Molecular and microstructural cues for starch digestive heterogeneity in Indian pearl millet (Pennisetum Glaucum)

Pearl millet (PM) is a nutrient-rich, climate-resilient cereal with potential for low-glycemic food applications. This study examined molecular and microstructural determinants of in vitro starch digestibility in 11 PM genotypes. Variation in starch composition (amylose: 18.27–27.68%; amylopectin: 30.62–51.12%) influenced the distribution of digestible fractions. Rapidly digestible starch ranged from 26.32% (HHB-67 Improved) to 44.74% (PC-701), while slowly digestible starch varied from 14.65% (Pusa-1803) to 27.44% (Chanana Bajri) and was negatively correlated with predicted glycemic index (pGI: 54.63–58.87; r = −0.633). Rheological analysis showed an inverse relationship between peak viscosity and pGI ( r = −0.828), suggesting restricted starch gelatinization reduces enzymatic accessibility. X-ray diffraction revealed that higher crystallinity (18.44–26.97%) was also associated with lower pGI ( r = −0.788). The Principal Component Analysis grouped Chanana Bajri, PC-701 and 86M94 as structurally compact, slowly digestible types, while Dhodsar Local and Pusa-1803 aligned with higher RDS and pGI, confirming microstructure-governed digestibility variation.