Gastric viscosity and sugar bioaccessibility of instant and steel cut oat/ milk protein blends Fatemah M. AlHasawi a , Derrick Fondaco a , Maria G. Corradini b , Richard D. Ludescher a , Douglas Bolster c , YiFang Chu c , Yongsoo Chung c , Jodee Johnson c , Michael A. Rogers d, * a Department of Food Science, School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA b Department of Food Science, University of Massachusetts Amherst, Amherst, MA 01003, USA c PepsiCo, Inc., Barrington, IL 60010, USA d Department of Food Science, University of Guelph, Guelph, Ontario, N3C3X9, Canada article info Article history: Available online 12 April 2018 Keywords: Oats Sugar bioaccessibility Milk protein concentrate Dynamic digestion model Luminescence spectroscopy abstract Milk protein concentrate (MPC; 0 g, 5 g, and 10 g) was added to two commercially available oat products (instant oats and steel cut oats) to examine how MPC addition, and consequent changes in meal formulation, manipulates both gastric lumen viscosity and intestinal carbohydrate-digestion kinetics, in vitro. We used the TNO Intestinal Model-1 (TIM-1) to simulate gastrointestinal digestion of the oats- based meals. Meals containing 5 g or 10 g MPC yielded significantly less total bioaccessible sugar compared with those containing 0 g MPC, while the rate of starch digestion was significantly higher in meals containing 5 g or 10 g MPC. The TIM-1 was coupled with fluorescence spectroscopy and a lumi- nescent molecular rotor to report changes in gastric viscosity in situ, showing that the gastric viscosity was higher in the meals containing MPC. Those findings suggest that MPC in oats-based meals signifi- cantly modifies the kinetics of carbohydrate digestion and increases gastric viscosity. © 2018 Elsevier Ltd. All rights reserved. 1. Introduction Designing foods by modifying their form and formulation is becoming a plausible strategy to control how foods behave and are digested in the gastrointestinal tract (GIT). The resultant changes in the physiological impact of modified foods may serve as a dietary intervention to combat diet-related chronic diseases. Starch-rich foods are of special concern, given the persistence of the type II diabetes pandemic (Prevention, 2015; Whiting, Guariguata, Weil, & Shaw, 2011). Therefore, there is a great need for dietary in- terventions that target postprandial glucose levels. Oats are a staple starchy food that is typically consumed after exposure to hydro- thermal processing (cooking); which involves gelatinization of the starch and the formation of a biphasic paste with an aqueous, continuous phase and a dispersed phase of swollen starch granules (Tecante & Doublier, 1999). We previously investigated the effect of differences in oat form, which are ultimately a consequence of different commercial processing techniques, on the digested gastric chyme viscosity and the biophysics of digestion of their carbohy- drate composition (AlHasawi et al., 2017). Similarly, manipulating meal formulation facilitates control of the physical properties of the starch-paste matrix and the consequent physiological responses. For example, hydrocolloids have a high water retention capacity that was found to contribute to an increase in digesta viscosity throughout the GIT (Norton, Fyer, & Moore, 2006). Increased gastric digesta viscosity impedes motion and access of enzymes to the substrate, consequently reducing nutrient hydrolysis (Endress & Fisher, 2001; Montagne, Pluske, & Hampson, 2003; Tharakan, Norton, Fryer, & Bakalis, 2010), as well as hinders diffusion of the hydrolysis by-products to the luminal brush border and renders absorption less effective (Endress & Fisher, 2001; Montagne et al., 2003; Tharakan et al., 2010). The subsequent reduction in rate and extent of starch digestion, attributed to increased digesta vis- cosity (Cummings & Stephen, 2007) has been associated with controlling postprandial glycemia (Brennan, 2005; Brennan & Cleary, 2005; Malkki, 2004; McKeown et al., 2004; Sahyoun, Jacques, Zhang, Juan, & McKeown, 2006; Trepel, 2004). b-glucan is a soluble fiber found in oats that is capable of entrapping water in its network (Battilana et al., 2001; Dikeman & Fahey, 2006) and increasing chyme viscosity in the GIT. These properties of b-glucan * Corresponding author. Department of Food Science; University of Guelph, Guelph, Ontario, N3C3X9, Canada. E-mail address: mroger09@uoguelph.ca (M.A. Rogers). Contents lists available at ScienceDirect Food Hydrocolloids journal homepage: www.elsevier.com/locate/foodhyd https://doi.org/10.1016/j.foodhyd.2018.04.014 0268-005X/© 2018 Elsevier Ltd. All rights reserved. Food Hydrocolloids 82 (2018) 424e433