Clean-label approaches to produce slowly digestible rice flour via starch modification: elucidating digestion mechanisms via small intestinal α-glucosidase and in vivo levels

Rice flour is primarily composed of starch and is widely used as an ingredient in processed foods. However, excessive consumption of white rice, the raw material for rice flour, induces a rapid postprandial glucose spike, increasing the risk of metabolic diseases such as obesity and type 2 diabetes. In this study, rice flour was biocatalytic modified by glycogen branching enzyme derived from Rhodothermus obamensis (RoGBE) to impart slowly digestible properties. The enzyme-modified rice flour exhibited a reduced molecular size distribution and degree of polymerization, together with an increased proportion of α-1,6 linkages. Notably, the content of highly branched α-limit dextrins produced by α-amylase was markedly elevated, leading to slow hydrolysis and sustained energy release with attenuated glucose spike at the in vitro and in vivo levels. In conclusion, the slowly digestible RoGBE-treated rice flour is a clean-label food that can be produced through a simple process without chemical treatment. In addition, no significant differences in structural and hydrolytic properties were observed between dry-milled and wet-milled rice flour after enzymatic modification. These results suggest the use of dry milling with lower wastewater and energy consumption together with a clean-label approach. Overall, RoGBE-treated rice flour produced from rice has the potential to be utilized as a functional food ingredient to prevent metabolic diseases such as type 2 diabetes and obesity. Furthermore, it can be used as a food additive to provide sustained energy to the body, thereby enhancing the added value and usability of rice flour.