Effect of α-Amylase on the Structure of Chia Seed Mucilage

Abstract

Thanks to its nutritional and mechanical properties, chia seed mucilage is becoming increasingly popular in the food industry as a small biomolecule. The mechanical properties of an ingredient are a key element for food appreciation during chewing. Therefore, with this study, we explore for the first time the structural changes that chia seed mucilage undergoes when treated with α-amylase, the most abundant enzyme in human saliva. First, rheological time-sweep tests were performed on samples with different enzyme and constant chia mucilage concentrations. Then, the effect of increasing the chia mucilage concentration at a constant enzyme content was investigated. The results show that structural changes occur after enzyme treatment. Rheological measurements show a thickening of the material with an increase in the elastic modulus depending on the concentrations of α-amylase and chia used. This effect is attributed to the release and aggregation of insoluble fibrous aggregates that naturally form the mucilage after the cleavage of the α-1,4-glucoside bond between the α-D-glucopyranose residue and the second β-D-xylopyranose residue by α-amylase. Thus, our data suggest an α-amylase-mediated restructuring of the chia mucilage network that could have implications for the commercial processing of this material.

Keywords: chia mucilage; food; rheology; structural studies; thickeners; α-amylase.

Figure 1

Images of chia suspensions with different α-amylase concentrations over time (0–6 h) with a close-up of the samples at 6 h to better see the differences (a), and illustration of the repeating unit of the chia mucilage tetrasaccharide and the putative cleavage site of the α-amylase (b).

Figure 2

Mechanical changes of chia mucilage suspensions as a function of α-amylase concentration, showing normalized storage modulus G’ (a), loss tangent trend over time for each chia-α-amylase mixture (b), and exponent b () linear dependance on α-amylase concentration (c).

Figure 3

Chia mucilage storage modulus G’ changes over time at varying chia concentrations (0.7%, 0.8% and 1% w/v) (a), and increment of elastic response over time (600 s) as a function of chia concentration (b).