April 12, 2019

We thought it would be interesting to see the effects the filter has on home brewing cold brew coffee.  We did not go all scientific method on this experiment and we definitely have a pretty small sample size.  But the results were interesting to look at.

We kept the following the same:

  • Bean Blend (roasted and blended on the same date - our Connection Blend (102))
  • Water (store bought spring water)
  • Amount of cold brew coffee grounds
  • Amount of water
  • Brewing time
  • Temperature

The true variable was the filter we used and regarding the stainless steel filter was part of a different brewing system (KitchenAid), so that is a little different as well...

We used 2 different types of one time use filters (different vendor and the size was slightly larger on the one) and the other filter was a stainless steel filter.

One thing we could not determine was the micron size of the filter.  By observations, I will say the stainless steel filter was the smallest in micron size.

We used a spectrometer to measure the TDS (it takes a series of 15 samplings to produce the result).  The spectrometer also measured temperature. We measure the yield by weighing the resulting concentrate on a scale.

Brew ID

Filter

Yield Percentage

TDS

Extraction % Concentrate

1

Smaller Bag

71%

3.9

13.7

2

Larger Bag

69%

3.9

13.4

3

Stainless Steel

68%

3.8

12.8


So what did you find?  When you consider a standard deviation of the spectrometer, the Total Dissolvable Solubles (TDS) did not change.  So what gives the coffee flavor from an extraction stand point that process was still able to occur. In theory if we knew the micron size and could control that variable better we might be able to see differences.  But I am assuming since no significant difference in TDS, the micron size was not small enough to impede the extraction process.

Yield saw a little bit of a difference, my theory here is the bags actually absorb some of the oils and the water.  Which seems to make sense given the smaller bag has a higher yield. A bit of a curve ball is the stainless steel have the lowest yield, there would be no absorption of water or oils via this filter.  But the brewing apparatus was different, so my guess is that there is a lower yield due to the brewer. Another plausible reason for the higher yield using the bags was that when the bags were removed from the jar the bag was compressed and liquid squeezed out from the grounds within the filter whereas the stainless steel filter was only drained using gravity.

So that was the data that we were measuring.  What was interesting was the taste, Kayla (daughter), Lynne, and I were doing taste tests (for them they did not know which sample was from which batch).  We all agreed each batch tasted differently. The stainless steel was very smooth and I believe that was from more sediment being removed from the concentrate.  The other 2 tasted different as well, notes of flavor was highlighted differently in each batch. There was not one that tasted poorly. But there was a difference in taste.

So the moral of the journal, in addition to a ton of variables that makes a difference in the taste of your cold brew, be mindful that how you filter your brew also affects the flavor profile as well.