 Hey guys, welcome back to my YouTube channel. This is Daniel Rosal here for today's video. We are going to be going down the brief rabbit hole regarding cold brew coffee and trying to answer from science that is just out there for free download on the internet how much caffeine cold brew coffee actually contains. Cold brew is my latest culinary fascination. This is the end of my daily cold brew batch, but I learned the hard way very quickly that this stuff can really, really pack a high caffeine content. I ended up drinking the batch of cold brew I made for the day and saying, oh, this is pretty good. I'll just have a small bit more. And boom, massive panic attack. It was horrible. It was the first time and I've been drinking coffee every day for more years than I can remember. It was the first time I've had a panic attack from caffeine in potentially ever, probably not, but for a very long time and it really caught me off guard. So I found some really interesting science on Google regarding how much caffeine there is in cold brew coffee. Lots of people make guesses on YouTube and in recipes and I think it's better to just sort of look to people that have actually measured the stuff in a lab. So this is, I did another video where I looked at a few different papers I came across on Google Scholar, but this in my opinion is the best one and it's also completely free at the paper that I'm going to show. You can just get it as a PDF from the internet. So here is my presentation of its findings. Be aware or disclaimer. I'm not the author of this research. I'm only presenting this for entertainment purposes. Do not rely upon it for your caffeination planning or lack thereof. Okay. So this is the paper. I'm just gonna move myself over to this side so you can see everything on my screen here. It's called the effect of time, roasting temperature and grind size on caffeine and chlorogenic acid concentrations in cold brew coffee. And it was published in scientific reports as by two researchers, Megan Fuller and Nini Zhez-Rau. So I basically found this by, you know, putting cold brew coffee into Google Scholar. And they do say in the introduction to this paper that like there is almost no research or there was almost no research regarding the caffeine concentration in cold brew before they came along. So I'll put a link to it on the video description. And as I mentioned there, you can actually get the full text PDF of this just by downloading this. This is what it looks like. It's a nicely designed paper with loads of interesting info. And as I mentioned, I'll pop a link to that in the video description. So basically, okay, here's how they did this experiment. They got coffee from regular commercial sources and they quantified the caffeine of four different types of coffee. The first one was a medium roast. So you can see they've noted here, this is the roast and this is the grind size. So firstly, a medium roast with a medium grind size. Then a medium roast with a coarse grind. Then a dark roast with a medium grind size. And finally, a dark roast with a coarse grind size. So those are the four variables. Now, it's really important. They didn't actually really emphasize this in the paper, but they cold brewed at room temperature right at the end of this paper under the methods section. They say the cold brewing process was carried out at room temperature, ranging from 21 to 25 degrees. So like pretty standard ambient room temperature and adopted from a home brewing recipe suggested by the New York Times. Regarding how they measured caffeine, this is all the detail. I don't really understand it, but I trust that they measured it scientifically using some sort of a liquid chromatography system, HPLC. All right, now here's where the juicy stuff for the interesting parts of their findings are to be found. This is one of the first figures in the paper. It's called caffeine concentration over time. Now what we're looking at is the four different types of coffee that I mentioned. We can see that the light orange dot, this one, the medium roast coarse grind actually had the most caffeine and then the dark roast coarse grind had, the two dark roasts are the yellow triangles and the green triangles. And that's actually kind of to be expected because from what I've read before, typically your dark roasts have less caffeine content because as you continue the roasting process, you're roasting away or you're cooking away a little bit of the caffeine content in the beans. So this is buried out by this chart. We can see that the dark roasts have less caffeine and the medium roasts have more caffeine and it's the coarse grind that actually has more caffeine than the medium grind, which actually I find really interesting to me because if we're talking about the surface area as you go towards a finer grind, you're increasing the surface area, but they find that the coarse grind actually had more caffeine slightly than the medium grind. So here's kind of the way I suggested looking at this. Now everyone can interpret this graph in their own way, but to me it looks like about this point where I put the red line and that's after about 600 minutes where they describe it as approaching steady state. In other words, the caffeine content, they're, remember they're doing this at room temperature so they're leaving out their caffeine, their cold brew, four vats of them in wherever they did this research and then they're periodically measuring them using chromatography. And what it seems like to me is that you can see there's kind of this like steep increase in the caffeine concentration over the first, they say 180 minutes, which looks about right to me, that would obviously be three hours. Then from 180 to 360 and 360 minutes is six hours. So then for the next three hours, the curve is flattening and it's coming up less. And then from they, this is where they drew a line in the research, it's at 360. You can see there that the medium roast coarse grind is still edging up slightly. In fact, most of the lines are still trending up slightly. For me, it's a kind of like 600, I would say 600 minutes that it looks like if you look at this dot here and this dot here where I've done the second red line on the right, there is almost no difference. So after 600 minutes or 10 hours of cold brewing, basically you're not getting any more caffeine out of the quantity of coffee that you're immersing. Between 360, which is six hours and 600 minutes, which is 10 hours. So between six and 10 hours, the rate of increased caffeine content is becoming negligible basically. So that's quite interesting. A lot of recipes I've seen talk about, you should cold brew for 24 hours because after 12 hours, we're gonna, there's still lots of caffeine in the bean. And this is basically saying that is not the case at all. After 10, after just 10 hours, so a 12 hour infusion, there's pretty much you're gonna be getting, it's diminishing returns on steroids or maybe on caffeine would be a better way describing it, you're getting a lot less. So this is how they actually described us. The researchers in all coffees sampled, fast initial extraction was seen over the first 180 minutes with a