Toward a more standardised and accurate evaluation of glycemic response to foods: recommendations for portion size calculation

The effects of different processes on enzyme resistant starch content and glycemic index value of wheat flour and using this flour in biscuit production

Enzyme resistant starch (ERS) is a indigestible form of starch and it can behave like dietary fibre that are the indigestible food components essential for a healthy lifestyle. The aim of this study was to examine the changes of the ERS content of wheat flour with ultrasonication, at four different flour/water ratios (1/5, 1/10, 1/15 and 1/20), three different pH values (6.1, 5.5 and 4.5) and three different temperatures (80 °C, 100 °C and 121 °C). Furthermore, possibility of addition this flour in four different proportions (0%-control, 25%, 50% and 75%) for biscuit production as a dietary fibre source was also investigated. The applied processes increased the dark colour and water holding capacity, but decreased the moisture content of flour samples. The ERS content of wheat flour increased about 30-fold and the sample that had the highest ERS content (ERS-enriched flour) of 3.30% was produced at 121 °C (autoclaving), pH 6.1 and 1/15 flour/water ratio with ultrasonication. ERS-enriched flour had higher melting point and lower estimated glycemic index (eGI) value compared to the wheat flour. In biscuit production, the biscuits with medium eGI (61.82-67.31) was obtained and the increase of ERS-enriched flour proportion increased the ERS content of biscuits, decreased the eGI, hardness and fracturability. During storage, while the light colour and moisture content of biscuits increased; eGI, hardness and fracturability decreased. The biscuits were considered as sensory acceptable by panellists. As conclusion; the ERS-enriched flour can contribute to the production of the medium or low GI foods rich in carbohydrates.

Equicarbohydrate partial exchange of kiwifruit for wheaten cereal reduces postprandial glycaemia without decreasing satiety

Kiwifruit is a carbohydrate food of low glycaemic potency which could potentially be exchanged for starch-based foods in management of postprandial glycaemia. The effect of equicarbohydrate partial exchange of kiwifruit varieties ‘Hayward’ green (GR) and ‘Zesy002’ (SunGold; SG) for a starchy wheat-based breakfast cereal (WB) on the characteristics of the postprandial glycaemic response and satiety was therefore determined. A total of twenty non-diabetic subjects (mean age 36 years; mean BMI 24·5 kg/m²) consumed four meals, each containing 40 g available carbohydrate, in random order, after an overnight fast. The meals were: (1) glucose; (2) 70·29 g breakfast cereal; (3) 200 g of GR plus breakfast cereal (30·93 g); and (4) 200 g of SG plus breakfast cereal (27·06 g). Throughout the 180 min postprandial period, capillary blood glucose concentrations were monitored, and satiety rated by a visual analogue scale. Partial kiwifruit substitution of WB significantly reduced postprandial glycaemic response amplitude (glucose, 3·91; WB, 3·66; WB + GR, 2·36; WB + SG, 2·31  mmol/l; least significant difference (LSD) 0·64; P < 0·001) and incremental area under the blood glucose response curve (0–120 min) (glucose, 228; WB, 180; WB + GR, 133; WB + SG, 134 mmol/l × min; LSD 22·7; P < 0·001). The area between baseline and response remained positive in kiwifruit-substituted meals but became negative after 120 min with glucose and WB, indicating that kiwifruit improved homeostatic control. Kiwifruit substitution of cereal did not significantly reduce satiety. We conclude that either ‘Hayward’ or ‘Zesy002’ kiwifruit may be used in equicarbohydrate partial substitution of starchy staple foods to reduce glycaemic response and improve glucose homeostasis without decreasing satiety.