Agriculture Reference
In-Depth Information
gelling agents, to improve the texture of the gelled product, for example, in an
ambient stable table jelly where the aim is to match the texture of a gelatin jelly.
An unusual property is the ability to form fl uid gels - smooth pourable structured
liquids that exhibit weak gel structure and can suspend particles in beverages.
8.3 Natural hydrocolloids: their manufacture, properties
and applications
Many of the hydrocolloids widely used in the food industry are extracted from
plants, including their seeds, fruit, tubers and even tree sap. One downside is that
many of these hydrocolloids suffer from variable supply, leading to signifi cant
variations in price over the years.
8.3.1 Locust bean gum
Collectively called galactomannans, the three main seed gums are guar, locust
bean and tara.
Locust bean gum is produced from the seed of the locust bean tree (carob tree),
Ceratonia siliqua
, which grows in countries bordering the Mediterranean,
especially Spain, Portugal, Morocco, Algeria, Cyprus and Crete. The locust bean
tree is very drought resistant, but slow growing, not bearing fruit in commercial
quantities until about 15 years old. The tree produces pods, each containing up to
ten hard, brown uniform seeds - the locust 'beans'.
The seeds are separated from the pods using a process known as 'kibbling'.
The pods are broken between two rollers and the seeds separated from the rest of
the pods using special screens. The hull is removed using acid and heat (chemical
peeling), or heat and mechanical abrasion. These processes also facilitate the
separation of the germ from the endosperm. The endosperm is then ground and
graded by particle size and viscosity, and sold as locust bean gum. Production of
locust bean gum is pretty stable, though there have been years (e.g. 2003-2004)
when poorer crops have lead to signifi cant price increases.
Locust bean gum (LBG) has been known since Biblical times and a paste of
carob was used by the ancient Egyptians in the binding of mummies. It is therefore
considered to have good credentials as a natural hydrocolloid. As the terms
'natural' and 'clean label' become more scrutinised, the method of production of
locust bean gum may become more signifi cant, as the chemical peeling process
does not meet with many interpretations of these terms. It has also been rumoured
that the name makes this gum unpopular with some consumers, as they believe
that it comes from the insects called locusts. LBG is non-digestible and may be
classed as a soluble fi bre.
LBG is a non-ionic galactomannan consisting of
D
-mannose units joined by
1,4-linkages to form long straight chains. Galactose units are attached to mannose
units by 1,6-glycosidic linkages. LBG has an average ratio of 1:4 galactose to
mannose units, with the galactose units attached in blocks (Fig. 8.1) known as
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