Hydrocolloid Gums – Their Role and Interactions in Foods - Practical Food Rheology - page 78

Taking a microstructural approach also appreciates the importance
of process impact on hydrocolloid location in the product and therefore
its functionality. Such process steps might include one or more of the
following: temperature changes, pressure changes, different ionic/pH
environments, high/low shear and varying points of addition of the
hydrocolloid in the process. Developments in microscopy techniques
have enabled for the determination of the exact location of hydrocolloids
in food microstructures.
Of the synergistic interactions mentioned in the previous section,
carrageenan-galactomannan interactions are used in milk-based prod-
ucts for thickening and particle stabilisation and as veggie-gel gelatin
replacers. The weak synergistic interaction between xanthan and guar
galactomannan is often used in formulations to maintain the required
viscosity/weak-gel properties, with a reduction in the amount of xan-
than compared to the properties of xanthan at higher usage levels when
used as a single ingredient. With guar being a much cheaper ingredient
than xanthan, this can often be a cost benefit to the manufacturer, with-
out compromising the consumer perception of the product. The firmer
xanthan-LBG gel has recently seen a re-emergence as the gelling agent
in the new jelly bouillons.
Associative phase separation has been used for encapsulation and
delivery vehicles (van Benthum et al ., 2004), in which fat/oil has been
encapsulated for controlled release/digestion. Schmitt (2010) has shown
how coacervate particles can be used as stabilisers in ice cream foams.
Segregative phase separation is the most common occurrence in food
microstructures. An example is ice cream, which typically contains
polysaccharides LBG and kappa carrageenan, mixed with the milk pro-
teins from either whole milk or cream or solutions made with skimmed
milk powder. Schorsch et al . (1999) established a phase diagram for
skimmed milk protein and galactomannan and also identified that the
carrageenan was located in the protein phase. The inclusion of car-
rageenan in the milk thickens and slows down 'wheying off' (bulk sepa-
ration into two layers). The LBG phase gels in the ice cream process and
the small gel particles aid stabilisation of the ice cream microstructure.
An application of the galactomannan-milk protein phase diagram was
in the replacement of sahlep in Maras ice cream, enabling novel texture
control for frozen desserts. The unusual property of Maras ice cream
is its extensibility, which provides stretchy textures at frozen temper-
atures, at which conventional ice cream would fracture. Daniel et al .
(2000) measured the differences in texture by cutting dog-bone shaped
test samples at 25 ◦ C, then loading and tempering the sample before −

14 ◦ C.
The surface activity of some hydrocolloids has been mentioned in
the previous section, due to the hydrophobic patches/stretches on the

extension at −