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Saturday, October 25, 2014
Food / Drink ... Practical Advice ...

I’ve become a fan of cold-brewed coffee. Not that I go around seeking local coffee shops or bakeries that serve it. I’m talking about producing my own home brew. Thus far I’ve make it in the simplest way possible; I get out an iced tea pitcher, dump in a few cups of ground coffee (decaf, please, I’m a bit oversensitive to caffeine), pour in about 3 to 4 cups of water for every cup of java, stir it up, and into the refrigerator overnight. (Albeit, I have experimented with keeping it at room temperature for 12 hours and then refrigerating it, as to boost up the flavor extraction process a bit; thus, I often go this route). I let the grounds settle and harden, and then just pour out the liquid on top, perhaps straining the final cup for excess sediment. The end result is really good coffee, in my book; a lot smoother and a touch sweeter than the hot-brew.

I’ve always had a love-hate relationship with coffee; I love the smell of a nice steaming cup of joe, but it usually becomes a different animal in the mouth, with all sorts of intertwining acids and bitter / sour notes competing for attention. Cold brewing seems to leave most of these “foreign” notes behind, and you get something a good bit closer to what the vapors once promised, the first time you ever got near that black potion of the gods. The main trade-off with cold-brewing, interestingly, is the wonderful vapors themselves; cold-brewing leaves behind many of the “voluables” that hot brewing brings out. So even if you heat up a cup of coffee that was produced cold, you won’t get the same wonderful fragrances. If you want the best of both worlds, then, make a cup of hot-brewed coffee and sniff it, then pour a cup of cold-brew for actual drinking!

Cold brewing seems like the better way to go, in my coffee book. However, there’s a problem with the way I’ve been doing it. Coffee has oily elements in it (i.e., “diterpenes”), and one of those is called cafestol. Most of the oil is ok, but cafestrol can raise a person’s harmful cholesterol levels (i.e., LDL’s and triglycerides) and possibly contribute to heart disease over time. If you don’t somehow filter your joe, you’re going to get a pretty good wallop of cafestol (and never even notice it, taste-wise). However, common methods of hot-brewing coffee remove most of the cafestol and make coffee relatively safe from cholesterol worries. These brewing techniques include the popular “grounds in a paper filter” method, and the good old percolator, where the grounds sit in a perforated metal cup with hot water splashing thru it. By comparison, you get a nasty dose of cafestol when you make hot coffee using a French press, i.e. where you pour hot water intp a container with coffee grounds, then push a perforated metal plate over the grounds to tamp them down and squeeze out the coffee liquid on top.

So, the question comes up as to whether you would likewise get too much cafestol when you cold brew your coffee without any filtering, or with French-press style filtering. I couldn’t find a quick answer to this issue, but the common opinion appears to be that cold brewed coffee is bad for you unless you take the extra step of straining it thru a paper filter; even a gold cone-like or basket-like filter won’t save you from a potential heart attack, according to what many coffee enthusiasts seem to think. The difference in temperature does not necessarily get cold-brewing off the hook; a study indicates that cafestol gets released in water quite quickly, as cafestol levels were found not to be sensitive to how long coffee is hot-brewed. Obviously the stuff quickly leaches out of the grounds; therefore, 12 hours in cold water may do just as good a job of flushing it as one minute in boiling hot water.

However, I did some more research, and it appears that the paper filter is NOT the only path to cardiovascular salvation for us cold-brewers. (I personally think that it’s a pain to strain cold-brewed coffee thru a paper cone; it takes forever and is pretty messy, given the higher micro-sediment content of cold-brewed coffee.) A metal basket or mesh filter CAN do the job, if used properly. First off, consider the humble old percolator; it uses a metal cup with holes in the bottom, not particularly tiny holes either. The hot brewing water has to make its way by gravity thru an inch or two of piled up grounds. And yet, despite the lack of a paper filter, percolator coffee is relatively cafestol-free. Another study indicates that Indian coffee and Singapore “sock” coffee are also low in cafetrol, even though brewed hot. In both methods, once again, water is poured thru a stack of grounds in a porous container (the sock in Singapore, the metal basket in India), and works it way out by gravity. This study also made a direct comparison of filtering versus no filtering for hot coffee, in the case of Indonesian coffee. The “sock filter” version or a metal mesh filter yielded Indonesian cafestol levels a bit under 1 mg per cup, roughly on the edge of the safety level. By comparison, unfiltered Indonesian hot coffee had levels around 4.4 mg per cup, clearly in the danger zone (if you drink 2 or more cups per day, which a lot of people do).

[Note: I’m not sure just how the filtered Indonesian coffee was prepared in this test; I suspect it was first boiled and brewed in a pot, then the top liquid was poured through the sock or metal mesh into the drinking cup; this would differ from Singapore, where the coffee grounds are placed in the sock and the brewing takes place within it. Such a difference would explain why the Singapore sock was much more effective in eliminating cafestol versus the Indonesian sock.]

