24
mixture followed by drying (Winowiski et al. 2005). In other words, physical modifications of the starch that affects enzyme binding and the rate of digestion can be
used to modulate starch digestibility for formation of SDS and RS.
Enzyme Treatment
Controlled enzymatic treatment of starch with α-amylase, β-amylase, isoamylase,
pullulanase and transglucosidase is an alternative approach to change the chainlength of starch supramolecular structure in order to achieve appropriate digestibility and glycemic response (Shah et al. 2018). RS has been prepared from high
amylose starch by gelatinization followed by treatment of slurry with debranching
enzymes like pullulanase and isolating the starch product by drying/extrusion
(Haralampu and Gross 1998). RS products having at least 50% RS content were
manufactured by forming a water-starch suspension, heating the suspension in an
autoclave at 100 °C so that full starch gelatinization takes place and then cooling to
allow retrogradation of amylose. The best results were obtained at a temperature of
134 °C, with four heating-cooling cycles and a starch: water ratio of 1:3.5 (Pomeranz
and Sievert 1990). RS was also prepared by gelatinizing the starch (common corn
starch and waxy maize starch), followed by treatment with a debranching enzyme,
isoamylase or pullulanase and precipitation of the debranched starch. For precipitation, the suspension was allowed to cool at room temperature, which reduced the
solubility of the starch and then the precipitate was heated at 70 °C to dissolve a
small portion of the precipitate. Reprecipitation was then employed by cooling of
the suspension. This repetition of the dissolving and precipitation processes
improved the temperature stability of the resulting aqueous dispersion (Harris and
Little 1995). Increased yields of RS were obtained by subjecting the starch to enzymatic hydrolysis (pullulanase, 40 U/g/10 h), autoclaving (121 °C/30 min), storing
under refrigeration (4 °C/24 h), and lyophilizing (Reddy et al. 2013).
SDS has been prepared by debranching starch using pullulanase or isoamylase
(Shi et al. 2003). In the case of waxy starches, shorter debranching time and high
concentrations of debranching enzymes are more suitable for debranching starch to
form SDS (Guraya et al. 2001b). A low GI maize starch with some branched structure has been developed by partial α-amylase treatment and retrogradation, and the
slow digestibility was retained even after cooking (Han et al. 2006). Shorter chains
of amylopectin and noncrystalline amylose molecules were rapidly digested, while
DP n 121 chains showed the greatest resistance to digestion, followed by DP n 46
chains. A similar trend was reported in the formation of SDS from commercial
starch by controlling the hydrolysis of gelatinized starch with α-amylase (Hamaker
and Han et al. 2006). A novel slowly digestible storage carbohydrate comprising of
more than 90% amylopectin was produced by treating a native root or tuber starch
with a branching enzyme derived from a microorganism with a branching degree of
at least 8.5–9% (Vander-Maarel et al. 2008). Moreover, it was reported that both the
increase in branch density and the crystalline structure of starch enhances its slow
B. A. Ashwar et al.
mixture followed by drying (Winowiski et al. 2005). In other words, physical modifications of the starch that affects enzyme binding and the rate of digestion can be
used to modulate starch digestibility for formation of SDS and RS.
Enzyme Treatment
Controlled enzymatic treatment of starch with α-amylase, β-amylase, isoamylase,
pullulanase and transglucosidase is an alternative approach to change the chainlength of starch supramolecular structure in order to achieve appropriate digestibility and glycemic response (Shah et al. 2018). RS has been prepared from high
amylose starch by gelatinization followed by treatment of slurry with debranching
enzymes like pullulanase and isolating the starch product by drying/extrusion
(Haralampu and Gross 1998). RS products having at least 50% RS content were
manufactured by forming a water-starch suspension, heating the suspension in an
autoclave at 100 °C so that full starch gelatinization takes place and then cooling to
allow retrogradation of amylose. The best results were obtained at a temperature of
134 °C, with four heating-cooling cycles and a starch: water ratio of 1:3.5 (Pomeranz
and Sievert 1990). RS was also prepared by gelatinizing the starch (common corn
starch and waxy maize starch), followed by treatment with a debranching enzyme,
isoamylase or pullulanase and precipitation of the debranched starch. For precipitation, the suspension was allowed to cool at room temperature, which reduced the
solubility of the starch and then the precipitate was heated at 70 °C to dissolve a
small portion of the precipitate. Reprecipitation was then employed by cooling of
the suspension. This repetition of the dissolving and precipitation processes
improved the temperature stability of the resulting aqueous dispersion (Harris and
Little 1995). Increased yields of RS were obtained by subjecting the starch to enzymatic hydrolysis (pullulanase, 40 U/g/10 h), autoclaving (121 °C/30 min), storing
under refrigeration (4 °C/24 h), and lyophilizing (Reddy et al. 2013).
SDS has been prepared by debranching starch using pullulanase or isoamylase
(Shi et al. 2003). In the case of waxy starches, shorter debranching time and high
concentrations of debranching enzymes are more suitable for debranching starch to
form SDS (Guraya et al. 2001b). A low GI maize starch with some branched structure has been developed by partial α-amylase treatment and retrogradation, and the
slow digestibility was retained even after cooking (Han et al. 2006). Shorter chains
of amylopectin and noncrystalline amylose molecules were rapidly digested, while
DP n 121 chains showed the greatest resistance to digestion, followed by DP n 46
chains. A similar trend was reported in the formation of SDS from commercial
starch by controlling the hydrolysis of gelatinized starch with α-amylase (Hamaker
and Han et al. 2006). A novel slowly digestible storage carbohydrate comprising of
more than 90% amylopectin was produced by treating a native root or tuber starch
with a branching enzyme derived from a microorganism with a branching degree of
at least 8.5–9% (Vander-Maarel et al. 2008). Moreover, it was reported that both the
increase in branch density and the crystalline structure of starch enhances its slow
B. A. Ashwar et al.