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MPM: VI. Applications of Macroanalytical Methods to Field Testing and Factory Sampling

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Macroscopic methods may be adapted by agency inspectors as field tests for examination of imported raw agricultural products on the wharf or for examination of semi-finished foods packed in bulk. Similarly, macroscopic procedures may be adapted by industry personnel for examination of raw food materials and in-process foods during factory inspection. This chapter introduces the concept of applying macroscopic methods to field testing and to factory sampling. An outline of wharf examination considerations is presented, followed by a description of three macroscopic field tests which have been adapted from the relevant methods contained in Chapter V. At the conclusion of this chapter is a brief discussion of factory sampling. The chapter is organized as follows:

  1. Introduction
  2. Wharf Examination
  3. Field Applications of Macroscopic Methods
    • Whole bag screening
    • Wheat carload sampling and field examination
    • Wharf examination of coffee for macroscopic filth
  4. Application of Macroanalytical Methods to Factory Samples

(1) Introduction (VI-1)

Where appropriate, it is advisable that the field test for a particular food follow as closely as practical the macroscopic method that would be used in the laboratory for that product. For example, if a field examination is made of dried fruit during an inspection of a processing operation, the visual classification of rejects described in Chapter V, Section 9.F., should be utilized. Field tests are an inexpensive and time-saving approach for obtaining analytical findings that may be adequate for evaluation of a lot.

In a number of instances, macroscopic field tests are coordinated with sampling plans and analytical procedures designed for laboratory analyses. Analytical findings obtained by field inspection and examination of subsamples from the lot on location, supplemented by further laboratory examination of subsamples from the lot, provide a comprehensive characterization of a lot. A combined effort of this kind may be desirable in situations such as evaluation of a reconditioned lot.

(2) Wharf Examination (VI-1)

Wharf examination is an important means of applying macroscopic field tests. The Inspection Operations Manual (IOM 465) defines a "Wharf Examination" as

"The examination of a product in import status sufficient in scope to determine that the product appears to be in compliance for the attributes for which the lot was examined. A Wharf Examination may be conducted on products discharged from vessels onto the wharves (piers), pier sheds, and other locations; products in trucks, trains, etc., at border entry points; or on products set aside for FDA examination."

A wharf examination is the most in-depth examination of a product short of collecting a sample for analysis at the laboratory. A complete wharf examination involves the actual physical examination of the product and an expression of the findings of this examination. The result of the wharf examination may be a finding that the product appears to be in compliance for the attributes for which it is examined or that a sample of the product should be collected for further analysis at the laboratory. Wharf examinations can be carried out only for certain combinations of product commodities and problems. These are limited by the container, the attribute, and the product.

Since wharf examinations may be based on smaller sample sizes than macroscopic laboratory examinations, the statistical confidence limits for the results of the examination are narrower than those provided by the laboratory sampling plan. To compensate for this, a more stringent "level of acceptance" is applied in determining whether to sample for further laboratory analysis.

(3) Field Applications of Macroanalytical Methods (VI-2)

In order to be useful as field tests, the macroanalytical procedures described in this manual require varying degrees of adaption. To illustrate adaption of these methods, this section describes three field tests which are based on macroscopic methods.

  1. Whole-Bag Screening

    Shelled peanuts, dried beans, and similar free-flowing solid products packed in large containers (such as 50-125 lb bags) may be examined on location by screening the entire contents of the container. This screening will allow the field inspector to detect contamination of the product due to defects such as live or dead insects, rodent excreta pellets, or other obvious filth. Portable folding whole-bag screening apparatus is available for this purpose  see Chapter V, Section 10.B.(6)â. Make the examination in a well-lighted area. Set up the screen at a convenient height so that the product can be poured directly onto the high side of the screen. Place a bag or container on the screen's low side to catch the screened product.

    Place a sheet of clean paper (butcher paper works well) in the screen body to catch screenings and insert screen wire over the paper.

