AACC 28-40

Extraneous Matter
AACC International Method
28-40.01
Page 1 of 2
Acid Hydrolysis Method for Insect Fragments
and Rodent Hairs—Wheat-Soy Blend
Final approval October 15, 1997; Reapproval November 3, 1999
Objective
To recover, quantitate and evaluate rodent, insect, and other light filth elements in wheat-soy blends.
Apparatus
1. No. 230 sieve. See Method 28-01.01, paragraph 8.
2. Separatory funnel. See Method 28-01.01, paragraph 9.
3. Filtration funnel. See Method 28-01.01, paragraph 4.
4. Beaker, 1-liter.
5. Magnetic stirrer.
6. Probes.
7. Stir bar and retriever.
8. Wash bottle.
9. Glass stir rod.
10. Wide-mouth funnel, glass or stainless steel.
11. Petri dishes.
12. Filter paper, S&S no. 8, ruled.
13. Wide-field stereoscopic microscope.
Reagents
1. Isopropyl alcohol.
2. HCl, 5% in water.
3. Mineral oil. See Method 28-02.01, paragraph 13.
4. Detergent.
5. Glycerin-alcohol (50:50).
Procedure
Defatting
1. Weigh 50 g onto U.S. no. 230 sieve and rinse on sieve with isopropyl alcohol to defat, using 500-ml portions (under hood), and discard rinsings.
2. Let stand under hood, after extraction, until alcohol has evaporated.
3. Rinse sample, on sieve, continuously with hot tap water to remove starchy
material. Rinse until effluent is clear.
Digestion and separation
1. Transfer residue on sieve to 1-liter beaker and rinse sieve with 5% HCl,
adding rinsings to same beaker.
2. Bring volume of HCl to about 600 ml, and add 50 ml light mineral oil.
http://dx.doi.org/10.1094/AACCIntMethod-28-40.01
©AACC International, Inc.
Extraneous Matter
AACC International Method
28-40.01
Page 2 of 2
Acid Hydrolysis Method for Insect Fragments and Rodent
Hairs—Wheat-Soy Blend (continued)
3. Stir vigorously 5 min, or add stir bar for 5 min, operating fast enough to
form vortex, without splashing.
4. Lift stir bar, rinse bar and retriever with hot tap water, allowing rinsing to
flow into beaker.
5. Transfer beaker contents to funnel or percolator. Rinse beaker with hot
water, adding rinsing to funnel or percolator. Retain beaker.
6. Fill funnel or percolator with hot water to within 1 in. of top.
7. Allow to set 30 min, stirring several times with glass rod during first 10
min.
8. After 30 min, drain off water layer, retaining about 1 in. water and oil
phase in funnel or percolator, and discard.
9. With wash bottle, rinse sides of funnel or percolator with hot water.
10. Refill to halfway with cool water. Let stand 10 min.
11. Repeat draining and filling twice, only if necessary.
12. Place retained beaker under funnel or percolator and drain contents into
beaker.
13. Wash sides of funnel or percolator and allow to drain into beaker.
14. Transfer contents onto ruled filter paper with suction funnel.
15. Rinse beaker with hot water and add to same filter paper.
16. Add enough glycerin-alcohol solution to wet paper without floating residue. Examine paper microscopically. See Method 28-03.02, Microscopic
examination of filter paper.
17. Report each hair or hair fragment by type, if known, and length in mm.
18. Report insect fragments in number and type, if known.
19. List whole insects, equivalents (heads), and cast skins by number and
type.
20. List aphids, thrips, and mites separately.
Note
Refer to Method 28-03.02 for special techniques, such as filtration.
Reference
U.S. Department of Agriculture. Method developed by E. L. Tucker. USDA, FGIS, Beltsville, MD.
©AACC International, Inc.