisture, but often retains mechanical integrity better than gelatin | Hygroscopic or moisture-sensitive fills; plant-based products |
| Pullulan | Lower moisture sorption than gelatin; moisture retention differs from HPMC | Can still become brittle if sufficiently dried | Moisture variation can alter mechanical properties | Plant-based products, especially where other barrier properties are also important |
For a deeper material comparison, see Jinlu’s Gelatin Capsule vs HPMC Capsule guide, Pullulan Capsule guide, Và Hướng dẫn sử dụng viên nang rỗng. Jinlu’s existing content also helps avoid overloading this article with capsule-material topics that deserve their own search intent.
Tốt bao bì viên nang does not “freeze” the capsule’s moisture content. Its job is to control the rate at which the outside environment changes the internal system.
USP <671> evaluates container performance using moisture-vapor transmission, and pharmaceutical packaging research shows why that matters: different package structures can produce very different rates of moisture ingress and therefore different product stability.
| Packaging option | Relative moisture protection | Practical guidance |
| PVC blister | Low to moderate | Economical for formulations whose stability data shows that this barrier is sufficient |
| PVC/PVDC blister | Higher than plain PVC | Useful when more moisture protection is required without moving directly to cold-form aluminum |
| Cold-form Alu-Alu blister | Rất cao | Strong candidate for highly moisture-sensitive products or demanding distribution environments |
| HDPE bottle + effective closure/induction seal | Potentially high at system level | Performance depends on bottle, liner, đóng cửa, khoảng trống trên đầu, seal integrity and opening pattern |
| Cái chai + chất hút ẩm | Active humidity control | Desiccant type and quantity should be selected from stability/moisture-equilibrium data, not by assuming “more is better” |
In one published accelerated study of a moisture-sensitive oral product, plain PVC blister packaging performed substantially worse than higher-barrier blister structures, while cold-form aluminum and an induction-sealed HDPE bottle provided markedly stronger protection. The exact numbers are product- and geometry-specific, so the lesson is not to copy another product’s package—it is to validate the barrier against your own formulation.
The same principle applies to chất hút ẩm. Desiccants lower package-headspace humidity and can be extremely useful for moisture-sensitive fills. But because gelatin shell flexibility itself depends on water, aggressively drying the headspace can theoretically shift equilibrium water away from the shell. This is an engineering inference from established shell/fill moisture-transfer and desiccant-equilibrium models: the correct objective is a validated moisture balance, not the lowest achievable RH.
For more packaging detail, Jinlu already has a dedicated Hướng dẫn đầy đủ về các lựa chọn đóng gói viên nang, so this article should remain focused on moisture failure rather than repeat a full blister-material guide.
Các filling machine of capsule is often where an upstream moisture problem becomes visible.
A brittle shell may survive storage and feeding but fracture when the capsule body is pulled from the cap, when the body enters the segment, or when closing force is applied. A softened shell can create the opposite problem: dimensional changes and higher surface tack may interfere with smooth feeding, định hướng, cap/body separation, and locking. Dry conditions can also increase static-related handling problems, while moist or cohesive powder can create its own feeding and dosing difficulties.
This is why production teams should resist the instinct to compensate immediately with more vacuum, more closing pressure, or slower speed. First inspect unused capsules from the same lot. Compare their physical condition with capsules that have spent time in the filling room. Review warehouse and room RH records, open-bag time, formulation moisture behavior, and shell moisture if your QC program measures it. Then inspect vacuum, căn chỉnh dụng cụ, điền vào khối lượng, cài đặt liều lượng, and closing depth.
Ví dụ, if empty capsules already crack during gentle manual handling, increasing machine vacuum will not correct the underlying problem. If capsules are sound before filling but split only after an overfilled body reaches the closing station, the machine or dosing process deserves more attention.
của Jinlu Khuyết tật làm đầy viên nang: Các vấn đề thường gặp, Nguyên nhân & Hướng dẫn khắc phục sự cố covers the mechanical side—including separation failure, sự vỡ vụn, đổ đầy, trống, căn chỉnh, and closing settings—in greater detail.
When capsules suddenly become brittle, mềm mại, hoặc dính, use the same sequence every time:
Capsule humidity troubleshooting table
| triệu chứng | Likely cause | What to verify first | Quick corrective direction |
| Shell cracks easily | Moisture loss / low RH | Room RH, shell moisture, open exposure | Restore controlled conditions; segregate suspect shells |
| Capsules break during separation | Brittle shell or excessive vacuum/mechanical stress | Unfilled shell condition + vacuum/tooling | Fix environmental issue before increasing vacuum |
| Capsules become soft | Excess moisture uptake | RH, storage history, package barrier | Reduce exposure and review barrier protection |
| Capsules stick together | High moisture, nhiệt, sự biến dạng | RH, nhiệt độ, package seal | Môi trường kiểm soát; evaluate affected lot |
| Capsules are normal empty but brittle after filling | Hygroscopic/very dry fill | Fill aw, sorption data, shell-to-fill moisture transfer | Reassess formulation-shell compatibility |
| Powder becomes sticky or flow worsens | Powder moisture uptake | Powder aw, RH, Bao bì | Control exposure and evaluate formulation/package |
| Problems appear only after months in the pack | Package equilibrium or moisture ingress | Stability data, MVTR, đóng cửa, chất hút ẩm | Reassess final container-closure system |
These symptom-to-cause relationships are supported by gelatin moisture-transfer studies, recent capsule humidity research, USP packaging principles, and filling-machine troubleshooting evidence.
