GB/T 17811-2025 in English

Background and Significance of the Revision of GB/T 17811-2025

GB/T 17811-2025, "Determination of Pepsin Digestibility of Protein Feeds of Animal Origin - Filtration Method," is an important feed testing standard issued by the State Administration for Market Regulation and the Standardization Administration of China, replacing the 2008 version. The revision of this standard reflects the continuous progress of standardization work in my country's feed industry and provides a more scientific and accurate technical basis for the quality evaluation of animal protein feeds.

In-depth Analysis of Major Technical Changes

Compared with the 2008 version, the 2025 version of the standard has undergone significant upgrades and improvements in technical content:

Detailed explanation of the core content of the standard

Determination principle and methodology

This standard is based on the principle of biochemical digestion and uses Using a thermostatic shaker and a Büchner funnel, animal-derived protein feed is digested for 16 hours using a 20U/mL pepsin solution. The pepsin digestibility is calculated by measuring the undigested crude protein content in the digestion residue. The standard specifies the reagent specifications and instrument accuracy requirements: pepsin must be derived from porcine stomach, with a CAS number of 9001-75-6; the analytical balance must have an accuracy of 0.1mg; the thermostatic shaker must have a temperature control accuracy of ±1°C and a speed range of 15-300 rpm; and the electric forced air drying oven must have a temperature control accuracy of ±2°C.

Key Points for Optimizing and Implementing Operational Procedures

Sample Pretreatment Specifications

Sample preparation was performed in accordance with GB/T20195, requiring all solid samples to pass through a 0.84mm pore size test sieve, be thoroughly mixed, and then stored in a sealed container. Petroleum ether (boiling range 30-60°C) was used for degreasing. After degreasing, the sample was air-dried at room temperature to ensure accuracy in the subsequent digestion reaction.

Digestion Reaction Conditions

The digestion process was performed in a 250mL stoppered ground-mouth bottle. 150mL of pepsin solution, preheated to 45°C, was added and the sample was shaken at 45±1°C for 16 hours. After the reaction, the sample was tilted and allowed to stand for at least 15 minutes to allow the residue to fully settle.

Residue Handling and Measurement

The sample was filtered using a Buchner funnel lined with fast filter paper and washed with anhydrous ethanol to ensure complete removal of the residue. After drying the residue at 105°C, the undigested crude protein content was determined according to the Kjeldahl method in GB/T 6432.

Calculation Formula and Data Processing

The new standard improves the calculation formula system and adds a specific formula for calculating undigested crude protein content:

w₁ = [(V-V₀)×c×6.25×14] / (m₁×1000) ×100

The formula for calculating pepsin digestibility is: X₁ = (w₂ - w₁) / w₂ ×100

Where w₂ is the mass fraction of crude protein in the defatted sample, and w₁ is the mass fraction of undigested crude protein. The results are expressed as the arithmetic mean of replicate measurements, rounded to three significant figures.

Appendix A: Pepsin Activity Assay Specification

This newly added normative appendix provides a detailed method for the determination of pepsin activity, including reagent preparation, enzyme solution preparation, reaction conditions, and calculation requirements. Absorbance is measured by UV spectrophotometry at a wavelength of 275 nm to ensure the accuracy and comparability of enzyme activity.

Implementation Recommendations and Precautions

Laboratory Condition Requirements

Implementation of this standard requires a laboratory environment that meets the requirements, including temperature and humidity control, ventilation facilities, and an instrument calibration system. All instruments and equipment must be regularly calibrated and maintained to ensure the accuracy of measurement results.

Personnel Training Requirements

Operators should receive professional training and be familiar with the standard operating procedures, instrument usage, and safety precautions. In particular, the preparation of pepsin solution and enzyme activity determination must strictly follow the requirements of Appendix A.

Quality Control Measures

Laboratories are advised to establish a comprehensive quality control system, including blank testing, replicate analysis, and verification of reference materials. Regularly participate in proficiency testing activities to ensure the reliability and comparability of test results.

Application Value of the Standard and Industry Impact

The implementation of GB/T 17811-2025 will have a profound impact on the feed industry: providing a unified method for evaluating the quality of animal protein feeds, promoting the improvement of feed product quality; providing a technical basis for feed production companies to optimize formula design; and providing a basis for law enforcement for regulatory authorities to regulate market order.

The technological advancement of this standard reflects the trend of international integration of my country's feed testing standards and provides important technical support for improving the quality and safety of my country's feed products.