Information on energy and components

Energy
Food energy is calculated from the amounts of protein, fat, available carbohydrates, dietary fiber and alcohol. The energy is expressed in kilojoules (kJ) and kilocalories (kcal). The following conversion factors are used for calculation of energy:                      

Protein
Protein is calculated by multiplying the amount of nitrogen with a nitrogen-to-protein conversion factor, depending on food type.

Fat and fatty acids
Data for total fat and fatty acid groups are given. The fatty acid groups are saturated, cis- monounsaturated, cis-polyunsaturated and trans fatty acids. The sum of these four groups gives the total amount of fatty acids. Polyunsaturated fatty acids are either cis- or trans fatty acids, depending on the nature of the fatty acids (geometric isomerism). Trans fatty acids include both monounsaturated and polyunsaturated fatty acids.

Information is given on three subgroups of cis-polyunsaturated fatty acids; n-6, n-3 and n-3 long fatty acids. cis-Polyunsaturated fatty acids n-3 long, characteristic of seafoods, is a sum of cis-polyunsaturated fatty acids containing 20 or more carbon atoms.  

Since fat is made up from both fatty acids and glycerol, a fatty acid conversion factor is needed, together with results from fatty acid analysis, to calculate the amount of fatty acids from fat. A few fatty acid conversion factors are reported in the table below.  

Cholesterol
Cholesterol is expressed in mg/100g. Most of the values for cholesterol are based on calculations according to Danish research¹. Cholesterol in meat is calculated according to the following equation:

Cholesterol in meat = a * (protein) + (fat)     a = 3.25 (lamb)

                                                                      a = 2.65 (beef)

                                                                       a = 2.65 (pork)

Cholesterol content in milk is closely related to the amount of milk fat. Calculations of cholesterol in milk fat are based on the following:

Milk, low-fat milk                       4 mg cholesterol / g milk fat

Skimmed milk                         11 -

Cheese, cream                        3.3 -

Whole milk powder                 4   -

Skimmed milk powder          25 -

Carbohydrates
Total amount of available carbohydrates is shown together with sugars and added sugar. Sugars include e.g. glucose, fructose, lactose and sucrose. Added sugar is defined as refined or industrially manufactured sucrose used as an ingredient in foods.  

Dietary fibre
Dietary fiber is now used in energy calculations. See information under energy above. Values for dietary fiber depend on the analytical method used. The limited analysis of dietary fiber in Iceland have used the AOAC method.

Fat soluble vitamins
Vitamin A is given as retinolequivalent (RJ) but retinol and β-carotene are given separately. One RJ equals one µg retinol and 12 µg β-carotene.

Vitamin E is given as α-tocopherolequivalent (α-TJ). Only d-α-Tocopherol contributes to vitamin E activity.  

Retinolequivalent  =  Retinol  +  β-carotene/12

1 µg retinol  =  12 µg β-carotene  =  3,33 IU

1 µg cholecalciferol  =  40 IU                      

Values for fat soluble vitamins in dairy products are usually obtained by calculations. Calculations of retinol and β-carotene are based on measurements of Icelandic milk but calculations of vitamins D and E are based on Danish information.¹ Annual averages are used.

Retinol:            9.2 µg/g milk fat

β-carotene:     4.5 µg/g milk fat

D-vitamin:       0.0086 µg/g milk fat

E-vitamin:       0.023 mg/g milk fat

Water soluble vitamins
Total niacin activity is expressed as niacinequivalents calculated as Niacinequivalent  =  Niacin  +  tryptophan/60. Niacin refers to nicotinamide, nicotinic acid and derivatives that exhibit biological activity. The amino acid tryptophan is presented for calculations of niacinequivalents. Tryptophan is about 1% of most food proteins. Following information has been used:

Meat and fish proteins                     1.1% tryptophan

Milk proteins                                      1.4% tryptophan

Egg proteins                                      1.5% tryptophan

Corn proteins                                     0.6% tryptophan

Proteins from other cereals            1.0% tryptophan

Fruits & vegetable proteins             1.0% tryptophan

Proteins of unknown origin             1.0% tryptophan

List of components
Data for the following components are presented on the Matis website. Data for more components are available in the ÍSGEM database.  

References
1.      Anders Møller & Erling Saxholt, 1996. Levnedsmiddeltabeller. 4th edition. Levnedsmiddelstyrelsen. Denmark.