Analyzing dietary fiber content plays a crucial role in evaluating the quality of raw materials and finished animal feed products. However, many testers currently face major nightmares in the lab. These include persistent filter membrane clogging, sample loss during cup transfer, and inaccurate results due to incomplete removal of starch and fat. These technical barriers directly reduce productivity and affect the results of laboratory competency assessments according to ISO 17025 standards.
This article will provide you with a comprehensive scientific overview of NDF, ADF, and ADL fiber parameters, and offer a breakthrough solution with modern filter bag technology to help laboratories optimize their testing processes to meet international standards.

1. The Scientific Nature of NDF, ADF, and ADL

1.1 Chemical Definition of NDF, ADF, and ADL Fibers

To establish an accurate analysis, we first need to understand the structure of each fiber fraction. Plant cell walls are divided into components with different solubilities and nutritional values:
NDF (Neutral Detergent Fiber): This is the fiber portion that does not dissolve in a neutral detergent environment. This fraction represents the entire cell wall in an acidic detergent environment. This fraction consists of only two more difficult-to-digest components: cellulose and lignin. This residue, remaining after treating ADF with 72% (12 M) sulfuric acid, represents the most difficult-to-decompose pure organic lignin in the structural plant cell wall, as shown by the following mathematical relationship:
Hemicellulose = NDF – ADF
Cellulose = ADF – ADF
For ruminants, the NDF index is inversely correlated with feed intake (due to the feeling of fullness), while ADF is inversely proportional to the actual digestibility of the diet. Therefore, accurate quantification of each component is essential for creating the most economically efficient feed formulation.

1.2 The Breakthrough of the Van Soest System Compared to Traditional Crude Fiber

For decades, the classical standard TCVN 4329:2007 (ISO 6865:2000) for crude fiber analysis of CF was the only reliable method. However, the CF method, using dilute acid (0.13 mol/L H2SO4) combined with dilute alkali (0.2 mol/L KOH), inadvertently dissolved approximately 80% of the hemicellulose and 50-90% of the lignin present in plant samples. This resulted in consistently lower fiber content compared to the actual macroscopic cell wall.
The introduction of the Van Soest fiber analysis system (including the combination of NDF, ADF, and ADL parameters) has revolutionized the animal feed nutrition testing industry. This method selectively separates fiber components using specialized detergents, preserving the integrity of insoluble plant polymer bonds. To keep up with this technological trend, leading laboratories are now proactively equipping their labs with top-of-the-line modern laboratory equipment, completely eliminating the systematic errors of the old manual method.

Comparison Criteria	Crude Fiber Method	Van Soest Method (NDF, ADF, ADL)
Sampling Separation Mechanism	Continuous boiling in dilute acid (H2SO4 0.13 mol/L) and dilute alkali (KOH 0.23 mol/L)	Mainly Cellulose, with significant loss of Hemicellulose and Lignin
Applications	Preliminary evaluation of animal feed	In-depth nutritional standardization for ruminants

2. Current International Standards and Administrative Regulations

National Standards TCVN and International Standards ISO AOAC

For test results to have global commercial legal validity, our laboratory is required to strictly adhere to current international standards. For acid fiber and lignin, the national standard TCVN 9589:2013 (completely equivalent to the international standard ISO 13906:2008) is the most standard technical guideline for determining the ADF and ADL content in animal feed. This standard specifies details from sample particle size, extraction solution concentration to weighing, drying, and ashing methods to minimize random errors.

Furthermore, for neutral fiber content, the AOAC 2002.04 method developed by expert Mert requires the use of heat-resistant amylase enzyme during the extraction process to determine the neutral fiber content after starch removal according to ISO and AOAC standards. This not only ensures absolute repeatability of the analytical results but is also a prerequisite for the laboratory to easily pass accreditation assessments according to ISO/IEC 17025 standards.