    Open stitches of the bag being examined just enough to permit a portion of approximately 10-20 lb. at a time to enter onto the high side of screen. Gradually work the product across the screen to the low side and into the receiving container. Do not push large quantities rapidly across the screen, because insects, eggs, stones, excreta pellets, etc., will be carried along with the product and will not sift through the openings. Practice developing a bouncing technique to effectively screen out filth, while quickly passing the product across the screen.

    Briefly examine the screenings from each bag macroscopically. Subjectively report findings as to live or dead insects, rodent excreta pellets, or other obvious filth for each unit container size (subsample) examined. Submit screenings as separate subsamples for further laboratory analysis if actionable.

  2. Wheat Carload Sampling and Field Examination

    In some instances, it may be appropriate to examine wheat directly from the rail car or truck. The following procedure for wheat carload sampling has been adapted from the IOM, Chart 4.

    1. (i) Equipment -- Inspectors should have the following items on hand before beginning the examination:

      • Double tube compartment trier, 60 in. long
      • Sampling cloth at least 60 in. long
      • 1,000 mL graduated cylinder (plastic preferred)
      • Paper bags or other suitable containers capable of holding more than 1 quart of sample (do not use canvas bags)
      • Fumigant (chloroform preferred)
      • Absorbent cotton or equivalent
      • FDA metal car seals for resealing rail cars
      • Aluminum ladder (optional)
      • Block and tackle to open car door
    2. (ii) Drawing sample -- The principal sources of samples are gra in shipments in railroad cars and trucks. Draw 5 probes (in duplicate) for each sample taken as described below. However, if the sample is to be examined in the field, an initial sample of 5 probes drawn as indicated below will be sufficient. Collect probe samples from railcars and trucks as follows:

      • Probe #1 -- from the center of the car
      • Probe #2 -- from 3 to 5 feet back from the door post toward the end of the car and approximately 2 feet in from one side of the car
      • Probe #3 -- from 3 to 5 feet from the same end of the car, but approximately 2 feet from the opposite side as in probe #2
      • Probe #4 and 5 the same as from probe numbers 2 and 3, but from the opposite ends and sides of the car

      Figure VI-1 illustrates the approximate location of the sampling points for two different sampling plans.

      Figure VI-1


      Insert the trier in the grain at an angle of about 10 from the vertical, with slot up and closed. Open slots, and give trier 2 or 3 short up-and-down motions, so that all openings will fill. Close slots, withdraw trier, and empty it carefully over sampling cloth.

    4. (iii) Field examination -- Examine each pocket of the probe separately. Look for evidence of pink wheat, rodent pellets, insect damage, and uneven loading or plugging  see (vi) belowâ. Note any insect infestation and record types of insects and whether dead or alive. Count and record for each probe the number of rodent pellets or rodent pellet fragments  follow procedure in (v) belowâ. Count as pellets any that are large enough to be readily identified by size, shape, surface coating, and/or presence of rodent hairs. Report the number of rodent pellets per probe. Measure the volume of each probe in quarts and calculate the average number of pellets per quart as described in (v) below. Place pellets from each probe in separate vials and submit with each wheat subsample. Place each of the wheat subsamples in a clean, suitable container such as an ice cream carton or, temporarily, in a clean paper bag.

      Do not use canvas bags which might raise the question of sample contamination and do not take glass jars into railcars. If during the sampling operation uneven loading is suspected, take as many additional probings as may be necessary to establish the fact. Draw a profile diagram showing the actual "plugging" pattern. Use the same procedures in sampling truck loads, barge loads, or other lots. Substantially larger loads will require additional probings or larger samples taken from falling grain during loadings or unloading operations.

      Submit all suspect samples to the laboratory for confirmatory analysis.

    5. (iv) Procedure for non-violative samples -- When the field examination shows a sample as non-violative, return the grain to the car, unless the District desires the samples for pesticide examination. Report results under "Remarks" on the Collection Report.
    6. (v) Procedure for violative samples -- When the field examination shows a sample as potentially in violation, use the following guidance to classify the contamination.

