Objective: Short-soluble amylose chains have been documented to form an amylose coat over waxy corn starch granules inhibiting gelatinisation and retrogradation. However, certain key questions remain unanswered viz., how does the amylose coat modulate, a) viscosity decay, and b) textural mouthfeel of coated waxy corn starch gels when subjected to simulated oral processing? This study explores these key questions under simulated consumer sensory experience with slow swallowing initiation.

Methodology:Waxy corn starch (ca. 99 % amylopectin, Amioca powder TF-04400108) and isoamylase enzyme (≥10 ⁷ units mg ⁻¹ protein) were purchased from Ingredion Inc., USA and Megazyme, Ireland, respectively. Mucin type II was purchased from Sigma-Aldrich, India. Short-soluble amylose (DP _av ~700) 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 the ratio, 1:50 (parts by weight) (AP25W-3) while uncoated waxy corn starch gel was used as control. Flow curves were obtained at 37 °C, 1 to 100 s ⁻¹ , fitted to the Ostwald-de Waele model (σ = kɣ̇ ⁿ ) where, σ is the shear stress (Pa), k is the consistency index (Pa.s ⁿ ), ɣ̇ is the shear rate (s ⁻¹ ), and n is the flow index. Changes in viscosity during simulated oral processing were registered using a starch pasting cell, adapted to a controlled stress rheometer (Anton Paar) with a Peltier concentric cylinder system to control the temperature (37 °C) while shearing (10 s ⁻¹ ) at 37 °C for 120 s using a continuous ramp. To model the viscosity breakdown during the simulated oral digestion, viscosity data under oral conditions (constant shear and, with and without SSF+mucin) was fitted into a second order structural equation, where ɳ is the viscosity at a given time, t is time in seconds. Symbols represent initial apparent viscosity (ɳ₀, Pa.s), the equilibrium apparent viscosity (ɳ_e, Pa⋅s), and the rate of structure breakdown (k).

Results and Conclusion: Amylose-coated waxy corn maintains an initial smoother texture (0.8 Pa.s), as compared to uncoated waxy corn (1.35 Pa.s) for oral processing without salivary α-amylase. Upon oral processing with salivary α-amylase, the amylose-coated gels retain relatively stable viscosity decay at ca. 40% breakdown while there is a rapid viscosity decay for uncoated gels at over 2× times the amylose coated rate ca. 90% breakdown. In practical terms, starchy food made with amylose-coated waxy corn could feel less “rapidly” watery during oral mastication, as studies explicitly link salivary α-amylase action to rapid in-mouth thinning, a critical window for consumers with slow swallowing initiation.

Such a design could potentially shape starchy food formulations and thickeners for slow-eating children, older adults and dysphagia patients usually with slow swallowing initiation. Hypothetically, this will assist health care providers to tweak the residual oral viscosity and achieve tailored formulations with suitable breakdown during the critical window (oral hold time), thereby reducing the risks of choking from thick or rapidly thinning foods.

Keywords.Amylose coat, Waxy corn starch, Oral processing, Viscosity decay, Slow swallowing initiation, Dysphagia

● Conference Theme: Behavior of food biopolymers during digestion