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U.S. Department of Health and Human Services

Food

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MPM: III. Reagents for Macroanalytical Methods

This chapter of the manual lists some of the reagents which are of special significance to the methods contained in Chapter V. For each listed reagent, special notations on applications and/or preparation are highlighted. All reagents used for filth extraction should be filtered, except concentrated acids and alkalies. Except where noted, technical grade reagents are acceptable.

  1. Alcohol -- Use 95% commercial ethanol unless otherwise specified. Make all dilutions by volume.
  2. Chloral Hydrate -- Prepare solution from equal parts of chloral hydrate and water, or use Hertwig's solution (see below). Used for clearing plant and insect materials.
  3. Crystal Violet -- Used to detect mold in pickle relish. Either a water-based or alcohol-based solution may be used. To prepare the water-based solution, dissolve 5 g dye (Color Index 681) in 100 mL water. To prepare the alcohol-based solution, dissolve 10 g dye (Color Index 42555) in 100 mL alcohol.
  4. Detergent Solution -- Prepare aqueous sodium lauryl sulfate solution as required.
  5. EDTA -- Used to clean sieves.
  6. FAA -- Used in fixation of parasites in fish flesh. Consists of a mixture of formalin, alcohol, and acetic acid. Combine 10 parts 37-40% formaldehyde, 70 parts 95% ethanol, 15 parts water, and 5 parts acetic acid.
  7. Heptane -- Use commercial n-heptane containing less than 8% toluene.
  8. Hertwig's Solution -- Also known as acidified chloral hydrate-glycerol solution. Dissolve 45 g chloral hydrate crystals in 25 mL HCl (1 + 8) and 10 mL glycerol. Useful for clearing plant and insect materials. Use only for temporary mounts, not for permanent slides.
  9. Hydrogen Peroxide -- Used to demonstrate catalase activity in raisins. Use 5% solution.
  10. Iodine in Potassium Iodide (I-KI) -- Used to detect foreign starch grains in peanut butter. Dissolve 0.5 g I and 1.5 g KI in 25 mL water.
  11. Isopropanol -- Use 100% isopropanol.
  12. Pancreatin Solution -- Used to clean sieves. Use USP or soluble pancreatin kept refrigerated at 10C. Use fresh solution. Mix at rate of 5 g/100 mL water at less than or equal to 40C. Stir with malted milk unit or blender 10 min, or let stand 30 min with frequent shaking. Centrifuge at 1500 rpm and filter supernatant through S&S No. 8 paper, or equivalent. Alternatively, filter through cotton pads 10-13 cm thick and then through rapid No. 8 paper in Hirsch funnel with suction.
  13. Petroleum Ether -- Used to defat peanut butter and potato chips.
  14. Sodium Phosphate Solution -- Use technical grade Na3PO4. Used to wash olive oil away from sample. Prepare 5% solution.
  15. Stabilizer Solutions -- 0.5% Na carboxymethylcellulose preferred (Hercules Inc., Cellulose and Protein Products Dept. 1313 Market St., Wilmington, DE 19899). Place 500 mL boiling H20 in high-speed blender. With blender running, add 2.5 g Cellulose Gum and 10 mL ca 37% HCHO soln w/w, and blend ca 1 min. Alternatives: 3-5% pectin or 1% algin. Add required amt of stabilizer directly to H20 while agitating in high-speed blender. Treat soln with vac. or heat to remove air bubbles. Add 2 mL HCHO soln/100 mL soln as preservative. (If blender is not available, mix dry stabilizer with alcohol to facilitate incorporation with H20.) Adjust to pH 7.0-7.5. Filter soln thru 8 membrane filter (Millipore No. SCWP-047-00, or equiv.) using suitable vac. filtration app. (Millipore No. XX15-047-00, or equiv.).
  16. Water -- Unless otherwise specified, tap water is to be used in all procedures.