(2) fixed oils & fats

fixed oils & fats

esters of long-chain fatty acid & glycerol

fixed oil

are normally liquid at room temperature and are isolated from plants

fats

are normally solid at room temperature and are isolated from animals

glycerol
trihydric alcohol
long-chains of fatty acid

the structure of fixed oil and fats are

fatty acid

• a hydrocarbon chain with a carboxyl group (COOH)

• it interacts chemically as an acid

water is released

when such acid combines with a hydroxyl group of the glycerol, __

monoglyceride

if only one acid is attached to the backbone

diacylglyceride

if two acids are attached to the backbone, it is a __

triacylglyceride

if three acids are attached to the backbone, it is a __

number of carbons
position of the carbon atoms relative to one another
number of double bonds between carbon atoms

fatty acids differ from one another involve:

saturated fatty acid

• with only a single bond

• C_nH_2nO₂

monounsaturated fatty acid

• has one double bond

• C_nH_2n(2x # of db)O₂

polyunsaturated

more than one double bond

rancidity

most fats and oils with age develop a bad odor and taste leading to __

oxidative rancidity

caused by the oxidation of unsaturated fatty acids at their double bonds

shorter-chained acids
aldehydes
ketones

oxidative rancidity production of __

antioxidants

oxidative rancidity is corrected by the use of __

hydrolytic rancidity

the bad odor and taste are due to the free fatty acids liberated when the fat is hydrolyzed

non-drying oils

• < 100

• more of oleic acid

• coconut oil, peanut oil, olive oil

semi-drying oils

• 100-120

• more of oleic acid and linoleic acid

• corn oil, cottonseed oil, wheat oil, sesame oil, Brazil oil, soybean oil

drying oils

• > 120

• more of linoleic and linolenic acid

• linseed oil, sunflower oil, poppyseed oil

acid value

• acid number / acidity index

• number of milligrams of KOH necessary to neutralize the free acids in 1g of oil, fat, wax, resin, balsam and other similar substances

V x N x 56.11 / wt of sample

acid value formula

saponification value

• Koettsdorfer number

• The number of milligrams of KOH necessary to neutralize the free acids and saponify the esters contained in 1 g of oil, fat, wax, resin, balsam, and other similar substances

(V_bl - V_sa) x N x 56.11 / wt of sample

saponification value formula

iodine value

• Number of grams of iodine absorbed under specified conditions by 100 g of oil, fat, wax, or other similar substances

• Measures the proportion of unsaturated fatty acids present

(V_bl - V_sa) x N x 0.1269 / wt of sample x 100

iodine value formula

3

weight in grams (±) 0.1: __
iodine expected value: <5

1

weight in grams (±) 0.1: __
iodine expected value: 5-20

0.4

weight in grams (±) 0.1: __
iodine expected value: 21-50

0.2

weight in grams (±) 0.1: __
iodine expected value: 51-100

0.13

weight in grams (±) 0.1: __
iodine expected value: 101-150

0.10

weight in grams (±) 0.1: __
iodine expected value: 151-200

ester value

Number of mg of KOH required to saponify the ester in 1g of substances

saponification value - acid value

ester value formula