Potato Beer

Q: A lady told me that she heard of using potatoes to brew beer — so I tried it! My spud ale came out quite good, but I need to do some refinement. Any advice?
— Jack Tillman • Etna, California

A: When I was a graduate student at UC-Davis I attended a Master Brewers meeting at the local Sudwerk Privatbrauerei Hübsch brewery where I worked part-time as a brewer. The speaker at this particular meeting was a retired brewmaster from the Lucky Lager Brewing Company in San Francisco, which closed in 1978. The retired Lucky brewmaster talked about what he did during WWII to keep beer flowing from the brewery when corn and rice adjuncts were rationed and unavailable to brewers. He told of using potatoes as a replacement for rationed raw materials commonly used by brewers as adjunct grains. If my memory serves me right (this talk was given in 1993 or 1994) he used dried potato spuds. Before diving into this question I bought some dried potato spuds and verified that they are easy to handle and could have been received, stored and conveyed like other dry raw materials used by brewers. They also are extremely easy to hydrate.

So there is a precedent for potato beer. When you add potatoes to beer, be they boiled and mashed or dehydrated spuds, you must recognize that you are adding starch. This starch must be converted by amylase enzymes into fermentable sugars, just like any starchy brewing ingredient. The gelatinization temperature of potatoes is around 140 °F (60 °C) The other thing about potatoes is that they have a distinctive sulfur aroma and I would remove these compounds before fermentation. That’s another plus of using dehydrated potato spuds, since a lot of the sulfur aromatics in wet potatoes are driven off with moisture during the dehydration process.

The nice thing about potato starch is that it is not so different from barley starch. It normally contains a bit more amylose than barley starch (different varieties of potatoes and barley have different amylose and amylopectin profiles), but usually is about 50% amylose and 50% amylopectin. It also has a gelatinization temperature similar to barley starch (of course the dehydrated spuds are already gelatinized). What this means is that potato starch will behave quite normally in the mash and even if you decided to use “raw” potatoes instead of dehydrated spuds you would not have to boil the potatoes before mashing. If you shredded your tubers using a cheese grater as if preparing hash browns the potatoes will hydrolyze like the endosperm of malt when added to the mash.

I think the use of potatoes makes a lot of sense and you do have history on your side. But you also know now that their use by US brewers seems to have stopped after the rationing of food crops during WWII . . . so one has to wonder why it was discontinued. ‘Taters are certainly cheap, so my guess is that off aromas may be an issue in some cases.

If I were you I would brew some more batches, but would use step mashing to convert the potato starch into fermentable sugars.

While we’re on the subject, I have to admit that I have considered using potatoes for an Irish dry stout for a really geeky reason; Ashton, Idaho is known as the potato seed capital of the world, my name is Ashton and there was something in Ireland’s history related to potatoes. Like I said, pretty geeky!