Direct in-vitro assay of resistant starch in phosphorylated cross-linked starch

The objective of this study was to develop a method to solubilize the RS fraction in phosphorylated (0.4% phosphorus) CL wheat starch (RS4) after its incubation with α-amylase and amyloglucosidase for 16h at 37°C as directed by the RS assay AOAC Method 2002.02. The residue was hydrolyzed and solubilized by conducting two back-to-back incubations with thermostable α-amylase for 30min at 100°C and pH 5.0, cooling to 50°C, then incubating quickly with amyloglucosidase at 50°C for 1h at pH 5.0. Importantly, the cooling process after α-amylase incubation was done by placing the mixture in a water bath at 50°C. The degree of hydrolysis of the CL phosphorylated wheat starch was determined as D-glucose using high-performance anion-exchange chromatography with pulsed amperometric detection (99.0%), glucose-oxidase/peroxidase (95.3%), and phenol-sulfuric acid determination of total carbohydrate (105.2%). Based on those findings, we propose a direct determination of RS in foods containing phosphorylated CL wheat starch.
Source: Bioactive Carbohydrates and Dietary Fibre - Category: Food Science Source Type: research