engleski

Starch characterization using spectrophotometry and direct potentiometry

Starch consists of two poymer types ; amylose and amylopectine. Their ratio is starch origin- dependent. Triiodide ions bind characteristically to the amylose and amylopectin molecules of the starch. This can be monitored using spectrophotometry, but recently also direct potentiometry with platinum redox sensor. The absorbance and electrical potential change of the starch- triiodide complex were measured for wheat, potato, corn, rye, barley, rice, tapioca and commercial starch. The results showed characteristic curves for each starch type, corresponding to the specific amylose/amylopectine ratio. The curves were used to determinate starch type-specific parameter values ; for spectrophotometry: starch-triiodide peak wavelength maximum (λmax/nm), maximum absorbance change for λmax (ΔA) and for the direct potentiometry: slope (S) for the linear response region, maximum potential change (ΔE) and relative sensitivity (mV/mg) for potential change in the corresponding starch concentration. Data comparison using these two methods revealed that methods serve to distinguish starch types based on specific triiodide bounding to starch components, but when absolute data changes between starches were compared, no correlation between them has been found.

spectrophotometry ; direct potentiometry ; starch triiodide complex

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