tl;dr – You can make a beer using 90% waste bread. Maybe more.
Two key changes to the normal brewing process were used to overcome the difficulty in creating fermentable wort with high proportions of bread: Enzymatically active wort and a long beta-glucan/gelatinisation rest. This resulted in a higher than expected original gravity and a lower than expected final gravity, improving the efficiency of the process.
According to the charity Feedback, almost half of all bread produced in Britain is wasted. In order to promote an alternative use for unwanted bread they are developing a concept called Toast Ale, based on a similar project in Brussels, that encourages the use of bread as an adjunct in brewing. A representative from the charity came to a meeting of London Amateur Brewers to discuss issues relating to the development of just such a beer, and to ask for advice and opinions.
The most obvious problem with this plan is that bread (although mostly made from wheat, which is often used in brewing) has no diastatic power, which means there are no enzymes available to turn the starch into fermentable sugars. This isn’t an uncommon problem, of course; many adjuncts used in brewing have low or no diastatic power and generally you just mash them with something that has diastatic power to spare. Generally speaking, most people wouldn’t use much more than 20% of their grain bill as these kinds of adjuncts.
The problem with this approach is that it doesn’t really address the issue the charity are trying to press. Bread as an adjunct doesn’t have many apparent benefits; it doesn’t give colour and roasted flavour like dark malt, it doesn’t improve mouthfeel like oats, it doesn’t even provide an easy source of fermentable sugar like rice. It’s eminently possible that benefits exist, if used in the right way, but as it stands I get the impression that the cost-benefit wouldn’t favour the use of bread, even if breweries were given it for free.
The other option is to try and push the limits. Make a Bread Beer, rather than a Beer with bread. With that in mind, I attempted to find out how much bread it was possible to use in a brew.
Normal malted barley has enough enzymes to convert itself and between two and three times as much adjunct, which gives us a theoretical ceiling of 75% bread. However, a very interesting article on Braukaiser talked about using enzymatically active wort to increase attenuation.
The enzymes that convert starches to sugars during the mash work best at temperatures around 60-65°C, but are then destroyed when the sugary wort is boiled. The principle of enzymatically active wort involves saving some of these enzymes during the mash and adding them to the fermenter after the rest of the wort has been boiled and cooled. Fermentation temperatures of around 18°C aren’t ideal for these enzymes, so they work slowly, but they have up to two weeks to slowly convert starches to sugars while fermentation is taking place.
In this case, the mash consisted of:
- 95% bread, mixture of brown, white and wholemeal, dried and loosely broken into small lumps, between 1cm and 5cm.
- 5% Marris Otter, in the main mash to provide some diastatic power (theoretically enough to convert around 20% of the bread)
The mash schedule for the main mash involved a 20 minute beta-glucan rest at 45°C and a 60 minute gelatinisation rest at 55°C. Earlier experiments indicated that extended rests in this temperature range resulted in a much higher specific gravity being achieved. It’s unlikely, of course, that this increase in specific gravity is the result of dissolved sugars, but rather suspended starches and other similar molecules due to the breakdown of starch granules and the breaking of intermolecular bonds.
- 5% Marris Otter, mashed separately from the rest of ingredients at 62°C for 60 minutes.
The liquid was decanted off, pasteurised for 2 hours at 70°C, and added to the fermenter.
The main mash was lautered and boiled for 60 minutes with a small amount of Hallertau hops. After cooling, a small amount was set aside as a control, and the enzymatically active wort was added to the rest. California Ale yeast was pitched as it’s generally a good attenuator (and it was what I had to hand). Fermentation was for two weeks at room temperature, followed by force carbonation.
It’s important to note that this was principally a test to see if it’s possible to make a beer from 90% bread, not whether that’s at all desirable or even advisable. In that respect, it can largely be considered a success.
Due to a miscalculation, the original gravity was much lower than intended, at 1.027 from 1.25kg of bread, which gave a respectable PPG (points per pound per gallon) of 32. This is an improvement over previous test mashes, without extended low temperature rests, that resulted in around 22PPG. Of course, it’s unclear whether this is as a result of the temperature or a much longer overall mash.
Nonetheless, the fermentation with enzymatically active wort finished with a final gravity of 1.003 (89% attenuation), compared to the control fermentation at 1.015 (44% attenuation). As such, I think it can be said that long gelatinisation rests and the use of enzymatically active wort in the fermenter are effective methods for overcoming the difficulties in brewing with bread. In fact, it could be said that the proportion of bread could be increased.
It’s worth bearing in mind, though, that change in specific gravity is only a proxy measurement of alcohol production and, while almost always true in most cases, it’s possible here that the change in specific gravity is due to other factors such as, for instance, settling out of suspended unconverted starch molecules.
It’s also worth bearing in mind that it wasn’t a particularly nice taste, although, in my defence, that’s not what I was really aiming for. Clarity was poor, which could have been due to a range of issues, perhaps residual starch molecules. There was also a strong salt taste, that was common to all the beers produced with bread, which will have to be addressed before a truly good beer can be made this way.