Oral Digestion and Perception of Starch: Effects of Cooking, Tasting Time, and Salivary α-Amylase Activity

Since starch is a significant part of human diet, its oral detection would be highly beneficial. This study was designed to determine whether starch or its degradation products can be tasted and what factors influence its perception. Subjects were asked 1) to taste 8% raw and cooked starch samples for 5, 15, and 35 s and rate perceived intensities of sweetness and "other" taste (i.e., other than sweet), 2) to donate saliva to obtain salivary flow rate (mg/s) and salivary alpha-amylase activity (per mg saliva), and 3) to fill out a carbohydrate consumption survey. Subsequently, in vitro hydrolysis of starch was performed; saliva was collected from 5 subjects with low and high amylase activities and reacted with 8% raw and cooked starch at 2, 15, and 30 s. Hydrolysis products were then quantified using a High performance liquid chromatography. The results showed cooking increased the digestibility of starch such that the amount of hydrolysis products increased with reaction time. However, cooking did not influence taste ratings, nor were they influenced by tasting time. Subjects' salivary amylase activities were associated with the efficacy of their saliva to degrade starch, in particular cooked starch, and thus the amount of maltooligosaccharide products generated. Effective alpha-amylase activity [i.e. alpha-amylase activity (per mg saliva) x salivary flow rate (mg/s)] and carbohydrate consumption score (i.e. consumption frequency x number of servings) were also independently associated with sensory taste ratings. Human perception of starch is undoubtedly complex as shown in this study; the data herein point to the potential roles of salivary a-amylase activity and carbohydrate consumption in the perception of cooked starch.