Decision No. 57/2000/QD-BNNPTNT-KHCN on issuing industry standards

 

Pursuant to …;

Regarding the issuance of industry standards

THE MINISTER OF AGRICULTURE AND RURAL DEVELOPMENT

Pursuant to Decree No. 73/CP dated November 1, 1995 of the Government stipulating the functions, tasks, powers, and organizational structure of the Ministry of Agriculture and Rural Development;

Pursuant to Decree No. 86/CP dated December 8, 1995 of the Government stipulating the division of responsibilities for state management over product quality.

Considering the proposal of the Director of the Department of Science, Technology, and Product Quality

Pursuant to …;

Article 1: Now promulgates the following industry standard:

10TCN 422-2000: Agricultural products - Determination of lysine content in grains. Spectrophotometric method.

10TCN 423-2000: Soybeans and soybean products. Method for determining soluble protein in 0.2% potassium hydroxide solution.

10TCN 424-2000: Rice. Method for determining gel strength.

10TCN 425-2000: Rice. Method for determining white rice ratio, silver-white ratio, and silver-white degree.

Article 2: This Decision shall take effect fifteen days from the date of signature.

Article 3: The Heads of the Office, Directors of the Science and Technology Department and Product Quality, and leaders of related organizations and individuals are responsible for implementing this Decision.

 

STANDARDS

Agricultural products - Determination of lysine content in grains.

Spectrophotometric method 10 TCN 422-

(Issued pursuant to Decision No. 57/2000/QĐ-BNN-KHCN dated May 23, 2000)

This standard applies to cereal grains (rice, wheat, corn, etc.), legume seeds (soybeans, green beans, etc.) and specifies the spectrophotometric method for determining lysine content.

1. Sample collection

Sampling shall be conducted according to TCVN 5451-91 (ISO 950-1979).

2. Principle

Based on the color complex formation reaction between free e-NH groups of lysine in the protein molecule with ninhydrin reagent and measurement of optical absorbance of the formed color complex at 540nm wavelength. The standard solution used is the lycine solution because the lycine molecule is equivalent to lysine and contains only one e-NH group.₂ 3. Reagents₂.

All reagents must be analytical grade purity. Water used must be distilled water or water of equivalent purity.

3.1 Buffer solution

Dissolve 30g sodium formate in 60ml distilled water, add 10ml 86-88% formic acid solution, and then add distilled water to make up to 100ml.

3.2 Ninhydrin reagent

Place 1g pure ninhydrin and 1g CdCl

.2,5H₂O in a dark bottle with a ground stopper. Add 25ml buffer solution (3.1) and 75ml ethylene glycol, shake until completely dissolved. The reagent is stable for one month at 4₂C in darkness.⁰3.3 20% and 95% ethanol solutions.

3.4 2% and 4% sodium carbonate solutions.

3.5 Standard lycine solution

Weigh 100mg pure lycine accurately to 0.1mg into a 100ml volumetric flask, dissolve completely with 20% ethanol solution and dilute to the mark with this solution. 1ml of the standard lycine solution contains 1mg lycine.

4. Equipment - Analytical balance with accuracy of 0.0001g

- Sample grinder

- Sieve with 250mm mesh size

- Spectrophotometer with 540nm wavelength

- Automatic temperature-controlled water bath

- Test tubes with 18x150mm dimensions

- Volumetric flasks with 100ml and 500ml capacities

- Pipettes with 1ml, 2ml, 10ml, and 20ml graduations

- Aluminum test tube rack

- Funnel with 4.0-4.5cm diameter

Quantitative filter paper.

5. Testing procedure

5.1. Establishing the calibration curve

Into 100ml volumetric flasks, sequentially add 0, 10, 20, 30, and 40ml of the original standard lycine solution (section 3.5). Dilute each solution to the mark with 20% ethanol solution and shake well. The corresponding lycine concentrations in these standard solutions will be 0, 100, 200, 300, and 400mg/ml. Using a pipette, accurately add 0.5ml of each standard solution into separate test tubes. Then add 0.5ml of 4% sodium carbonate solution and 2ml of ninhydrin reagent to each test tube. Shake the samples thoroughly and heat them in a water bath for 30 minutes. Afterward, cool the test tubes by immersing the rack in cold water. Add 5ml of 95% ethanol solution to each test tube, shake vigorously, and measure the optical absorbance on the spectrophotometer at 540nm wavelength.

