ZnS04 * 7H2O

A few people have emailed me to ask me what, exactly, I mean when I say to add a “Zinc solution” to the end of their boil when they ask for advice on how to reduce their lag time. A few different things can cause a slow start to fermentation: old yeast, an insufficient yeast pitch rate, and poor quality wort. The quality and quantity of your yeast is easy usually to figure out and fix. Your wort chemistry, however, is different, and to play it safe many brewers add yeast nutrients to their boil to avoid problems. If you’ve spent any time brewing you have most likely heard of yeast nutrients, and when I advise that you add zinc to your boil I’m basically advising the same thing.

So why go through the trouble of making your own nutrient solution? Simple: Cost and Precision. Most yeast nutrient blends are a hodgepodge of different chemicals and biologicals, often with a proprietary and secret formula, and they can play absolute hell on your water chemistry and salt ratios if you’re not careful. Many aren’t even designed for wort, and are often geared towards the longer-established wine industry.

Even if they’re perfect for wine musts these blends fail to take into account that many of the nutrients they seek to add are already present in malted barley. While certainly not a cure-all for poor quality ingredients or bad processes adding just the barest amount of zinc to your wort can, according the professional brewing world and literature, drastically reduce yeast stress. This leads to improved fermentation performance, improved flocculation, and decreased turnover time (De Nicola, Raffaele, and Graeme 2009).

At the commonly recommended dry pitch rate of 1 gram of zinc sulfate heptahydrate per 15 barrels that comes out to just over 11 milligrams of zinc per 5 gallon batch at the homebrew level.  At the brewery I intern at we do something similar, and I suspect the pitch rate is the same.

So how to you add such a small volume? Easy: create a solution out of it using the following steps.

Steps

  1. In a 500ml graduated cylinder measure out 400ml of distilled water.
  2. To this dissolve in 1 gram of zinc sulfate heptahydrate.
  3. After all of the zinc has dissolved top up the water to 450 ml.
  4. You now have a 1 ml per gallon liquid zinc solution. Conveniently enough this comes out to 1 tsp (5 ml) of solution per 5 gallon batch.

For larger volume batches (10 gallons or larger) you may want to consider doubling the concentration to avoid watering down your wort.  You can do this by either adding 2 grams to your 450 ml total or cutting your total water down to 225 ml.

With a proper zinc dosing you should find that your fermentation lag time, and total fermentation time, will noticeably reduce. A well fed yeast is a happy yeast, and a happy yeast works harder without stress or complaint. The end result? You get your beer faster. What’s not to like?

De Nicola, Raffaele, and Graeme MWalker. “Accumulation and cellular distribution of zinc by brewing yeast.” Enzyme and microbial technology 44.4 (2009):210-216.