Gels and Gums: Psyllium Husk Fiber and Xanthan in Gluten-Free Breads

In order to keep abreast of current trends in gluten-free technology from the consumer perspective, the author recently purchased the gluten-free cookbook put out by the writers at America’s Test Kitchen. The company’s so-called The How Can It Be Gluten Free Cookbook (2014) is something of a mixed bag; many of the recipes are retooled versions of their particular recipes, such as their five-banana banana bread, for particular gluten-free reformulations available to the lay cook. Some of the recipes are nothing more than a bit of legerdemain to fill space and were never contaminated by gluten to begin with, however, and the book does lose some points for this bait-and-switch maneuver. For the recipes that are present, however, the cogent and usually decently accurate depictions of the chemistry accompanying the processes and the storytelling of how each variation of a recipe was tested are useful guides to the home cook.

This post is not intended as a review of the book, although I consider it a worthy enough text. Rather, I want to dedicate the present discussion to a curious observation made within its pages on the superiority of psyllium husk in yeast-dough baked goods, such as pizza crust and sandwich breads. The Editors at America’s Test kitchen attribute this to the fact that it “binds more effectively with water… [as] a result, psyllium does a better job of strengthening the protein network so it is capable of holding in lots of gas and steam during baking” (p 16). Later, the Editors write that “its chemical composition is similar to that of xanthan gum, but it has a higher viscosity, so it is able to bind water even more effectively… psyllium interacts strongly with the proteins in gluten-free flours… providing a strong enough structure to support highly leavened bread once the bread cools” (p 21). The Editors note that this advantage is only observed in yeasted products; chemically-leavened doughs and batters were generally drier and had an objectionable texture when psyllium was used (p 16).

These statements are, to my eye, somewhat conflicting. They raise several key questions that will be explored here:

1.)    Is the mechanism as to why psyllium works in the way that it does strictly related to its viscosity?

2.)    Is the chemical structure of psyllium truly comparable to that of xanthan gum?

3.)    What is the reason for psyllium’s superior performance in yeasted products in particular?

4.)  What is the reason for the comparatively poorer performance of psyllium fiber in chemically-leavened breads.

Acetic Acid and Postprandial Glycaemia - RS as an Explanation?

Not so long ago now, a certain Doctor Carol Johnston of Arizona State University’s Nutrition Department came to present at my university. Doctor Johnston is a highly accomplished nutrition researcher, and one whose work that I admit I read from time to time. Perhaps her most notable accomplishment – that is, most notable in that it has trickled down  into the popular press and actually helped some people – is her investigation into the attenuation of postprandial glycaemia by the simple presence of vinegar taken prior to or concurrent with the meal. Obviously, such a simple measure could be of use to those people suffering from the metabolic defects of diabetes or who have generally sluggish metabolisms that prevent the rapid disposal of glucose from the bloodstream – no need to go into detail on mechanisms here, as I will treat those at a later time. My thesis advisor at the time was a very well-known researcher in the field of starch science and happened to inquire after the seminar whether the mechanism of complex formation with acetic acid (i.e. a type of RS5) had been considered as a plausible mechanism behind the observed metabolic effects of the vinegar doses in vivo employed by Johnston’s group.

Well, no. Starch is an esoteric enough field that few people think of that. And so, I volunteered for the task and designed an experiment to test the proposition in vitro.

The long and the short of it is this: no, Virginia. No, it does not account for the mechanism. However, the negative result was never published at my advisor’s will and the matter was dropped. Because these data would otherwise die in a notebook never to be opened again and I believe would be of benefit to this field of investigation, I am putting up the original paper that I wrote at the time for public viewing here, unaltered from its original state.

The result that we obtained at the time might have been a definitely negative one, but I am not without an hypothesis as to how the mechanism occurs. The paper is to be found below the break, and I shall address what I believe to be a quite probable cause as to the lowering of postprandial blood sugars by the mere imbibing of vinegar in the next post, for to the best of my knowledge, the exact nature of the biomolecular interplay has never been elucidated.

Persorption of Resistant Starch Granules: Should We Be Worried?

I recently wrote a piece that I thought I would try to publish in one of the main-line nutritional journals on a topic in the field of starch that no one in my field seemed to know anything about when I brought up the subject to them. However, when I cast about looking for a journal that would publish the piece, which was not quite long enough for a mini-review, too long for a brief communication, and certainly was no new research paper in its own right, I found only rigid requirements that would not bend and high publishing fees that I can not afford at the time of writing this piece. Thus, I am instead publishing the piece online for all eyes to see.

