AOAC Official Method 974.32 Light Filth in Shrimp (Canned)
Flotation Method
First Action 1974
Final Action 1988
For shrimp <2.5 cm long, place entire contents of can into 2 L beaker containing magnetic stirring bar. For larger shrimp, skewer on probe, and wash each shrimp with hot (55–70°C) H2O from plastic squeeze bottle over 2 L beaker containing stirring bar. Discard shrimp. Wash can thoroughly, pouring washings into beaker. Bring H2O level in beaker to ca 925 mL with hot tap H2O. Add 25 mL HCl and 50 mL light mineral oil, 945.75C(p) (see 16.1.01). Boil and stir magnetically, 970.66B(c) (see 16.1.02), 3 min. Transfer promptly to percolator, 945.75B(h)(2) (see 16.1.01), which has its rubber hose fitting clamped shut as close to tubulation opening as possible and containing ca 200 mL hot tap H2O. Reserve beaker. Add ca 800 mL
additional hot tapH2O. Let stand 10 min. Drain oil layer to ca 7.5 cm from bottom, using rod to force shrimp tissue through tubulator, if necessary. Remove rod, and wash with hot H2O into reserved beaker. Reserve rod for further washings. Drain percolator to 300 mL mark, let stand 1 min and slowly drain and discard remaining aqueous phase until minimum volume remains. Do not let vortex form, as it may cause loss of oil. Drain oil layer into reserved beaker.
Filter through ruled paper. Wash paper with 55–70°C hot tap H2O. Alternately wash percolator and rod with 5% detergent solution, 945.75C(i) (see 16.1.01), and hot tapH2O. Filter onto the ruled filter paper and examine microscopically.
Reference: JAOAC 57, 691(1974).
