Chemistry Reference
In-Depth Information
4
Hydrocolloid Gums - Their Role
and Interactions in Foods
Tim Foster and Bettina Wolf
4.1
INTRODUCTION
Hydrocolloid gums are applied in foods mainly for their thickening and
gelling properties. As 'hydrocolloid' implies, these are water-soluble
gums and, therefore, tend to be applied in the water-continuous foods.
Additionally, low-fat spreads with a dispersed aqueous phase structured
and stabilised using hydrocolloids have also been designed. Inclusion of
the hydrocolloid is crucial in certain domains of the product microstruc-
ture to obtain a stable product with acceptable mouthfeel. Typically,
only relatively small amounts of hydrocolloid are required to impart the
desired rheological and/or textural properties of the food. This chapter
introduces fundamentals of rheology relating to the behaviour of hy-
drocolloid gums in solution as well as fundamentals of gel rheology
to cover the two types of actions of hydrocolloids in an aqueous envi-
ronment: thickening and gelling. Then, in Table 4.1 a general overview
of commonly applied hydrocolloids is provided. The majority of this
chapter has been dedicated to presenting the effect of hydrocolloid inter-
actions on the rheological/textural behaviour, followed by a discussion
of systems applied in foods.
4.2
BEHAVIOUR OF HYDROCOLLOID GUMS
IN SOLUTION
Introducing relatively small amounts of hydrocolloid gums into the
aqueous phase of food formulations can lead to a dramatic change in
food texture. The nature of the hydrocolloid gum combined with the
solvent conditions, for example the presence of salt and the temperature
history of the product, will determine whether a 'simple' thickening
effect or gelation has been achieved. The focus of this section is on
