PDF GB/T 10742-2008 English (GB/T 10742-1989: Older version)
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Raw fiber material - Determination of pectin content
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GB/T 10742-2008: PDF in English (GBT 10742-2008) GB/T 10742-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 85-010
Y 30
Replacing GB/T 10742-1989
Raw fiber material - Determination of pectin content
ISSUED ON. AUGUST 19, 2008
IMPLEMENTED ON. MAY 01, 2009
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative references... 5
3 Method 1, Gravimetric method... 5
4 Method 2, Carbazole colorimetric method... 9
5 Test report... 12
Raw fiber material - Determination of pectin content
WARNING. Personnel using this Standard shall have practical experience in
regular laboratory work. This Standard does not address all possible safety issues.
It is the responsibility of the user to take appropriate safety and health measures
and to ensure compliance with the conditions which are set by the relevant national
regulations.
1 Scope
This Standard specifies the determination methods of pectin content in raw fiber
material.
This Standard applies to the determination of pectin content in various raw fiber
materials.
This Standard provides two determination methods of pectin content, namely the
gravimetric method and the carbazole colorimetric method. The two determination
methods of are equal validity.
2 Normative references
The terms in the following documents become the terms of this Standard by reference
to this Standard. For dated references, all subsequent amendments (not including errata
content) or revisions do not apply to this standard. However, parties to agreements that
are based on this Standard are encouraged to study whether the latest versions of these
documents can be used. For undated references, the latest edition applies to this
Standard.
GB/T 2677.1, Fibrous raw material of sampling for analysis
GB/T 2677.2, Determination of moisture content in fibrous raw material
GB/T 6682, Basic requirements on exhibition logistics service (GB/T 6682-2008,
ISO 3696.1987, MOD)
3 Method 1, Gravimetric method
3.1 Principle
Use ammonium oxalate solution to extract the pectin in the raw material; then, add an
ethanol solution containing hydrochloric acid, to separate the pectin from the extract;
then, use a dilute ammonia solution to dissolve the obtained pectin; then, add sodium
hydroxide to hydrolyze all the pectin into soluble pectinate; finally, use calcium
chloride to precipitate calcium pectinate. Use the content of calcium pectinate to
express the content of pectin.
3.2 Reagents
Unless otherwise stated, use only reagents that are identified as analytical reagents in
the analysis.
3.2.1 Water, GB/T 6682, grade 3.
3.2.2 Benzene-alcohol mixture. Measure 33 volumes of ethanol and 67 volumes of
benzene and mix them.
3.2.3 1% ammonium oxalate solution. Weigh 5 g of anhydrous ammonium oxalate and
dissolve it in water; then, add water to adjust the volume to 500 mL.
3.2.4 0.5% ammonium oxalate solution. Weigh 2.5g of anhydrous ammonium oxalate
and dissolve it in water; then, add water to adjust the volume to 500 mL.
3.2.5 Ammonia water, NH3H2O, aqueous solution of ammonia, ρ = 0.90 g/mL.
3.2.6 Ethanol solution containing hydrochloric acid. Measure 1 000 mL of ethanol; add
11 mL of hydrochloric acid (ρ＝1.19 g/ mL); mix well.
3.2.7 Ethanol washing solution containing hydrochloric acid. Measure 1 000 mL of
ethanol, 11 mL of hydrochloric acid (ρ＝1.19 g/mL) and 250 mL of water; mix well.
3.2.8 0.1 mol/L sodium hydroxide solution. Weigh 4 g of sodium hydroxide and
dissolve it in water; then, add water to fix the volume to 1 000 mL.
3.2.9 1 mol/L acetic acid solution. Measure 29 mL of glacial acetic acid (99% ~ 100%);
add water to adjust the volume to 500 mL.
3.2.10 1 mol/L calcium chloride solution. Weigh 110 g of anhydrous calcium chloride
and dissolve it in water; add water to adjust the volume to 1000 mL.
3.3 Apparatus
Commonly used apparatus in the laboratory and the following apparatus.
3.3.1 Electronic balance, sensitivity 0.001 g.
3.3.2 Soxhlet extractor.
3.3.3 500 mL conical flask with reflux condenser.
3.3.4 Thermostatically controlled hot plate.
3.3.5 Oven, adjustable at 105 ℃ ± 2 ℃.
3.4 Test procedure
3.4.1 Sample collection and processing
Follow the provisions of GB/T 2677.1.
3.4.2 Weighing of samples
Accurately weigh 1 g ~ 3 g (accurate to 0.001 g) of the sample and prepare two parallel
samples. If the pectin content of the sample is high, adjust the sample amount according
to the test value, where the minimum shall not be less than 1 g. At the same time, weigh
another sample and determine the moisture content according to GB/T 2677.2.
3.4.3 Purification of sample
Use qualitative filter paper to wrap the sample; tie it with thread; put it into the Soxhlet
extractor (3.3.2). Add 100 mL of benzene alcohol mixture (3.2.2); place it in a boiling
water bath for extraction for 3 h to remove interfering impurities; take out the sample
and spread it out to air dry.
Note. The test shall be carried out in a fume hood. The used benzene-alcohol mixture
can be distilled and purified before reuse.
3.4.4 Extraction of pectin
Transfer the air-dried sample (3.4.3) to a 500 mL conical flask (3.3.3); add 100 mL of
1% ammonium oxalate solution (3.2.3); install a reflux condenser; heat in a boiling
water bath for 3 h. Filter out the extract by pouring; try to keep the residue in the conical
flask; do not let it flow into the filter paper. Add 100 mL of 0.5% ammonium oxalate
solution (3.2.4) to the conical flask; install a reflux condenser; put it back in a boiling
water bath; heat for 2 h to fully extract the pectin. Use the filter paper used last time to
filter out the extract. Use hot water to wash the residue and filter paper three times;
combine the filtrate obtained twice and the washing liquid in a 500 mL beaker.