Construct the calibration curve with the y-axis representing the measured optical absorbance values and the x-axis representing the lycine concentrations from 0 to 400mg/ml.

5.2. Preparing the sample₂Add distilled water to make up to 1 liter of solution.₃ From the average sample, grind approximately 10g of the sample to pass entirely through a 250mm sieve.

5.3. Conducting the test

Into test tubes, add 200-250mg of clean glass beads, weigh accurately 30mg of the prepared sample (section 5.1) into each test tube. Each sample is analyzed twice in parallel. Add 1ml of 2% sodium carbonate solution to each test tube. Mix the sample with the glass beads, place it on the aluminum rack, and put it into the water bath preheated to 80

C for 10 minutes. Stir the solution thoroughly with a glass rod to achieve uniformity. Add 2ml of ninhydrin to each test tube. Shake the samples thoroughly and heat them in a water bath for 30 minutes. Afterward, cool the test tubes by immersing the rack in cold water. Once cooled, add 5ml of 95% ethanol solution to each test tube, shake vigorously, and filter through quantitative filter paper on a funnel with a 4.0-4.5cm diameter. Measure the optical absorbance of the filtrates on the spectrophotometer at 540nm wavelength, following the same procedure as when coloring.

If the sample produces a blue color, it may be diluted with 95% ethanol solution, and the calculation must take into account the dilution factor.

The lysine content of the samples is calculated using the calibration curve (section 5.1) corresponding to lycine solutions with concentrations from 0 to 400mg/ml.₂Add distilled water to make up to 1 liter of solution.₃ 6. Calculating results⁰The lysine content (X

, %) in the sample is calculated using the formula:

C: lycine concentration found on the calibration curve, mg/ml.

m: weight of the sample, mg

6.1. 1000: conversion factor from mg to mg₁1.11: conversion factor from lycine to lysine

Where:

The test result is the arithmetic mean of two parallel analyses.

The lysine content in the sample based on dry matter (X

, %) is determined using the following formula:

: lysine content in the dried sample, %

W: moisture content of the sample, %

6.2. Note:₂In research, the lysine content in the sample is usually expressed as a percentage of protein (X

Where:

X₁, %), using the following formula:

: lysine content in the sample based on dry matter, %

* P: protein content in the sample based on dry matter, %

Soybeans and soybean products - Method for determining soluble protein in 0.2% potassium hydroxide solution 10TCN 423-2000₃This standard applies to soybeans, products made from soybeans, and specifies the method for determining soluble protein in a 0.2% potassium hydroxide solution.

Where:

X₂Sampling shall be conducted according to TCVN 4847-89 (ISO 5506-1988).

Protein in the sample is extracted with a 0.2% potassium hydroxide solution and nitrogen in the extract is determined by the Kjeldahl method.

 

STANDARDS

Soluble protein content in 0.2% potassium hydroxide is calculated by multiplying the nitrogen content by the factor 5.71.

(Issued pursuant to Decision No. 57/2000/QĐ-BNN-KHCN dated May 23, 2000)

All reagents must be analytical grade purity. Water used must be distilled water or water of equivalent purity.

1. Sample collection

3.1. 0.2% potassium hydroxide solution (equivalent to 0.036N; pH=12.5)

2. Principle

3.2. Reagents used for nitrogen determination according to the Kjeldahl method (TCVN4295-86)

Sample grinder

All reagents must be analytical grade purity. Water used must be distilled water or water of equivalent purity.

Sieve with 250mm mesh size

3.1. Potassium hydroxide solution 0.2% (equivalent to 0.036N; pH=12.5)

3.2. Reagents used to determine nitrogen according to the Kjeldahl method (TCVN4295-86)

- Sample grinder

Sample grinder

Sieve with 250mm mesh

Analytical balance with accuracy of 0.0001g

Magnetic stirrer

Centrifuge with speed of 2700rpm

Triangular flask with volume of 250ml

Pipette with volume division of 10, 20ml

Equipment for determining nitrogen according to the Kjeldahl method.

