When the fatty acids provided by a given weight of food are being calculated, allowance must be made for the fact that the total fat in a food includes triglycerides (of which a proportion is glycerol, i.e. not fatty acid), phospholipids and unsaponifiable components such as sterols.
In foods where the total fat is virtually all triglyceride, a correction factor based on the average chain length of the fatty acids present is adequate. The factors for foods containing appreciable amounts of phospholipids and unsaponifiable matter depend on the class of foodstuff. Suggested values for these factors are given in Table A5.1.
|
Table A5.1 Conversion factors to be applied to total fat to give values for total fatty acids in the fat | |||
|
Food |
Factor |
Food |
Factor |
|
Wheat, barley and rye1 |
|
Beef3 |
|
|
wholegrain |
0.72 |
lean |
0.916 |
|
flour |
0.67 |
fat |
0.953 |
|
bran |
0.82 |
Lamb, take as beef |
|
|
Oats, whole1 |
0.94 |
Pork4 |
|
|
Rice, milled1 |
0.85 |
lean |
0.910 |
|
Milk and milk products |
0.945 |
fat |
0.953 |
|
Eggs2 |
0.83 |
Poultry |
0.945 |
|
Fats and oils, all except coconut |
0.956 |
Brain4 |
0.561 |
|
Coconut oil |
0.942 |
Heart4 |
0.789 |
|
Vegetables and fruits |
0.80 |
Kidney4 |
0.747 |
|
Avocado pears |
0.956 |
Liver4 |
0.741 |
|
Nuts |
0.956 |
Fish5 |
|
|
|
|
fatty |
0.90 |
|
|
|
white |
0.70 |
Sources:
1Weihrauch, Kinsella and Watt (1976).
2Posati, Kinsella and Watt (1975).
3Anderson, Kinsella and Watt (1975).
4Anderson (1976).
5Exler, Kinsella and Watt (1975).
These factors are used as in the following examples:
If 100 g goat milk contains 4.5 g fat, then
4.5 ¥ 0.945 = 4.25 g total fatty acids in 100 g goat milk
When individual fatty acid data are available, the values can be converted from a g/100 g food basis to g/100 g total fatty acid basis. For example, if 100 g goat milk contains 1.15 g palmitic acid, the following equation is applied to calculate palmitic acid in g/100 g total fatty acids:
100/4.25 ¥ 1.15 = 27 g/100 g total fatty acid
When data on fatty acids per 100 g total fatty acids and total fatty acids are available, they can be converted to a g/100 g food basis. For example, if we know that the palmitic acid level in goat milk is 27 g/100 g total fatty acids and the total fatty acid value is 4.25 g/100 g food, the following equation is applied to calculate palmitic acid in g/100 g food:
4.25 ¥ 27/100 = 1.15 g /100 food
Source: Paul and Southgate,1978
