Abstract
The objective of this study was to evaluate the effect of pulsed electric fields (PEF) on the in vitro starch digestibility properties of oat flour. A wide range of PEF process intensity was investigated (electric field strength between 2.1 and 4.5 kV/cm and specific energy inputs between 52 and 438 kJ/kg using 20 mu s square wave bipolar pulse at 100 Hz). The results revealed that PEF applied at a high electric field strength and energy <216 kJ/kg was favourable in slowing down the rate of starch digestibility (by 48%) during in vitro gastrointestinal digestion. This is accompanied by a significant decrease (from 15% to 7-10%) in the proportion of rapidly digestible starch (RDS) and a significant increase (from 77% to 84-85%) in resistant starch (RS) fraction. The application of PEF at energy level >421 kJ/kg at any field strength intensities raised the RDS (from 15% to 19-20%), but the rate of starch digestion was not affected (maintained at 3.3-3.7 x 10(-2) min(-1) vs. untreated at 3.8 x 10(-2) min(-1)). Further analysis of the structure, particle size, and thermal stability of PEF-treated oat flour through fractionation into three distinct flour segments revealed that PEF could cause major modifications in the particle size, damage and aggregation of starch granules, and destruction of the long- and short-range ordered structures of starch. Data gathered in this study indicate that PEF treatment can be a reliable strategy to modulate the in vitro starch digestibility of oat flour, either by reasonably slowing down the digestion rate or enabling a slightly higher amount of starch to be readily accessible by digestive enzymes without affecting the digestion rate.