slower rate of extraction after 180 minutes. This analysis concluded that extraction times greater than 400 minutes. And again, it really depends what you view as significant increases to make this determination, but they put it at 600 minutes, which I'm just gonna jump back here for a second. So 600, sorry, 400 minutes would be approximately, I guess this is here, where they've drawn the red line 300, 400, 500, 600, yeah. This is what the broken line represents here, 400 minutes. After 400 minutes, 6.67 hours, do little to increase the caffeine concentration of the resulting coffee. So really, this is my sort of overlay on their charts. I suggest that you can look at this in terms of four stages. Phase one, being the first 180 minutes of fast caffeine extraction. Phase two, between 180 and 360 minutes being slower extraction, the curve is flattening. Phase three, between six hours and 10 hours were almost at steady state, negligible increase in caffeine. And from 10 hours on, it's almost as good as steady state. It looks to me, now they didn't include all their data, raw data in this paper, but it looks to me as if between this orange dot just under caffeine, the word caffeine, and this orange dot over time, it looks to me like there's actually no increase in caffeine at all. So the way they sum this up is that coarse grain samples, both medium and dark roast, showed a considerable deviation in caffeine concentration between hot and cold brew extractions. In both samples, the cold brew coffee was trying to have the higher concentration of caffeine. Medium grain samples also showed higher concentrations of caffeine and cold brew extraction. However, the difference was not statistically significant. So I just kind of pulled these out of the paper again to make this more obvious. Corescreen has more caffeine when cold brewed. So what you're looking at here, as you can see, is on the right, the two graphs to the right, this is coarse grind, and the two graphs to the left are medium grind. And the blue circles and the orange triangles are the cold brew and the hot brew is, the hot brew caffeine line is the straight line with that kind of orange color. Now what's interesting, the hot brew caffeine line is steady, right? All the caffeine is extracted pretty much instantaneously and it doesn't change over time, that's how they're depicting it. But we can see that the cold brew is increasing over time, up to again, about that 600 minute or 10 hour point at which point the increase is very modest. And using the medium grind, we do end up with the cold brew caffeine a tiny bit above the hot caffeine, the hot brew caffeine line. And I'm actually just gonna turn on my cursor and wave it around so I can show exactly what I'm pointing to. I'm circling my cursor there, right? This is the dark roast medium grind. We can see that the caffeine content is slightly more. And waving my cursor again here, medium roast medium grind, we can see it's again slightly above, but dark roast, the two coarse grind, medium and dark roast, the difference above the hot brew caffeine line in orange is significant. We're looking at a difference of between about 1,000 milligrams of caffeine per liter and 1,200, so that's about 20% more, versus we're looking here at about kind of 100, I would say 1,100, 1,150 is approximately where that is, so smaller. So in other words, the difference is more substantial for a coarse grind. And I'm gonna go ahead now and turn off my cursor. So for medium, medium grind, cold versus hot brew, as I mentioned, just to blow this up to make it a bit easier to see. Looking at the orange stuff, which is the caffeine, and the triangle is the cold brew, and the steady state line is hot brew. We end up with a tiny bit more caffeine after this period here, but it's not very much, whereas medium roast, once we get past about the kind of, it's actually about 300 minutes, 300 minutes, which is five hours that we're starting to see for a coarse grind, we're starting to see significantly more caffeine than using conventional hot brewing. This is the data just sort of actually tabulated here, or some of the key data points, and I've added arrows to kind of draw your attention to cold brew versus hot brew. And what we can see again is that with the coarse grinds we are seeing, and this is this rows two and four, we're seeing significantly more caffeine, and the medium, sorry, yes, the medium grind rows one and three, we are seeing more 1180 and 1080 versus 1040 and 1060, but it's not a, they deemed it not to be a statistically significant difference. Again, this is where they regard that their increased caffeination is negligible. They regard that as being at 400 minutes, after 600 minutes, it's for sure very negligible, versus 24 hours. And we can see again that the caffeine concentration across all four samples was really not significantly different. So basically after seven hours to 10 hours, certainly after 10 hours, but mostly after seven hours, you're really barely increasing the caffeine concentration in your cold brew coffee. So these aren't the findings from the paper. These are just what I'm suggesting to be the findings. Cold brew for more than 10 hours and really six if you're not nitpicking, doesn't do much to increase the caffeine concentration of the finished beverage. Naturally, the concentration of other flavor-giving compounds may rise over this period, but the concentration of caffeine peaks at about 10 hours. Using a coarse grind, cold brew has significantly more caffeine than hot brewing. To me, it looked like about 20%, but if anyone wants to read this paper and crunch those numbers, they are welcome to do so. Using a coarse grind, cold brew has significantly more caffeine than hot brewing, however the difference when the medium grind size is reached is not statistically significant, but the caffeine content is still the same as hot brewing. In fact, it's a little bit greater. If I go back to this for a second, we can see that the caffeine concentration is indeed, sorry, it was the previous slides. Here we go. The medium is one and three, so we're seeing 1180 and 1080 versus 10 at 1040 and 1060, so there is still more caffeine even when we're just looking at the medium roast. And that's it guys. So basically, if you are cold brewing and you want to control the caffeine, so you wanna get sort of a good quantity of caffeine out, but not too much, I'm personally now cold brewing for 12 hours. And if you do want to sort of get significantly more caffeine from it about 20% more than hot brewing, you can opt for a coarse grind or you can flip this logic on its head and say that in order to not produce an overly caffeinated batch, it's actually better to go with a medium grind size so that for the same quantity of beans whether using them hot or cold, they're going to be pretty similar. If you're into cold brewing, hope this run through of the caffeine was interesting. Of course, I'm just presenting the research that is out there on the internet. I'll put a link in the description. Thank you guys for watching. If you do want to get more videos from me on this and other subjects, do consider subscribing to this YouTube channel.