Here’s What Happens if Your Mash pH Is Too Low

Mash pH is a crucial element in the brewing process, determining the effectiveness of various mashing parameters and affecting the overall quality of beer. So, what happens if the pH value falls below the optimum?

If your mash pH is too low, it can result in a less pronounced taste and reduced body. The beer would still be good, but, generally speaking, maintaining a pH level between 5.2 and 5.8 is optimal. If the pH falls to 2, the brewing enzymes won’t be active.

In the following sections, I’ll be diving further into the effects of mash pH being too low, the optimal level of mash pH, the relevance of the indicator, and how to adjust mash pH to achieve a better-tasting result. Let’s get started!

The Effects of Mash pH Being Too Low

It is important to pay attention to the pH value while preparing mash. Typically, so long as all the previous steps of the brewing process have been handled well, it should fall within the optimal range without the need for any additional help.

However, due to various reasons, the main one usually being the water alkalinity, the mash pH can be lower than expected. While lower pH is typically not as bad as too high of a pH, it is still an issue that shouldn’t be overlooked.

How Low Is Too Low

Before we get into more detail on the subject of low mash pH’s effects on the result of beer brewing, it is essential to determine from the start what value should be considered too low.

Everything below pH 5 is lower than the optimal pH value for mash. Everything under pH 4 falls into the category of not recommended, and a pH of 2 or less indicates that the fermentation simply won’t happen.

Ideally, the mash pH should not be lower than 5.2. That is the consensus of most professionals. 

Recommendations can differ slightly depending on what sort of beer is being brewed. As dark beers are known to drop to lower pH levels than light ones during the fermentation process, for them, the lowest pH point can be more stretched.

A pH range of 4.25 – 4.6 is widely recognized as appropriate for all malt beers. For adjunct beers, mash pH can be as low as 4.0, and it can go even lower than that for sour beers.

The Effects on Flavor

For many brewers, the taste of beer can be considered the primary characteristic of the finished product. While evaluating beer taste might be subjective, we have chemistry at our service to determine the basic flavor qualities and in what way they are affected by low mash pH.

The pH value will influence the taste of beer directly. The recommended mash pH is 5.2-5.6, and during the boiling and fermentation processes, it will decrease, with ales ending up in the range of 3.8-4.2 and lagers in the range of 4.2-4.75.

However, if the mash pH is lower from the beginning, it will result in the beer pH dropping beyond the desired values in subsequent brewing phases as well.

At pH lower than 4, the following effects on the beer flavor have been reported:

  • Reduced body, meaning the reduced fullness of taste and ‘thickness’.
  • Increased bitterness and sourness in the taste.
  • Drying in the aftertaste.
  • Reduced flavor stability (poorer flavor qualities over a period of time).

The Effects on Enzyme Activity

While enzymes can be active at pH values lower than the recommended standard, the process will take significantly longer. 

At pH lower than 4, a rapid decrease in catalytic enzyme activity has been reported, meaning that the mash time can double or even triple depending on the exact value.

It is strongly recommended against letting the mash pH drop below two since, at that value, enzymes lose most of their catalytic activity

If enzymes experience denaturation due to the decreased pH value, their activity won’t be restored. At that point, the process is irreversible.

As there are different enzymes involved, you may find varied information regarding the ideal mash pH level for each. However, the stated optimum of 5.2-5.6 works well for most mashes. 

The Optimal Mash pH Level

In short, mash pH is formed when the malt meets water. Water is an alkaline component that pushes mash’s pH to be higher, while the malt acids tend to reduce the overall pH value. 

As a result, the two main factors that influence mash pH are water and malt. Other factors also influence the process, but their effects are not fully studied yet. 

Despite the complexity of determining the impact of these variables on the pH value and their precise effects on the end result, a general consensus on the optimum figures of mash pH does exist.

Most experts agree that the desired optimal level for mash pH is between 5.2 and 5.6. This number is backed by scientific data regarding the general influence of the pH value on mashing parameters.

Research Data

In his article ‘PH in brewing: An overview,’ Bamforth provides the following table that reflects the optimum mash pH values for a range of parameters based on two researched data sources.

Briggs et al.Bamforth & Simpson
Highest Extract yield5.2-5.45.3-5.8
Highest Fermentability5.3-5.45.4-5.8
Fastest Wort Filtration“mash impossibleto filter < 4.7”4.4-4.6
Highest Total Soluble Nitrogen4.64.7-5.0
Highest Free Amino Nitrogen4.64.7-5.2

Although the numbers vary to different extents, the data proves the maximized effectiveness at pH between 5.2 and 5.6. It is evident that within that range, the extract yield and fermentation are most rapid.

We can see that the numbers for filtration differ rather drastically. While Bamforth & Simpson’s study suggests an optimum of 4.4-4.6, the Briggs et al. data states that at pH under 4.7, filtration becomes impossible.

The differences in data can be explained by another variable involved in the process. You’ll often have to use additional components, such as acids or calcium, to achieve the desired pH value.