3.4.5 Precipitation of pectin
Place the filtrate on a thermostatically controlled hot plate; place an asbestos net on it;
control the temperature so that the filtrate does not boil; evaporate and concentrate to
70 mL ~ 80 mL; cool it down and transfer it to a 100 mL volumetric flask; add water to
the mark; shake it well. Transfer 25 mL of this solution to a 500 mL beaker; then slowly
add 90 mL of ethanol solution containing hydrochloric acid (3.2.6) under constant
stirring; let it stand overnight; filter. Use about 30 mL of ethanol washing solution
containing hydrochloric acid (3.2.7) to wash the precipitated pectin substance three
times.
3.4.6 Dissolution of pectin
additional sample shall be tested. After excluding abnormal values, take the average of
the three test values as the reported value.
4 Method 2, Carbazole colorimetric method
4.1 Principle
Use ammonium oxalate solution to extract the pectin in the raw material; then, add an
ethanol solution containing hydrochloric acid, to separate the pectin from the extract.
Then, use a dilute ammonia solution to dissolve the obtained pectin, which is
hydrolyzed in a strong acid to generate galacturonic acid, and reacts with carbazole to
form a purple-red solution that can be used for colorimetric determination. Use the
content of galacturonic acid to express the content of pectin.
4.2 Reagents
Unless otherwise stated, use only reagents that are identified as analytical reagents in
the analysis.
4.2.1 Water, GB/T 6682, grade 3.
4.2.2 1% ammonium oxalate solution. Weigh 5 g of anhydrous ammonium oxalate and
dissolve it in water; then, add water to adjust the volume to 500 mL.
4.2.3 0.5% ammonium oxalate solution. Weigh 2.5g of anhydrous ammonium oxalate
and dissolve it in water; then add water to adjust the volume to 500 mL.
4.2.4 Ammonia water, NH3H2O, aqueous solution of ammonia, ρ = 0.90 g/mL.
4.2.5 Ethanol solution containing hydrochloric acid. Measure 1 000 mL of ethanol; add
11 mL of hydrochloric acid (ρ = 1.19 g/mL); mix well.
4.2.6 Ethanol washing solution containing hydrochloric acid. Measure 1 000 mL of
ethanol, 11 mL of hydrochloric acid (ρ = 1.19 g/mL) and 250 mL of water; mix well.
4.2.7 1000 mg/L galacturonic acid standard solution. Weigh 0.1 g (accurate to 0.000 1
g) of galacturonic acid; dissolve it in water; add water to adjust the volume to 100 mL.
4.2.8 0.15% carbazole anhydrous ethanol. Weigh 0.075 g of carbazole; dissolve it in
anhydrous ethanol; use anhydrous ethanol to adjust the volume to 50 mL.
4.2.9 Concentrated sulfuric acid, H2SO4, ρ = 1.84 g/mL, mass fraction 95% ~ 98%.
4.3 Apparatus
Commonly used apparatus in the laboratory and the following apparatus.
4.3.1 Electronic balance, sensitivity 0.000 1 g.
4.3.2 500 mL conical flask with reflux condenser.
4.3.3 Thermostatically controlled hot plate.
4.3.4 Ultraviolet-visible spectrophotometer.
4.4 Test procedure
4.4.1 Collection and processing of samples
Follow the provisions of GB/T 2677.1.
4.4.2 Weighing of samples
Weigh 1 g (accurate to 0.001 g) of the sample accurately and prepare two parallel
samples. If the pectin content of the sample is high, adjust the sample amount according
to the test value and reduce the sample amount to 0.2 g. At the same time, weigh another
sample and determine the moisture content according to GB/T 2677.2.
4.4.3 Extraction of pectin
Place the sample in a 500 mL conical flask (4.3.2); add 100 mL of 1% ammonium
oxalate solution (4.2.2); install a reflux condenser; heat in a boiling water bath for 3 h.
Filter out the extract by pouring; try to keep the residue in the conical flask; do not let
it flow into the filter paper. Add 100 mL of 0.5% ammonium oxalate solution (4.2.3) to
the conical flask; install a reflux condenser; put it back in a boiling water bath; heat for
2 h to fully extract the pectin. Use the filter paper used last time to filter out the extract.
Use hot water to wash the residue and filter paper three times; combine the filtrate
obtained twice and the washing liquid in a 500 mL beaker.
4.4.4 Precipitation of pectin
Place the filtrate on a thermostatically controlled hot plate; place an asbestos net on it;
control the temperature so that the filtrate does not boil; evaporate and concentrate to
about 70 mL ~ 80 mL; cool it down and transfer it to a 100 mL volumetric flask; add
water to the mark; shake it well. Transfer 25 mL of this solution to a 500 mL beaker;
then slowly add 90 mL of ethanol solution containing hydrochloric acid (4.2.5) under
constant stirring; let it stand overnight; filter. Use about 30 mL of ethanol washing
solution containing hydrochloric acid (4.2.6) to wash the precipitated pectin substance
three times.
4.4.5 Dissolution of pectin
Put the precipitate obtained after filtration together with the filter paper into another
small beaker; pour 75 mL of hot ammonia solution [mixed from 75 mL of boiling water
and 1.5 mL of ammonia solution (4.2.4)] on the filter paper; boil for several minutes;
filter. Pour a small amount of hot water into the beaker containing the filter paper; boil
for several minutes; filter. Repeat this process 2 ~ 3 times; collect all the filtrate in a
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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