In vitro Starch Digestibility and Nutritionally Important Starch Fractions in Processed Roots and Tubers

Abstract

AbstractIn view of the nutritionally important starch fractions it has become essential to generate data on starch digestibility of commonly used foods. The present investigation was aimed at evaluating the effect of processing on the nutritionally important starch fractions and the extent of in vitro starch digestibility in six roots and tubers commonly consumed in the Indian cuisine, using controlled enzymatic digestion with pancreatin and amyloglucosidase. The samples were subjected to open‐pan and pressure cooking. Rapidly available glucose (RAG) was also measured to derive a starch digestion index (SDI), a measure of the relative rate of starch digestion. The total starch and amylose content in the raw samples ranged from 41% (w/w) to 80% (w/w) (dry basis) and 0.91 to 26.80% (w/w) (dry basis), respectively. Pressure cooking of roots and tubers significantly (p<0.05) decreased the amylose content. The levels of the individual starch fractions varied depending on the cooking method and were characteristic for each sample. Processing significantly influenced the various starch fractions in yam and knollkohl. The SDI of samples subjected to the two cooking methods was only different for beet root and radish. Radish and carrot contained the highest dietary fiber content. The simple in vitro measurement of starch fractions could serve as a tool for characterizing dietary carbohydrates with respect to their digestion in the intestine.