Psyllium powder experiment

A number of vegetarian and vegan recipes online call for the use of psyllium powder, the ground-up husk of the seed of Plantago ovata and related species. As I wrote in the previous post about vegan options for thickening and binding foods, psyllium contains a "mucilage" that swells to many times its volume in water, producing a fluid suspension with unusual properties. I had on hand a small quantity of psyllium powder and decided to play with it a little.

Half a teaspoon of the brown powder mixed well with half a cup of water and allowed to stand for 10 minutes produces a greyish, mobile fluid that seems to have low viscosity yet which holds the brownish particles of undissolved psyllium husk in what looks to be indefinite suspension with no evidence of settling.

Heating this suspension in a double-boiler arrangement causes a large increase in viscosity. Whether this is because the hot water dissolves more of the mucilage out of the psyllium powder or because there's some chemical change caused by heat (as happens with starch) is not clear to me. If the mucilaginous substance were isolated and purified it might be possible to determine the truth but that's getting rather far away from a cooking experiment. A fork dipped into the hot liquid and slowly raised draws out a long but weak strand, somewhat reminiscent of the "slimes" produced by cross-linking solutions of guar gum or polyvinyl alcohol with borax.

When the hot mixture is cooled to room temperature, its viscosity increases yet further and it begins to exhibit some gel-like properties. The mixture can still be poured very slowly and, when poked with a fork, the surface deforms without any resistance to pressure. Yet, even when the fork is poked in fairly deeply and then removed, the surface bounces back nearly to its original position. Refrigeration only amplifies this curious property. A finger poked into the refrigerated mixture comes away dry.

What use in cooking does this behavior suggest? The psyllium mucilage suspension, even before heating, is excellent at keeping floating particles dispersed. This suggests that the mucilage might be good at stabilizing colloids and perhaps foams. The great elasticity of the mixture after heating and cooling suggests that it might substitute to some extent for gluten in retaining the bubbles of CO₂ produced during baking bread, keeping the bread light; but since psyllium mucilage does not seem to "thermoset", at least at temperatures near to the boiling point of water, it seems possible that a bread held together with the mucilage would not have the desired resilience and would be easy to compress. The fact that, unlike starch or gelatine, psyllium powder leaves insoluble particles behind when it is dispersed in water might limit its utility--maybe trying to purify the mucilage is worth investigating.