Back in 1998, Mort O'Sullivan, a graduate of the International Centre for Brewing and Distilling in Edinburgh, Scotland provided some excellent insights into the question of crystal malt fermentability. Those comments are provided as follows, with emphasis added by me!
Apologies for the long and somewhat technical post, but the info should help you in answering the question of "why bother with a mash when I can simply steep a heap of crystal or speciality grains and make beer with that?"...Date: Thu, 2 Jul 1998 22:12:04 +0100
From: "Mort O'Sullivan" <tarwater>
Subject: RE: crystal malt: call for discussion
Jeff Renner calls for a discussion on crystal malt, primarily questioning whether it is really true that the sugars from crystal malt are less fermentable than those from standard malts - ((It seems to me that there is nothing inherent about this procedure that should produce more unfermentables than a standard mash. If a temperature regime is used in stewing that would result in higher unfermentables in a conventional mash, the result should be the same.
Now it may be that the stewing is indeed done at such temperatures routinely, resulting in high unfermentables. I think that maltsters have
researched the results of temperature regimes, both regarding sugar profiles and protein profiles, and control these precisely. And, of course, the caramelization of most crystal malts' sugars adds an important flavor component not easily (or at all?) achieved otherwise. Perhaps it is these caramelized sugars that are less fermentable than they would be uncaramelized? I don't think so, but I'm trying to think of all of the angles.))
These are very good questions. The starting point for creating crystal malt is usually well modified green malt at >43% moisture and the initial air on temperature is usually 65-70*C. Holding at this saccharification temperature is often compared to mashing within the kernel, but some important differences should be kept in mind. First, at about 43% moisture, the liquor:grist ratio is much lower than in a normal mash; and second, the "grist" is never milled but simply consists of starch-and-protein-containing endosperm cells whose walls have been degraded during germination by endoproteases and beta glucanases. These conditions limit the amylase enzymes' access to substrate compared to normal mashing conditions. There are still plenty of reducing sugars released to react with the primary amines in Maillard reactions to form the reductones, furans, pyrroles, pyrazines and countless intermediates that provide the characteristic flavors and colors to crystal and caramel malts. Once caramelized, these sugars are no longer sugars, and so are not fermentable by yeast. However, only a small percentage of the sugars actually undergo Maillard reactions and so presumably there are plenty of other sugars, dextrins, and partially degraded starch molecules remaining that would eventually contribute to fermentability, especially after they are mashed in the presence of the "healthy" enzymes from the normal malt that makes up the majority of your grist. But this is not the case.
Why?
Starch molecules in barley are approximately 25% amylose, and 75% amylopectin. Due to the limited enzyme mobility described above, the amylopectin is preferentially broken down because the complexity of the molecules "entraps" enzymes in microchannels on the surface of the amylopectin molecules. The much longer, straight-chain amylose molecules are solubilized, but survive the process relatively unscathed. During the later, high temperature stages of kilning and subsequent cooling, these solubilized amylose molecules tend to recrystallize in a process called retrogradation. For reasons not entirely understood, these recrystallized amylose molecules are very resistant to enzymic hydrolysis and so will not yield fermentable sugars.
It has also been noted by many researchers that regardless of the type of malt being produced, there is an inverse relationship between the time spent at high temperature in kilning and the fermentability of a malt. As crystal and caramel malts can spend quite a long time at temperatures as high as 150*C, it makes sense that their fermentability may be severely reduced.
Hope this helps.
Mort O'Sullivan
Edinburgh, Scotland
Cheers,
TL