The higher value for filtration in Briggs’s study can likely be explained by the use of calcium, while in the other research, acids were used, and hence the filtration optimum was lower.

As mentioned, the impact of each component on the overall result isn’t yet studied thoroughly. However, the provided data suggests that the agent used to adjust the pH of mash impacts the optimum value for mashing parameters.

The Relevance of Mash pH

It is crucial to understand in what way ensuring the proper mash pH value impacts the quality of beer and the effectiveness of processes during the brewing. As it happens, the impact is quite significant.

We have already discussed the effects of mash pH on enzyme activity and beer flavor. While those points are crucial for the overall beer quality, there is still more to unpack.

Tannin Extraction

Tannins are chemical compounds that originate in beer from the malt. The right amount of tannins is important for the quality of beer and its flavor.

The pH level of mash has a prominent effect on the tannin extraction. Simply put, the higher the mash pH is, the more tannins will be extracted.

The optimal pH level of 5.2-5.8 is low enough to ensure the right amount of tannins that will contribute to the body and flavor.

However, excessive tannin extraction will have negative effects on the flavor. The beer will taste bitter as a dry and puckering sensation will appear in the aftertaste. It is called astringency.

You may find the effect familiar to that of strong tea. While tannins can be pleasant, their excess resulting in astringency won’t improve the quality of beer, but rather do the opposite.

Hop Extraction

The optimum mash pH level is also crucial for the process of hop extraction. The taste component related to hop extraction is the level of bitterness.

The impact is similar to the effect on tannin extraction: higher mash pH results in more bitterness. Similarly, too low pH will result in beer lacking in flavor

On the other hand, the optimum pH level ensures the bitterness is smooth and compliments the taste of beer.

Yeast Health

Last but not least, the proper pH level is crucial to ensure a healthy fermentation process. Yeast lowers the pH of the beer while increasing its own pH level, enhancing maltose absorption.

The capacity of yeast to reduce the pH of beer is essential for lowering yeast stress and ensuring healthy fermentation. Not maintaining the proper conditions for the process will decrease its effectiveness.

Maintaining the optimal pH level will ensure yeast is healthy and able to perform its function successfully. This allows for yeast to be reused multiple times.

How To Adjust Mash pH

Now that we’ve discussed the importance of mash pH in further detail, it’s time to talk about how this level can be adjusted to ensure the perfect result. Here are some methods for decreasing and increasing the pH level, so you can choose the one that works best for you.

Use Acids

You can use acids to decrease the mash pH if needed. Mineral acids or lactic acid can be used for this purpose.

Phosphoric Acid

Phosphoric acid can effectively reduce the water pH in the mash. It is safer than most analogs and is widely used in soft drinks.

1/4 tsp (1.23 ml) phosphoric acid per 5 gallons (18.93 liters) of water should be enough to reduce the pH to the optimum value. Make sure not to use it excessively.

Muriatic Acid

This one, also known as hydrochloric acid, also works well for the purpose of decreasing mash pH, but it can be dangerous, so proceed with caution.

Only get food-grade acid and be cautious while using it since it can damage your skin and eyes if it comes in direct contact. Adding too much muriatic acid will result in a salty beer flavor.

Lactic Acid

This one is an organic acid and would be a safe choice for brewers. 0.25 g lactic acid per liter will reduce the mash pH without negatively affecting the flavor. When used in excess, lactic acid can make beer taste sour.

Add Gypsum

Calcium Sulfate, also known as gypsum, works well for reducing the mash pH. Again, you don’t want to use it excessively, so it doesn’t have any adverse effects on the end result.

Add the gypsum at ½ or ¼ tsp (1.23 or 2.46 ml) at a time. After each addition, mix well and measure the pH level. This method will ensure you use just enough gypsum and not more than needed.

Use Calcium Carbonate

Using calcium carbonate, on the other hand, is an excellent way to increase the mash pH if it is too low.

You can add it manually, starting with ½ tsp, mixing well, then measuring pH and adding more if necessary. Do not add more than 2 tsp overall.

Try the Slaked Lime Method

This method is quite practical, but it should be studied in detail before being used. Here you can find the detailed instructions and the spreadsheet calculating the required amounts for everything.

Put shortly, the method works as follows. You will need salt, lime, and chalk. Add the ingredients to water and mix well, reducing the uptake of atmospheric carbon as much as possible. Measure the pH and ensure its value is somewhere between 9 and 11.

Let settle overnight and measure the pH to determine the final result. After settling, the pH level will decrease, but it should still be higher than it was initially.

This method works best for reducing water alkalinity while also reducing the pH level. It is crucial that water contains enough calcium in order for this solution to work.

Final Thoughts

Keeping mash pH at an optimal level is crucial for the quality of beer. While pH being slightly lower than the desired value is not a catastrophe, it will still have notable negative effects on the speed of the process and overall beer flavor.

About HomeBrewAdvice

Hello, my name is Simon. Together with a group of writers I write about brewing beer and making wine. We all share a passion for the great things in life, such as making stuff from scratch.

The business of HomeBrewAdvice is to bring you great information, stories and product reviews from brewing at home, and making wine


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