Coffee Acidity Mini Series - Part 2

April 08, 2020

Measuring Coffee Acidity pH

Part 2 – Actual Measured and Perceived Acidity in Coffee, Water and Other Beverages

This is the second part to our mini series of blog posts on acidity in coffee. In part 1 we discussed the differences between perceived and measured acidity in coffee. In part 2 we will lay out what exactly we’re testing and how we carried out those tests. In part 3 we will present our findings on the perceived and measured acidities of everything we tested. Then we’ll discuss our findings and talk about some potential theories regarding what might account for the results of our experiments.

*As mentioned in part 1, the findings presented here are purely a product of our own experimentation and we cannot guarantee the acidity of anything that we did not directly measure in our investigations. If you have specific health or dietary reasons to seek out beverages with particular acidity levels please consult with your physician before making any decisions about what is safe or ideal for you to consume.

Standardized Testing

By now you’re probably wondering what specific  experimentation we carried out. Our goal at the outset was to keep things as simple as possible. As we alluded in part 1, there are a ton of different variables at play here and only some of those variables are within our capacity to measure. We do not, for example, have the equipment to measure specific mineral content in our brew water or what quantity of any specific acids are present in our brewed coffee. So, we aimed to stick to what our instruments and sensory faculties could tell us while holding as many other variables as possible constant.

We used our digital pH meter to assess the measured acidities and our tongues to assess the perceived acidities of a handful of different solutions. A digital pH meter served our purposes better than litmus strips would have because the digital meter offers much finer measurements than litmus strips do. A litmus strip can typically pick up differences of .5 pH while the digital meter picks up differences as fine as .01 pH. Our tongues are what we use every day when carrying out our quality control cuppings (cuppings are structured tastings that allow for consistent analysis of different coffees and roasts). So we figured it was fitting to use those to assess the perceived acidities of the coffees we had on hand.

We also used our total dissolved solids (TDS) meter to check the extraction of our brews. This tool doesn’t directly tell us anything about the acidities of what we’re testing, but rather, allows us to check the strength of our brew. It shows how much of the solution in question is made up of something solid suspended or dissolved in water. The more dissolved solids in brewed coffee, for example, the stronger the cup. Having this knowledge allowed us to check the consistency of our brews which was important because, as mentioned before, variations in brew parameters can cause variations in acidity.

In an effort to get a grasp on the full picture of what is going on we carried out three separate experiments whose results all inform one another.

Baseline Brew Water Acidity

The first experiment we carried out was relatively straightforward. We wanted to see what sort of variation in pH one might expect to find in the different types of water that they might be using to brew coffee. Our reasoning here was that brewed coffee is usually 98-99% water (espresso is usually in the realm of 91-94% water). Given that water is the main component in brewed coffee we wanted to get a baseline; what level of acidity are we starting with before even beginning the brew process? In order to answer this question, we tested five different types of water:

  • Tap water from our QC lab
  • Filtered water from our QC lab
  • Bottled water
  • Alkaline bottled water
  • Distilled water

This  test was fairly simple. We used our digital pH meter to test the pH of each water at room temperature and we tasted each water to see if there was any perceptible “acidity”. For good measure, we also used our TDS (total dissolved solids) refractometer to check and see if there was a measurable amount of dissolved or suspended solids in each type of water.

Testing acidity of beverages

Does Brew Water Affect Acidity of Brewed Coffee?

After getting an idea of how acidic different brew waters can be, we wanted to see if that difference in baseline acidity translated into a difference in the acidity of the actual brewed coffee. In order to do this, we brewed a single type of coffee on a fixed recipe with each different type of water. As mentioned in part 1, differences in brew parameters can alter the perceived and measured acidity of the brewed coffee. For this reason, it was important that we keep our brew parameters consistent. That way, the differences that we perceived/measured in the brewed coffee reflected the differences in the water used to brew. We then used our digital pH meter and our taste buds to assess the measured and perceived acidity of each brew. We also checked the TDS to make sure we were extracting a more or less consistent amount of “stuff” from the coffee grounds during each brew. Our recipe is as follows:

  • 18 grams of Sträva Courage Coffee ground medium fine (we set our Mahlkonig EK43 grinder to 11)
  • 290 grams of water @ 204 degrees Fahrenheit
  • Brew in a Hario V60 pour over according to the following:

35g water to bloom -> Pour to 170 grams @ 45 seconds -> Pour to 290 grams @ 1 minute 30 seconds -> Let all water drain through.

Pourover Coffee CBD

How do the Acidities of Different Coffees Compare?

After establishing a baseline for the variation in the acidity of our brew water and how that translated to the acidity of brewed coffee, we were ready to move on to see how various coffees compare to one another and to a few other common beverages. In order to do this, we obtained seven different coffees:

The “Low Acid” coffees are coffees that are not produced by Sträva and are advertised as having lower acidity than your typical coffee. We’re curious as to whether there might be anything to those claims.

We then took these seven coffees and brewed each one on a fixed recipe. As mentioned earlier, we wanted to keep all brew parameters consistent; this time with the goal of highlighting the differences in the various coffees we were using (as opposed to the differences resulting from the brew water used). For even greater consistency, we decided to use our countertop automatic drip pot to brew each coffee rather than having a human brew them on pour over (even the best baristas don’t get their pours perfectly identical every single time). We then used our digital pH meter and our taste buds to assess the measured and perceived acidity of each brew. We also checked the TDS to make sure we were extracting a consistent amount of “stuff” from the coffee grounds during each brew. Our recipe is as follows:

Brewing CBD Coffee

  • 40 grams coffee ground medium (12.5 on our EK43 grinder)
  • 650 grams of our filtered water in our Bonavita countertop drip machine

After brewing each coffee, we also tasted and measured the pH of three common beverages:

  • Organic Whole Milk
  • Orange Juice
  • Cold Brew Coffee

Results of Experimentation

So what did we find? Well, you’ll have to tune in when we post part 3 of the mini series to get a full breakdown and discussion of our results.

 

Milk pH Testing





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