Food additive - Determination of oxidized hydroxypropyl starch

Baijia.net - a professional third-party testing and inspection platform that provides testing services for food additives such as oxidized hydroxyprop

A. 1 Safety Reminder

Some reagents used in the inspection methods of this standard are toxic or corrosive, and caution should be exercised during operation! If splashed onto the skin, rinse immediately with water, and in severe cases, seek immediate treatment

A.2 General Provisions

Unless otherwise specified, only reagents confirmed as analytical pure and Grade III water specified in GB/T6682 shall be used in the analysis.

. The standard titration solution, impurity determination standard solution, formulation, and product used in the test method shall be prepared in accordance with the provisions of GB/T601, GB/T602, and GB/T603 unless otherwise specified; When no solvent is specified, the solution used refers to an aqueous solution

A.3 Identification test

A.3.1 Microscopic detection

Hydroxypropyl starch phosphate ester without gelatinization treatment to maintain particle structure can be directly observed and identified by microscope to identify the shape, size, and characteristics of starch particles.

. Under the polarized light of the microscope, a typical polarized cross can be observed

A.3.2 Iodine staining

Add 1g of the sample to 20mL of water to form a suspension, and add a few drops of iodine solution. The color range should be dark blue to brownish red.

A.3.3 Copper Reduction; Preparation of alkaline copper tartrate test solution

A.3.3.1.1 Solution A: Take 34.66g of copper sulfate (CuSO4 · 5H2O), which should be free from weathering or moisture absorption, and dissolve with water to a constant volume of 500mL. Store this solution in a small sealed container

Solution B: Take 173g of potassium sodium tartrate (KNaC4H4O6 · 4H2O) and 50g of sodium hydroxide, dissolve with water to a constant volume of 500mL. Store this solution in a small alkali resistant container

Mix solution A and solution B in equal volumes to obtain alkaline copper tartrate test solution

A.3.3.2 Analysis Steps

Weigh 2.5g of the sample and place it in a flask. Add 10mL of 0.82mol/L hydrochloric acid solution and 70mL of water, mix well, reflux in a boiling water bath for 3h, and cool.

. Take 0.5mL of cooling solution and add 5mL of hot alkaline copper tartrate test solution to produce a large amount of red sediment

A.4 Determination of Hydroxypropyl

A.4.1 Method Principle

Oxidize hydroxypropyl starch in sulfuric acid to generate propylene glycol, which is further dehydrated to produce propanal and propanol. These two dehydrated products can form purple complexes with ninhydrin in sulfuric acid medium.

. Measure its absorbance at 590nm using a spectrophotometer, with a concentration range of 5-50mg, in accordance with Lambert Beer's law

A.4.2 Reagents and Materials; Sulfuric acid

A.4.2.2; Ninhydrin

A.4.2.3; Sodium bisulfite

A.4.2.4 Ninhydrin solution: Dissolve ninhydrin in a 5% sodium bisulfite solution to prepare a 3% ninhydrin solution

A.4.2.5 Sulfuric acid solution: c (1/2H2SO4)=1.0mol/L

A.4.2.6; 1,2-propanediol

A.4.2.7 Starch: Undenatured starch from the same plant source

A.4.3 Instruments and Equipment

Spectrophotometer

A.4.4 Analysis Steps

A.4.4.1 Preparation of Standard Solution

Prepare 1.00mg/mL of 1,2-propanediol standard solution. Take 1.00mL, 2.00mL, 3.00mL, 4.00mL, and 5.00mL of this standard solution into a 100mL volumetric flask, dilute with water to the mark, and obtain standard solutions with concentrations of 10ug/mL, 20ug/mL, 30ug/mL, 40ug/mL, and 50ug/mL, respectively

A.4.4.2 Preparation of Sample Solution

Weigh 50mg to 100mg of the sample, accurate to 0.1mg, place it in a 100mL volumetric flask, and add 25mL of sulfuric acid solution.

. Heat in a boiling water bath until the sample dissolves, cool and dilute with water to 100mL. If necessary, further dilution can be carried out to ensure that the hydroxypropyl content in every 100mL does not exceed 4mg, and then blank starch can be diluted in the same proportion

A.4.4.3 Determination

Take 1mL of each of the five standard solutions and transfer them into 25mL of stoppered graduated test tubes. Place the test tubes in cold water, add 8mL of sulfuric acid dropwise, mix well, and then place the test tubes in a boiling water bath to accurately heat for 3min. Immediately transfer the test tubes to a cold water bath to cool down. Carefully add 0.6mL of ninhydrin solution along the tube wall. Immediately shake well and keep in a 25 ℃ water bath for 100 minutes. Adjust the volume of each test tube to 25mL with sulfuric acid, and invert the tube several times to mix well (without shaking). Immediately transfer a portion of the solution into a 1cm colorimetric cell of the spectrophotometer, let it stand for 5 minutes, measure the absorbance value at 590nm, and draw a standard curve

Take 1mL of the sample solution and transfer it into a 25mL graduated test tube with a stopper. Follow the determination process of the standard solution and use the starch blank solution as a reference to determine the absorbance value

A.4.5 Result Calculation

The mass fraction of hydroxypropyl w0 is calculated according to formula (A.1):

Where:

c - the content of propylene glycol in the sample solution read from the standard curve, in micrograms per milliliter (ug/mL)

0.7763- Conversion coefficient of propylene glycol content to hydroxypropyl content

f - Final volume of the sample after dilution, in milliliters (mL)

m - sample mass, in milligrams (mg)

1000- Conversion factor

Function of testing report:

1. Project bidding: Issue authoritative third-party CMA/CNAS qualification report

2. Online e-commerce platform entry: Quality inspection report recognized by major e-commerce platforms

3. Used as a sales report: issuing legally effective testing reports to make consumers more confident

4. Papers and research: Provide professional personalized testing needs

5. Judicial services: providing scientific, fair, and accurate testing data

6. Industrial problem diagnosis: Verify the troubleshooting and correction of industrial production problems

BAIJIAN testing process:

1. Telephone communication and confirmation of requirements

2. Recommend solutions and confirm quotations

3. Mail samples and arrange testing

4. Progress tracking and result feedback

5. Provide reports and after-sales service

6. If urgent or priority processing is required

Our Competitive Edge:

1. The testing industry is fully covered, meeting different testing needs

2. Fully cover the laboratory and allocate localized testing nearby

3. Engineers provide one-on-one services to make testing more accurate

4. Free initial testing, with no testing fees charged

5. Self service order delivery for free on-site sampling

6. Short cycle, low cost, and attentive service

7. Possess authoritative qualifications such as CMA, CNAS, CAL, etc

8. The testing report is authoritative and effective, and is generally used in China