## 2 Materials and Methods  
### 2.1 Oat Sample Preparation and Pulsed Electric fields (PEF) Treatment  
Dehulled intact oat groats (_Avena sativa_ cv. Armstrong) donated by Harraway and Sons, Ltd. (Green Island, Dunedin, New Zealand) were milled to flour and sieved (850 \(\upmu\)m aperture, BS410/1986, Endecotts Ltd., London, England). Only the fine portions (containing 77% total starch, 11% crude protein, 5% crude fat, and 1% \(\beta\)-glucan content (dry weight basis)) were collected, vacuum-packed (Audion Elektro, Weesp, TheNetherlands) and stored at \(-\)20 \({}^{\circ}\)C until use. PEF treatment was conducted using a batch setting of ELCRACK(r) HVP 5 PEF system (German Institute of Food Technologies, Quakenbruck, Germany) with a treatment chamber made up of two parallel stainless steel (4 cm distance) electrodes. For each PEF treatment, thirty-five milliliters of flour suspension (8% oat flour dissolved in cold distilled water) was subjected to PEF treatment at electric field strength levels of 2.1-2.2 kV/cm (referred as \"2\") and 4.2-4.5 kV/cm (referred as \"4\"), with pulse energy from 1.2 to 9.7 J. This is combined with a range of specific energy levels of 42-53 kJ/kg (referred as \"A\"), 216-218 kJ/kg (referred as \"B\"), and 421-438 kJ/kg (referred as \"C\"). The different combinations of PEF treatment parameters reported in this study were coded as: electric field strength-specific energy input (i.e., \"2-A\" is an oat flour that was PEF-treated at 2.2 kV/cm and 53 kJ/kg). The PEF processing conditions were achieved by applying 20 \(\upmu\)s square wave bipolar pulse at 100 Hz with pulse number ranging from 307 to 7778. The pulse characteristics (shape: square wave, width: 20 \(\upmu\)s, rise and fall times: \(<\)1 \(\upmu\)s) during PEF treatment was monitored using a digital oscilloscope (model UTD2042C, UNI-T, Dongguan City, Guangdong, China). The flour suspension was freshly prepared exactly 3 min before PEF treatment. The flour and cold water were appropriately mixed to break flour clumps and ensure no bubble formation. The temperature and conductivity of the flour suspension were monitored before (kept below 9 \({}^{\circ}\)C) and after PEF processing using CyberScan CON 11 conductivity meter (Eutech Instruments, Singapore). Evaluation of the Starch Digestibility of PEF-Treated Oat Flour Using an In Vitro Static Digestion Method  
The extent of starch digestion in both PEF-treated and untreated oat flour (0.5 g per sample), within a 3-stage static _in vitro_ digestion method [17] with modifications [18], was determined. At oral phase (stage 1), oat flour was firstly diluted with saliva juice (consisted of 2 mM NaCl, 2 mM KCl, and 25 mM NaHCO\({}_{3}\)) before \(\alpha\)-amylase solution (0.0125 g/mL) was added. Then, 1 M HCl (Ajax Finechem, Seven Hills, New South Wales, Australia) was added until pH 3.0 \(\pm\) 0.2 was reached to deactivate the enzyme prior to the commencement of gastric phase. The acidic mixture was added with 2 mL gastric juice, which consisted of pepsin (4% _w/v_) in 151 mM NaCl and 28 mM KCl in 1 L 1 mM HCl at pH 3, and incubated for 120 min at 37 \({}^{\circ}\)C. Then, 1 M NaOH was added until pH 7.0 \(\pm\) 0.2 was reached. The gastric-chyme sample mixture was then added with 4 mL intestinal juice consisted of porcine pancreas pancreatitis (1% _w/v_) and porcine bile extract (0.8452% (_w/v_)) in 0.1 M NaHCO\({}_{3}\) at pH 7. Small intestinal phase digestion was allowed to proceed for a total of 120 min. One mL aliquot digest from each flour sample was removed at 0, 20, 60, 90, and 120 min along the 2 h long intestinal digestion. The aliquots were immediately added with 80% (_v/v_) ethanol (Anchor Ethanol, Auckland, New Zealand) to deactivate the digestive enzymes, mixed thoroughly, centrifuged (1090\(\times\)_g_, 20 min, 4 \({}^{\circ}\)C), and the supernatant was removed and analysed immediately. All incubation during digestion was conducted at 37 \({}^{\circ}\)C (Jeio Tech IB-15G, Seoul, Korea) at 55 strokes per min using rocking shaker (DLAB SK-R1807-S, Dr.