The presentation is officially made by me. Preparation of liquid food sample for analysis SYBSc- Microbiology SIWS College, Wadala Mumbai University

1. PREPARATION OF LIQUID FOOD
SAMPLE FOR ANALYSIS

2. Considerations
FOOD
• Edible materials
• Essential body nutrients
• Required for life and growth, such as proteins, carbohydrates, fats, vitamins,
or minerals.
Moisture content
• Affects the extent of sample heterogeneity.

3. Considerations
Post-mortem or postharvest physiological changes
• Affects the extent of sample heterogeneity.
Enzymatic changes
• Result in appreciable changes of certain food components(CHO & N components).
• Inactivate food enzymes by denaturation in boiling methanol-water or ethanol-water
mixtures
Produce small, discrete primary and secondary samples
• Representative of the entire food material, with minimal error.

4. How does foodstuffs are classified?

5. General classification of food samples according to
their content

6. How much sample for analysis?
To measure
minute quantity
of compound of
interest.
Large
quantity For the macro
analysis of
gross food
components.
To measure
crude fat, crude
protein, crude
fibre, or ash.
Small
quantity

7. Food pretreatment
Removal of extraneous matter
Sample reduction
Determination of moisture content
Removal of co-extractives

8. Food pretreatment
• By filtration or separated by centrifugation.
• Sediment present in liquids such as beer, wine, juice, or cooking oil.
Removal of extraneous matter

9. Food pretreatment
• To obtain smaller subsamples
• Used as a representative analysis of the whole
• Methods include mechanical grinding, mixing, agitating, stirring, macerating,
pulverizing, mortar and pestle, mechanical high-speed beaters or blenders,
etc.
Sample reduction

10. Food pretreatment
• Affect the chemical and physical nature of the foodstuff.
• Important in terms of food quality.
• Affects food freshness, preservation, and resistance to deterioration.
Determination of moisture content

11. Food pretreatment
Removal of co-extractives
Interferences
in sample
extracts
Generation of
emulsions
Contamination or
plugging of
equipment
Masking of the
analytical signal for the
target analyte
Increase in the method
limit of detection
Sample turbidity

12. Food pretreatment
• Removed during a post-extraction clean-up
• Passing the liquid extract through a clean-up column for sorption or
filtration of the interferences.
• Analyte enrichment.
Removal of co-extractives

13. Sample preparation
Step 1
• Sample
dilution
Step 2
• Evaporation
Step 3
• Distillation
Step 4
• Microdialysis
Step 5
• Liquid-Liquid
Extraction(LLE)
or
Lyophilization

14. Techniques for sample preparation
Techniques Advantages Disadvantages
Dilution • Simple
• Cheap
• High throughput
• No cleanup
• No enrichment
Filtration • Simple
• Fast
• No enrichment
• Potential analyte binding
Centrifugation • Simple cleanup
• High throughput
• No enrichment
• Cumbersome
Liquid-Liquid
Extraction (LLE)
• Best non-chromatographic cleanup
• Enrichment
• Cumbersome
• Expensive
• Lots of solvent usage
Solid Phase
Extraction (SPE)
• Best cleanup and fast
• Enrichment
• Easy to automate
• Many sorbents available for cleanup
• May need multiple steps
• Not well understood

15. Liquid-Liquid Extraction(LLE)

16. Solid Phase Extraction(SPE)

17. Membrane techniques
Membrane
techniques
Non-Porous
membrane
technique
Supported Liquid
Membrane
extraction (SLM)
Polymeric
Membrane
Extraction (PME)
Membrane-
Extraction with a
Sorbent Interface
(MESI)
Microporous
Membrane Liquid-
Liquid Extraction
(MMLLE)
Porous membrane
technique
Dialysis

18. END
Reference
 Sampling and sample preparation for food analysis by
Meredith S.S. Curren and Jerry W. King
 Basic food microbiology by George J Banwart
 Wikipedia
 Google image search
 YouTube
 Other sites