Native, modified and clean label starches in foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 164

tendency to foam. The small granules of wheat starch contain much more protein
(1.6%) than the large granules (0.1%).

7.3.4 Phosphorus
The phosphorus in the cereal starches is mainly present as phospholipids. The root
starches (tapioca) contain a very low amount of phosphorus compounds. Potato
starch is the only commercial starch that contains an appreciable amount of
chemically bound phosphate ester groups.

7.3.5 Flavour and odour substances
The pre-gelatinised common cereal starches (maize, wheat) have a relatively raw
cereal fl avour. These starches impart cereal-type fl avours to the foods in which
they are incorporated. Potato and tapioca starches contain only a low amount of
fl avour substances and this may be due to their low lipid and protein content.

7.4 Amylose and amylopectin
Starch can be considered to be a condensation polymer of glucose, consisting of
anhydroglucose units. The glucose units are linked to one another through the C-1
oxygen in what is known as a glucoside bond. The glucoside linkage is stable
under alkaline conditions and hydrolysable under acid conditions. The glucose
unit at the end of the polymeric chain has a latent aldehyde group and is known as
the reducing end group. Most starches are a mixture of amylose and amylopectin,
each having a wide range of molecular sizes. Starches of different origin have
different amylose to amylopectin ratios (Table 7.1). Table 7.1 also shows the
average degree of polymerisation (DP) of both fractions in various starches.
In summary, starch is considered to be a condensation polymer of glucose. The
glucose units in the starch polymer are present as anhydroglucose units (AGU).
Most starches contain two types of glucose polymers: amylose and amylopectin.
Amylose is a linear chain of glucose units while amylopectin is a branched polymer

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Table 7.1 Amylose and amylopectin contents and degree of polymerisation of various

starches

Percentage content Average DP

Starch

Amylose Amylopectin Amylose Amylopectin

Rice 22 88 4000 2 000 000

Wheat 26 74 1000 2 000 000

Maize 28 72 1000 2 000 000

Potato 21 79 4000 2 000 000

Tapioca (cassava) 17 83 4000 2 000 000