2. SAMPLING DEFINITION
• the action or process of taking samples of something for analysis.
• Or
• Lot: A quantity of food or food units produced and handled under
uniform conditions.
• Sample: A number of food units that resembles the characteristics of
the lot
• A sample is a limited quantity of something which is intended to be
similar to and represent a larger amount of that thing(s). The things
could be countable objects such as individual items available as units
for sale, or a material not countable as individual items.
3. Importance of Sample Collection
• Sample collection is very important to ensure that analytical data is reliable
and to draw a representative sample.
• Activities in Analysis
• 1- Collection of representative sample
• 2- Sample preparation
• 3-Analysis using proper methods & instruments
• Potential sources of variation for above activities to be identified and
minimized or avoided Proper sample size, suitable containers for sampling or
use of appropriate preservatives to prevent spoilage damage before analysis.
4. Precautions during sampling
• 1- The condition of the sample received for examination is of primary importance.
• 2- representative sample is essential when pathogens or toxins are sparsely distributed within the food.
• 3- The number of units that comprise a representative sample from a designated lot of a food product
must be statistically significant.
• 4- The proper statistical sampling procedure, according to whether the food is solid, semisolid, viscous,
or liquid, must be determined by Method analysis at the time of sampling.
• 5- Clean, dry, leak-proof, wide-mouthed and sterile containers of a size suitable for sample of the
product must be used.
• 6- Sample must be submitted in original and in sealed condition.
• 7- Dry or canned foods that are not perishable and are collected at ambient temperatures need not be
refrigerated.
• 8- Collect frozen samples in pre-chilled containers.
• 9- Follow storage norms
5. Sampling plan
• The criteria should be considered in formulating a sampling plan:
• 1- type of food product
• 2-the size of food articles to be sampled
• 3-the degree of hazard to human health
• 4-the potential for fraud
• 5-acceptance and rejection criteria:
• A- adulteration
• B- tolerance limits
• C- compositional standards
• C- net contents
6. Sampling tools and containers
• Samples collected from bulk packages or unpackaged foods sold at retail must be
placed in suitable containers for storage and handling to be presented for laboratory
analysis.
• Sampling tools:
• Common tools such as pliers, spoon, screwdriver and knife are useful for opening
containers, cutting bags of food products.
• Sample containers:
• In general,
• 1- For liquids, the PERSONE Officer should use clean dry containers of appropriate
waterproof and leakproof material including glass, stainless metal, and suitable plastic
material which can be sterilized by heat if necessary
• The containers must have a secure closure of rubber or plastic stoppers or a screw-cap
of metal or plastic coated.
• 2- For solids or semi-solids, should be used clean, dry, wide-mouth, cylindrical
receptacles of suitable water proof.
• 3- For Oil or butter, suitable wide-mouth jars should be used. The butter must not be
allowed to come into contact with the paper or any water or fat-absorbing surface.
7. Sample Collection Techniques:
The Person Officer must obtain the following Information
1. Name of the food
2. Lot number (Number of sample)
3. Container size or sizes
4. Product code numbers
5. Labelling information
6. Condition of the lot, i.e., broken packages, Evidence of rodent or insect
infestation, debris
8. Quantity of Food Samples to be collected for Analysis
Approximate quantity to be supplied
Article of food
500 ml/ 250 ml/250 gm
Milk/Sterilized Milk-UHT Milk/Milk Powder
300 gm/200 gm
Yoghurt/Butter+Butter Oil+Ghee
100 gm
Baking Powder
300 gm
Tomato Sauce/Ketchup/Tomato Paste, Jam/ Jelly/
Marmalade/ Tomato Puree/Vegetable Sauce
6 sealed cans
Canned Foods .
200 gm
Biscuits and Rusks
200 gm
Chocolates
250 gm
Pickles and Chutneys
250 gm
Oilseeds/Nuts/Dry Fruits
200 gm
Sugar Confectionery/Chewing Gum/Bubble Gum
9. Preparation of Samples
• In order to obtain precise analytical results, the laboratory sample must
be made as homogeneous as possible so that, within the limits of
analytical method used, the replicate analyses agree as closely as
possible.
• The purpose of sample preparation is to mix thoroughly a large sample in
the laboratory. This apparently homogenous sample must be then
reduced in size and amount for subsequent analysis.
10. The problems encountered by the analysts in the
preparation of samples for analysis include
1. Preparing representative small samples from large samples
2. Loss of plant material
3. Removal of extraneous material from plants without removal of plant
constituents,
4. Enzymatic changes before and during analysis,
5. Compositional changes or Metal contamination during grinding
6. Changes in unstable components, and Special preparation problems
in analysis of oilseed materials.
