A-A-20032F
6.3 Product verification. When USDA verification of analytical requirements is specified in the solicitation, contract, or purchase order, the following procedures will be followed.
6.3.1 Sampling Procedures. USDA inspection service will select the number of product containers based on USDA inspection service sampling procedures and plans.
6.3.2 Preparation of sample. The sample to be analyzed shall be a one-pound composite sample derived from a composite of the three containers. Prepare a clean, dry Waring Blender or similar mill by grinding a sample and then discarding it. Grind approximately 100 grams of the well-mixed sample in the prepared Waring Blender or similar mill for one minute. (Type II Mashed, Style A Granule potatoes need not be ground or screened.) Place the ground material in a small, dry, tightly-closed container for at least ½ hour. Pass the ground material over a U.S. Standard No. 20 sieve nested on a U.S. Standard No. 40 sieve. That portion which passes through the 20 mesh screen but not the 40 mesh screen is to be analyzed and shall be weighed immediately or placed in a small, dry container with a tightly closed lid until ready for analysis (a one-half pint Mason jar is satisfactory).
6.3.3 Further preparation of sample for reducing sugars test. Weigh 25 grams of potato granules or ground, sieved material into a 250 mL centrifuge bottle, add 75 mL of water, mix, and allow to stand for ½ hour. Add 100 mL of 95 percent ethyl alcohol plus 1 gram of calcium carbonate. Heat in a hot water (90 degrees Centigrade) bath for 1 hour while stirring frequently Centrifuge sample at 1,500 rpm for 10 minutes and decant the liquid portion into a 600 mL beaker.
Repeat extraction three more times, each time using 75 mL of 80 percent ethyl alcohol, heating in the hot water (90 degrees Centigrade) bath for 15 minutes while stirring frequently. Centrifuge at 1,500 rpm for 10 minutes and decant the liquid into the 600 mL beaker. Evaporate combined extracts on a steam bath to a volume of 50 to 75 mL. Quantitatively transfer extract into 250 mL volumetric flask with hot distilled water, cool, add 10 mL of saturated, neutralized lead acetate 4/, and bring to volume. Filter liquid through No. 2V Whatman or equivalent filter paper into a 250 mL Erlenmeyer flask containing about 4 grams of potassium oxalate. Mix filtrate thoroughly and allow precipitate to settle. To remove excess lead, add a few potassium oxalate crystals. Decant liquid through No. 2V Whatman or equivalent filter paper into a 250 mL glass-stoppered Erlenmeyer flask. Reagents used shall be American Chemical Society Reagent Grade.
4/ A saturated solution of neutralized lead acetate is prepared by adjusting the solution to pH 6.8 with 1N sodium hydroxide.
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