Potato Starch

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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Portions of the monograph text that are national USP text, and are not part of the harmonized text, are marked with symbols (⧫) to specify this fact. 

1 DEFINITION 

Potato Starch is obtained from the tuber of Solanum tuberosum L. 

2 IDENTIFICATION 

A. Procedure 

Analysis: Examine under a microscope using a mixture of equal volumes of Glycerol and water. 

Acceptance criteria: It presents granules, either irregularly shaped, ovoid or pear-shaped, usually 30–100 µm in size but occasionally exceeding 100 µm, or rounded, 10–35 µm in size. There are occasional compound granules having 2–4 components. The ovoid and pear shaped granules have an eccentric hilum and the rounded granules acentric or slightly eccentric hilum. All granules show clearly visible concentric striations. Between orthogonally oriented polarizing plates or prisms, the granules show a distinct black cross intersecting at the hilum. 

B. Procedure 

Sample solution: 20 mg/mL in water 

Analysis: Boil for 1 min, and cool. 

Acceptance criteria: A thick, opalescent mucilage is formed. 

C. Procedure 

Sample solution: 1 mL of the mucilage obtained in Identification test B 

Analysis: Add 0.05 mL of iodine and potassium iodide TS 2 to the Sample solution. 

Acceptance criteria: An orange-red to dark blue color is produced, which disappears upon heating. 

3 IMPURITIES 

Residue on Ignition 〈281〉: NMT 0.6%, determined on a 1.0-g sample 

Change to read: 

Limit of Iron 

Standard iron stock solution A: Equivalent of 10 µg/mL of iron prepared as directed under Iron 〈241〉, Procedures, Procedure 1 (CN 1-Jun 2023) 

Standard iron stock solution B: 1 µg/mL of iron from Standard iron stock solution A in water 

[Note—Prepare immediately before use.] 

Standard iron solution: Transfer 10 mL of Standard iron stock solution B to a test tube, and add 2 mL of citric acid solution (2 in 10) and 0.1 mL of thioglycolic acid. Add 10 N ammonium hydroxide until the solution is distinctly alkaline to litmus, and dilute with water to 20 mL. Sample solution: Shake 1.5 g of Potato Starch with 15 mL of 2 N hydrochloric acid, and filter. Transfer 10 mL of the filtrate to a test tube, and add 2 mL of citric acid solution (2 in 10) and 0.1 mL of thioglycolic acid. Add 10 N ammonium hydroxide until the solution is distinctly alkaline to litmus, and dilute with water to 20 mL. 

Acceptance criteria: After 5 min, any pink color in the Sample solution is not more intense than that in the Standard iron solution, corresponding to a limit of 10 ppm of iron. 

Limit of Sulfur Dioxide 

Carbon dioxide: Use carbon dioxide, with a flow regulator that will maintain a flow of 100 ± 5 mL/min. 

Bromophenol blue indicator solution: 0.2 mg/mL of bromophenol blue in dilute alcohol. Filter if necessary. 

Hydrogen peroxide solution: Dilute 30% hydrogen peroxide with water to obtain a 3% solution. Just before use, add three drops of Bromophenol blue indicator solution, and neutralize to a violet-blue endpoint with 0.01 N sodium hydroxide. Do not exceed the endpoint.

Apparatus: Figure 1 

Figure 1 

In this test, the sulfur dioxide is released from the sample in a boiling acid medium and is removed by a stream of carbon dioxide. The separated gas is collected in a dilute hydrogen peroxide solution where the sulfur dioxide is oxidized to sulfuric acid and titrated with standard alkali. The apparatus consists essentially of a 500-mL three-neck, round-bottom boiling flask, A; a separatory funnel, B, having a capacity of 100 mL or greater; a gas inlet tube of sufficient length to permit introduction of the carbon dioxide within 2.5 cm of the bottom of the boiling flask; a reflux condenser, C, having a jacket length of 200 mm; and a delivery tube, E, connecting the upper end of the reflux condenser to the bottom of a receiving test tube, D. Apply a thin lm of stopcock grease to the sealing surfaces of all of the joints except the joint between the separatory funnel and the boiling flask, and clamp the joints to ensure tightness. Sample: 25.0 g of Potato Starch 

