The mechanical properties of short-dough biscuits of various composition we
re determined in three-point bending tests. The temperature during dough pr
eparation and the dough water content affected the air volume fraction and
the mechanical properties to an extent which depended on the fat content. T
hese results suggest that the air volume fraction of the biscuits is likely
to be related to the rheological properties of the doughs. The temperature
at which measurements were made affected the mechanical properties of the
biscuits, especially at higher fat contents. The diffusion of Sudan III int
o the biscuits also depended on the fat content. The mechanical properties
were markedly influenced by water content; as a result of the plasticising
effect of water, the matrix underwent a glass transition. The effect of sug
ar type on mechanical properties depended on the type of biscuit. Iris conc
luded that low-fat biscuits are fat-dispersed systems and that high-fat bis
cuits are bicontinuous. Whether biscuits are in a glassy or rubbery state c
annot be predicted from their water contents in relation to the state diagr
ams of either gluten or sucrose. (C) 1999 Academic Press.