11. Fixed oils (Lipids- corn oils) Flashcards
What are lipids?
“Chemically Lipids can be defined as the esters of long-chains of fatty acids and alcohols”
What are fixed oils?
Fixed oils: Lipids are the ester of long-chain fatty acids & alcohol or of closely related derivatives but in fixed oils fatty acid is unsaturated and liquid at room temperature.
What are some characteristics of fixed oils?
- Also called as natural non-volatile oil.
- Fixed oils do not evaporate at room temperature
- They require some specific techniques for extraction.
- Some type of spot (permanent stain) left after evaporation
- Fixed oils can be easily saponified.
- Esters of higher fatty acids & glycerin are called as fixed oils.
- These are optically inactive.
- Their major source is seeds of the plant.
Give examples of fixed oils?
CASTOR OIL
COTTON SEED OIL
OLIVE OIL
PEANUT OIL
SUNFLOWER OIL
CORN OIL
COCUNUT OIL
ALMOND OIL
LINSEED OIL
MUSTARD OIL
SESAME OIL
SOYA OIL
What is saponification number?
Saponification value or saponification number represents the number of milligrams of potassium hydroxide or sodium hydroxide required to saponify one gram of fat under the conditions specified. It is a measure of the average molecular weight of all the fatty acids present in the sample in form of triglycerides.
What is iodine number?
The iodine value is the mass ofiodineingramsthat is consumed by 100grams of achemical substance.
What is iodine number used for?
Iodine numbers are often used to determine thedegree of unsaturation infats,oils andwaxes.
Infatty acids, unsaturation occurs mainly asdoublebonds which are very reactive towardshalogens, the iodine in this case.
Thus, the higher the iodine value, the more unsaturation are present in the fat.
What are the methods of extraction of oils?
- By expressions
- By solvent
What is the expression method for oil extraction?
Fixed oils are obtained by expression in hydraulic presses. If the expression is carried out in the cold, the oil is known as a “cold-pressed oil.” In contrast, if the expression is carried out in heat, the oil is known as a “hot- pressed oil.”
Why screw-presses are better than hydraulic presses?
Screw presses are normally used to express oils from plant material because they give a better yield than older hydraulic presses. They also operate at higher pressure and continuously (not in batches.
Why are protein rich seeds cooked before extraction?
Before undergoing expression, seeds rich in proteins are cooked at 90ºC frees the oil by bursting the cell structures & coagulates the proteins. A fast drying step normally follows.
What is cold expression?
Oils for medicinal uses are extracted at room temperature. Only a portion of the oil is obtained. Oil is normally less viscous with less odor than with hot expression (better quality). The remaining pressed material may then be ground, heated and pressed to express any remaining oil.
What is hot expression?
The residue left after cold expression is broken down and treated with steam. This causes the remaining oil cells to rupture. Even after hot expression, 10 % of the oil remains in the plant material.
What is extraction by solvent?
This type of method is used only for technical oils (not medicinal oils).
Seeds used: Intact or partially extracted by expression. Solvent: Normally hexane (BP: 65 ºC)
What is the method of extraction by solvent?
Solvent is added to the cleaned, hulled & roughly milled seeds. The organic phase is recovered. (Organic phase: solution containing the oil in the solvent (called miscella) , and also solvent soaked defatted meal).
Oil recovery: 95 – 99%
What is the botanical origin of castor oil?
Ricinus communis
Which is the part used for castor oil?
ripe seed
What is the preparation of castor oil?
Oil is obtained from castor seeds after removing the seed coats and expressed at room temperature with 1-2 tons pressure per square inch till about 30 % oil is obtained.
The oil contains toxic principle RICIN (a toxalbumin) and enzyme Lipase
What % oil is obtained from pressing castor oil?
The yield of the “cold-pressed” oil separated by hydraulic pressure is 60% and represents a light-colored, good grade.
What is iodine number of castor oil?
In castor oilseed, the average range of iodine value is83-93g (12/100g oil)