To get the nutritional data for a range of food, samples are analysed as shown below. The market share of consumption of that group of foods such as fruit and vegetables in the UK is taken.
From the surveys done between 1982 and 1990, the results of 2013 were very similar but new types of fruit and vegetables have been introduced.
This is how the main nutrients are analysed:
Protein – Leco instrument and Dumas procedure.
The sample is combusted in oxygen, and the nitrogen is measured. Protein can be worked out with a special formula.
Fat –The sample is hydrolysed in hydrochloric acid and fat is extracted and measured.
Extracted with water and chromatographically separated and then calibrated.
Dietary fibre – 2 methods for different types of fibre
The sample is defatted then gelatinised and treated with an enzyme to remove starch and protein. The dietary fibre is dried and weighed.
Englyst NSP Non starch polysaccharides
Englyst Fibrezym kit is used with colorimetric end point.