Into 100ml volumetric flasks, sequentially add 0, 10, 20, 30, and 40ml of the original standard lycine solution (section 3.5). Dilute each solution to the mark with 20% ethanol solution and shake well. The corresponding lycine concentrations in these standard solutions will be 0, 100, 200, 300, and 400mg/ml. Using a pipette, accurately add 0.5ml of each standard solution into separate test tubes. Then add 0.5ml of 4% sodium carbonate solution and 2ml of ninhydrin reagent to each test tube. Shake the samples thoroughly and heat them in a water bath for 30 minutes. Afterward, cool the test tubes by immersing the rack in cold water. Add 5ml of 95% ethanol solution to each test tube, shake vigorously, and measure the optical absorbance on the spectrophotometer at 540nm wavelength.

5.1. Sample preparation

From the average sample, grind approximately 10g of the sample until it passes completely through a 250mm sieve.

5.2. Protein extraction

Accurately weigh from 1.5 to 2g of the prepared sample according to (5.1) and place it into a triangular flask with a volume of 250ml. Each sample is performed twice simultaneously. Add 75ml of 0.2% KOH solution and mix the sample mixture thoroughly on the magnetic stirrer for 20 minutes at room temperature. The protein extraction time may exceed 20 minutes if necessary. Then centrifuge the mixture at a speed of 2700rpm for 15 minutes. Transfer the supernatant protein extract (from the upper part of the centrifuge tube) to a clean triangular flask for analysis of protein soluble in 0.2% potassium hydroxide.

5.3. Inorganic analysis of protein extract and determination of nitrogen

Use a pipette to accurately draw 10-20ml of the protein extract (5.2) and place it into a combustion bottle for inorganic analysis of protein and determination of nitrogen content according to the Kjeldahl method (in accordance with TCVN 4295-86).

m: weight of the sample, mg

6.1. The content of protein soluble in 0.2% KOH solution expressed as a percentage by weight (X₁, %) is calculated using the formula:

Where:

a, b: volume of 0.1N NaOH solution used for titration of blank and sample, ml.

test, ml.

V₁: volume of protein extract subjected to inorganic analysis, ml

V₂: volume of 0.2% KOH solution used for protein extraction in the sample, ml

m: weight of the test sample, g

0.0014: conversion factor corresponding to 1ml of 0.1N standard solution

H₂SO₄0.1N

5.71: conversion factor from nitrogen to protein in soybeans.

The result of the test is the arithmetic mean value of two parallel analyses if the difference between them does not exceed 0.3%. The final result is rounded to the first decimal place.

6.2. The content of protein soluble in 0.2% KOH solution expressed as a percentage relative to total protein (X₂, %) is determined using the following formula:

Where:

X₁: Content of protein soluble in 0.2% KOH solution, %

P: Total protein content,%

 

STANDARDS

Rice method for determining gel strength 10TCN 424-

(Issued pursuant to Decision No. 57/2000/QĐ-BNN-KHCN dated May 23, 2000)

This standard applies to milled rice or rice flour and specifies the method for determining gel strength.

1. Sample collection

Sampling according to TCVN 5451-1991 (ISO 950-1979)

2. General concepts

Gel strength based on the long flow characteristic of milled rice starch gel and can be classified as follows:

3. Method content

Perform gelatinization of milled rice flour by hydrolysis in a weak alkaline solution, then cool and measure the flow length of the gel.

4. Reagents

All reagents must be analytical grade purity. Water used must be distilled water or equivalent quality.

4.1. 95% Ethanol solution containing 0.03% methylene blue

4.2. 0.2N KOH solution

5. Equipment

Analytical balance with accuracy of 0.0001g

Sample grinder

Sieve with 150mm mesh

Small shaker: Genic mixer

Gas stove with temperature adjustment

Water bath

Test tube size 13 x 100mm (Pyrex 9820 tube)

Aluminum test tube rack

Pipette with volume division of 1, 2ml

6. Procedure

6.1. Sample preparation

From the average sample, grind approximately 10g of the sample until it passes completely through a 150mm sieve.

6.2. Accurately weigh 100mg of the prepared rice flour and place it into a 13x100mm test tube. Each sample is performed three times simultaneously. Add 0.2ml of 95% ethanol solution containing 0.03% methylene blue to each test tube and shake evenly.

* Note: The 95% ethanol solution is used to prevent the agglomeration of flour particles at gelatinization temperature, while methylene blue colors the paste for easier reading of results.

