October 21, 2008 - 10:49am
Pre-Ferment Questions
Hey all, some questions about the pre-ferment...
In my past I was a very experienced brewer and know from that pursuit that how you handle the yeast PRIOR to getting it into the wort (brew) had some pretty drastic effects on the final product. So...
- Does the time length of the pre-ferment effect final outcome in either taste/crumb/loaf shape/etc?
- Does the hydration of the pre-ferment effect any of the above? In other words, does a really wet, soupy pre-ferment do better or worse than a dry, doughy one?
And also, brewers have access to some seriously high-quality and specialized yeasts, do bakers have anything similar?
Thanks all!
Just starting up a batch of Jason's Quick Focaccia right now. I'm using the basic Fleishmann's grocery store yeast but I put it and the 475g (!!!) of warm water into the mixer and that's just starting to bubble. Man, I love that smell.
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1. Absolutely, to all of the above. Extended fermentation can lead to gluten breakdown, and that affects texture as well as final crumb. And the taste will change as well... long, cold fermentation, in particular, enhances flavour by giving time for bacteria and enzymes to break down starches into sugars and proteins, which means a sweeter, nuttier loaf. This will also affect crust texture (more sugar == more caramelization). Long warm fermentation is a little less interesting, as the yeast will gobble up the sugars before the bacteria has time to work. The upshot, here, is that in general, long, cool fermentation of the preferment is really the ideal solution for maximizing flavour.
2. Also absolutely. Higher hydration means the yeast have more free access to those broken out sugars. If you're dealing with sourdough, lower hydration is said to lead to increased sourness, for this very reason (as the yeast activity will be slowed down (or retarded, as they say in the biz), giving the bacteria room to grow). Is the result "better"? That I can't really say. I tend to use wetter preferments in the form of a poolish, but of course many bakeries use the "old dough" technique, which will be at standard hydrations.
3. On the topic of yeast, I'm not aware of any "specialized" varieties. Really, the debate ends up being between instant and fresh yeast (seriously, don't even bother with active dry), and I've seen no clear winners in that one (although others may disagree :).
Thanks FP, you kicked off my brewer's brain and some stuff is making sense...
So in brewing we learn that as any yeast consumes sugars it will give off byproducts that alter the environement to suit it's needs. In other words any ale yeast is specially suited to live in the acidity and alchohol content of an ale beer. Most other organisms aren't, so an ale yeast that is brisk and lively will quickly change the liquid so it will kill off any competitor organisms and result in a cleaner tasting product.
If we take that process and apply to bread (it's still yeast, sugar and grain products) then we get...
More hydration makes for a livelier yeast, less makes for a slower yeast. Either way you can help control other organisims this way. Maybe you DO want sour flavors, maybe you don't, up to you.
Also the more time the yeast has to work on the sugars, the more complete the ferment will be, with all of it's by-products and flavorings.
Sound about right?
It's close. However, you should never forget the effect of enzymatic and bacterial action on the starches, sugars, and proteins in the flour. While yeast is thought of as *the* prime actor during dough fermentation, those other elements are also very important. As such, in general, you'll find that bread bakers tend to favour long, cool fermentations that favour balanced action by all three elements, thus maximizing flavour complexity.
For example, Reinhart's pain a l'ancienne, which produces an absolutely gorgeous, sweet, nutty, white french-style bagette, uses a cold dough that's innoculated with yeast and then put in the fridge overnight. The next day, the dough is brought out, warmed up, and allowed to double up before baking. The first stage allows enzymes and bacteria to break down proteins and starches into amino acids, sugars, and other by-products. The second stage gets the yeast going, generating flavour by-products of it's own while leavening the dough.
So, alpha-amylase and beta-amylase defnitely effect the final beer BUT only by altering which sugars get converted from the grains during the mash. Since with bread baking there is no mash step how do those enzymes come into play?
Also, where the heck do the sugars come from? I'm guessing the pre-ferment? But if I just take yeast and flour and go from scratch does that mean there's little/no time for starch to sugar conversion?
Dang, such a simple change from beer to bread and SO MANY changes in all the underlying science. Sigh. But, as with beer, even the failures are usually pretty darn tasty.
Hi LazySumo,
Just a couple of thoughts to add to the excellent advice from foolishpoolish.
