Structural, Techno-Functional, Digestibility, and Prebiotic Characteristics of Spray-Dried Starch-Stearic Acid Complexes From Sorghum and Corn.

Abstract

The present study developed a novel resistant starch (RS-5) using a pilot-scale jacketed tank where sorghum/corn starches were separately complexed with stearic acid (SA) at 1%, 3%, and 5% levels during the gelatinization stage. The complexes containing starch slurry were spray-dried to obtain RS-5 in powdered form. These spray-dried starches were analyzed for long-range X-ray diffraction (XRD) and short-range Fourier transform infrared spectroscopy molecular order, along with determination of thermal, rheological, and digestibility properties and in vitro prebiotic potential. Complexation with 5% SA led to the highest RS content in both corn (63.76%) and sorghum (67.87%) starches. The increase in RS content correlated with the increase in complexation index and XRD percent crystallinity, while the 2θ peaks at 13° and 20° further confirmed the formation of V-type complexes in all RS5 samples. The V-type starch-SA complexation was found to reduce retrogradation enthalpies measured through a differential scanning calorimeter after 14 days of cold storage. Higher thermal stability in terms of higher decomposition temperatures was specifically observed for spray-dried corn starch-SA complexes. The corn and sorghum starches complexed with 1%-3% SA showed a higher in vitro prebiotic activity score (0.01-0.19) after 80 h. PRACTICAL APPLICATIONS: The spray drying results in a less dense powder with a very fine particle size between 25 and 37 µm, which may allow easy blending in wheat flours. Spray-dried starches complexed with SA resulted in higher RS content and reduced GI (glycemic index), making it lucrative for utilization in medium- to low-GI pasta, breads, and breakfast cereals with an improved sensory profile as compared to conventional dietary fibers.