Optimization of an In Vitro Starch Digestibility Assay for Rice

Abstract

In vitro starch digestibility assays are more reproducible and less expensive than in vivo assays and are therefore important tools which assist breeding cereal cultivars with desirable starch digestibility. However, current in vitro starch digestibility assays often use non-mammalian digestive enzymes combined with the glucose oxidase peroxidase colorimetric (GOC) method of glucose detection which requires multiple steps. A new, simple, in vitro rice starch digestibility assay is developed by trialling several combinations of mammalian digestive enzymes and comparing blood glucose meter based glucose detection methods with the classic GOC method. The glucometer based detection methods had wider glucose concentration detection windows with good reproducibility compared with the GOC method. Digestion with a rat intestinal acetone powder (RIAP) alone was comparable (R 2 > 0.99) with digestion using a combination of α-amylase, pepsin, pancreatin, and RIAP. The optimized in vitro starch digestibility assay correctly estimated the digestibility of rice samples which differed by in vivo glycemic index (GI). This rapid accurate assay only requires a small quantity of sample (15 mg) and can meet the high-throughput phenotyping requirement of breeding programs in order to develop healthy cereal grains such as low GI rice.

Application of a Rapid In Vitro Method Based on Glucometer for Determination of Starch Digestibility and Estimated Glycemic Index in Rice

“…Therefore, it should be suitable for use during product development in the food industry. Glucometer has been successfully used for starch digestion in various starchy foods such as rice, [ 27 ] rice porridges, [ 15 ] rice noodles, [ 16 ] and tapioca starch. [ 17 ] Glucometers utilize different enzyme systems to detect glucose and of these the glucose dehydrogenase (GDH) based glucometers are the most sensitive to glucose.…”

“…GDH‐NAD based glucometers are sensitive to glucose only which avoids this problem. [ 27 ] Most glucometer readings were independent of pH and temperature of the glucose solution. [ 14 ]…”

A Review of Rice Starch Digestibility: Effect of Composition and Heat‐Moisture Processing

“…[21] In vitro starch digestibility assays using a range of digestive enzymes from different sources are often employed as a simple alternative to in vivo assays. Individual enzymes such as human and porcine salivary α-amylase, [22,23] porcine pancreatic α-amylase, [22] porcine pepsin [22] and invertase, [24] fungal α-amyloglucosidase [25] as well as enzymes from porcine pancreas (pancreatin) [26] and enzymes from rat intestine (rat intestinal acetone powder) [27] have been used for in vitro starch digestibility assays. Detection systems such as colourimeter, [28,29] polarimeter, [22] gas chromatography [30] and glucometer [26] are used to detect end point glucose concentration.…”

Standardized methods for testing the quality attributes of plant‐based foods: Milk and cream alternatives

“…Starch digestion : Starch digestion typically begins in the mouth, but is then completed in the small intestine, due to the presence of oral and pancreatic amylases (Tian et al., 2019). The rate and extent of starch hydrolysis can be assessed by measuring the formation of oligosaccharides, maltose, glucose, or reducing sugars in the supernatant collected from the sample, for example, using chromatographic methods (Ahmadi‐Abhari et al., 2013), chemical methods (Bustos et al., 2017), enzymatic methods (Chen et al., 2020; Fernandes et al., 2020), or glucose meters (Khatun et al., 2018; Sopade & Gidley, 2009).…”