Study on the structure, physicochemical properties and in vitro digestibility of cage-like complexes formed by different proteins and starch under spray drying

The cage-like structure formed by proteins on starch surfaces is of considerable interest due to its digestion regulation. The structural, physicochemical and digestive properties of cage-like complexes formed by highland barley protein isolate (HBPI), prolamin (Pro), glutenin (Glu), and the combination of Pro and Glu (Pro+Glu) with highland barley starch (HBS) under spray drying (SD) were investigated. SD treatment significantly enhanced the inhibition of different proteins on HBS digestion, with the maximum RS content of 23.62% and the minimum C∞ of 78.54% observed in HBS with Glu. After SD, Pro was observed to significantly reduce the peak viscosity of HBS during pasting by 354 cP, while others significantly enhanced by 881.50–1615.00 cP. Low-field nuclear magnetic resonance results indicated that the strongly and weakly bound water in all gel samples partially transformed to free water after SD. The thermogravimetric analysis demonstrated that SD treatment resulted in a redshift of the thermal degradation peak at 150−450 °C for all samples. The structural properties of all samples revealed that SD treatment reduced short-range orderings, remained the A-type crystalline of HBS, and reduced the peak intensity of the diffraction peak at 20°. Furthermore, the microstructures of HBS with different proteins after SD exhibited distinct characteristics, with Glu forming a continuous cage-like structure on starch surfaces while Pro forming larger aggregates. This study offers methodological and theoretical support for targeted regulation of starch digestibility.