Determining and comparing psyllium quality

The swelling test in the picture below shows how much water a fixed amount of psyllium can hold. Three things should catch your eye: obviously the different amount of gel that is formed, but also the colour and the ash content (that’s visible when you zoom in). These are all parameters that determine quality, but the swelling capability is the most useful.

All kinds of names are in circulation, such as swelling index, swelling volume, swelling factor and swelling number. These all measure the swelling of psyllium differently and give different values. Producers and distributors use different kinds and sometimes it is not clear which one they mean. And some are difficult to perform at home, but not this one. It’s called Swelling Number and it’s a modified and easy-to-use version of the Swelling Index. This method is also applied at the supplier’s site as a quality control measure for the buyer and is considered a binding agreement within the target specification between the buyer and the supplier. For you it’s just a matter of accurate measuring, shaking a lot and waiting. Would be great if we could all use this test as a standard.

When the test is done, a gel is formed at the bottom of the cylinder. Left shows 17, right 25, meaning the one on the right is much more powerful as a hydrocolloid. But you could have already known by looking at it after mixing, as the colour is lighter and the purity higher (a lower ash content).

The wonderful and unique thing about this comparison is that you can easily calculate how much psyllium you have to use compared to another quality. The calculation is very simple: the left psyllium is 25/17 = 1,47 times weaker which means you have to add 1,47 times more of it to your dough. It’s a great way of checking the quality of a new psyllium batch and calculating how much you have to adjust from the previous batch, so that baking with the new psyllium will be great, straight from the start. And it standardizes quality to enable bakers to talk about the same thing and not comparing apples and oranges.

Having tuned the amount of psyllium does not mean the quality of your bread is the same. Make one loaf with high quality psyllium and the other with lower quality, a lot of things will stand out. The low-quality psyllium will result in a crumbier dough structure, a loaf that doesn’t rise as well in the oven and therefore doesn’t turn out as nice, but most importantly, it will yield significantly less volume, between 7 and 10%! The ultimate proof you should use always use the highest possible quality.

To perform the swelling test you need a precision scale that can weigh in milligrams, a regular digital scale to measure water in grams (preferably 0,1 grams) and one or two 100 ml cylinders with a stopper (measuring cups won’t work). The exact process will feature in my book.

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