Abstract: The ash content of wheat flour is used to evaluate its quality but the conventional method of analysis takes several hours. This paper proposes using the potassium ion concentration of wheat flour samples instead of the ash content since the correlation between the two is very good (the correlation coefficient was 0.99). A flow injection analysis (FIA) system based on a potassium ion selective electrode took less than 10 min per measurement with a coefficient of variation less than 3%.

Abstract: Starch (1.2-4 g) was dissolved in 4 mL of 0.5 M NaOH and, if necessary, heated in a boiling water bath for 10 min for complete dissolution. The solution were diluted to 50 mL with 0.1 M acetic acid solution of pH 2.7, to give a final pH of 4.6. A 15 µL portion was injected into a stream of Ca(NO2)2 in 0.05 M acetate buffer of pH 6 (0.17 ml/min) in the FIA system before passing into the Termamyl reactor. After merging with a second flow of 0.1 M acetate buffer of pH 4.5 (0.33 ml/min) and passing through the amylerglycosidase reactor, the effluent was merged with 0.2 M phosphate buffer of pH 7.4 containing 4 mM NAD+ (1 ml/min). The effluent passed through the glucose dehydrogenase/aldose 1-epimerase reactor and a flow-through detector and was monitored at 340 nm. The peak height and integrated peak areas were evaluated by a computer program. Lipids, proteins and chemical modifications of starch interfered with the determination probably due to steric hindrance of the enzymes resulting in incomplete degradation to glucose; detection limits and RSD are not given. The FIA system can be fully automated. The cited method was applied to wheat, corn rice and potato starch.