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

Abstract

Measuring the glycemic index (GI) of rice in vivo is time consuming and costly. A simple, reliable, and cost-effective in vitro digestion assay suitable for use during rice breeding and rice product development is required. The purpose of this study is to propose the use of an in vitro enzymatic starch digestion assay based on a glucometer to determine the estimated GI (eGI) of rice in both raw and cooked forms. Four rice cultivars differing in amylose contents are examined. The known GI rice cultivar, Doongara, is used as the reference. The assay includes the digestion of ground rice using all of the enzymes require to simulate the human digestive tract. The glucose released during digestion is determined using a portable hand-held glucometer over a 120-min period. The obtained starch digestograms are modeled using a first-order kinetic model, and eGI values are calculated. The assay is applicable to both raw and cooked rice samples. It can be used to classify rice according to its eGI as affected by cultivars and cooking methods. The protocol is robust, high-throughput, and adaptable to non-laboratory settings. It can benefit rice breeders, farmers, and manufacturers of rice products.

Endosperm structure and Glycemic Index of Japonica Italian rice varieties

“…Instead, the varieties Arborio, Lince, Duilio, Castelmochi, Padano, Puma, Baldo, CL18, CL35, CL71 were found to have a high GI (>70). Unexpectedly, the highest GI value was registered for Arborio (92.31 ± 8.35) (having a Long A chalky grain), followed, with similar values, by Lince (88.93 ± 9.22) and Duilio (86.22 ± 10.18), both characterized by an almost crystalline endosperm, and by the Castelmochi variety (84.71 ± 10.65) that, having a glutinous endosperm (and a particularly low amylose content), was supposed to show the highest GI, according to the results of previous publications (Srikaeo, 2023).…”

“…Several studies have calculated the GI of rice varieties using different methods, both "in vivo", i.e., on the basis of the glycemic curves detected in volunteers subjected to tests, and "in vitro" (simulating digestion) (Miller et al, 1992;Hettiarachchi et al, 2001;Indrasari et al, 2010;Fitzgerald et al, 2011;Oko et al, 2012;Nisanka and Ekanayake, 2016;Kumar et al, 2018;Bhagya, 2019;Dwiningsih and Alkahtani, 2023;Srikaeo, 2023). However, currently available data are still limited compared to the thousands of rice varieties grown all over the world, especially as regards varieties cultivated in Italian and European rice area.…”

“…In view of the increasing number of people affected by diabetes all over the world and of the important role that a such a widely consumed and valued staple food could play in enhancing human nutrition (Dwiningsih and Alkahtani, 2023;Srikaeo, 2023), a careful diet based on low-GI rice varieties could represent a successful strategy to prevent diabetes and reduce the impact of other metabolic disorders, halting the progression of prediabetes and preventing the development of hyperglycemia and its related complications, such as cardiovascular diseases (Abdullah et al, 2009;Blaak et al, 2012), thus improving the health condition of affected subjects. It is therefore of paramount importance to identify and develop rice varieties characterized by a low GI, without neglecting grain quality and its organoleptic characteristics to better meet the needs of consumers.…”

“…Many factors, such as cooking method and time, condiments and accompaniments, presence of antioxidant components (phenolic compounds in pigmented varieties), degree of polishing of the grain and industrial treatments, can affect rice GI (Hallfrisch and Behall, 2000;Larsen et al, 2000;Hettiarachchi et al, 2001;Sun et al, 2010;Boers et al, 2015;Dwiningsih and Alkahtani, 2023;Ngo et al, 2023;Srikaeo, 2023;Yao et al, 2023); however, comparing different varieties under the same conditions also reveals the existence of a strong genetic component. A wide study conducted by the International Rice Research Institute (IRRI) and the Commonwealth Scientific and Industrial Research Organisation's (CSIRO) Food Futures Flagship on 235 rice varieties from all over the world, highlighted a great variability in GI, with values between 48 and 92 (average value 64), compared to glucose (100) (Fitzgerald et al, 2011).…”

Understanding starch digestibility of rice: a study in white rice

“…In vitro starch digestibility of rice continues to interest researchers, with studies on different behaviours and parameters that are dependent on varieties, structural properties, non‐starch components, processing, and treatments (Tamura et al ., 2021; Srikaeo, 2022). More studies are, however, needed to maximally benefit consumers by thoroughly understanding rice varietal effects and properly modelling in vitro starch digestograms with reproducible, objective, and consistent procedures.…”