11. The sample to be prepared should be first homogenized and the method of
homogenization will depend on the type of food being analyzed.
A number of very efficient electrical mechanical devices are available to reduce
the size of food particles and to mix food products thoroughly.
Mincers, graters, blenders and homogenizers (for dry, moist and wet foods) and
various types of powder mills or grinders are essential equipment in a food
laboratory. Both the nature of food material and the analysis to be performed
must be considered in the selection of instrument for grinding.
Taking samples from one substance to another changes and the way to get
samples is different:-
12. Preparation of dry food samples
• Dry foods needs to be ground to at least coarse powder by means of a
mechanical grinder and then mix thoroughly with a spoon or spatula.
• Bulk samples of dry or powdery foods can be reduced in size by the process
known as quartering
• For this spread the material on the large sheet of glazed paper, glass or clean
surface of laminated bench or table. Draw a cross over the heaped material
Quartering Process
13. • For grinding of dry materials, mechanical methods range from the simple pestle and mortar to
elaborate and effective devices for grinding.
• For fine grinding of dry materials, power-driven hammer mills are widely used.
• Hammer mills are used to grind such materials as cereals, oil meals and most foods, which are
reasonably dry and do not contain excessively high amounts of oil or fat.
• Grinding of oil seeds or oil rich samples present special problems.
• Dried fruits should be passed through chopper three times and mixed thoroughly.
• If needed, initially, grinding can be done by coarse cutting blade.
• During sampling, it is important to keep the chemical, physical and enzymatic degradation of lipids
to a minimum.
Hammer mills
14. Preparation of moist solid foods
• Moist solid foods such as meat products are best homogenized by chopping rather than mincing
• Cheese and chocolates are best grated followed by hand mixing of the, rated material
• For disintegrations of moist materials various fine-slicing devices are available
• Some moist materials are disintegrated best by bowl cutters (leafy vegetables, fleshy tubers and roots) or meat
mincers (fruits, roots and meat products).
• Chilled ball mills can be used to grind frozen materials without preliminary grinding.
• Grinding of frozen foods reduces undesirable chemical changes.
• The commercially available tissue grinders are also used for small sample of soft material For preparation of
sample of fresh fruits and vegetables,
• first of all it is essential to remove adhering soil or sand by washing or wiping with damp cloth. Excessive washing
should be avoided to prevent leaching of soluble solids. Then, separate the fresh tissues into core, outer and
inner tissue depending on the objectives of analysis.
• For large size fruits and vegetable cut these in four/eight equal portions containing inner to outer portion of
fruits or vegetables
15. • Remove the pits from the flesh of stone fruits and then comminute the prepared
material in the blender.
• For canned fruits and vegetables if analysis is to be made on the composite
sample, mix and
• comminute the entire contents.
• But, if analyses are to be made on solid and liquid portions separately, drain the
contents on a sieve and comminute the solid matter or collect the liquid as
required for analysis.
16. Preparation of semi-solid/liquid foods
• Fluid foods are best emulsified by top or bottom driven blenders.
• Fruit juice beverages containing insoluble matter, should be blended
using high-speed blender to get uniform sample
• Pureed products such as tomato puree, ketchup, fruit pulps and
strained fruits and vegetables should be thoroughly shaken before
sampling.
• Gentle warming and mixing easily prepare oils and fats.
• Butter and margarine may be re-emulsified by shaking by hand in a
glass jar after warming to 35°C to melt the fat.
17. PACKING AND SEALING THE SAMPLES
• In order to maintain integrity, packages containing exhibits should be secured or sealed to
prove their authenticity, i.e., to ensure that they could not have been tampered
• The stopper shall first be securely fastened so as to prevent leakage of the contents in transit
• The bottle, jar, or another container shall then be completely wrapped in fairly strong thick
paper. The ends of the paper shall be neatly folded in
• and affixed by means of gum or other adhesive.
• A paper slip of the size that goes round completely from the bottom to top of the container
• bearing the signature of the Designated Officer and code number and phone number and
date or time of the sample
• shall be pasted on the wrapper, the signature or thumb impression of the person from
whom the sample has been taken, shall be affixed in such a manner that the paper slip and
the wrapper both carry a part of this signature or the thumb impression
18. DISPATCH OF SAMPLE
• All samples packaged for dispatch must be secured with shock-
absorbing materials to protect them from damage and route.
• Samples of frozen foods to be sent overnight may be packed in
insulated cartons containing dry ice that will last for that length of time.
• If special precautions in handling or storing samples are needed, the
person Officer should ensure that persons who will be handling the
samples are informed.
