Brewing is as much an art as it is a science. As craft brewers and homebrewing enthusiasts delve deeper into the intricacies of the brewing process, the importance of various stages and techniques becomes a topic of debate. Among these, the use of acid and protein rests has garnered significant attention. But how necessary are they? Let’s dive into the science and scholarly research to find out.

For a deeper dive into proteins, DEFINITELY check out my forming Ultimate Guide to Proteins in Beer Brewing series.

What are Acid and Protein Rests?

Before we delve into the nitty-gritty, it’s essential to understand what these rests are. During the mashing process, grains are soaked in water to convert their starches into fermentable sugars. This process involves various enzymatic activities, and the temperature at which mashing occurs can influence these enzymes.

1. Acid Rest: This is a lower temperature rest (typically around 95°F or 35°C) that encourages the production of phytase, an enzyme that lowers the pH of the mash. A correct pH level is crucial for the subsequent enzymatic activities and overall efficiency of the brewing process.
2. Protein Rest: Conducted at slightly higher temperatures (usually between 113°F and 131°F or 45°C to 55°C), this rest targets proteolytic enzymes. These enzymes break down large proteins into smaller peptides and amino acids, which can improve the beer’s clarity and stability.

So, Are They Necessary?

The answer, as with many things in brewing, is “it depends.” Modern malting processes have evolved, and many of the malts available today are well-modified. This means that they’ve already undergone some degree of protein breakdown during the malting process. For such malts, a protein rest might be redundant or even counterproductive, leading to a thin-bodied beer.

If you are targeting a more pronounced mouthfeel, mash on the lower end at 113F to 122F and keep the rest below 20 minutes.

If you are targeting a thin bodied brew, aim for the higher side from 122F to 131F, and definitely keep your mash time under 20 minutes here otherwise you may impact foam stability.

On the other hand, if you’re using under-modified malts or specific traditional grains, a protein rest can be beneficial. Similarly, the acid rest’s necessity largely depends on the water chemistry and the grains used. Brewers with water that’s naturally closer to the desired mash pH might find the acid rest less critical.

Also see our other article on Protein rests and the impact they have on body, mouthfeel and head retention!

Conclusion

Brewing is a dynamic process, and what works best can vary based on the ingredients, equipment, and the desired end product. While acid and protein rests have their place and scientific backing, it’s essential for brewers to understand their specific needs and adjust their processes accordingly. As always, the best beer is the one you like the most, so experiment, learn, and most importantly, enjoy the journey!