Bulking and Fat-Replacing Agents - Sweeteners: Nutritional Aspects, Applications, and Production Technology - page 403

modiication decelerates retrogradation, improves gelling properties and prevents syneresis, and
improves paste clarity and sheen, paste and gel texture, ilm formation, and adhesion (BeMiller
1997). Over the last few decades, starch has been modiied by various methods to achieve func-
tionalities suitable for various industrial applications. Basically, there are four broad-based kinds of
modiications: chemical, physical, enzymatical, and genetical.
Maltodextrins depict the products of starch hydrolysis with dextrose-equivalent (DE) values of
less than 20. The hydrolysis of starch is brought about by the application of heat and acid or a speciic
enzymatic treatment (Marchal et al. 1999). These treatments result in a variety of depolymerized
oligomers, and the resulting mixture mainly consist of glucose, maltose, and a number of oligosac-
charides and polysaccharides. The extent of hydrolysis is relative to glucose and is expressed as DE,
with 100 depicting the complete hydrolysis to glucose monomers. The acid hydrolysis involves the
treatment of starch with a strong acid at high temperatures, where the extent of hydrolysis and, thus,
DE value is achieved by temperature and time control (Marchal et al. 1999). Enzymatic hydrolysis
is mainly performed by α-amylase (1,4-α-d-glucan glucanohydrolase; EC 3.2.1.1) extracted from
Bacillus sp. and pullulanase (pullalan 6-gluconhydrolase; EC 3.2.1.41). The α-amylases are distin-
guished by two features: the formation of products that have the α-coniguration at the reducing end
anomeric carbon of the newly formed products and an endomechanism of cleaving off glucose resi-
dues in the interior parts of the starch chain. As a result, maltodextrins produced by α-amylases are
the results of the extensive hydrolysis of amylose and only partially of amylopectin. Their tempera-
ture optimum is in the range between 60°C and 90°C, and the pH optimum is approximately 6-7.
Pullulanases are capable of cleaving starch at branch points, speciically α-(1,6) linkages; they have
a lower pH (5) and temperature (60°C) optimum. Some endo α-amylases are capable of releasing
small linear oligosaccharides such as maltotriose, maltotetraose, and maltohexaose during starch
hydrolysis (Marchal et al. 1999).
Depending on the type of hydrolysis and the origin, the maltodextrins produced contain linear
and branched oligomers and polymers. While DE is one of the important properties related to the
number of glucose units, maltodextrins with the same DE value may have very different charac-
teristics. The origin of starch (i.e., wheat, maize, oats, and cassava) is also an important factor gov-
erning the properties of maltodextrins. This is mainly due to varying ratios between amylose and
amylopectin, which depend on the starch source (Aprianita et al. 2010). Considering this complex-
ity, these molecules in the sol state are hydrated and expanded, with the extended helical regions
interrupted by short disordered regions (Marchal et al. 1999). At concentrations above the critical,
these molecules aggregate, forming crystalline domains—a characteristic of thermally reversible
gels. Gels are characterized by low elasticity, small mechanical stability, high rigidity, and turbidity.
Furthermore, due to varying DE values, maltodextrins have varying physicochemical properties; for
example, hygroscopicity, solubility, osmolality, and ability to reduce water activity and depress the
freezing point are directly correlated with the DE value, and as it increases, these properties will
increase as well.
With DE values below 20, maltodextrins are highly digestible, easily blended with other ingre-
dients, with fast dissolution and low viscosity in solution (Roller 1996). Low-DE maltodextrin gels
have low energy density of approximately 4.2 kJ/g. Due to their ability to form weak (soft) thermo-
reversible gels that melt upon heating and reset upon cooling, their physical behavior is comparable
to that of fat. Therefore, maltodextrins are capable of producing a fat-like mouthfeel that can be
applied in a variety of products as fat mimetics (Roller 1996). Due to structural organization and
particle size, maltodextrins are positioned in layers resembling the shape and size of fat crystals.
In addition, they may act as bulking agents but retrograde as the native starches. For this reason,
many stable starches used as fat mimetics are chemically modiied to be resistant to temperature,
shear, and low pH levels encountered in processing (Fuentes-Zaragoza et al. 2010). However, as
noted above, some starches and low-DE maltodextrin derivatives would behave differently, depend-
ing on the source; for example, potato starch retrogrades at a slower rate than other starches due to