Methods and Principles behind some extraction methods. Presented in MPhil Food Engineering Class.

1. EXTRACTION
presented by:
CECILLE ABOAGYE DINAH ADOMAKO EMMANUEL BERKO

2. INTRODUCTION
• Method of removal of a soluble fraction in the form of
a solution from an insoluble medium with the help of
a suitable solvent.
• Process by which a solute is transferred from one
phase to a new phase.
• Removal of soluble constituents from a phase with the
means of suitable solvent.
• Separation can be due to gravitational force or

3. TYPES OF EXTRACTION
• Liquid-Liquid (Solvent extraction)
• Solid-Liquid (Leaching)
• Gas-Liquid (Absorption)

4. LIQUID-LIQUID
• Involves using a liquid solvent to remove a liquid
component from a liquid mixture.
• The component dissolves preferably in the solvent.
(Lewis, 2007)

5. APPLICATION OF LIQUID-LIQUID
EXTRACTION
• Removal of vitamins from aqueous solutions
• Aromatic compounds from crude oil fractions

6. SOLID-LIQUID
• Allows soluble components to be removed from solids
using a solvent.
• Soluble material is dissolved into the solvent and
solvent is evaporated to recover the solute(s) in
powder or crystalline form.
(Lewis, 2007)

7. APPLICATION OF SOLID-LIQUID
EXTRACTION
• Drinkable coffee (solvent with dissolved flavors).
• Obtaining oil from oil seeds
• Leaching of metal salts from ore

8. GAS-LIQUID
• This involves the use of a densified gas (solvent) to
extract a medium from a liquid mixture.
• Heavy volatile compounds often require this process.
• Principle behind extraction is Change in Pressure
and/or Temperature.

9. APPLICATION OF GAS-LIQUID
EXTRACTION
• Solvent used mostly is Carbon dioxide (CO2) and
Extracts are usually Esters, Alcohols etc.
extra
ct

10. CONSIDERING SELECTION OF A
SOLVENT
• Solvent must form a separate phase from the feed
solution.
• Able to extract the solute from the feed solution.
• Chemical reactivity and stability
• Flammability and Toxicity
• Cost analysis of process.

11. FACTORS THAT AFFECT RATE OF
EXTRACTION
Holding time – (depending on the solvent and solute of
interest)
• The longer the holding time, the more solutes are
extracted.
• Takes a shorter time if the solute is easily soluble in
the solvent.
Temperature
• the higher the temperature the faster the rate of

12. FACTORS contd.
Surface area of the solids exposed to the solvent
• the larger the surface area, the faster the rate of
extraction.
• implies reduction of size for solids.
Viscosity of the solvent
• the thicker the solvent, the slower and more difficult
the rate of extraction.
• the solvent would not be able to penetrate into the

13. EQUIPMENT USED
(EXTRACTOR)

14. SINGLE STEP MIXER – (SEPARATOR)
•It is the simplest form of extraction
•Uses the principle of gravitational force.
•Has a High efficiency rate of extraction per
step.
•Requires large amounts of solvent.
• Hence expensive.

15. Solvent

16. MIXER-SETTLER-CASCADE
• This involves a multiple stage separation of liquid
mixtures.
There are two designs:
• Box type – mixing and settling zones are separated by
plates
• Tower type – the single steps are one above the other
so that less ground area is used.

18. CENTRIFUGAL EXTRACTORS
• Heavier phase is transported to the periphery and the
lighter phase to the center.
• Centrifugal force is responsible for the counter current
flow of the phases.
• There’s high throughput, low amounts of solvent
needed.
• High cost of operations.

20. APPLICATION TO COFFEE
EXTRACTION
PRINCIPLES

21. CONCEPT
• Coffee extraction is a solid-liquid type of extraction.
• Solvent used is water.
• Extract of interest are soluble flavors.
• Generally involves the transfer of solutes from a solid
(coffee grains) to a fluid (water).

22. FACTORS CONSIDERED
• Quantity of coffee grains/water used (mass/weight).
• Grind precision (size particles).
• Correct degree of extraction (efficiency).
• Controlled by correct Temperature and Time.

23. SCHEMATIC DIAGRAM OF THE COFFEE
GRAIN
• Øh – volume fraction of
intergranular pore
• (1– Øh) – volume fraction of
grains
• Øc – soluble volume fraction
• Øs,i – insoluble volume
fraction

24. SETUP FOR THE EXTRACTION

25. INTERACTION OF WATER & COFFEE
GRAINS

26. Terms Used
Total Dissolved Solids (TDS)
• TDS is expressed in parts per million (ppm).
Strength
• Also known as "solubles concentration", measured by
Total Dissolved Solids – how concentrated or watery
the coffee is.
Brew ratio
• The ratio of coffee grounds (mass) to water (volume)
• how much coffee is used for a given quantity of water.

27. EQUATION INVOLVED
Extraction yield (%)
• The percentage by mass of coffee grounds that ends
up dissolved in the brewed coffee.
Extraction yield % =
Brewed Coffee[g] x TDS[%]
Coffee Grounds[g]
NB: TDS (mg/L) = 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑟𝑒𝑠𝑖𝑑𝑢𝑒(𝑚𝑔) ×1000
𝑚𝑙 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒

28. EXAMPLE
• 18 grams of coffee was placed in an espresso and this
brewed 36 grams of coffee from it. It is observed that 10%
of solids are dissolved from the grounds. Calculate the
extraction yield of this coffee grounds.
Assumption: 1 milliliter (ml) of water = 1 gram of water
• 𝐸𝑥𝑡𝑟𝑎𝑐𝑡𝑖𝑜𝑛 𝑦𝑖𝑒𝑙𝑑 = 36𝑔 𝑏𝑟𝑒𝑤𝑒𝑑 𝑐𝑜𝑓𝑓𝑒𝑒 × 10% 𝑇𝐷𝑆
18𝑔 (𝑐𝑜𝑓𝑓𝑒𝑒 𝑔𝑟𝑜𝑢𝑛𝑑𝑠)
= 20%

29. CONCLUSION
• Substance distribution between two liquids determines
its potential to be extracted.
• Extraction generally involves separation of elements.
• Solutes can be obtained by concentrating impurities.
• Solutes can form part of the solvent as a desired
solution.

30. REFERENCES
• Lewis, R. J. (2007). Liquid-Liquid Extraction. PreLab,
73–92.
https://doi.org/10.1002/9780470114735.hawley098
99
• Gamse, T. (n.d). Extraction. Department of chemical
engineering and environmental technology, Graz
university of technology.
• http://www.cst.ur.ac.rw/library/Food%20Science%20b
ooks/batch1/Food%20Processing%20Technology%20Pr

31. Thank
you