      • Rodent Pellet Contamination -- The current guideline for determining whether wheat is violative due to rodent contamination is "9 mg or more rodent excreta pellets and/or fragments of rodent excreta pellets per kg of wheat." Since it is impractical to actually weigh rodent pellets and wheat in the field while sampling, the following approximation can be used in field calculations: Mouse pellets average approximately 8.7 mg each; a kilogram of wheat is about 2.35 pints. Thus, one pellet per quart of wheat or pellet per pint is roughly equal to 9 mg/kg.
      • Where field examination reveals one or more rodent pellets (or where sufficient fragments of rodent pellets exist to be substantially equivalent to one pellet) in a quart of wheat, take duplicate probes to furnish the claimant's portion. Take the duplicate probes from the same locations where the original probes were taken. Place the duplicates in separate containers and identify these to correspond with the original probes.
      • Pink Wheat -- Where evidence of pink wheat or other fungicide treatment is found, collect 15 probe samples. Take 5 probes from each end of the car and 5 probes from the center of the car. Submit the three 5-probe portions separately, using new, clean containers.
      • Insect-Damaged Kernels -- The violative status of these samples should be established by laboratory analysis because of the difficulty of performing an adequate field examination. When any evidence of insect damage is revealed by cursory examination, take duplicate samples and submit for laboratory analysis.
    7. (vi) Procedure for actionable cars -- If field examination reveals an average of one or more rodent pellets per quart, gross evidence of insect-damaged kernels, evidence of plugging, or "pink wheat" contamination, contact the supervisor immediately for advice on embargoing. Also, report any movement of car or other disposition of grain.
    8. (vii) Preparation of sample for laboratory analysis -- If a sample can be delivered to the laboratory promptly and if confirmatory analysis can be handled expeditiously, fumigation of the FDA probes is not necessary. The claimant's portion of the sample, however, must be fumigated. Otherwise fumigate all probes with chloroform. Use about 5 mL per pint of wheat if transferred to glass jars. If in ice cream type containers, use at least 10 mL. Do not put fumigant directly on the grain; saturate a piece of blotting paper or other absorbent material with the fumigant and add to each container. Label to show sample as fumigated. Officially seal all probes. Keep upright so that fumigant vapors will run down through the grain.
    9. (viii) Special reporting -- Provide a detailed description of observations, physical subdivisions reflecting the violative nature of the lot and exhibits corroborating the report of observations.

      Record (in a field diary and subsequently in C/R Remarks, or on C/R continuation sheet, or on Analyst Worksheet FD 431), the results of unit-by-unit examination of the lot. Observations should be specific; avoid generalities. Report the general storage conditions, the violative condition of the lot, the physical relationship of the violative lot to other violative lots in the area, how examination was made, and how many units were examined. Wherever possible, record quantitative observations.

      Report the number and location of live and dead insects, pellets, or other adulteration discovered inside the container, as well as on its exterior surface. Provide graphic measurements of areas of urine or chemical stains on each container and the extent of penetration. Correlate findings of the unit-by-unit examination with any photographs and the physical subdivisions collected.

      Where the field examination is carefully described and documented, the sample collected from obviously violative lots may be reduced to carefully selected exhibits. The field examination and the report of findings will serve as the analysis. In this case, prepare Form FD-431, Analyst Worksheet (see IOM Exhibit 440-A).

  3. Wharf Examination of Coffee for Macroscopic Filth

    Examine a minimum of 6 bags of coffee beans at the wharf, regardless of lot size, following instructions below. If no contamination or minimal defective beans are found, discontinue the examination. However, if a significant number of defective beans or significant contamination is found, continue the examination, using the following wharf examination procedure.

