Moisture (DOC)

							Moisture

Measured by weight difference after drying at 103ºC. For high sugar products
the sample is dried under reduced temperature and pressure. Usually
moisture is the largest single component of a food sample and can vary
significantly within a product and between products.

Ash

Sample is heated in a furnace at 530ºC after which only minerals remain.
Salt is contained in ash so ash cannot be less than salt content

Fat

Laboratory fat analysis is usually based on extraction of the fat with a solvent.
The solvent is evaporated and the extracted fat is weighed. Total fat methods
include a hydrolysis step to free any fat bound to proteins or carbohydrates.
Fatty acid profiles are produced by separating the component fatty acids
using gas chromatography.

Protein

Protein in food is determined by analysis of the nitrogen in the sample and
applying an approved factor to calculate protein. The two main methods used
are the Kjeldahl method and the Dumas method.
Protein = Nitrogen x 6.25

Salt & Sodium

Salt is Sodium chloride (NaCl). Routine salt analysis measures the chloride
content of the food. The Mohr method requires the sample to be ashed and
the chloride titrated. The Volhard method titrates the food sample directly.
Measuring chloride causes problems with low salt products as potassium
chloride is used as a replacement. Sodium is determined by ashing the
sample, dissolving in dilute acid and measuring the sodium directly using
Atomic Absorption Spectroscopy

Carbohydrate

A group of food components which include sugars, starches, and fibre and is
usually calculated by difference. The assumption is that food consists of fat,
protein, ash, water and carbohydrate so if you subtract the measured
parameters from 100, what is left is carbohydrate. Errors associated with
carbohydrate by difference are high due to the summation of errors
associated with the other analytes. For some products the measured sugar
result may be higher than the carbohydrate by difference. Total carbohydrate
includes all sources of carbohydrate including fibre. Available carbohydrate
excludes fibre.
“Low carbohydrate” samples can be problematical.
Sugar

The most common sugars found in food are Glucose, Galactose, Fructose,
Sucrose, Lactose and Maltose. Sugars are usually determined by extraction
into water and separation and quantisation using chromatography. Total sugar
is the sum of each of the previously mentioned sugars. Some sugars can
rapidly be consumed by micro-organisms once the sample is homogenised.

Fibre

The definition of fibre has been debated for many years. A basic definition
would be carbohydrates that cannot be digested and thus provide energy for
the body. Methods for fibre analysis involve the removal of fat and sugar,
drying and enzyme digestion to remove protein and starch. What is left is
fibre! Until recently the Englyst fibre method was required for food labelling.
An EU decision has changed this to an AOAC fibre method. Both have very
high sources of error and both are arbitrary. AOAC results are usually higher
than Englyst.

Energy

Energy is calculated by using known factors for the energy in fat, protein and
carbohydrate. Energy values on labelling are expressed in two different units
kJ (kilo Joules) kcal (kilo calories) expressed per 100g of product. Labelling
energy should be based on full nutritional data as this will provide available
carbohydrate – fibre has zero energy.