Reducing the glycaemic index and increasing the slowly digestible starch content in gluten-free cereal-based foods: a review

Commercially available gluten-free (GF) cereal-based foods are generally characterised by a lower nutritional quality than their gluten-containing counterparts, relatively lower resistant starch (RS) content, along with higher glycaemic index (GI) often being reported. To overcome this nutritional imbalance, extensive research has been conducted to investigate the preparation of a new generation of staple GF products. This review reported the main strategies currently adopted in GF cereal-based food recipes to formulate products with overall slowly digestible starch properties. They are mainly obtained by the utilisation of alternative ingredients to be incorporated into standard food formulation (including native starch and GF flours) or by technological treatments that may contribute to impact starch digestibility. Considering data from invitro digestion trials, indications suggested that, aiming to obtain a RS content of about 5% (dry weight) and lowering the invitro GI values, the minimum high amylose starch (amylose >60%) replacement level in GF bread and cookie formulations should be in the order of 20% by weight of total flours. Overall, with respect to un-substituted GF foods, two- to three-times higher RS contents, along with a parallel invitro GI decrease (up to -50%), were obtained for GF pasta and ready-to-eat snacks enriched with legume flours at inclusion levels from 40% to 100% by weight of total flours. The use of flours from pseudocereals (e.g., quinoa, amaranth and buckwheat) with and without sourdough did not always guarantee favourably slowly digestible starch GF foods.