SOP: Determination of Extraneous Material in Dried Fruits
GIFSQ — Global Institute for Food Safety & Quality
1. Principle
Dried fruits are examined for insect infestation, mites, mould, hairs, fibres, sand, soil and other extraneous material; pitted dried fruits are additionally examined for pits and pieces of pit. The examination is visual, aided by lenses and microscopes where needed. Defects are classified by category and reported as percent defectives per analytical unit (and, for pitted fruits, as pits and pieces of pit per 100 units), to judge compliance with Sections 4, 5 and 7 of the Food and Drugs Act.
The method applies to dried fruits for use or sale with no further cleaning or sorting, including but not limited to:
- Apples (Malus sylvestris) — peeled, cored, sliced and artificially dried, frequently treated with sulfur dioxide
- Apricots (Prunus armeniaca L.) — picked when ripe and sun dried or artificially dried; may be blanched with burning sulfur or a bisulfite solution
- Peaches and nectarines (Prunus persica L.) — halved, pitted, usually exposed to sulfur fumes, then sun dried or artificially dried; nectarines are smooth-skinned varieties of peaches
- Pears (Pyrus communis L.) — halved and cored before sulfuring and dehydration by sun or artificial means
- Prunes — dried fruit of certain varieties of the European plum (Prunus domestica L.); current industry practice is heat drying the prunes in dehydrators
2. Apparatus required
- Sharp knife
- Illuminator
- Magnifying lens (3–5×)
- Stereoscopic microscope (10–30×)
- Compound microscope (100×)
- U.S. standard No. 230 sieve
- Shallow pan
3. Sample collection
- A lot is the amount of the food (volume, weight, etc.) 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.
- Scrutinize the lot for live infestation. If live infestation is found, do not sample until after fumigation or other effective treatment.
- Obtain eight sample units selected at random from the lot, each of at least 50 units of dried fruit, using appropriate sampling equipment and containers. Eight sample units constitute a sample.
- Keep each sample unit separate and label them 1, 2, 3, etc. Record complete information on the lot size, the weight of individual containers, the country of origin, the exporter, the importer, and product and lot identification; this information accompanies the sample.
4. Procedure
If appropriate, freeze the samples prior to analysis to minimize the possibility of a live infestation of the laboratory
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Prepare the analytical units: from each of the eight sample units, take 50 units of dried fruit in a random fashion — each 50 units constitutes one analytical unit; repeat for the remaining seven sample units
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Examine for defective dried fruits:
- For unpitted dried fruit, cut each in half lengthwise with a sharp knife and remove the pit
- Examine the outer surface and the pit cavity of each dried fruit using an illuminator and a magnifying lens (3–5×) for insects, mites and their damage, mould and dirt, as classified below. Use the stereoscopic microscope (10–30×) only to confirm questionable areas. Confirm mould filaments by transferring questionable particles to a glass slide and observing with the compound microscope (100×)
- For prunes: place in a shallow pan and cover with water; let soak overnight; drain on the No. 230 sieve and examine the prunes and the sieve retainings
- Repeat the examination for the seven remaining analytical units
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Examine for pits and pieces of pit (for pitted dried fruits only): examine the 400 units of dried fruit for pits and pieces of pit ≥ 2 mm in longest dimension
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Classify each unit of dried fruit into one of the following categories. A unit showing more than one defect is classified only as a multiple defective:
- (a) Insect damaged — units containing insects or their parts, insect tunnels, excreta, eggs or webbing; report the kind and approximate number of insects and parts if present
- (b) Mite infested — units containing sufficient numbers of mites to be seen by examining the sample as a whole, i.e. more than 20 mites per unit of dried fruit; often a dusty, sugary or encrusted appearance with mite bodies on the dried fruit
- (c) Mouldy or sour — units with mouldy or rotten areas ≥ 5 mm in diameter, singly or in aggregate
- (d) Dirty — units showing bird, rodent or other mammalian excrement or excreta ≥ 5 mm in length, singly or in aggregate, or other attached extraneous material such as sticks, stones, dirt clumps, hairs, feathers, fibres, paper, straw, string or plastic
- (e) Multiple defectives — units showing more than one of the above defects
Acceptable dried fruits are units that do not show any of the above defects.
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Calculate and record the percent of each defect category separately for each analytical unit
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For pitted dried fruits only: calculate the number of pits and pieces of pit ≥ 2 mm (longest dimension) per 100 units of dried fruit
5. Calculation
Percent of each defect category, separately for each analytical unit, to the nearest 1%:
- Percent insect damaged (a) = [total number of insect-damaged dried fruits ÷ total number of dried fruits examined] × 100
- Percent mite infested (b) = [total number of mite-infested dried fruits ÷ total number of dried fruits examined] × 100
- Percent mouldy or sour (c) = [total number of mouldy or sour dried fruits ÷ total number of dried fruits examined] × 100
- Percent dirty (d) = [total number of dirty dried fruits ÷ total number of dried fruits examined] × 100
- Percent multiple defectives (e) = [total number of multiple defectives ÷ total number of dried fruits examined] × 100
Combine the percent of each category to obtain the total percent defectives for each separate analytical unit:
Total percent defectives = (a₁ + b₁ + c₁ + d₁ + e₁)% for analytical unit #1
Total percent defectives = (a₂ + b₂ + c₂ + d₂ + e₂)% for analytical unit #2, and so on
Where,
– a = percent of only insect-damaged defectives in the analytical unit
– b = percent of only mite-infested defectives in the analytical unit
– c = percent of only mouldy-or-sour defectives in the analytical unit
– d = percent of only dirty defectives in the analytical unit
– e = percent of multiple defectives in the analytical unit
6. Common insect and mite pests
The method notes that it is not necessary to identify each species of insect found. Most insect species of the orders Hemiptera, Homoptera, Coleoptera, Lepidoptera and Diptera, and those of the mite orders, are pests. Some of the most common are:
- Homoptera: Quadraspidiotus perniciosus (San José scale), Lecanium spp. (lecanium scale), Argyrotaenia velutinana (red-banded leafroller)
- Hemiptera: Lygus lineolaris (tarnished plant bug)
- Lepidoptera: Grapholitha molesta (oriental fruit moth), Cydia pomonella (codling moth), Anarsia lineatella (peach twig borer), Plodia interpunctella (Indianmeal moth)
- Diptera: Rhagoletis pomonella (apple maggot)
- Mites: Eriophyoidae (rust mites), Carpoglyphus lactis (dried fruit mite)
7. Interpretation of results
Judge compliance with Sections 4, 5 and 7 of the Food and Drugs Act using the “Guidelines for the General Cleanliness of Food — An Overview” (Compendium of Analytical Methods, Volume 1), cited by this method.
8. Precautions
- If live infestation is found in the lot, do not sample until after fumigation or other effective treatment.
- If appropriate, freeze the samples prior to analysis to minimize the possibility of a live infestation of the laboratory.
References
Health Canada, Compendium of Analytical Methods, Volume 4 — Laboratory Procedure ExFLP-08, January 2019: “Determination of Extraneous Material in Dried Fruits” (Extraneous Matter and Food Packaging Unit, Greater Toronto Area Laboratory, Canadian Food Inspection Agency; replaces ExFLP-08 dated September 1995).
The method’s own bibliography:
- Pietrzak, E. 2009. Guidelines for the General Cleanliness of Food – An Overview. In: Volume 1. Compendium of Analytical Methods.