GB/T 17811-2008 English PDF (GBT17811-2008)

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GB/T 17811-2008: Determination of pepsin digestibility in animal protein feeds -- Filtration method
GB/T 17811-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 65.120
B 46
Replace GB/T 17811-1999
Determination of pepsin digestibility in animal protein feeds
- Filtration method
ISSUED ON: APRIL 9, 2008
IMPLEMENTED ON: JULY 1, 2008
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Principles ... 5
4 Reagents and materials ... 5
5 Instruments and equipment ... 5
6 Sample preparation ... 6
7 Measurement steps ... 6
8 Presentation of analysis results ... 7
Determination of pepsin digestibility in animal protein feeds
- Filtration method
1 Scope
This standard specifies the method for the determination of pepsin digestibility of
animal protein feedstuffs.
This standard is applicable to the determination of pepsin digestibility of all animal
protein feeds, and its value has no direct relationship with in vivo digestibility.
2 Normative references
The provisions in the following documents become the provisions of this standard
through reference in this standard. For the dated references, the subsequent amendments
(excluding corrections) or revisions do not apply to this Part, however, parties who
reach an agreement based on this standard are encouraged to study if the latest versions
of these documents are applicable. For undated references, the latest edition of the
referenced document applies to this standard.
GB/T 6432 Determination of crude protein in feeds - Kjeldahl method
GB/T 6433 Determination of crude fat in feeds (GB/T 6433-2006, ISO 6492:1999,
IDT)
GB/T 6682 Water for analytical laboratory use - Specification and test methods
(GB/T 6682-1992, neq ISO 3696:1987)
GB/T 14699.1 Animal feeding stuffs - Sampling (GB/T 14699.1-2005, ISO
6497:2002, IDT)
GB/T 20195 Animal feeding stuffs - Preparation of test samples (GB/T 20195-2006,
ISO 6498:1998, IDT)
Veterinary Pharmacopoeia of the People’s Republic of China Part 1 of the 2005
Edition
5.3 Soxhlet extractor and degreasing equipment: According to the equipment
regulations in GB/T 6433.
5.4 Nitrogen determination instruments and equipment: According to the equipment
regulations in GB/T 6432.
5.5 Instruments and equipment commonly used in the laboratory.
6 Sample preparation
Sampling shall be carried out according to GB/T 14699.1, and samples shall be prepared
according to GB/T 20195. Crush the sample until it can pass through a 0.84 mm sieve
(20 mesh), mix well, then put it in a sealed container and store it for later use.
7 Measurement steps
7.1 Degreasing
Weigh 3 g~4 g of the sample and degrease it with ether (4.2) (if the fat content is less
than 1%, degreasing is not required; if the fat content is 1%~10%, degreasing is
recommended; if the fat content is more than 10%, it shall be degreased). The
degreasing method can refer to the crude fat extraction method in GB/T 6433. The
degreased sample needs to be air-dried at room temperature to remove ether.
7.2 Pepsin digestion
Weigh 1.000 g (the weight shall be accurate to ±0.010 g) of the degreased and air-dried
sample (7.1), put it into a 250 mL grinding mouth bottle with a cover, add 150 mL of
pepsin solution (4.1) that has been freshly prepared and preheated to 42 °C~45 °C, and
ensure that the sample is completely wetted by the pepsin solution; tightly cap the bottle,
clamp the bottle on a constant temperature shaker (5.1), and stir it at a constant speed
and 45°C for 16 hours to carry out heat preservation and enzymatic digestion.
7.3 Treatment of digestive residues
Remove the grinding mouth bottle from the agitator, place it at an angle of 45°, let the
residue settle for more than 15 minutes, and then do suction filtration on a Buchner
funnel covered with fast filter paper; firstly, wash the residue on the bottle cap to the
filter paper with a small amount of water, then move the grinding mouth bottle to the
Buchner funnel at the angle as it was during precipitation, and slowly pour out the
contents to form a continuous trickle after passing through the filter paper; any
unnecessary agitation shall be avoided. The speed of the liquid passing through the filter
paper shall be the same as the speed of pouring into the funnel.
After the upper liquid has been filtered, add 15 mL of acetone (4.3) to the bottle, cover
the bottle mouth with the thumb and shake vigorously, then release the thumb; block
the bottle mouth with the thumb again, shake the bottle upside down above the filter
paper, release the thumb, and let the acetone and residue flow onto the filter paper. Then,
wash with another portion of 15 mL of acetone, shake and pour out as above. Check the
bottle and wash it again with acetone. When all the liquid has been filtered, use a
washing bottle to wash the residue on the wall of the funnel twice with a small amount
of acetone, and drain the filter. Carefully remove the filter paper loaded with residue
from the Buchner funnel, transfer it into a Kjeldahl flask without damage, and place the
Kjeldahl flask in an oven at 105°C for drying.
7.4 Determination of crude protein
Use the dried residue (7.3) to measure the crude protein mass fraction (w2) according
to the method in GB/T 6432. During the determination of the residual crude protein, the
blank value of the enzyme solution shall be subtracted from the residual crude protein
of each sample. At the same time, weigh several grams (the weight shall be accurate to
0.0002 g) of the degreased and air-dried sample (7.1), and directly measure the mass
fraction (w1) of crude protein in the degreased and non-enzymatic hydrolyzed sample
according to the method in GB/T 6432.
8 Presentation of analysis results
8.1 The pepsin digestibility X of the sample is expressed as the mass fraction, and the
value is expressed in % and calculated according to the formula (1):
where:
w1 --- The mass fraction of crude protein in the degreased and non-enzymatic
hydrolyzed sample, %;
w2 --- The mass fraction of crude protein in the residue after degreasing and
enzymatic hydrolysis, %.
8.2 After each sample is degreased and air-dried, take two samples for enzymatic
hydrolysis, measure the mass fraction of the residue crude protein in parallel, and take
the arithmetic mean as the measurement result (rounded to three significant figures),
and the relative deviation of the measurement result shall be ≤ 6%.