It is necessary to adhere to national standards TCVN and international standards such as ISO and AOAC to ensure that fiber analysis results meet standards

>> To receive more documents on international standards such as ISO 6865 & 92/89 EEC, ISO 16472 aNDF, AOAC 2002.04 aNDF, ISO 150 13906 ADF & ADL, please leave your information here, and the Duc Duong team will send the documents to you via email.

3. Technical procedures for chemical preparation and sample processing in standardized labs

3.1 Accurate preparation techniques for NDS and ADS extraction solutions

The key to a successful fiber extraction reaction lies in the homogeneity and stability of the detergent solutions. For neutral detergent solutions (NDS), we need to dissolve Sodium Lauryl Sulfate (SDS) sequentially. The tester must use a pH meter to rigorously check that the solution reaches the standard pH range of 6.9–7.16.9 – 7.16.9–7.1 at 25°C. For acidic detergent solutions (ADS), the preparation procedure requires precisely dissolving 20g of Cetyltrimethylammonium Bromide (CTAB) in 1 L of 0.5M sulfuric acid (H2SO4) solution. Note that a crucial technique is to gently heat the distilled water during the dissolution of CTAB to avoid clumping or crystal precipitation when stored in a low-temperature laboratory.

3.2 Impact of Heat-Stable Amylase Enzyme and Anhydrous Sodium Sulfite

When analyzing starch-rich samples such as cereals or mixed feeds, membrane clogging is the most common error. To completely overcome this, the use of heat-stable α-amylase is mandatory in the method of breaking α-1,4-glucosidic bonds, hydrolyzing starch into short-chain dextrins that are completely soluble in water, preventing the anhydrous effect (Na2SO3) which plays a key role in breaking the protein bonds adhering to the fiber residue, preventing the increase in the illusory mass of neutral fiber as soon as the extraction solution begins to boil in the digestion chamber and in the fat removal pretreatment process for specific samples.

3.3 Fat Removal Pretreatment Process for Specific Samples

For samples with high fat content such as soybeans (>5% fat) or concentrated feed (>10% fat). The mandatory solution here is to pre-treat the sample by soaking it in an organic solvent such as Petroleum Ether or fire safety measures: Absolutely do not place the filter bag containing the sample that has just been soaked in Acetone directly into a drying oven at 105°C. The flammable solvent vapors accumulating in the sealed drying oven, when exposed to a high heat source, will directly lead to an extremely dangerous fire and explosion risk for the testing personnel.

4. Filter Bag Technology Solution for Effective Clogging Prevention

4.1 Superior Advantages of Multidimensional Filter Membranes Compared to Gooch Filter Cups

The traditional Gooch filter cup method uses a porous glass disc as a filter membrane support. Under unidirectional vacuum suction, fine plant debris particles are easily compressed and clog the tiny pores. This process not only prolongs the filtration time to hours but also easily causes the glass disc to crack due to the excessively large pressure difference. Conversely, modern filter bag technology uses a multidimensional filter membrane woven from special synthetic polymer fibers with a standard pore size of 25 μm. This structure allows the extraction solution and wash water to continuously permeate from all directions while retaining even the smallest fiber particles intact.
To achieve this optimal performance, we recommend using the Sonnen FB25 fiber extraction bag in conjunction with Duc Duong’s Sonnen FB25 fiber extraction bag solution. This solution ensures absolute preservation of sample volume, completely eliminates manual sample transfer between drying and incineration stages, thereby minimizing errors caused by manual handling by the inspector.

Use Sonnen FB25 fiber extraction bags to ensure accurate NDF, ADF, and ADL analysis

4.2 Method for Calculating the White Filter Bag Correction Factor to Compensate for Errors

During fiber analysis using filter bags, a very small amount of polymer constituting the filter bag fibers may dissolve or lose mass due to the effects of concentrated acid/alkali solutions and a drying temperature of 105°C. To completely eliminate this systematic error, the white filter bag correction factor C1 is determined, or the system C1 = Mass of the bag after chemical treatment and drying / Initial empty bag mass.

