GB/T 8622-2006 English PDF (GBT8622-2006)

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GB/T 8622-2006: Determination of urease activity in soya bean products for feeds
GB/T 8622-2006
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 65.120
B 46
Replacing GB/T 8622-1988
Determination of urease activity in soya bean products for
feeds
ISSUED ON: JUNE 09, 2006
IMPLEMENTED ON: SEPTEMBER 01, 2006
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 Terms and definitions ... 4
4 Principles ... 5
5 Instruments and equipment ... 5
6 Reagents and solutions ... 5
7 Preparation of specimens ... 6
8 Measurement steps ... 6
9 Calculation of results ... 7
Determination of urease activity in soya bean products for
feeds
1 Scope
This standard specifies the determination of urease activity in soybean products and
their by-products.
This standard applies to the determination of urease activity in soybeans, soybean
products, and by-products. By this method, it can understand the degree of moist heat
treatment of soybean products.
2 Normative references
The provisions in 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 Standard; 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.
GB/T 601 Chemical reagent - Preparations of standard volumetric solutions
GB/T 6682 Water for laboratory use - Specifications (neq ISO 3696)
3 Terms and definitions
The following terms and definitions apply to this standard.
3.1
Urease activity in soya bean products
The mass of amino nitrogen, which is released by the decomposition of urea per
minute per gram of soybean product, at 30 °C ± 0.5 °C and pH7.
Note: Expressed in urease activity unit per gram (U/g).
Weigh 0.1 g of methyl red. Dissolve it in 95% of ethanol. Dilute it to 100 mL. Then
weigh 0.5 g of bromocresol green. Dissolve it in 95% ethanol and dilute to 100 mL.
Mix the two solutions in equal volumes. Store in a brown bottle.
7 Preparation of specimens
Use a pulverizer (5.1), to pulverize a representative sample, so that it all passes through
the sample sieve (5.2). For special samples (samples that cannot be crushed due to their
high moisture or volatile content), it shall be pre-dried at the laboratory temperature
before crushing. The weight loss on dryness shall be included in the calculation of the
results.
8 Measurement steps
Weigh about 0.2 g of the prepared specimen (Chapter 7), accurate to 0.1 mg, into a glass
test tube (if the activity is very high, it can weight 0.05 g of specimen). Add 10 mL of
urea buffer (6.1). Immediately cover the test tube cap and shake vigorously.
Immediately place the test tube in a constant temperature water bath (5.4), at 30 °C ±
0.5 °C. Perform timekeeping for 30 min ± 10 s. It is required that the time interval for
adding urea buffer solution to each specimen shall be consistent. When the reaction is
stopped, add 10 mL of hydrochloric acid solution (6.2), at the same time interval. Shake
and cool to 20 °C quickly. Transfer all the contents of the test tube into a small beaker.
Use 20 mL of water to rinse the test tube several times. Use a sodium hydroxide
standard solution (6.3), to titrate it to pH 4.70, through an acidity meter (5.6). If it
chooses to use an indicator, transfer all the contents of the test tube into a 250 mL
conical flask. Add 8 ~ 10 drops of the mixed indicator (6.4). Use sodium hydroxide
standard solution (6.3), to titrate, until the solution turns blue-green.
Take another test tube for blank test. Weigh about 0.2 g of the prepared specimen
(Chapter 7), accurate to 0.1 mg. Put it in a glass test tube (if the activity is very high, it
may weigh 0.05 g of specimen). Add 10 mL of hydrochloric acid solution (6.2). After
shaking, add 10 mL of urea buffer solution (6.1). Immediately cover the test tube and
shake vigorously. Immediately place the test tube in a constant temperature water bath
(5.4), at 30 °C ± 0.5 °C. Perform the timekeeping for 30 min ± 10 s. Cool the test tube
rapidly to 20 °C, when the reaction is stopped. Transfer all the contents of the test tube
into a small beaker. Use 20 mL of water to rinse the test tube for several times. Use a
sodium hydroxide standard solution (6.3) to titrate to pH4.70, through an acidity meter
(5.6). If it chooses to use an indicator, then transfer all the contents of the test tube into
a 250 mL conical flask. Add 8 ~ 10 drops of mixed indicator (6.4). Use sodium
hydroxide standard solution (6.3) to titrate, until the solution turns blue-green.