42. 42
4. Ester Number (Ester value)
is the number of mg of KOH required to saponify the esters present in
1 g of the substance.
Ester value = Saponification value - Acidvalue.
43. 43
4. Ester Number (Ester value)
Method:
- Weigh accurately about 2 g of the sample. Add 25ml
of ethanolic KOH
- And boiled under reflux condenser on a water-bath for1hour.
- Add 20ml of water and titrate the excess of alkali with 0.5 M HCl
using a further 0.2ml of phenolphthalein indicator.
- Repeat the operation without sample. (Blank reading)
- The difference between the titrations represents the alkali required to
saponify the esters.
44. 44
4. Ester Number (Ester value)
Significance:
Ester value = Saponification value - Acidvalue.
- The ester value shows the amount alkali consumed in the saponification
of the esters and is possible identify and differentiate the fats with this
value.
45. 45
5. Reichert-Meissl number
Synonym : [Reichert Meissl (RM) value]
It is defined as the ml of 0.1 N KOH required to completely neutralize the
soluble volatile fatty acids distilled from 5 gfat.
- RM number is useful in testing the purity of butter since it contains a good
concentration of volatile fatty acids (butyric acid, caproic acid and caprylic
acid).
- Butter has a RM number in the range 25-30, while it is less than 1 for most
other edible oils. Thus any adulteration of butter can be easily tested by this
sensitive RM number.
46. 46
Is saponified using glycerol-alkali solution & acidified by sulphuric
acid to liberate free fatty acids.
- the liberated fatty acids are steam distilled and the steam volatile fatty
acids are collected (as condensate). The cooled condensate of the
volatile fatty acids is filtered for separation of water soluble and water
insoluble fatty acids.
- The water soluble fatty acids is titrated with alkali to give RMvalue,
- water - insoluble fatty acids is titrated to give the polenskevalue.
5. Reichert-Meissl number
Principle:
47. 47
5. Reichert-Meissl number
Significance:
- It is a measure of water soluble steam volatile fatty acids
chiefly butyric and caproic acids present in oil or fat.
- No other fat contains butyric acid glycerides, and therefore, the
Reichert Meissl value of the butter fat is higher than that for any
other fat.
- These determinations have been used principally for analysis of
butter and margarines.
48. 48
6. Acetyl Number (Acetyl value)
is the number of mg of KOH required to neutralize acetic acid
liberated by the hydrolysis of 1 g of the acetylated substance.
49. 49
Method:
- Boil 10g of sample with 20 ml of acetic anhydride for 2 hr.
- Add 600 ml water and boil for 30 min.
- Separate and wash the acetylated product
- Determine the saponification value of the acetylated substance(b ml).
- Determine the saponification value of the substance(a ml).
6. Acetyl Number (Acetyl value)
50. 50
Significance:
- Is the measure of hydroxy acids in lipids.
- Increased number of acetyl value indicates more amount of free
fatty acids.
6. Acetyl Number (Acetyl value)
