The document outlines various sampling techniques in food analysis, emphasizing their importance for food safety and quality. Key methods include random, systematic, stratified, and composite sampling, each with its specific applications and advantages. Additionally, it covers microbiological analysis techniques for natural and drinking water, highlighting proper sample collection and analysis procedures.

2. TOPIC:TYPES OF SAMPLING TECHNIQUES
IN FOOD ANALYSIS
Presented by KUMI ATEMENA MICHELLE
MOLUH YOUGKEH ROSELYN

3. INTRODUCTION
• Sampling techniques in food microbiology are critical for ensuring
food safety and quality.
• Below are the main types of sampling techniques useed in food
microbiology laboratories, along with detailed descriptions of each :

4. • Random Sampling: Samples are taken randomly from a lot or batch to
avoid bias. This sampling technique is useful for general quality
assessment; ensuring every unit has an equal chance of being selected.
• Systematic Sampling: Here samples are taken at regular intervals from
a population. After determining the interval samples are are taken
consistently at these intervals It is effective for large batches where
random sampling may miss certain areas and are easy to implement
providing a structured approach.

5. • Stratified Sampling: The population is divided subgroups (stata), based
on specic characteristicsand samples are taken from each stratum.
Here the strata is defined based on relevant factors, then randomly or
systematically select samples within each sternum. This method
ensures that various segments of the population are represented.
• Composite sampling: Multiple small samples are taken from different
locations or times within the same batch and combined to form a
single ‘composite’ sample. Samples are taken

6. • here from different locations or points in time and thoroughly mixed
to create a single composite sample. It is useful for getting an overall
picture of the microbial load across a whole batch rather than
individuals.
• Judgmental (Selective) Sampling:The sampling is based on the
judgment of the investigator, often focusing on areas that are more
likely to contain contaminants or specific areas of interest. Here a
trained investigator selects samples from spots known to have a higher
risk of contamination.

7. • Convenience sampling: This is based on ease of access to certain samples
rather than scientific rigor. While it may introduce bias, it can be pactical in
certain scenarios.
• Grab sampling: A single sample is taken from a specific point in time and
location. Its useful for assessing the condition of a batch at a particular
moment.
• Swab sampling: This method uses swabs to collect microorganisms from
surface in the laboratory, food processing environment, or on food products
directly.

8. • Surface rinse sampling: A solution is used to rinse a food product or
surface to recover microorganisms.
• Air sampling : Used to assess the microbial quality of air in the
laboratory or food-processing environment important for ensuring
sterile conditions.

9. • Environmental sampling: Samples surfaces, air, and water from food
processing environments to monitor microbial presence. It helps
identifies contamination sources and supports hygiene monitoring. It is
used in routine checks in food processing plants for compliance with
hygiene standards.
• Test portion sampling: Here, we analyze a portion of a larger food item
or batch. It is practical for large items (like whole fish or large cuts of
meat). It is used in testing large cuts of meat or whole fruit
contaminants).

10. MICROBIOLOGICAL TECHNIQUE USED FOR NATURAL WATER AND WATER USED FOR HUMAN
CONSUMPTION, METHOD OF SAMPLE COLLECTION AND ANALYSIS.
• The microbiological analysis of natural water and water used for human consumption is essential for
assessing water quality and ensuring public health. Various techniques are employed to detect and quantify
microorganisms in water samples. Here’s an overview of the methods for sample collection and analysis:
• Microbiological Techniques for Water Analysi
• 1. Sampling Methods
• A. Sample Collection for Natural Water (e.g., rivers, lakes, ponds)
• - Equipment : Use sterile containers (usually 1-liter polyethylene or glass bottles) with screw caps and, if
necessary, a sterile dipper for surface water collection.
• - Procedure :
• - Rinse the sterile container with the water to be sampled at least three times to reduce contamination from
the container.

11. • Collect the sample from mid-water (not from the surface or bottom) to avoid contamination.
• - Fill the container, leaving some air space at the top (approximately 1-2 cm).
• - Seal the container immediately and label it with the date, time, location, and sampler's name.
• - Transport the sample to the laboratory as soon as possible, preferably within 6 hours, and keep it cool
(4°C) during transport.

12. • Sample Collection for Drinking Water (e.g., tap water, bottled water)
• - Equipment :Use sterile collection bottles as mentioned above. For tap water, a clean faucet is required.
• - Procedure :
• - Allow the tap to run for a few minutes to flush out stagnant water in the pipes.
• - Collect the sample directly from the tap without allowing the bottle to touch the faucet.
• - Fill the container to the indicated mark, leaving the appropriate air space.
• - Seal and label the bottle immediately.
• - Transport as described above, keeping the sample cool.
•

13. • . Analysis Methods
• A. Membrane Filtration Technique
• - Purpose : Used for analyzing water samples with low microbial counts (e.g., natural water or treated
drinking water).
• - Procedure :
• - Filter a known volume of water (usually 100 mL) through a sterile membrane filter (0.45 µm pore size).
• - Place the filter on a selective agar medium (e.g., MacConkey agar for coliforms, or m-Endo agar for E.
coli).
• - Incubate the plates at appropriate temperatures (e.g., 35-37°C for 24 hours).
• - Count the colonies formed on the filter and calculate the conc