Water is present in practically every foodstuff. The water content has sign
ificant importance for a number of reasons. The determination of water cont
ent is therefore the most frequent general analysis performed on foodstuffs
. A survey of the most widely used methods is given. They are classified in
to direct and indirect methods. Direct methods aim at the determination of
the water as such. The physical techniques among them are based on a separa
tion of the water. Heating techniques which measure a mass loss under certa
in conditions are principally problematic as they cannot distinguish betwee
n water and other volatile matter. Chemical direct methods are based on a c
hemical reaction of the water molecules. The most important technique is th
e Karl Fischer titration. Indirect methods can either measure a property of
the sample that depends on the water content, or they observe the response
of the water molecules to a physical influence. The latter group comprises
the use of low-resolution nuclear magnetic resonance, near infrared spectr
oscopy and microwave techniques. These extremely rapid methods need a very
product specific calibration against a reference method, because water mole
cules in different bonding situations may behave differently. (C) 2001 Else
vier Science Ltd. All rights reserved.