Some sugar is imparted to the flour during the milling process. Some of the starch chains get broken as the wheat gets milled, leaving some simple sugars for yeast to feast on as soon as they are mixed with the flour and water. Apart from that, sugar is produced by enzyme action. A slower fermentation allows more sugar to be broken out from the starch via amylase enzyme action.
FP mentioned this with respect to Reinhart's Pain a l'Ancienne. The original for that recipe mixes flour and cold water and lets them rest overnight, without yeast. The enzyme action breaks a substantial amount of sugar out from the flour, before the yeast are even mixed in. Some of this sugar gets consumed by the yeast, next day, but some remains in the bread, giving it a special flavor.
Preferments help provide flavor, both through fermentation and this enzymatic action. Fermentation provides, as you note, many other by-products into the flavor mix. In addition, preferments also provide strength to your final dough, in the form of the gluten that forms, and allow for using less yeast in the final dough.
The idea is to either use the preferment when it has reached its peak, or to refrigerate it at that time, for later use. If you refrigerate a preferment, you want to give it at least an hour out of the fridge before using it in your dough.
Let us see your results, please?
Soundman (David)
"FP mentioned this with respect to Reinhart's Pain a l'Ancienne. The original for that recipe mixes flour and cold water and lets them rest overnight, without yeast."
Interesting... so I wonder why Reinhart, in his formulation of the recipe, incorporates the yeast prior to refrigeration? Maybe just to ease dough construction, as then you don't have to try and incorporate dry yeast into an already-formed dough?
Sorry, fancypantalons! My apologies
I got my fp's mixed up!
Reinhart says he wanted to make it easier for the home baker. David Snyder has posted some beautiful baguettes made with Gosselin's actual recipe, assuming that he gave the real recipe to Reinhart.
http://www.thefreshloaf.com/keyword/philippegosselin
The point is that the enzyme action happens without any yeast being present.
Soundman (David)
Very interesting read folks, thanks for the information.
I realized after I posted yesterday that the long primary ferment prior to baking would be where a lot of enzyme action would take place. But to me it's weird talking about enzyme actions occuring at such low temps. When we're brewing we work very hard to control the temperature of the mash (grain product, plus water, no yeast, sitting for an hour or so. Is this the brewer's autolyze step??) to an exact range so that our enzymes create the best sugars possible for us. Sugars produced outside of the target temperature range are usually inedible by the yeasts that brewer's use. I'm guessing that baker's yeast are built to eat a wider range of sugars.
Hmmm.... so what would happen if one were to bake with one of the high-grade strains of brewer's yeasts? White Labs is known to produce some of the best yeast for homebrewers out there... I may have to order up a batch and do some testing.
LazySumo,
Your description of the mash step in brewing is very interesting. It does remind me somewhat of the autolyse, though that process is more about building the gluten without over-oxidizing the dough. The autolyse allows gluten to form with very little mixing, and for enzyme action to start, including the work of protease, which breaks down protein. This always seems a bit at odds with itself, but the protease helps the dough's extensibility, so you get gluten without oxidation, and extensibility for free into the bargain. Any break-out of sugars I suppose is lagniappe, so to speak.
"Sugars produced outside of the target temperature range are usually inedible by the yeasts that brewer's use. I'm guessing that baker's yeast are built to eat a wider range of sugars."
In bread baking it appears that if there are "inedible sugars" for the yeast, that those sugars become available for helping make a crisp golden brown crust and for the palette. The yeast seem to be able to find enough sugars they can munch on to make the CO2 and raise the bread, assuming the gluten structure is in place.
Soundman (David)
Kind of helped to answer my own questions with this page here:
King Arthur's Preferment FAQ
Good read!
lazysumo,
as in brewing, there is a lot of experience in baking bread with or without preferments in the world, but the deeper biochemical and fysical processes of the mixing, moulding, fermenting and baking of bread are only understood for about 1 or 2%........ I hope.
the extensive site below is produced by a flemish bakery-technologist. so not all of it is applicable for at home-bakery but there's a lot of usefull information:
http://www.classofoods.com/ukindex.html
kees
Kees, great link, thank you very much. But I think I'm gonna need a beer before diving into that read! :) I'll tackle it next week when I'm back from vacation.