Frequently asked questions
What are the limitations of the data set?
As very few foods have a constant composition, users should be aware that the data does not represent absolute values. The purpose of the database is to present a reflection of the usual composition of foods as available and/or consumed.
Why don't the polyunsaturated, monounsaturated and saturated fatty acids add up to the total fat value?
The classes of fatty acids may not add up to the total lipid value provided in the database because the fat value may include some non-fatty acid material, such as glycerol, phosphate, sugar or sterol. Lipid conversion factors for specific fats define the amount of fatty acid (in grams) per gram of fat. The lipid conversion factors used in the New Zealand Food Composition Database are available on request from Plant & Food Research.
What are the differences of the various energy calculations used in the NZFCD?
In FOODfiles 2014 Version 01, the energy values are calculated in four different ways according to the energy values according to the FAO/INFOODS guidelines (FAO/INFOODS 2012) and Standard 1.2.8 (Food Standards Australia New Zealand 2013). The energy values can be expressed as either kilocalories (kcal) or kilojoules (kJ). The values are calculated from the energy-producing food components (carbohydrate, available; protein; fat, total; and alcohol) with and without dietary fibre and other energy producing food components, using the appropriate energy conversion factors.
The calculations for various energy values are explained below.
Energy based on FAO/INFOODS
Energy, total metabolisable:
Energy, total metabolisable is calculated from the values of energy-producing food components and appropriate conversion factors. The energy-producing food components taken into account are: protein; available carbohydrates by weight; fat, total; and alcohol.
Energy, total metabolisable (including dietary fibre):
Energy, total metabolisable (including dietary fibre) is calculated from the energy-producing food components and appropriate conversion factors. The energy-producing food components taken into account are: protein; available carbohydrates by weight; fat, total; alcohol and fibre, total dietary.
Energy based on FSANZ Standard 1.2.8
Energy, total metabolisable, carbohydrate by difference:
The FSANZ value is calculated according to Standard 1.2.8. The energy-producing food components taken into account are: protein; carbohydrates by difference; fat, total; alcohol, dietary fibre and organic acids.
Energy, total metabolisable, available carbohydrates:
The FSANZ value is calculated according to Standard 1.2.8. The energy-producing food components taken into account are: protein; available carbohydrates; fat, total; alcohol, dietary fibre and organic acids.
How is dietary fibre analysed for the NZFCD?
The NZFCD is now using the Prosky method of analysis for total dietary fibre (AOAC 991.43). The Joint Australia New Zealand Food Standards Code prescribes the Prosky method of analyses for the purpose of food labelling. Prior to 2006, dietary fibre was measured at Plant & Food Research using an in-house modification of the Englyst method (Englyst & Cummings, 1988).
Why is some of the data in the NZFCD different to the information on product labels?
Some manufacturers choose to get their specific product(s) individually analysed for nutrient composition. A Nutrient Information Panel can also be created using a calculation based on the composition of the ingredients and manufacturing processes. The quality of this result will depend on the skill of the person performing the calculation, the source of the data used in the calculation (could be from New Zealand or overseas), and how representative this data are of the actual ingredients in the product. Differences between NZFCD values and the NIP are because the NIP is for an individual product and the NZFCD is generally a composite of similar products.