To do this, the laboratory needs to run at least one empty bag containing no sample in parallel in each fiber extraction batch under the same temperature and pressure conditions. The final dried mass of the white bag will be multiplied by the mass of the initial sample bag to compensate for the actual mechanical loss, providing the highest accuracy and repeatability for the experiment.

5. Sonnen F20 Semi-Automatic Fiber Extraction Machine – A Solution to Enhance Lab Efficiency

5.1 Solving the Sample Overload Problem with a Capacity of 30 Samples per Batch

If your laboratory is facing an increasing frequency of receiving samples for dietary fiber analysis, using manual single-sample extraction equipment will inevitably lead to serious data bottlenecks. The Sonnen F20 semi-automatic fiber extraction machine with filter bag method is the perfect answer to this productivity problem. The device boasts a wide temperature control range from room temperature to 105°C with an optimized digestion chamber capacity, shortening the total standard extraction time, and is extremely durable, incorporating Teflon tubing that withstands chemical corrosion from concentrated acids/alkalis, combined with an intelligent semi-automatic exhaust valve system to provide maximum protection for the analyzer from steam hazards.
Sino-Sonnen Fiber Analyzer > To upgrade your testing capabilities to meet ISO 17025 standards, you can refer to our catalog of high-quality equipment at the top list of modern laboratory equipment essential for labs, distributed officially by Duc Duong in Vietnam.

> If your lab is experiencing technical issues regarding result repeatability or needs advice on the optimal configuration of NDF ADF ADL fiber analysis equipment, please connect with our application engineering team immediately via the Duc Duong Testing Solutions Consultation Registration page to receive timely support and cost-effective solutions.

6. The ROI Economic Analysis and Technical Support Services from Duc Duong

6.1 Optimizing Operating Chemical and Labor Costs

Investing in a Sonnen F20 semi-automatic filter bag fiber filling system is not simply purchasing a piece of ordinary lab equipment, but a strategic step to help businesses optimize long-term operating costs. Thanks to multidimensional membrane filter bag technology, the amount of cleaning solution consumed per sample is reduced by up to 60% compared to the environment, significantly saving hazardous waste treatment costs for the factory.

Furthermore, it frees up the manual labor of the testing staff from 1-2 days of manual operation to less than 1 day, freeing up time to focus on other complex, highly specialized tests, improving the overall productivity of the testing center.

6.2 Technical Support Services from Duc Duong Co., Ltd

When choosing fiber analysis solutions from Duc Duong, customers can rest assured about the stability of the equipment. Duc Duong Co., Ltd is committed to providing a comprehensive turnkey solution: from installation services, instruction on operating methods according to international standards (IQ/OQ/PQ) to providing a full range of consumables such as Sonnen FB25 filter bags or specialized bag sealing equipment.
Our team of experienced application engineers is always on standby and ready to respond to and resolve technical issues on-site nationwide. This in-depth technical support is a solid foundation that helps your laboratory maintain smooth operation, ensuring the reliability of analytical data and confidently passing all rigorous ISO 17025 audits.

Conclusion

Strict control of NDF, ADF, and ADL dietary fiber parameters using the Van Soest method is a mandatory requirement to enhance the nutritional value of animal feed products. Combining this with the Sonnen F20 semi-automatic fiber extraction system supplied by Duc Duong is a strategic step that helps laboratories achieve breakthroughs in productivity and completely eliminate clogging errors. Remember: “Investing in a modern fiber extraction solution is not simply buying a piece of laboratory equipment; it is an investment in the credibility of test data and the long-term competitiveness of your business.”
To receive an immediate special quote for the Sonnen F20 fiber extraction system and access to standard operating procedures for error-free filter clogging, please leave your information on the Duc Duong Technical Consulting Contact page or contact our leading lab experts directly via Hotline today!

 

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