Quantitation of fat
are certain chemical parameters used for the characterization of fats:
value (or “neutralization number” or “acid number”) is the number of milligram
of potassium hydroxide (KOH) that is required to neutralize one gram of fat.
Thus, acid number is an indication of the quantity of free fatty acid present
in the fat. The fat which has been processed and stored properly has a very low
saponification number is the milligrams of KOH required to saponify 1 g of fat.
Thus it provides the information about the average chain length of the fatty
acids in the fat. The saponification number varies inversely with the chain
length of the fatty acid.The shorter the average chain length of the fatty
acid, the higher is the saponification number.
number is expressed as the number of grams of iodine absorbed by 100 g of fat.
Not only iodine, but other halogens will also bind at double bonds. Hence
bromine is often used instead of iodine because it is more reactive. The iodine
number is a measure of the degree of unsaturation of the fatty acid in the fat.
iodine numbers of linseed oil (PUFA), olive oil (MUFA), and coconut oil
(saturated fatty acid) are approximately 175–201, 77–91, and 8–9.5,
Polenske value indicates the level of volatile fatty acid in the fat. It is
equal to the number of milliliters of 0.1N alkali (KOH) solution necessary to
neutralize the water insoluble fatty acids. The value is named after the
chemist who developed it, Eduard Polenske.
Reichert value (Reichert-Meissl-Wollny number) measures the quantity of short
chain fatty acid in the fat molecule. It is the number of milliliters of 0.1 N
KOH solution necessary to neutralize the soluble, volatile fatty acids derived
from 5 g of fat. The value is named after the chemists who developed it, Emil
Reichert and EmerichMeissl.
number is the measure of the free hydroxyl groups in a substance (as a fat or
oil). It is the number of milligrams of potassium hydroxide required for
neutralization of the acetic acid formed by the saponification of 1gm of fat
after it has been acetylated.