Chemistry Reference
In-Depth Information
to cyclodextrin glycosyltransferases (CGTase). A major difference is that in the Novamyl
enzyme, a pentapeptide insertion (residue 191-195) is present that is absent in CGTase.
17
Deletion of this loop resulted in the production of cyclodextrin by the mutant Novamyl.
Recently, a second maltogenic-like anti-staling amylase was launched by the Danish
ingredient company Danisco under the trade name Grindamyl.
43
This amylase, derived from
a
Bacillus clausii
BT21 strain, is optimally active at 55
◦
C and pH 9.5. It is active on soluble
starch, amylopectin and amylose and produces mainly maltohexaose and maltotetraose via
an exo-acting mode of action.
18
This maltogenic amylase is being marketed under the
trade names GRINDAMYL
TM
PowerFresh for bread baking and PowerFlex
TM
for tortillas.
Besides reducing the length of the amylopectin side chains, the Grindamyl amylase leads to a
balanced fragmentation of the amylose resulting in an accelerated amylose recrystallization
prior to amylopectin retrogradation. The final result is less network formation of recrystallized
amylose and thus a further reduction in the crumb firming.
19
14.7
GLUCANOTRANSFERASES
The most commonly used starch-active enzymes are those that hydrolyze soluble starch, amy-
lopectin or amylose and produce smaller dextrins, maltooligosaccharides or glucose/maltose.
Several enzymes, designated as glucanotransferases, related to these hydrolytic enzymes per-
form a transglycosylation reaction in which part of the donor molecule is transferred to an
acceptor molecule (Fig. 14.2). The enzyme cyclodextrin glycosyltransferase is a good ex-
ample of such a transferase type of enzyme. In the initial part of its reaction, it breaks
an
O
-glycosidic linkage. In the second part of its reaction, this enzyme transfers the non-
reducing end to the reducing end to form a cyclic molecule. This type of transfer reaction is
designated as an intermolecular transfer, that is within the same molecule. The other type of
transferase reaction is of the intramolecular type, that is another molecule is used as acceptor.
Two types of glucanotransferase enzymes exist: the 4-
α
-glucanotransferases also known as
amylomaltases that form an
α
-1,4 linkage, and the glycogen/starch branching enzymes that
form an
-1,6 linkage (or branch point). Both types of enzymes have found commercial
application in the processing of starch to food ingredients in the last decades.
α
14.8
CYCLODEXTRINS
α
Cyclodextrins are cyclic
-1,4 linked glucooligosaccharides containing 6, 7 or 8 glucose
α
γ
residues (named
-cyclodextrins) and in early days named Schardinger sugars. Due
to the arrangement of the glucose residues, the inner part of the cyclodextrins is hydrophobic
while the outside is hydrophilic. This means that cyclodextrin can include hydrophobic
guest molecules, modifying the physical and chemical properties of these molecules. This
has attracted considerable attention and led to the development of various applications for
cyclodextrins. An example is the use of cyclodextrins as a deodorizing agent in Febreze of
Proctor and Gamble. In food products, cyclodextrins can be used to remove cholesterol, to
stabilize volatile and labile compounds or for the reduction of unwanted taste or odour.
20-22
The larger
-, β- and
-cyclodextrins are especially attractive to use.
23
γ
-Cyclodextrins are marketed as a non-digestible, fully fermentable dietary fibre by
Wacker Chemie. Cyclodextrins are produced by liquefying starch and then adding the enzyme
α
