The Fresh Loaf

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Refrigeration, phytic acid, and enzyme/yeast activity

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saradippity's picture
saradippity

Refrigeration, phytic acid, and enzyme/yeast activity

Okay, so I can't seem to find one particular answer to one particular question. I have heard that the process that neutralizes phytic acid in sourdough takes place over approximately six hours at room temperature. I can not find how long this takes in the refrigerator. This is the most important aspect of the question.

I'm also curious about whether or not enzyme activity is slowed down with yeast activity (and bacterial activity) through refrigeration or not, or if it's only specific enzymes. For instance, obviously yeast feeds more slowly, but overnight refrigeration is advised to enhance flavor. I can not find someone stating this overtly, but the implication seems to me that refrigeration prevents gluten breakdown while allowing starches to convert to sugars. Since enzymes are related to gluten breakdown and sugar development both, does this mean that some enzymes (gluten breakdown) are slowed while others (starch breakdown) are unaffected?

MJ Sourdough's picture
MJ Sourdough

I do not have answer, but I think your question is interesting. I hope some other Fresh Loaf users can provide some insight.

ccsdg's picture
ccsdg

I'm not an expert at all but from what i understand the process isn't nearly as straightforward as that, unfortunately. All processes with sourdough take longer or shorter depending on a number of variables including temperature (i suspect 'room temp' is not nearly specific enough), percentage inoculation (6 hours after what exactly?) and of course the activity of your starter and what else is in its environment (eg sugar or salt). (Not enough parentheses?)

The other thing is that other things could get to the gluten before you're looking at excess enzymatic activity. Plain old acidity also breaks down gluten (dissolve all that stuck-on gluten in your mixing bowl instantly with vinegar!). Sourdough, being sour and all, will eventually break down its own gluten. Excess gluten development will break down gluten, bizarrely enough, though you'd have to either do it deliberately or retard a very very long time.

Other TFLers way before me have been there done it got the bumper sticker. Try searching Debra Wink in the forum search bar for her posts about relative growth of yeasts and bacteria for more information than you ever dreamed existed about sourdough! - sorry, the exact thread eludes me just now.

lepainSamidien's picture
lepainSamidien

Although I have not studied microbiology of fermentation at the university level, my very, very (VERY) simplistic understanding of enzymes (from sophomore year biology) leads me to believe that refrigeration will certainly slow down enzymatic activity, quite considerably, given that, like yeasts, enzyme activity plotted against temperature will yield a right-leaning bell curve, of sorts. That is to say, enzymes have a "sweet spot" for temperatures, at which they will be most active, and anything outside of that will slow, or stop, activity.

Here are some great links to go a little bit deeper:

http://www.thefreshloaf.com/node/6815/how-develop-sour-flavor-sourdough

http://ethesis.helsinki.fi/julkaisut/maa/elint/vk/katina/ (this one is definitely an ambitious reading project, but a very thorough study all the same)

http://www.thefreshloaf.com/node/10375/lactic-acid-fermentation-sourdough

All of these have definitely helped me to better understand the whys and wherefores of the sourdough process, as well as provided some great troubleshooting.