Starch digestibility and quality of gluten-free cookies made from unpolished red rice: effects of combined germination and heat-moisture treatment

Abstract

Gluten-free cookies are well-received, but the substitution of wheat flour in the recipe remains a technological challenge. The objective of this study was to characterize the proximate compositions, physical properties, in vitro digestibility, and organoleptic profiles of cookies prepared from red rice flour subjected to germination or a combined germination and heat-moisture treatment (HMT). Both germination and HMT did not alter swelling index, water absorption capacity, and solubility of red rice flours, while they significantly reduced peak and final viscosities and increased breakdown and setback of germinated rice flours or combined germinated and heat-moisture treated rice flours. In terms of cookies quality, the complete replacement of wheat flour with red rice flour did not change their proximate compositions. Both germination and HMT resulted in a reduction in diameter, spread ratio, and hardness of cookies, but an improvement in their thickness compared to cookies made from untreated red rice flour. The resistant starch content of rice cookies decreased with increasing germination time, while the amounts of rapidly and slowly digestible starches in rice cookies remained unchanged. However, the gluten-free cookies made from rice flour contained higher amounts of slowly digestible and resistant starches than the wheat-based cookies. Moreover, no statistical discrepancies were witnessed in terms of all sensory attributes among all types of cookies. As a result, cookies made from combined germinated and heat-moisture treated rice flours could be used as a gluten-free product with satisfactory properties and improved human health benefits.