1175Short-soluble amylose chains inhibit longterm retrogradation and modulate in vitro digestion of waxy corn starch gels
Thoithoi Tongbram1,2*, Laxmikant Shivnath Badwaik1*,
, Pallab Kumar Borah2,3 and Gleb Yakubov2,4
1Department of Food Engineering and Technology, School of Engineering, Tezpur University, Napaam, 784028, India
1Food Materials Research Group, School of Biosciences, University of Nottingham, Sutton Bonington, LE12 5RD, United Kingdom
1Heinz Maier-Leibnitz Zentrum, Technical University of Munich, Lichtenbergstraße 1, 85748, Germany
2School of Food Science and Nutrition, University of Leeds, Leeds, LS2 9JT, United Kingdom
Objective: Short-soluble amylose has been documented to
inhibit gelatinisation and short-term retrogradation of waxy corn starch via
deposition of amylose coat over the granules. This study further
investigates the effects of short-soluble amylose chain envelopes on the
long-term retrogradation and in vitro digestibility of waxy corn
starch gels.
Methodology:Commercial waxy corn starch (Amioca TF) and
isolamylase were supplied by Ingredion Incorporated, USA and Megazyme,
Ireland respectively. Short-soluble amylose (DP ≤ 1000) was fabricated from
waxy corn starch by isoamylase hydrolysis (40 °C, pH 4.0, 24 h) coupled with
aqueous fractionation at 25 °C. Waxy corn starch: short-soluble amylose
chain was combined in ratios, 1:0.25, 1:50, 1:0.75 and 1:1 (parts by weight)
and named AP25W1-5 respectively. Samples prepared by DSC were used to assess
retrogradation enthalpy and retrogradation kinetics by using the Avrami
Equation. Samples prepared by RVA at week 0, followed by storage at 4 °C
were withdrawn from storage at the end of week1, 4 and 6, snap frozen at -80
°C and lyophilised for in vitro digestion and release kinetics.
Fig. 1.
Effects of short-soluble amylose chains on the thermal properties of
retrograded waxy corn starch gels during storage at week0 (■), week1 (●),
week4 (▲) and week6 (▼). Here, enthalpy is represented as a function of
degree of addition of 25W. AP-25W-1, AP-25W-2, AP-25W-3, AP-25W-4 and
AP-25W-5 represents waxy corn starch: short-soluble amylose chain ratios,
1:0, 1:0.25, 1:0.50, 1:0.75 and 1:1 respectively. For total mass balance,
75%, 68.75%, 62.5%, 56.25%, and 50% (w/w) water was added, respectively.
Black dashed line is a visual guide to indicate linear behaviour. Red, blue
and magenta dashed line are a visual guide to indicate second-order
polynomial behaviour. AP: amylopectin from waxy corn starch; 25W: soluble
amylose chains extracted from waxy corn starch at 25 °C; W: waxy corn starch
source.
Results and Conclusion: Short-soluble amylose is previously
known to inhibit gelatinisation and short-term retrogradation of waxy corn
starch amylopectin, and our study reveals further key findings from
long-term storage retrogradation. When blended with waxy corn starch at
different ratios (w/w), these short-soluble amylose chains can (a)
completely inhibit long-term retrogradation of amylopectin at higher
addition ratios (> 1:0.50, w/w) and (b) modulate susceptibility to
enzymatic digestion, co-relatable to the formation of slowly digestible and
resistant types of starches, as blending ratios (w/w) and storage times
(weeks) increase.
Our investigation reveals for the first time, a concentration-dependent
inhibitory and modulatory effect of short-soluble amylose chains on
gelatinised and retrograded waxy corn starch amylopectin. These findings
will allow food processors and manufacturers to fine-tune starch
structure-function (structure-digestion) to meet various food processing and
non-food application requirements. This study also promises a cleaner
additive label since amylose is a natural component of starch and exhibits
interesting potential for designing slow digestible and resistant starches
for glycemic index control in diabetes management and therapy.
Keywords.Soluble amylose, Waxy corn starch, Retrogradation,
Structure, Digestion