| Summary: | This study examined the effect of calcium hydroxide (Ca(OH)<sub>2</sub>, 0.6%, <i>w</i>/<i>w</i>) on structural, physicochemical and in vitro digestibility properties of the complexed system of Tartary buckwheat starch (TBS) and rutin (10%, <i>w</i>/<i>w</i>). The pre-gelatinization and co-gelatinization methods were also compared. SEM results showed that the presence of Ca(OH)<sub>2</sub> promoted the connection and further strengthened the pore wall of the three-dimensional network structure of the gelatinized and retrograded TBS-rutin complex, indicating the complex possessed a more stable structure with the presence of Ca(OH)<sub>2</sub>, which were also confirmed by the results of textural analysis and TGA. Additionally, Ca(OH)<sub>2</sub> reduced relative crystallinity (RC), degree of order (DO) and enthalpy, inhibiting their increase during storage, thereby retarding the regeneration of the TBS-rutin complex. A higher storage modulus (G′) value was observed in the complexes when Ca(OH)<sub>2</sub> was added. Results of in vitro digestion revealed that Ca(OH)<sub>2</sub> retarded the hydrolysis of the complex, resulting in an increase in values in slow-digestible starch and resistant starch (RS). Compared with pre-gelatinization, the complex process prepared with the co-gelatinization method presented lower RC, DO, enthalpy, and higher RS. The present work indicates the potential beneficial effect of Ca(OH)<sub>2</sub> during the preparation of starch-polyphenol complex and would be helpful to reveal the mechanism of Ca(OH)<sub>2</sub> on improving the quality of rutin riched Tartary buckwheat products.
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