Megazyme Digestible and Resistant Starch Assay Kit, 40 assays

The Digestible and Resistant Starch Assay Kit (K-DSTRS) method is based on the research of Englyst et al. (Ref) with some modifications. Digestion is performed using saturating levels of pancreatic a-amylase (PAA) and amyloglucosidase (AMG), but in stirred containers rather than shaken tubes, to simplify sample removal.

In line with Englyst definitions:

Rapidly digestible starch (RDS) is that starch which is digested within 20 min.

Slowly digestible starch (SDS) is that starch which is digested between 20 and 120 min.

A new term, ‘Total digestible starch (TDS)’ is introduced (and measured) to cover all starch that is digested within 4 h (the average time of residence of food in the human small intestine).

Resistant starch (RS) then, is that starch which is not digested within 4 h.

The incubation conditions parallel those used in AOAC Method 2017.16, a new, rapid integrated procedure for the measurement of total dietary fiber (Megazyme method K-RINTDF). This method is physiologically based and designed to fit the definition of DF announced by Codex Alimentarius in 2009.

 

Colourimetric method for the determination of digestible starch (RDS, SDS and TDS) and resistant starch (RS) in cereal products, foodstuffs, feeds and other materials. 

Principle:
(PAA + AMG, pH 6.0, 37°C, 20 min)
(1) Rapidly digestible starch + H₂O → D-glucose

(PAA + AMG, pH 6.0, 37°C, 120 min)
(2) Slowly digestible starch + H₂O → D-glucose

(PAA + AMG, pH 6.0, 37°C, 4 h)
(3) Total digestible starch + H₂O → D-glucose

Removal of 4 mL aliquot for RS determination:

(4) Aqueous ethanol wash + centrifugation to remove D-glucose

(5) Dissolution of resistant starch pellet in NaOH and neutralisation

(AMG, pH 4.5, 50°C, 30 min)
(6) Dissolved resistant starch + H₂O → D-glucose

                                    (glucose oxidase)
(7) D-Glucose + H₂O + O₂ → D-gluconate + H₂O₂

(peroxidase)
(8) 2H₂O₂ + p-hydroxybenzoic acid + 4-aminoantipyrine → quinoneimine + 4H₂O