
microflora. These include Lactobacillus acidophilus,
L. bulgaricus, and Streptococcus thermophilus. Bifi-
dobacterium longum is also used in the ‘bioyogurts’
which have now become popular. A culture contain-
ing the bacteria is added to the milk after it has been
homogenized and undergone heat treatment. The for-
mation of lactic acid causes the milk proteins to co-
agulate, forming a semisolid gel which entraps the fat
globules and the serum containing the dissolved com-
ponents. For ‘set’ yogurts, coagulation is carried out
directly in retail cartons, resulting in a gel-like prod-
uct. For ‘stirred’ yogurts, coagulation is carried out
when transferring through a cooler and then pack-
aging. A variety of gums are used in yogurt produc-
tion in order to reduce syneresis and enhance the
rheological and organoleptic properties. It should be
noted, however, that legislation in some countries
prohibits their use. It is important that the gums do
not mask the natural flavor of the yogurt and that
they are effective at the product pH of about 4.3.
Gums reportedly used are carboxymethyl cellulose,
guar gum, locust bean gum, pectin, alginate, agar,
carrageenan, and xanthan gum. However, the most
common are pectin, gelatin, and modified starch.
They are normally used at levels of 0.2–0.5%
depending on the gum and the milk solids content.
They are often added to the warm milk prior to
pasteurization in order to insure complete dissol-
ution. In some cases the gum is added to the coagulum
after incubation, in which case its microbiological
quality needs to be assured. Fruit-flavored yogurts
are produced by adding fruit pulp, consisting of fruit
pure
´
e( 50%), sugar (30%), and a suitable stabil-
izer to the yogurt prior to packaging. Low-ester
pectins (and low-ester amidated pectins) are particu-
larly effective stabilizers since they are able to provide
the optimum rheological properties at low pH and are
incorporated at typical concentrations of 0.6%.
0015 Cheese In cheese manufacture, lactic acid-producing
bacteria are added to milk and the mixture is stirred
at a constant temperature. When sufficient acidity has
developed, rennet, which is a natural enzyme, can be
added and this hydrolyzes the kappa-casein in the
milk, causing the casein micelles to coagulate and
form a gel. The gel is commonly referred to as curd
and is separated off from the liquid (known as whey)
and may be pressed, salted, and left to ripen
according to cheese type. Addition of gums such as
guar gum, locust bean gum, and carrageenan in-
creases the rate of coagulation and aids the recovery
process, thus increasing the yield of curd. In soft
cheeses, where there is a high water content (> 80%),
gums can lead to improvement in the body and tex-
ture of the product and are also reported to reduce
water loss. Blends of carrageenan and galactomannan
are particularly effective. Carrageenan is also used in
some processed cheeses, and this allows the cheese
content to be reduced whilst maintaining good mouth
feel and melting properties and improving grating
and slice integrity. The use of gums in cheese is,
however, subject to food additive regulations and
they are generally only allowed in composite cheese
products and spreads.
0016Whipped cream Whipping cream has a high milk
fat content (> 30%) and its functional requirements
include its ability to incorporate air (i.e., whippabil-
ity), foam stability, and resistance to serum separ-
ation. Sodium alginate, carrageenan, and modified
starches can be used to improve these characteristics.
Bakery Products
0017Bread In the process of bread making, flour, yeast,
salt, shortening, water, and so-called ‘improvers’ are
mixed together to form a homogeneous dough.
During the process the glutenin and gliadin proteins
present in the flour interact to form gluten, giving
the dough its elastic characteristics. On standing, the
yeast ferments the sugar components present in
the flour, producing carbon dioxide which distends
the dough, giving it a cellular structure. During
baking the starch granules dispersed within the gluten
matrix swell irreversibly (gelatinize), releasing amy-
lose and absorbing water, which adds to the structure.
The gluten is coagulated by the heat.
0018Although it is not common practice, gums such as
guar, locust bean gum, carboxymethyl cellulose, and
xanthan gum can be used in bread manufacture at
levels of up to 2%. They have been reported to speed
up the development of gluten during mixing, giving a
significant reduction in mixing time. In addition, it is
claimed that they enhance moisture retention, thus
retarding the staling process, which results from the
aggregation of amylopectin chains, a process referred
to as retrogradation.
0019Xanthan gum has been used in the preparation of
gluten-free bread. It is believed that the xanthan inter-
acts with the starch to form a matrix, allowing struc-
ture development comparable to normal bread to
occur during baking.
0020Cakes Gums such as xanthan gum, guar gum, and
carboxymethyl cellulose can be used in the produc-
tion of cakes and they have two major functions.
First, they can control the rheological properties of
the batter, which is important in large-scale manufac-
ture, where mixing, pumping, and filling stages are
encountered. Their shear thinning characteristics are
important since a low viscosity is preferable when
3004 GUMS/Food Uses