The Fresh Loaf

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Glycemic index with sourdough plus commercial yeast

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Carl Bergensis's picture
Carl Bergensis

Glycemic index with sourdough plus commercial yeast

I have a recipe that uses a teaspoon of instant yeast in addition to the starter. Will I still get the same lower glycemic index characteristic of sourdoughs?

jeremiahwasabullfrog's picture
jeremiahwasabullfrog

very hard to say.
The lower glycaemic index in sourdough probably comes from the microorganisms consuming the readily available (read high GI) sugars and starches, and converting them to something which is less readily available - alcohol, lactic acid, acetic acid etc. It would seem that normal bakers yeast isn't so good at this. For various reasons, a longer, slower rise is better for this.
So in very rough terms, if you allow a bread to rise quickly by adding bakers yeast, you might not get so much benifit. If you want low GI, add some bran or psillium husk to the mix. It has the same effect.
Good to see someone caring about GI!!
J

Carl Bergensis's picture
Carl Bergensis

Thanks. Since it already has rolled oats, pumpkin seeds, sunflower seeds, flax seeds and sesame seeds that may be as good as bran.


 


 

jeremiahwasabullfrog's picture
jeremiahwasabullfrog

the oats would certaily be working in that direction. I think the basic idea is to create a gel in your stomach which slows traps the sugars and slows absorption.


J

dsoleil's picture
dsoleil

Sounds like you might be concerned with diabetes.  Here's a great book that explains a lot about food:


 


http://www.nealbarnard.org/diabetes_book.htm

Ho Dough's picture
Ho Dough


maltose (môl'tōs) or malt sugar, crystalline disaccharide (see carbohydrate). It has the same empirical formula (C12H22O11) as sucrose and lactose but differs from both in structure (see isomer). Maltose is produced from starch by hydrolysis in the presence of diastase, an enzyme present in malt. Maltose is hydrolyzed to glucose by maltase, an enzyme present in yeast; the glucose thus formed may be fermented by another enzyme in yeast to produce ethanol. Maltose is important in the brewing of beer. It is an easily digested food.



 


Don't get excited......I'm only hypothesizing. I've made long fermentation, no knead breads using just commercial bread yeast. Mix it up, follow that with an 18 hour fermenation at room temps, followed by shaping and baking. Just simple flour, water, salt, yeast...very little yeast. Less than 1/4 tsp for a full loaf. I'm told commercial yeasts do have the ability to break down and digest maltose. It must, it works. Takes a long time to get started, but by 18 hours the yeasts have pretty much consumed what starch and sugar there is. A stretch and fold exposes what starches and sugars are left.....enough to get a rise in 2 hours. It will work, but isn't sour.


By contrast, I've read that in sourdough, it is the bacteria that breaks down the maltose to the fermentable sugars, which the compatible yeasts ferment to CO2 and alcohols. Sour comes from the byproduct of the bacteria..mainly acetic acid.


Just this week I also tried a combination of the two. I simply added 2 teaspoons of very ripe starter to the commerical yeast powered bread dough. The fermentation process still worked great and it produced a wonderful sour flavor.


As for it's GI, I don't have a way to test my blood sugar levels. Wish I did. The promise of a low GI bread is the main reason I'm working with sourdough. That plus it's ten times better tasting than any commercial bread you can buy.