Analysis: Add 150 mL of water to the boiling flask. Close the stopcock of the separatory funnel, and begin the flow of carbon dioxide at a rate of 100 ± 5 mL/min through the Apparatus. Start the condenser coolant flow. Add 10 mL of Hydrogen peroxide solution to a receiving test tube. After 15 min, without interrupting the flow of carbon dioxide, remove the separatory funnel from the boiling flask, and transfer the Sample into the boiling flask with the aid of 100 mL of water. Apply stopcock grease to the outer joint of the separatory funnel, and replace the separatory funnel in the boiling flask. Close the stopcock of the separatory funnel, and add 80 mL of 2 N hydrochloric acid to the separatory funnel. Open the stopcock of the separatory funnel to permit the hydrochloric acid solution to flow into the boiling flask, guarding against the escape of sulfur dioxide into the separatory funnel by closing the stopcock before the last few mL of hydrochloric acid drain out. Boil the mixture for 1 h. Remove the receiving test tube, and transfer its contents to a 200-mL wide-necked, conical flask. Rinse the receiving test tube with a small portion of water, add the rinsing to the 200-mL conical flask, and mix. Heat on a water bath for 15 min, and allow to cool. 

Add 0.1 mL of Bromophenol blue indicator solution, and titrate the contents with 0.1 N sodium hydroxide VS until the color changes from yellow to violet-blue. Perform a blank determination, and make any necessary correction (see Titrimetry 〈541〉). 

Calculate the content, in ppm, of sulfur dioxide in the Sample taken: 

Result = 1000 × 32.03 × (VN/W) 

32.03 = milliequivalent weight of sulfur dioxide 

V = volume of titrant consumed (mL) 

N = normality of the titrant 

W = weight of the Sample (g) 

Acceptance criteria: NMT 50 ppm 

Limit of Oxidizing Substances 

Sample solution: Transfer 4.0 g to a glass-stoppered, 125-mL conical flask, and add 50.0 mL of water. Insert the stopper, and swirl for 5 min. Transfer to a glass-stoppered, 50-mL centrifuge tube, and centrifuge to clarify. Transfer 30.0 mL of the clear supernatant to a glass stoppered, 125-mL conical flask. Add 1 mL of glacial acetic acid and 0.5–1.0 g of potassium iodide. Insert the stopper, swirl, and allow to stand for 25–30 min in the dark. Add 1 mL of starch TS. 

Analysis: Titrate with 0.002 N sodium thiosulfate VS to the disappearance of the starch–iodine color. Perform a blank determination, and make any necessary correction. Each mL of 0.002 N sodium thiosulfate is equivalent to 34 µg of oxidant, calculated as hydrogen peroxide. Acceptance criteria: NMT 1.4 mL of 0.002 N sodium thiosulfate is required (20 ppm, calculated as H2O2). 

4 SPECIFIC TESTS 

Microbial Enumeration Tests 〈61〉 and Tests for Specified Microorganisms 〈62〉: The total aerobic microbial count does not exceed 103 cfu/g; the total combined molds and yeasts count does not exceed 102 cfu/g; and it meets the requirements of the test for the absence of Escherichia coli. 

Loss on Drying 〈731〉 Sample: 1 g 

Analysis: Dry the Sample at 130° for 90 min. 

Acceptance criteria: NMT 20.0% 

pH 〈791〉 

Sample solution: Prepare a slurry by weighing 5.0 g of Potato Starch, transferring to a suitable nonmetallic container, and adding 25.0 mL of freshly boiled and cooled water. 

Analysis: Agitate continuously at a moderate rate for 1 min. Stop the agitation, and allow to stand for 15 min. Determine the pH to the nearest 0.1 unit. 

Acceptance criteria: 5.0–8.0 

5 ADDITIONAL REQUIREMENTS 

⧫Packaging and Storage: Preserve in well-closed containers. No storage requirements specied.