The impact of evolution in wheat milling on sugar bioaccessibility

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University of Guelph

Abstract

With obesity and diabetes reaching pandemic statuses over the past few decades, the need to regulate postprandial glucose levels via dietary interventions is rising. Maintaining starchy food’s intact native structures and retaining larger particle sizes through minimizing processing is a current strategy to modulate starch digestion in the gastrointestinal (GI) tract. Older processing methods are gaining popularity in preserving food’s native structures. However, since these techniques have been reintroduced into the food industry, their impact on food structure, digestibility, and nutrient bioaccessibility is understudied. Hard red wheat was milled by ancient (pestle and mortar), old (stone hand mill), and modern (roller and cyclone) milling techniques. Milling power was reflected in the particle size profiles of the resulting flours. Ancient flour (AF) was the coarsest flour (~70% of the particles have diameters exceeding 1000 μm), retaining the most intact structures. Old wholemeal flour (OWF) and old refined flour (ORF) had a similar particle size distribution that exceeded in diameter the modern refined flour (MRF) and modern wholemeal flour (MWF). In vitro starch digestibility assessed using TIM Gastrointestinal Model (TIM-1) show that porridges made with MRF and MWF had higher cumulative sugar bioaccessibility than those made with OWF and AF, with ORF porridge having an intermediate cumulative sugar bioaccessibility. The maximum sugar bioaccessibility and sugar release rate were significantly higher (p < 0.05) for MRF and MWF compared to OWF and AF porridges, while the induction times were shorter, demonstrating the importance of processing on modulating starch digestibility. In the second experiment, luminescence spectroscopy and molecular rotors (MRs) coupled with the TIM-1 model examine the in situ luminal viscosity of three starch samples with varying amylose-to-amylopectin ratio: normal, high amylose (AM) and high amylopectin (AP). TIM-1 secretions and pH did not influence MR emission, so digesta fluorescence intensity (FI) measurements were sensitive to viscosity changes during in vitro digestion. In the TIM-1 gastric compartment, samples can be arranged from highest to lowest FI, and thus viscosity was high AM > high AP > normal maize starches. This method can track changes in luminal viscosity in vitro when the microviscosity represents bulk viscosity.

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Keywords

Wheat milling, Luminescence spectroscopy, Milling evolution, In vitro sugar bioaccessibility, Starch digestion, Native/whole structure, Digestion kinetics, TIM-1, Dynamic digestionmodel, Molecular rotor, Molecular crowding, Microviscosity

Citation

Amer, H., Zhou, Z., Corradini, M. G., Joye, I. J., & Rogers, M. A. (2023). Wheat milling across history altered sugar bioaccessibility assessed using TIM-1 in vitro digestion model. Food Research International, 174, Article 113521. https://doi.org/10.1016/j.foodres.2023.113521
Amer, H., Alhasawi, F. M., Ludescher, R. D., Joye, I. J., Corradini, M. G., & Rogers, M. A. (2021). Luminescence spectroscopy–a useful tool in real-time monitoring of viscosity during in-vitro digestion. Food Biophysics, 16, 181-190. https://doi.org/10.1007/s11483-020-09660-w