Use of Amylomaltase to Steer the Functional and Nutritional Properties of Wheat Starch

Abstract

The fine molecular structure of starch governs its functionality and digestibility, and enzymatic approaches can be utilized to tailor its properties. The aim of this study was to investigate the in situ modification of starch by amylomaltase (AMM) from Thermus thermophilus in model starch systems subjected to hydrothermal treatments under standardized conditions and the relationship between molecular structure, rheological properties and in vitro digestibility. When low dosages of AMM were added to a wheat starch suspension prior to submitting it to a temperature-time profile in a Rapid Visco Analyzer, the increased peak viscosity observed was attributed to partial depolymerization of amylose, which facilitated starch swelling and viscosity development. At higher dosages, the effect was smaller. The low cold paste viscosity as a result of the activity of AMM reflected substantial amylose depolymerization. At the same time, amylopectin chains were substantially elongated. The longer amylopectin chains were positively correlated (R2 = 0.96) with the melting enthalpies of retrograded starches, which, in turn, were negatively correlated with the extent (R2 = 0.92) and rate (R2 = 0.79) of in vitro digestion. It was concluded that AMM has the potential to be used to deliver novel starch functionalities and enhance its nutritional properties.

Structural factors governing starch digestion and glycemic responses and how they can be modified by enzymatic approaches: A review and a guide

“…In a recent study, wheat starch slurries treated with amylomaltase from Thermus thermophilus were stored at 5 • C for 24 h to maximize the extent of retrogradation. The remarkable decrease in the rate and extent of starch digestion observed was related to the increased melting enthalpies of retrograded starch and thus the increased formation of crystalline structures consisting of longer AP chains (Korompokis et al, 2021a).…”

“…At the same time, the molecular weight of AP is reduced probably due to some activity of the enzymes to cleave internal AP chains in an endo-action pattern (Boonna et al, 2019;Cho et al, 2009;Do et al, 2012;van der Maarel et al, 2005). The newly formed very long AP chains have high propensity to retrograde and to form crystalline structures that melt at high temperatures (Cho et al, 2009;Hansen et al, 2009;Korompokis et al, 2021a).…”

“…This has been attributed to an increase in the content of AP chains with DP > 30 that associate and form crystalline structures. However, it is hard to imag-ine that AP chains would retrograde under the incubation conditions used by the authors (Jiang et al, 2014), because the high temperature (75 • C) used is close to the melting point of the crystals from amylomaltase-modified starches (Hansen et al, 2009;Korompokis et al, 2021a). In a recent study, wheat starch slurries treated with amylomaltase from Thermus thermophilus were stored at 5 • C for 24 h to maximize the extent of retrogradation.…”

Promotion of starch retrogradation by enzymatic elongation of amylopectin chains does not reduce glycemic responses: a randomized cross-over clinical trial

“…A liquid preparation of AMM from Thermus thermophilus of food grade quality was kindly provided by Royal Avebe (Veendam, The Netherlands). The enzyme activity assayed as described before 9 was 1170 units (U) per mL. One U of AMM enzyme activity is the amount that under the assay conditions produces 1 μmol of glucose per min at pH 6.5 and 70 °C.…”

“…8 Wheat starch that is modified with the thermoactive AMM from Thermus thermophilus and subsequently retrograded, has lower in vitro starch digestibility than its unmodified counterpart to an extent depending on the degree of AP chain elongation and starch retrogradation. 9…”