10
granules and suggests the degree of stability during cooking (Adebowale and Lawal
2003). Minimum viscosity, also called hot paste viscosity, holding strength, or
trough, marks the end of the holding stage at the maximum temperature of the RVA
test. The cooling stage begins and viscosity again rises (setback) which is caused by
retrogradation of starch, particularly amylose. Setback is an indicator of final product texture and is linked to syneresis or weeping during freeze–thaw cycles.
Viscosity normally stabilizes at a final viscosity or cold paste viscosity, which is
related to the capacity of starch to form a viscous paste or gel after cooking and
cooling (Newport Scientific 1998). Other components naturally present in the
starchy material or additives interact with starch and influence pasting behavior
(Newport Scientific 1998).
Modification of Starch
Native starch, extracted from plants, cannot always withstand the extreme processing conditions, e.g., high temperature, freezethaw cycles, strong acid and alkali
treatments, and high shear rates (Hermansson and Svegmark 1996; Wang and
Copeland 2015). In addition, retrogradation occurs after loss of ordered structure on
starch gelatinization, which results in syneresis or water separation in starchy food
systems. Therefore, its use is limited and it unacceptable in many industrial applications. However, these shortcomings of native starch could be overcome, by modifying the starches. Modification of starch alters the properties of starch, including
solution viscosity, association behavior, and shelf life stability in final products.
Different techniques are used to modify native starch to enhance or inhibit its inherent properties, or to endue its specific properties to meet the requirements of industrial applications. Common modification methods for starches include physical
(e.g., high pressure autoclave, osmotic pressure treatment, extrusion, irradiation,
etc.), chemical (e.g., oxidation, esterification, etherification, hydroxypropylation),
and enzymatic modifications (e.g., dextrin) (Liu et al. 2017). The commonly used
methods for starch modification are summarized in Table 4.
Chemical modification is the most widely explored modification method due to
the non-destructive nature of a select few of the processes and potential increases in
the functionality of the modified starch. Chemical modification is generally achieved
through derivatization, such as acetylation, cationization, oxidation, acidhydrolysis,
and cross-linking. These methods are however limited due to environmental concerns and consumer safety (Ashogbon and Akintayo 2014). Starches can also be
modified physically to improve their solubility and change particle size. The physical modification involves the treatment of native starch granules under different
temperature/moisture combinations, pressure, shear, and irradiation and this modification has been gaining wider acceptance because of the absence of chemical
reagents in the modified starch. Pre-gelatinization is the simplest of all starch modifications. It is effected by the cooking of aqueous starch slurry and subsequent drum
drying (Tharanathan 2005).
K. Gul et al.
granules and suggests the degree of stability during cooking (Adebowale and Lawal
2003). Minimum viscosity, also called hot paste viscosity, holding strength, or
trough, marks the end of the holding stage at the maximum temperature of the RVA
test. The cooling stage begins and viscosity again rises (setback) which is caused by
retrogradation of starch, particularly amylose. Setback is an indicator of final product texture and is linked to syneresis or weeping during freeze–thaw cycles.
Viscosity normally stabilizes at a final viscosity or cold paste viscosity, which is
related to the capacity of starch to form a viscous paste or gel after cooking and
cooling (Newport Scientific 1998). Other components naturally present in the
starchy material or additives interact with starch and influence pasting behavior
(Newport Scientific 1998).
Modification of Starch
Native starch, extracted from plants, cannot always withstand the extreme processing conditions, e.g., high temperature, freezethaw cycles, strong acid and alkali
treatments, and high shear rates (Hermansson and Svegmark 1996; Wang and
Copeland 2015). In addition, retrogradation occurs after loss of ordered structure on
starch gelatinization, which results in syneresis or water separation in starchy food
systems. Therefore, its use is limited and it unacceptable in many industrial applications. However, these shortcomings of native starch could be overcome, by modifying the starches. Modification of starch alters the properties of starch, including
solution viscosity, association behavior, and shelf life stability in final products.
Different techniques are used to modify native starch to enhance or inhibit its inherent properties, or to endue its specific properties to meet the requirements of industrial applications. Common modification methods for starches include physical
(e.g., high pressure autoclave, osmotic pressure treatment, extrusion, irradiation,
etc.), chemical (e.g., oxidation, esterification, etherification, hydroxypropylation),
and enzymatic modifications (e.g., dextrin) (Liu et al. 2017). The commonly used
methods for starch modification are summarized in Table 4.
Chemical modification is the most widely explored modification method due to
the non-destructive nature of a select few of the processes and potential increases in
the functionality of the modified starch. Chemical modification is generally achieved
through derivatization, such as acetylation, cationization, oxidation, acidhydrolysis,
and cross-linking. These methods are however limited due to environmental concerns and consumer safety (Ashogbon and Akintayo 2014). Starches can also be
modified physically to improve their solubility and change particle size. The physical modification involves the treatment of native starch granules under different
temperature/moisture combinations, pressure, shear, and irradiation and this modification has been gaining wider acceptance because of the absence of chemical
reagents in the modified starch. Pre-gelatinization is the simplest of all starch modifications. It is effected by the cooking of aqueous starch slurry and subsequent drum
drying (Tharanathan 2005).
K. Gul et al.