Backpack brew

I would like to start brewing small batches of beer while I am camping. I have most of the logistics figured out: set up camp next to a fresh water source, filter 1+ gallons, collect any local ingredients (e.g. blueberries), sleep, wake up and pack my campsite, brew a 1–gallon (3.8 L) extract recipe on a portable jetboil stove, filter into a jug and hike out. My question is, when should I pitch my yeast? I figure the hike out will aerate the wort but how much time (and movement of the wort) is too much?

Gabe Smoley
Spokane, Washington

I love the adventurous spirit of the West. Add this to the reflex for creative thinking common to homebrewers and out comes Gabe’s Nuts and Berries Trail Ale. I must admit that this idea sounds like a relaxing start to a day in the woods and, as long as you don’t have any grand plans to turn this into an all-grain endeavor, it should be fairly easy.

No matter the type of beer being brewed which relies on the introduction of yeast for fermentation (contrasting with beers like lambic that are inoculated with yeast and bacteria from the local area), it is extremely important to recognize the difference between the hot and cold sides of the brewing process. The hot side involves everything up to wort cooling and is notable with respect to sanitation because the penultimate step is usually wort boiling. The cold side involves handling cool wort and beer, both very good media for the growth of microorganisms, and success in the cold side of brewing really demands a clean and cleanable environment. The mountain trails around Spokane do not come to mind when I think of a cold cellar.

Wort boiling can correctly be referred to as a process that achieves commercial sterility, the semantics I will leave for personal research. In commercial breweries it is common to move the wort from the kettle to a whirlpool vessel before wort cooling and the hot wort is a form of sanitizer for the whirlpool, explaining why whirlpools, unlike fermentation vessels, are usually not sanitized after cleaning. Freshly boiled, scalding hot wort is not likely to become contaminated from the environment and wort contamination normally occurs during or after the wort chilling process. Wort cooling really does two things for beer. The most obvious achievement is that cooling permits the addition of yeast to the wort and subsequent transformation of wort into beer. Chilling also stops some of the chemical changes that happen to wort when it is hot, such as color development, conversion of S-methyl-methionine (SMM) to dimethyl sulfide (DMS) and isomerization of alpha acids into iso-alpha acids. The general rule is to cool wort quickly after boiling.

If I were serious about brewing out in the woods, I would disregard the rule about rapid cooling and take a lesson from the treatment of whirlpools before use. If you transfer your freshly boiled wort to a 1-gallon (3.8 L), heat resistant container that can be sealed, you are doing what food processors call “hot filling” the container. The hot fill process sanitizes the container with the heat of the product and is a common method of filling a variety of food packages. After hot filling you can then cool the wort to stop the reactions mentioned above. The one reaction I am most concerned about when holding hot wort after boiling is the transformation of SMM to DMS. You can use the fresh water source near your campsite to cool your hot-filled container of wort.

I wouldn’t be too concerned about precise temperature control, just knock the wort temperature down below about 120 ˚F (49 °C) to prevent DMS formation, which really is more of an all-grain concern because during the production of malt extract most of the SMM in malt is converted to DMS and removed. But cooling the wort down also will make your hike out a bit more comfortable since you won’t have a jug of hot wort strapped to your back! On your hike out I wouldn’t spend any time thinking about wort aeration because you really won’t have much of that happening if you follow my plan. You want the wort to remain commercially sterile after boiling. This will not happen if you aerate the wort because you would need to get air into your jug. You may get some air into the wort from the headspace, but hot filling works best when you minimize the headspace so aeration ideally will not happen on the hike out.

If you make it out of the woods, are able to avoid rush hour traffic and get back home within 2–3 hours, you probably will be successful in your endeavor. All you need to do is sanitize the outside of your jug. You also need to sanitize a fermenter and ready your yeast. After transferring the wort from transport vessel to fermenter, you will want to aerate, then pitch your yeast and carry on as usual. Some readers may be thinking I am reckless in my advice and that the best advice would be to tell you to take your idea for a hike! However, there is precedent for delaying yeast pitching in the method of trub removal called flotation. So for all of those opposed to Gabe’s somewhat zany idea, read up on wort flotation tanks and you will find some similarities in the methods.

Feeding yeast

What are yeast nutrients and how are they used?

James Warren
Albany, New York

Most yeast nutrient blends contain amino acids, inorganic nitrogen (ammonia), B-vitamins, sterols, unsaturated fatty acids and oftentimes autolyzed yeast which gives a mixture of all of these components. These blends are typically used when making wine, cider or high adjunct beers to provide critical growth factors required by yeast. Fermentations lacking yeast nutrients are usually sluggish with a tendency to become stuck.

Brewer’s wort is a very rich medium and has most everything that yeast require for a good fermentation. In fact, the practice of re-pitching yeast from one batch to another usually carries some autolyzed yeast with it and yeast extract is a good source of vitamins, amino acids and fatty acids. When yeast grows, amino acids and nitrogen are required for protein synthesis, sterols and fatty acids are used to build cell walls (yeast can synthesize these compounds as well as use external sources) and B-vitamins are used as co-factors in yeast metabolism.

Brewers typically do not add these sorts of nutrient blends unless brewing high adjunct or very high gravity brews. Zinc is one nutrient often added to wort, as yeast requires some zinc for growth. Wort zinc levels should be between 0.10–0.15 ppm. Zinc can come from copper when using copper brewing vessels, but most equipment is stainless steel, so zinc additions are helpful.

One problem with adding zinc salts, such as zinc sulfate, is that much of the zinc is lost in trub. Biologically available forms of zinc can be enhanced by growing yeast in a zinc-enriched media and then drying the yeast for use as a yeast nutrient. This form of zinc has lower trub losses when added to the brew kettle.

I use such a product for every batch of beer we brew at our brewery and have used this nutrient, called Servomyces, for the last eight years. If wort is low in zinc, lagging fermentations are seen as well as poorly flocculating yeast. A friend of mine working for a very large brewery told me that they have a target yeast density following primary before transferring to the lagering tanks and that this brewery adjusts wort zinc levels to influence cell density after primary. If the cell density is too low, they back off on the zinc to reduce yeast flocculation. If the cell density is too high, the zinc dose is slightly increased.

In my experience brewing all-malt beers and some beers with about 25% adjunct, I have never felt the need to add any nutrients to wort other than zinc since wort is really the ideal nutrient source for hungry yeast cells!