Agriculture Reference
In-Depth Information
with simple chemical processing but considered natural by some consumers) are
discussed in order to cover the grey areas.
8.2 The main types of hydrocolloids used in foods and
beverages
As seen in Table 8.1, a wide range of hydrocolloids is available for use in the
food industry, each with their own range of functionalities and applications.
Those considered to be natural will be discussed in more detail in Section 8.3
but, for completeness, all the other main hydrocolloids are discussed here to
understand the challenges of replacing those that are not considered natural. Most
hydrocolloids have many food applications, but in this section only the applications
where these hydrocolloids are particularly suited, and therefore diffi cult to replace,
are discussed.
It is worth starting with starch and cellulose, as these are the most abundant
materials in nature. With many different sources of raw material, there are many
different types of starch and cellulose available, each with different functionalities
in food. But man has signifi cantly improved the functionality of starch and cellulose
by modifi cation (physical, chemical and enzymatic). The abundant supply of raw
material also enables the production of thickeners at relatively low cost.
Modifi ed starches were introduced as far back as the 1940s to give improved
stability and shelf life, and a broader range of applications compared with the
native starches originally available. These were important in the development of
the convenience food market, but are less popular now as they are not considered
natural. Modifi ed starches tend to be high on retailers' lists of additives to be
removed, but their high resistance to acid and high levels of processing (e.g. in
pickles and long-life sauces) makes them diffi cult to replace yet still maintain the
desired product characteristics. With the drive for natural solutions, there has been
considerable development in the area of functionally enhanced native starches
using plant breeding. Clean label starches are covered in detail in Chapter 7 and
so will not be discussed further here.
A range of cellulose gums are used in the food industry, all of which are
obtained from cellulose through chemical modifi cation (Murray 2009). These are
methyl cellulose (MC), hydroxypropyl cellulose (HPC), hydroxypropyl
methylcellulose (HPMC), methyl ethyl cellulose (MEC) and carboxymethyl
cellulose (CMC). Unfortunately, their chemical-sounding names make them
unpopular in the current trend towards clean label foods and their chemical
modifi cation prevents them being classed as natural. However, each of the
cellulose gums has a functional property that is diffi cult to replace with other
hydrocolloids, as discussed below.
MC and HPMC are very unusual in that they exhibit reversible thermogelation,
i.e. they are liquid at low temperatures, but gel on heating, and then become liquid
again on cooling. Most hydrocolloids become liquid on heating and gel on cooling.
This thermogelling property makes them ideal for preventing boil out in fruit pies,
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