    1. (i) Sample collection -- Sample all suspect lots of imported coffee beans according to the following schedule for both wharf examination and laboratory analysis:
      Lot Size in Bags No Bags to be Sampled
      100 or less 6
      101-200 10
      200-1,000 15
      over 1,000 20

      Sample each bag with a trier, collecting a subsample consisting of pt. of beans from the top and pt. of beans from the bottom of the bag. (The total quantity of beans taken from each bag must be the same, since both wharf and laboratory examinations are to be performed on a composite sample of all beans collected.)

      Shake each sub on a No. 8 sieve nested in a pan. Dump the sifted beans from each sub into a bag of sufficient size to hold all of the subs to be collected from the lot and to permit mixing the composite. Composite the subs. Do not maintain individually.

    2. (ii) Examination for macroscopic filth -- Examine the siftings retained in the pan for macroscopic filth (live and dead whole insects or equivalent, excreta pellets, extraneous material, and sweepings), reporting findings for each sub separately (see IOM 447.13).

      Transfer any macroscopic filth, including all sifted material that may result in detention of the lot, to a second bag and submit to the laboratory for confirmation. If live insect infestation is encountered, be sure to fumigate the filth portion containing the insects and the composite coffee bean sample. Note use of fumigant on CR and FDA 525. The lot will be detained if a live insect infestation is encountered; however, proceed with the defect bean examination since the reconditioning process will depend on these results.

    3. (iii) Defect bean examination -- Thoroughly mix the composite sample of the coffee beans. Take 300 beans at random from the composite. Examine each individual bean visually (or at a 5X magnification) for insect tunneling and mold damage. Count as moldy only those beans with mold on 1/4 or more of the surface. NOTE: Each district office has examples of the various types of reject beans. Become familiar with these before conducting wharf examinations.
    4. (iv) Determination of Findings

      • Accept the lot if 20 or fewer rejects are found. Report wharf examination on a Program Data Sheet (FDA-2123); no Sample Collection Report is necessary. Discard the sample.
      • If 21 or more rejects are detected, submit the composite sample (and any filth portion that was collected) to the laboratory. Return examined beans to the composite. Stop the wharf examination as soon as 21 rejects are detected. Examination of all 300 beans is not necessary once 21 reject beans are found. When a sample is submitted to the laboratory, all wharf examination time is reported under the import sample collection operation and all necessary documents for a sample collected must be completed. 

(4) Application of Macroanalytical Methods to Factory Samples (VI-7)

The macroscopic procedures detailed in Chapter V of this Manual have been developed as part of the regulatory process to ensure that products which move in commercial channels meet FDA standards. However, the procedures can be readily modified and the techniques easily adapted by industry inspectors for examination of factory samples. Both in-line and end-product samples can be examined prior to packaging as part of a company quality assurance program.

Factory samples are routinely collected as specimens of defective material or insanitary conditions. Macroscopic methods should be useful in conducting analytical examinations of such product specimens. Specimens and samples of factory material should be preserved to prevent subsequent decomposition, deterioration, or further growth of any live insects.

The preceding sections of this chapter illustrate how macroscopic methods can be adapted for use as macroscopic field tests. Similarly, the methods contained in Chapter V can be extended and adjusted to factory sampling. Due to widely varying industry products, processing methods and factory conditions, this chapter does not attempt to suggest specific factory sampling applications of macroanalytical methods. Rather, industry quality assurance/quality control personnel are referred to Chapter V with the suggestion that appropriate procedures be adjusted to local problem situations.

* * * * * * * * * * *

The preceding field and wharf examinations are only a few examples of the applicability of macroscopic methods and procedures to inspection and evaluation of commodities on location. Some form of macroscopic examination is conducted in practically every establishment inspection. Many involve selective sampling and subjective evaluation of observations of defects and deficiencies that may occur in the production, storage, and distribution of commodities. Nevertheless, where similar problems occur frequently in certain products, standardized procedures permit better evaluation of compliance with good manufacturing practice.

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