How Does a Cold Brew Affect Caffeine?
 
 
One of our regular customers was recently considering a cold brew method for making tea, and in fact, posed the question “How much caffeine is released in cold brewing?”
 
 
This is a fair question, as many people might want less caffeine, some people might want more, and most of us probably do not want to see too much change in the caffeine that we consume.  Since the question is fair, and the answer was not clear, our team of experts did a little research on recent scientific articles that deal with this exact topic; cold steeping versus hot steeping tea in relation to the release of polyphenols, catechins, and caffeine.  For the sake of simplicity, this write-up will only concern itself with the caffeine levels that were measured by the studies.
 
 
The Method
Each study used different parameters and teas:
 
  1. The study (here to after referred to as Study A) by Damiani, Bacchetti, Padella, Tiano, and Carloni (2014) used only white tea in the study. 
  2. The study (here to after referred to as Study B) by Lin, Yang, Hsieh, Liu, and Mau, (2014) utilized only green tea in the study. 
  3. The study (here to after referred to as Study C) conducted by Yuann, Wu, Chang, and Liang, (2015) utilized green teas, oolong teas, and black teas as samples.                                       
     
 
The Results
 The results of the study were interesting in all respects.  Study A showed that the caffeine levels in the white tea tested to be significantly higher with the cold steep than with the hot steep.  In fact, presented figures show the caffeine in the white tea used may be up to 2-3 times that in the cold brew as is in the hot brew (Damiani, et al, 2014).  What is interesting is that the resultant higher caffeine count was seen in all eight samples of tea that were used in this particular study.

 

The other two studies, both Study B and Study C, showed that caffeine levels were lower, sometimes as much by 30% in each tea that was sampled, and this trend was present whether the tea was green (Lin, et al, 2014; Yuann, et al, 2015), black, or oolong (Yuann, et al, 2015). 

 

Discussion of Findings

 

It is important to note that the parameters of each study was markedly different, and that only one study considered white tea, and indeed the study that used white tea used only different samples of white tea.  In addition, the chemical and mechanical measurement of the caffeine levels varied from study to study. 

 

A single study does not demonstrate a trend or a scientific law, it simply sets the framework for additional studies, provided that the parameters that are used for the study are kept identical as to demonstrate the repeatability and transferability of the study.

 

Bearing these facts in mind, at the present time, the evidence is relatively inconclusive.  However, with only one study conducted in relation to white tea and the caffeine content differences between a cold and hot steep, this is a strong framework for additional study.  In the instance of green tea (and oolong, since it is closely related to green tea chemically) there seems to be a stronger evidence that a lower caffeine content results from a cold steep.

 

Enough Science… what does it mean?

Really, at this point, the studies seem to give more evidence to teas that are oxidized as having less caffeine drawn out of them during a cold steep.  This could be a result of the time, the temperature, or even the manner in which the scientists measured the results.  However, the fact that a 24 hour steep was conducted in one study offers evidence that a cold steep will simply not draw out the same caffeine levels.  This is likely due to the lack of a chemical change that occurs when heat is added to the tea leaves.

 

It also appears that white tea, which is largely not oxidized, may release more caffeine the longer it steeps regardless of the temperature of the water.

 

Really… overall, it looks like we need more information to really know the answer to this.  But at the moment, if you are watching your caffeine intake, you really should consider a cold steep when drinking black, green, or oolong tea.  At the present time, it is logical to assume that white tea will have more caffeine during a cold steep.  Either way, there is no evidence provided that either method will result in a complete lack of caffeine, or caffeine levels that will prove to be harmful.  So, drink more tea, whether it is white, oolong, black, or green, the tea is still healthy, whether steeped cold or steeped hot.

 

To your health!

 
 

References:

Damiani, E., Bacchetti, T., Padella, L., Tiano, L., & Carloni, P. (2014). Antioxidant activity of

different white teas: Comparison of hot and cold tea infusions.  Journal of Food

Composition and Analysis33(1), 59-66.

Lin, S. D., Yang, J. H., Hsieh, Y. J., Liu, E. H., & Mau, J. L. (2014). Effect of different brewing

methods on quality of green tea. Journal of Food Processing and Preservation38(3),

1234-1243.

Yuann, J. M. P., Wu, J. Y., Chang, H. H., & Liang, J. Y. (2015). Effects of temperature and

water steeping duration on antioxidant activity and caffeine content of tea.  MC-