Credit must be given to Doctor Ray Peat for first introducing me to the persorption phenomenon, which is really a very old discovery. The term refers to the paracellular transport of solid particulates across the intestinal “barrier” – which, coming from someone with numerous food allergies, is a laughable term in itself – and into the lymphatic and circulatory systems, including our main topic of discussion over these last few posts, the starch granule.

Because the research on starch granules was mostly old, not to mention in German, I believe that it has largely failed to cross the Atlantic and penetrate the consciousness of the larger food science and nutrition communities who have investigated the effects of dietary fibres, such as the various forms of resistant starch, ad nauseum. What little has crossed over has been in the pharmaceutical and medical journals, and so I set out to write a short piece on the matter to apprise my fellow food scientists of the phenomenon. I uncovered enough disturbing effects of persorbed starch granules and solid bodies that make their way into the tissues that this post will not be easily accepted. Let the reader judge for himself.

The paper can be found below the break.

Resistant Starch: An Introduction

Before the name of Hans Englyst became a name to conjure with, he was one among many nutritionists and chemists working in the United Kingdom on the problem of dietary fibre. In the 1980’s, this was a hot topic. But in 1982, Englyst and his collaborators noticed something rather queer: when they attempted to digest some starchy foods using an enzyme extract from the pig pancreas, a good surrogate for the human, broadly speaking, a small fraction consistently remained undigested. Puzzled and suspecting the influence of operator error, they repeated the experiments. The same results came up: 1 – 2 % of starch in some foods, 3 – 8 % in others, with all other factors being equal, were not digested under conditions simulating normal, physiological digestion of foods in the human. The fact that the proportion of undigested starch increased in some foods after cooking and storing at refrigeration temperatures, most notably potatoes, and remained relatively static in others, such as tapioca, opened up interesting lines of inquiry that have impacted the field of nutrition study to this day.

A (Brief) Primer on Starch

I would like to begin by introducing you, dear reader, to a good friend of mine. Meet Glucose.

She is a humble molecule by herself, yet she actually is aptly designed for what she has to do. Glucose is, simply, the end metabolic fate of almost every dietary carbohydrate that is burned for energy by higher animals, with the one major exception that I know of being hummingbirds (but that is another post). We may rely upon glucose for the main dietary energy, or we may rely upon fats. Students of organic chemistry will quickly note, if they build the model, that the heterocyclic form and orientation of the hydroxyl groups represents the absolute energetic minimum that can be achieved using the chemical formula C₆H₁₂O₆. The creation did not waste its effort in building an inefficient system.

Just What is this Mess?

For the last two years, my life has been given over to the study or use of carbohydrates in some form. After earning my M.S. in Food Science & Technology, I made the decision to turn my back on the academic study of food science. Academia is sick, people. Sick, sick, sick. It needs to crumble and die via όλεθρος before it can become well.

Nonetheless, I find myself with a great many thoughts still rumbling around in my head on the subject of carbohydrates in food, their metabolism and use in the human creature. I have seen just what we are calling food these days, what the industry says that it does, and what it more probably actually does. I have seen science chase after new fashions rise up and fall, contributed to reviews on the “hot topics”, and found that the memory of the field often doesn't go back beyond a decade, nor is the heterodox voice suffered for long. And so good men keep silent and are thought wise.

And yet my thoughts are not all bitter. Some are sweet and tasty, like a gluten-free sticky bun. Contrary to the opinions the Atkins and Low-Carb and Paleo faddists, all playing variations on the same tired motif, carbohydrate foods have sustained man throughout his recorded history, and there is much to be gained from their study. The baker’s art is ancient and not exhausted even to this day, and with the advent of gluten-free foods, we have even more frontiers to explore in food science.

Thus, I come to you, dear reader, with this blog. I have had the uncomfortable experience of the scales falling from my eyes through my studies, but I cannot divorce myself from the field that I loved enough to pursue a graduate education in. I might be embittered, but I have knowledge that can serve my fellow man and help him to better understand his staff of life. I know how it can harm, and how it can heal.

So, have a helping of my thoughts. Just be forewarned: they tend to stick to themselves like sushi rice. Good luck trying to pull them apart.