Taste perception of oligosaccharides derived from pullulan

Abstract

Recent studies indicate that humans can taste starch hydrolysis products (i.e. maltooligosaccharides; MOS). However, the structural specificity of oligosaccharides that elicit such perception is not known. This study investigated taste perception of pullulan-derived oligosaccharides (PDOS) that are structurally similar to MOS, but differ in that every third glycosidic linkage in PDOS is α-1,6, rather than α-1,4. Three food-grade PDOS stimuli were produced by limited-enzyme hydrolysis of pullulan. The resulting products were stimuli with degree of polymerization (DP) of 3, 6, and 9. Subjects discriminated all 3 stimuli from blanks at a significant level (P < 0.00001) in the absence of lactisole, a sweet taste inhibitor. In the presence of lactisole, the subjects could not detect DP 3 at a significant level (P > 0.05), but were able to detect DP 6 and 9 (P < 0.005), although the degree of detectability dropped significantly (P < 0.05). In a follow-up qualitative study, subjects made the target stimuli and glucose into 2 groups (glucose/DP 3 vs. DP 6/DP 9) and characterized both groups as mostly "sweet" with having different sweetness intensity. With lactisole, they described glucose and DP 3 as "taste like blank" (lactisole water) and found it challenging to describe DP 6 and 9 stimuli due to their subtle nature. These results suggest that taste perception of PDOS primarily depends on the sweet taste receptor, although they may elicit other sensory attributes; this is strikingly different from the reported taste of MOS. The potential impact of structural configuration on taste perception is further discussed.

Keywords: glycosidic linkage; oligosaccharide; pullulan; structural configuration; sweet; taste perception.

Fig. 1.

Structural representation of (A) linear MOS, (B) linear PDOS, (C) α-1,4 glycosidic linkage, and (D) α-1,6 glycosidic linkage. Linear MOS consists of glucose subunits linked via α-1,4 glycosidic bonds (shown in blue); PDOS consists of maltotriose units linked via α-1,6 glycosidic bonds (shown in red). Permissibly rotatable bonds linking glucose subunits are depicted with curved arrows.

Fig. 2.

Chromatograms from HPLC-ELSD of PDOS samples (A) DP 3, (B) DP 6, and (C) DP 9. The chromatograms have a common x-axis representing the retention time in minutes and the y-axis as the signal intensity in millivolts. The numbers at the top of the peaks signify the retention time (min) of the sample.

Fig. 3.

Discriminability of PDOS DP 3, 6, and 9 from blanks. d’ values were determined from triangle tests performed under 2 conditions, with and without lactisole. The dashed horizontal line indicates the value above which the d’ values are statistically significant (P < 0.05). The asterisk (*) indicates statistically significant difference (P < 0.05) in d’ values for each target stimulus with and without lactisole.