Add 2ml of 0.2N KOH solution and mix thoroughly on the Genic mixer at speed 6. Cover the test tubes with glass beads and place them in a boiling water bath for 8 minutes. During heating, ensure that the water in the water bath is boiling and that the upward movement of starch during cooking does not exceed 2/3 of the height of the test tube.

Remove the test tubes from the water bath, shake quickly on the Genic mixer, cool at room temperature for about 5 minutes, and then chill in ice water for 20 minutes to achieve good gel formation.

6.3. Preparation for reading results

After chilling, place the test tubes on a horizontal plane marked with 1mm divisions.

Read the length of the gel after 30 and 60 minutes.

6.4. Reading and recording gel length

Gel length (mm) is measured from the bottom of the test tube to the tip of the gel surface. The measurement result is the arithmetic mean of three parallel analyses.

6.5. Classifying gel strength

Based on the average gel length obtained, classify the gel strength of milled rice flour according to the classification table (section 2).

* Note: This determination is based on experimental evidence, so it is best to include three control samples with soft, hard, and medium gel strengths in each analysis series.

 

STANDARDS

Milled rice method for determining white ratio, silver white ratio, and silver whiteness TCN 425-2000

This standard applies to milled rice and specifies the method for determining white ratio, silver white ratio, and silver whiteness.
(Issued pursuant to Decision No. 57/2000/QĐ-BNN-KHCN dated May 23, 2000)

1. Definitions

The terms and definitions used in this standard are understood as follows:

1.1. White grain is a milled rice grain that is entirely white without any silver-white spots in the endosperm.

1.2. Silver-white grain is a milled rice grain that has silver-white spots appearing in the endosperm. Depending on the location of the silver spot on the endosperm, they are classified as belly silver, back silver, and middle silver.

* Belly silver grain is a rice grain with a silver spot on the same side as the germ.

* Back silver grain is a rice grain with a silver spot on the opposite side of the germ.

* Middle silver (middle silver) grain is a rice grain with a silver spot in the middle of the endosperm.

1.3. Silver whiteness point and silver whiteness degree are used to evaluate and classify the degree of silver whiteness among different varieties or batches of rice being analyzed.

2. Sampling

Sampling of milled rice according to TCVN 5451-1991 (ISO 950-1979)

Sampling of whole grains according to TCVN 1643-1992

3. Equipment

Analytical balance with accuracy of 0.01g

Silver whiteness measuring instrument

Sample container

Small tray capable of holding about 50g - 100g of rice

4. Testing procedure

4.1. Determination of white ratio and silver white ratio

4.1.1. Determination of white ratio

4.1.1. Determining the whiteness ratio

Mix the intact milled rice samples evenly using the diagonal method to divide the rice samples into analysis samples and reserve samples. From each analysis sample, weigh 50 grams, and conduct two parallel tests. Evenly spread the weighed sample on the surface of the whiteness meter (which includes a colored glass plate with an electric light source underneath). Select completely white grains from the intact rice sample and weigh their mass. The remaining grains are silver-white.

The percentage of inner white grains is calculated based on the weight of the original rice grains according to the formula:

 

 

 

4.1.2. Determining the percentage of silver-white grains

Percentage of silver-white grains (%) = 100% - percentage of inner white grains (%)

4.2. Determining the silver-white score and whiteness degree

4.2.1. Determining the number of silver-white scores

From the average sample, use the diagonal method to divide the sample and take out 100 intact grains. Then evenly spread the grains on the colored glass surface of the whiteness meter and classify them according to a six-level scale from 0 to 5 described as follows:

Count and record the number of grains classified at different levels, then calculate the average silver-white score for the rice sample according to the following formula:

Where:

X: Average silver-white score

Provincial People's Committees set specific prices₀/H₁/H₂/H₃/H₄/H₅ where X is the number of grains corresponding to the scores 0, 1, 2, 3, 4, 5

4.2.2. Determining the whiteness degree

Based on the average silver-white score obtained, evaluate the whiteness degree of the rice sample according to the following classification:

*Example: Select 100 intact milled rice grains and after classification, obtain the number of grains at different levels as follows:

Therefore, the average silver-white score of this rice variety is 150:100 = 1.50

According to the classification table, the whiteness degree of this rice variety belongs to the category: moderately silver.