Comparison of three different in vitro digestion methods for carbohydrates

Abstract

Spectrophotometer method, ELISA, and High-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) method have been widely used to quantify and characterize the glucose released from rice after in vitro digestion. Despite this, the results of the three methods may not be comparable. This work investigated the limitation of detection (LOD) and quantification (LOQ) of the glucose released after in vitro rice digestion. Intra-day and inter-day precision were evaluated through analyzing the contents of rapidly digestible starch (RDS), DS (RDS + slowly digestible starch (SDS)), and total starch (TS). Tests of accuracies were also conducted. The results demonstrated that all three methods showed good linear correlations, i.e., y = 0.3417x + 0.0799 (r² = 0.994), y = 0.1719x + 0.0900 (r² = 0.993), and y = 58078x + 6039.4 (r² = 0.999), respectively. Concerning the LOD and LOQ, HPAEC-PAD showed the lowest 0.07 and 0.24 mg/L, followed by the Spectrophotometer of 2.72 and 9.07 mg/L. ELISA showed the highest 9.95 and 33.16 mg/L. The recoveries of these methods ranged from 98.62% to 100.56%, 99.05% to 102.72%, and 96.71% to 103.27%, respectively. HPAEC-PAD method had lower contents of RDS, DS, and TS, indicating it may be poor. Combining above factors, Spectrophotometer was chosen and used in digestion of biscuits and steamed buns. RS of biscuits was the highest, possibly due to the formation of lipid-starch complex. Additionally, steamed buns had the highest RDS. These observations suggested that Spectrophotometer method was suitable for accurately and reproducibly analyzing carbohydrate digestion in different food systems.