Impact of the particle size of milled wheat ingredients of wire-cut cookies on their glycaemic response: A randomised cross-over human intervention study

High postprandial glycaemic responses are a disease risk factor. The endosperm cells in wheat farina are more intact than those in flour and their starch is somewhat protected from digestion. The impact of partially replacing flour by farina in wire-cut cookies on in vitro starch digestion and in vivo postprandial glycaemic response (PPGR) was examined. Healthy participants ( n = 55) on 2 days consumed 85 g of control or test cookies in which 65% flour was replaced by farina (both containing 35 g starch). We measured oral processing behaviour and gastric emptying to exclude confounding the primary outcome. Test cookie was digested in vitro to lower extent than control (57.7 ± 0.3% vs 70.0 ± 0.4, p < 0.01), and contained more slowly digestible starch (23 vs 12 g/100 g). Blood glucose response was lower after 90 ( p < 0.01) and 120 min ( p < 0.01) despite no difference in the overall PPGR. Despite different bolus particle sizes and degrees of saliva incorporation between control and test cookie, gastric emptying rate and oral processing parameters were not different. In conclusion, partially replacing flour by farina significantly increased the in vitro SDS content, but did not substantially improve the PPGR. • Two cookie types were produced with wheat flour and coarsely milled farina. • Impact of wheat particle size on starch in vitro/in vivo cookie digestion was studied. • Cookies made with coarse wheat particles had twice as much slowly digestible starch. • No differences in postprandial glycaemic responses were found in 55 healthy adults. • Replacing flour by coarse farina did not impact the digestion of starch in cookies.