Introduction to Fixed oils and Fats
Session 34: Introduction to Fixed oils and Fats
Total Session Time: 120 minutes
Prerequisites
Learning Tasks
By the end of this session students are expected to be able to:
Resources Needed:
SESSION OVERVIEW
|Step |Time |Activity/ |Content |
| | |Method | |
|1 |5 minutes |Presentation |Introduction, Learning Tasks |
|2 |25 minutes |Presentation |Distribution and Characteristics |
| | |Brainstorming |of Fixed Oils and Fats |
|3 |25 minutes |Presentation |Extraction of Fixed Oils and Fats |
|4 |30 minutes |Presentation |Evaluation of Fixed Oils and Fats |
|5 | |Small group |Uses of Fixed Oils and Fats |
| |25 minutes |discussion | |
| | |Presentation | |
|6 |5 minutes |Presentation |Key Points |
|7 |5 minutes |Presentation |Evaluation |
SESSION CONTENTS
STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)
READ or ASK students to read the learning tasks and clarify
ASK students if they have any questions before continuing.
STEP 2: Distribution and Characteristics of Fixed Oils and Fats (25
minutes)
o Fixed oils and fats are lipids (esters) of long chain fatty acids and
alcohol
o Fixed oils and fats are widely distributed and occur in both vegetative
and reproductive structures
o They are found often in seeds, where they may replace the carbohydrate
as reserve food material
o They are also associated with protein reserves
o As lipids, fats form an essential component of biological membranes
o Fixed oils occur in plant materials as small highly refractive drops
o Oil globules associated with aleurone grains can be well seen in
cotyledons of linseed and colocynth, and in the endosperm of nux vomica
o Fixed oils and fats are soluble in ether-alcohol, few exceptions such
as castor oil are sparingly soluble in alcohol
o At ordinary temperature fats are semisolid/ solid and fixed oils are
liquid at normal temperature
o Most vegetable oils are liquid at ordinary temperature but animal fats
are solid
o There are exceptions, e.g. coconut oil, in temperate temperature is
solid and tropic temperature it is liquid oil
o They are esters of long chain fatty acids and alcohols or closely
related derivatives of alcohols
o The fatty acids forming the oils can be saturated or unsaturated
o Most animal products contain saturated fatty acids while most plant
products contain unsaturated fatty acids
o A special group of unsaturated fatty acids (the ω-3fatty acids) are
vital to human health as they lower cholesterol levels in the body
|Activity: Brainstorming (5 minutes) |
| |
|Ask students to brainstorm on the following question: |
| |
|What are the chemical tests for fixed oils and fats? |
| |
|ALLOW few students to respond? |
| |
|WRITE their responses on the flip chart/ board |
| |
|CLARIFY and SUMMARIZE by using the content below |
Osmic acid
strong solution of ammonia slowly saponifies fixed oils and fats
resulting in observable characteristic soap crystals
STEP 3: Extraction of Fixed Oils and Fats (25 minutes)
depends on the botanical source of the oil
o Decortication –crushing to remove seed coat
o Expression – kernels are placed onto the oil presses and subjected to
pressure with or without application of heat
o Filtration – separates oil from other matters and may be done several
times to attain purity.
o Steaming -at high temperature to inactivate proteins and other
materials e.g. castor oil requires steaming
o Expression (cold or hot)
o Solvent extraction
STEP 4: Evaluation of Fixed Oils and Fats (30 minutes)
o Physical standards include;
o Acid Value
o Saponification Value
o Iodine value
o Ester value
STEP 5: Uses of Fixed Oils and Fats (25 minutes)
|Activity: Small Group Discussion (10 minutes) |
| |
|DIVIDE students into small manageable groups |
| |
|ASK students to discuss on the following question |
|What are the uses of fixed oils and fats? |
| |
|ALLOW students to discuss for 10 minutes |
| |
|ALLOW few groups to present and the rest to add points not mentioned|
| |
| |
|CLARIFY and SUMMARIZE by using the contents below |
STEP 6: Key Points (5 minutes)
liquid at normal temperature
Osmic acid
STEP 7: Evaluation (5 minutes)
References
Trease, G. E., Evans, W. C., & Evans, D. (2009). Trease and Evans
pharmacognosy. London: Saunders.
Joanne Barnes et al (2002), Herbal medicines 3rd Edition: Pharmaceutical
Press
Wallis, T. E. (2005). Textbook of pharmacognosy. New Delhi: CBS.
Robbers, J. E., Speedie, M. K., Tyler, V. E., & Tyler, V. E. (1996).
Pharmacognosy and pharmacobiotechnology. Baltimore: Williams &
Wilkins.
Heinrich, M., Kinghorn, A. D., Maizels, D., Gibbons, S., & Phillipson, J.
Churchill Livingstone/Elsevier.
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