Published by: POLYSCIENCE PUBLICATIONS, P.O. Box 1606, Station St-Martin, Laval, Quebec, Canada H7V 3P9. TEL.: 1-800-840-5870. FAX: (450) 688-1930.
Government of Canada Gouvernement du Canada
Laboratory Procedure ExFLP-6
April 1995
HEALTH PROTECTION BRANCH OTTAWA
DETERMINATION OF MAGNETIC METAL PARTICLES AND HEAVY FILTH IN MECHANICALLY SEPARATED MEAT
M.-A. Rivers
Research Division, Bureau of Microbial Hazards, Food Directorate, Postal Locator: 2204A2
Health Canada, Ottawa ON K1A 0L2
1. APPLICATION
This method is applicable to the sampling and examination of mechanically separated meat for magnetic metal particles and heavy filth to determine compliance with Sections 4, 5 and 7 of the Food and Drugs Act. This method replaces ExFLB No. 11.
2. DEFINITION OF TERMS
A lot is defined as that amount (volume, weight, etc.) of the food which is produced, stored and/or shipped under conditions as nearly uniform as possible, preferably designated by a common container code or marking, and, in any event, consisting of not more than one variety, grade or type of product from a single identifiable source.
3. COLLECTION OF SAMPLES
3.1 Obtain three sample units of at least 225 g each, selected at random from the lot using appropriate sampling equipment and containers. Three sample units constitute a sample.
3.2 Each sample unit must be kept separate and labelled 1, 2 and 3. Complete information respecting the lot size, weight of individual containers, country of origin, exporter, importer, or domestic manufacturer, and product and lot identification should be recorded and should accompany the sample.
4. MATERIALS AND SPECIAL EQUIPMENT
1) Balance
2) Stirrer hot plate
3) Smooth spin bar magnets, teflon coated (1 x 5 cm recommended) 4) Non-magnetic tweezers
5) Glass beakers (400 mL, 2 L)
6) Rubber policeman attached to a glass or plastic stirring rod
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7) Wash bottles 8) Strong magnet 9) Incubator (50EC)
10) Suction filtration apparatus with Buchner or Hirsch funnel
11) Ruled filter paper. Filter paper should be larger than funnel plate.
12) Ashless filter paper. Filter paper should be larger than funnel plate.
13) Emulsifier (Igepal CO 730; GAF Corp.) 14) 1 N HCl
15) Concentrated HCl 16) Concentrated NH4OH
17) Pepsin (1:10,000 - Difco Laboratories or equivalent) 18) Triton X-114 (Sigma Chemicals)
19) 1% sodium lauryl sulfate solution 20) Alcohol, 95%
21) Petri dishes to suit size of filter paper used
22) Fine, non-magnetic probe (platinum or glass recommended) 23) Glycerol-95% ethanol mixture (1:1)
24) Stereoscopic microscope (10-30x) 25) US standard No. 230 sieve 26) Platinum crucible
27) Muffle oven 28) Desiccator
5. PROCEDURE
The examination shall be carried out in accordance with the following instructions.
5.1 Analytical Units
5.1.1 In a random fashion from a sample unit weigh 225 g. This 225 g constitutes an analytical unit.
5.1.2 Repeat step 5.1.1 for remaining two sample units.
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5.2 Isolation - Magnetic Metal Particles (MMP)
5.2.1 Transfer a 225 g analytical unit to a 2 L beaker.
5.2.2 Add 900 mL warm water (50EC) and 20 mL of an emulsifier (Igepal CO 730).
5.2.3 Wash a magnetic stirring bar (5cm) with 1 N HCl and then with water to remove any magnetic metal particles and place in the beaker.
5.2.4 Stir 5 min on a magnetic stirrer.
5.2.5 Add 20 mL of conc. HCl and stir 1 min. The pH should be in the range of 1.5 to 7. If not, adjust with conc. HCl or conc. NH4OH.
5.2.6 Add 0.5 g of 1:10,000 pepsin and stir 1 min.
5.2.7 Place the meat slurry in a 50EC incubator and allow to digest overnight (18 hrs).
5.2.8 Add 5 mL of Triton X-114 and stir for 10 min.
5.2.9 Remove the magnetic stirring bar with a larger one and grip the first magnetic stirring bar in the centre.
5.2.10 With a strong stream from a wash bottle, wash the metal particles off the stirring bar removed from the slurry, into a 400 mL beaker, first with 1% sodium lauryl sulfate, then with 95% alcohol, and lastly with water. Make sure both ends are washed until no more particles are on the ends of the magnet.
5.2.11 Replace the magnet into the slurry and repeat the 10 min stir and wash 2 more times, collecting the washings in separate beakers.
5.2.12 Filter each washing through separate labelled ruled filter paper using suction filtration apparatus.
5.2.13 Transfer filter papers to petri dishes and moisten with glycerol-ethanol mixture.
5.3 Examination
5.3.1 Examine each filter paper with a stereoscopic microscope at 30x magnification for magnetic metal particles.
5.3.2 Count magnetic metal particles in the size ranges: 0.1-<2.0 mm and $2.0 mm.
5.3.3 For particles <0.1 mm, estimate their numbers on each plate by counting several fields, taking the average and multiplying by the total number of microscopic fields on the filter paper.
5.3.4 To ensure that a questionable particle does not consist of a cluster of particles, touch it with a fine non-magnetic probe. (Particles may: (a) be entire, (b) separate into several smaller ones, and/or (c) break into a fine dust (i.e. particles <0.1 mm).
5.4 Isolation - Heavy Filth (HF)
5.4.1 After the MMP isolation is completed, stir the slurry by hand for 1 min with a rubber policeman and allow to stand undisturbed for 1 h. Decant the slurry into a No. 230 sieve leaving the heavy residue in the beaker. With fingers feel the slurry on the sieve for bone fragments. Record the number and size of bone fragments found.
After checking for bone fragments on the No. 230 sieve discard contents of the sieve.
5.4.2 Fill the beaker with warm water to about the 1 L mark and allow to stand for 10 min.
5.4.3 Decant and discard slurry without disturbing the heavy filth at the bottom. If any meat material remains, refill and let it stand 10 min again and then decant. Do this until no meat material remains at the bottom.
5.4.4 Filter the heavy filth at the bottom of the beaker onto a preweighed oven-dried filter paper. If any fat remains on the paper, wash with hot detergent (1% sodium lauryl sulfate) and then rinse well with water.
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5.4.5 Dry the paper overnight in an oven and then reweigh. Determine weight of heavy filth by difference. Determine if the heavy filth contains any bone fragments by examining microscopically at 30x. If there is an appreciable amount of residue, transfer filter paper with contents to a preweighed platinum crucible, and ash in a muffle oven at 550-600EC for 2 h. Cool material in a desiccator and weigh. Determine ashed weight by difference.
5.5 Recording Results: ExFLP-6
5.5.1 Record the number of magnetic metal particles in the following size ranges: 0.1-<2.0 mm and $2.0 mm.
5.5.2 Record the number of estimated particles <0.1 mm.
5.5.3 Record the amount (mg) of heavy filth.
5.5.4 Record the number and size of bone fragments.
6. INTERPRETATION
6.1 Health Protection Branch considers hard and/or sharp pieces of extraneous material $2 mm a health hazard.
6.2 If there is a question as to the acceptability of the lot, contact Evaluation Division, Bureau of Microbial Hazards, Food Directorate, Health Protection Branch (Phone: (613) 957-0349 or FAX: (613) 952-6400).