For routine prevention, keep empty capsules sealed until use; monitor the actual production environment; minimize unnecessary open exposure; characterize hygroscopic formulations rather than judging them by appearance; select the shell material around the formulation; choose packaging from moisture-barrier and stability data; size desiccant scientifically; and confirm the finished product in the final market package through an appropriate stability program.
Tóm lại, capsule brittleness or stickiness is almost always a moisture issue. By controlling humidity, choosing the right capsule material, and using appropriate packaging, manufacturers can maintain capsule quality and avoid production headaches. Ví dụ, Jinlu Packing’s solutions include precise environmental controls and high-barrier packaging machinery to keep capsules in spec.
Maintaining 40–60% RH, storing at 15–25 °C (Gelatin), using foil blisters or desiccated bottles, and selecting moisture-stable capsule types are key to preventing brittleness or stickiness. When issues arise, refer to the troubleshooting checklist and flowchart above: identify if the problem is due to low or high moisture, then correct the environment or equipment accordingly. With best practices in place, capsules will fill and ship successfully, maintaining product efficacy and customer trust.
Sẵn sàng tối ưu hóa việc sản xuất viên nang của bạn? Jinlu Packing offers advanced encapsulation and packaging equipment engineered for moisture-sensitive pharmaceuticals. Contact our specialists for guidance on humidity control, giải pháp đóng gói, and high-speed filling lines that keep capsules perfectly stable from warehouse to patient.
Viên nang (especially gelatin) dry out when ambient RH is low. Gelatin shells normally have ~13–16% water; if RH drops (ví dụ. heated warehouse), the shells lose moisture and become brittle. Để ngăn chặn điều này, store them at ~40–50% RH and 15–25 °C. Using high-barrier bags or blisters also maintains their moisture.
When RH is high, capsules absorb moisture and soften. At elevated humidity or temperature, gelatin becomes gelatinous and can stick together. This is why blister packs or desiccants are used: they keep moisture out. If you see sticky capsules, check that the packaging was sealed and lower storage RH.
Đúng. A very dry powder inside can pull moisture from a moist gelatin shell, making it brittle. Tương tự như vậy, a very wet or oily fill may add moisture to a drier shell. Use capsules rated for your fill type (ví dụ. HPMC for hygroscopic powders) and equilibrate shell and fill humidity to minimize migration.
Monitor your production area’s RH. If it’s outside the recommended 35–65% range, humidity is likely the culprit. Also check the empty capsule moisture content if possible. Frequent failures at certain seasons (winter vs. summer) often indicate environmental RH issues.
HPMC capsules offer the best moisture resistance; they have very low base moisture and much lower moisture permeability. Pullulan is better than gelatin but not as good as HPMC. Gelatin is least moisture-resistant.
Desiccants can help in bottles or pouches, but use them judiciously. If you over-dry capsules with too much desiccant, they may become brittle. Tiêu biểu, one silica pack per bottle (sized appropriately) is sufficient. Test batches with and without desiccant to find the right balance.
Blister packaging seals each capsule in its own cavity, providing excellent moisture and light barrier (especially Alu-Alu foil). Studies (and Jinlu’s packaging guide) show blisters give “superior protection against moisture and light” compared to bulk bottles. Bottles are more economical for large volumes but rely on cap seals and desiccant.
KHÔNG. Moisture content measures the quantity of water present. Water activity describes the thermodynamic availability of water and is particularly useful when evaluating moisture transfer, chemical stability, and formulation behavior.
Thường, Đúng. Commercial HPMC shells generally contain much less water than gelatin and retain mechanical properties better at low RH. Qualicaps specifically positions HPMC capsules for hygroscopic formulations, and comparative research reports weaker moisture sorption for HPMC than gelatin or pullulan. Final selection still requires formulation compatibility and stability testing.
There is no universal winner. High-barrier blisters such as cold-form aluminum provide very strong protection, while a properly engineered HDPE bottle, induction seal, and desiccant system can also perform well. Choose according to the formulation’s moisture sensitivity, target markets, use pattern, MVTR, con dấu toàn vẹn, and stability results.
Tài liệu tham khảo：
1.A study on gelatin capsule brittleness: moisture tranfer between the capsule shell and its content —— PubMed
2.Gelatin capsule brittleness as a function of relative humidity at room temperature —— Khoa họcTrực tiếp
3.Tính chất hấp phụ và giải hấp ẩm của gelatin, Viên nang cứng HPMC và pullulan —— PubMed
4.Water Activity —— USP <922>
5.Đánh giá so sánh vỏ viên nang hít phải Gelatin và HPMC tiếp xúc với điều kiện độ ẩm mô phỏng —— PubMed
6.Package selection for moisture protection for solid, oral drug products —— Thư viện trực tuyến WILEY
Petty fu, Người sáng lập Jinlupacking, mang lại 20 năm kinh nghiệm trong lĩnh vực máy móc dược phẩm. Dưới sự lãnh đạo của ông, Jinlu đã phát triển thành một nhà cung cấp thiết kế tích hợp đáng tin cậy, sản xuất, và bán hàng. Petty đam mê chia sẻ kiến thức chuyên sâu về ngành của mình để giúp khách hàng giải quyết sự phức tạp của bao bì dược phẩm, đảm bảo họ không chỉ nhận được thiết bị, mà là mối quan hệ đối tác dịch vụ một cửa thực sự phù hợp với mục tiêu sản xuất của họ.