Interestingly enough, there is a study available regarding cafetol levels in cold brewed coffee; albeit, it is not a neutral scientific study, but instead was provided by a manufacturer affiliated with a special cold-brewing decanter who was seeking a US patent on dried instant coffee crystals derived from his brewing method. However, if the results can be believed, they nail down my point that you can filter cold-brewed coffee in a metal mesh basket and get most of the cafestol out, so long as the grounds accumulate in that basket. The study was done using the Neace “hourglass” cold-brewer. (Not the picture at left; that is my own little home-built system, more about that below.) The hourglass device has two containers, one on top of the other, connected by a metal mesh filter between them (in a narrow neck, giving the overall contraption its “hourglass” shape). You soak the grounds and water in the bottom container overnight, then turn the thing over so that the slurry of water and grounds get strained thru the mesh filter and falls into the other container. (It’s not all that different from the competing “Toddy” brewer.)

The hourglass company compared the cafestol levels from its own method versus cold-brewing using a French press. It was claimed in the patent application that the cold-brewed method using their device produced coffee with 88% less cafestol than hot-brewed coffee prepared using the French press method. It was also found to have 71% less cafestol than coffee brewed by the French press method using cold water. (Interestingly, the French-pressed cold brew had about 1/3 the cafestrol level of the hot French brew, indicating that perhaps temperature does influence cafestol extraction rates after all).

Bottom line, IMHO: it’s the coffee grounds that do most of the cafestol filtering. So long as you have something porous to hold in the grounds, whether a paper cone or a mesh basket or a cloth sock, you can strain out most of the bad stuff, no matter if the blend is hot or cold. By contrast, with a French press, you squeeze-filter from the top, thus avoiding the grounds, and thus circumventing the cafestol filtering that they do. What about espresso? That stuff generally has cafestrol levels around 1/2 to 2/3 of that for a French press or for plain boiled coffee — i.e., still fairly high compared to paper filtered or percolated coffee. Espresso brewing involves water seeping thru coffee grounds and being strained out through a metal filter; so then is my theory that the grounds do the cafestrol filtering wrong? I don’t think so, because espresso involves a lot of steam pressure pressing down on the coffee grounds. It makes sense that a lot of diterpene oils (including cafestol) are going to get through despite the metal filter basket in an espresso maker, because of the unique temperature and pressure combination for espresso brewing.

So now I have a Cuisinart gold mesh basket (same as the 4 inch Mr. Coffee basket) which fits neatly on top of a plastic quasi-pyrex measuring cup (the measuring cup needs to be 4 cup capacity; with a 2-cup measurer, there isn’t much room below the basket to accumulate the drip-off coffee). With this little rig, I can now conveniently filter and store a few cups at a time after a day or two of soaking. I get a big spoon and scoop out the settled grounds from the bottom of the cold-soak container, and pack them into the basket, right up to the rim. Then pour the soaked coffee-liquid thru this packed filter. This will HOPEFULLY catch most of the cafestol. And hopefully then, my doctor won’t get upset with my bloodwork test results the next time I get over to see him!

PS — If you like hot cinnamon tea, check out my post on possible ways to reduce coumarin, the liver toxin that is found in most forms of cinnamon.

◊   posted by Jim G @ 4:50 pm      

  1. Jim, A thorough explanation of how to get a good cup of coffee at home,as least one you like, as others may prefer something different–similar to one’s preferences in beer and wine; different people have different tastes.

    I’m glad you have found exactly how to make what you like when it comes to coffee. MCS

    Comment by Mary S. — October 26, 2014 @ 9:53 am

  2. I’ve always just poured my coldbrewed coffee through a paper filter in a largish plastic Melita conical form. I don’t see what the big deal is about running it through a paper filter; takes a couple of minutes. No muss, no fuss, no angst… :-)

    [Sure, OK — you can cold brew up a small batch, get a BIG plastic cone and a big paper filter, dump your sludge into the big cone and wait . . . that will work too, eventually. The point remains that SOME kind of filtering of the cold-brew mix thru grounds is needed. Jim G]

    Comment by Joe Schmoe — August 19, 2015 @ 3:58 pm

  3. A bit of additional cafestol info from a mayo clinic report…. The hotter the water used with coffee beans, and the longer the exposure to the water, the more cafestol. The reason the paper filter is a “must-have” is becasue the cafestol cannot penetrate paper. The report didn’t mention cloth, but it did specifically reference, “The paper filters, the article suggested, removed the coffee oils, which contain cafestol. The metal filters do not perform similarly.”

    [DYAN — thanks for that. Jim G]

    Comment by dyan — May 1, 2016 @ 11:18 pm

  4. Thank for the highly informative blog about cold brew. I’ve been wondering about this subject for a while and you blog was really enjoyable to reading and made sense. I hope you don’t mind if I share it on my Face book site.


    [why not? and stay tuned . . . post coming soon on the coumarin problem (liver toxin) in making hot cinnamon tea. Jim g]

    Comment by Susen — September 25, 2016 @ 6:50 pm

  5. Thanks for this post. As I search for best filter alternative for my Aeropress, I am thinking…

    Agree that temperature affects cafestol per the studies I saw.
    I like the theory that coffee grains themselves act as a filter bed, which explains higher cafestol in french press.
    Makes sense that pressure also affects cafestol retention by the filter or filter bed, which explains the cafestol levels in espresso.

    I am concluding that paper filters are safest way to go with Aeropress because some pressure in excess of gravity is used to push coffee through the filter bed. But I would love to see someone study this directly so I could ditch paper for permanent.

    Comment by Howard — January 3, 2017 @ 12:43 pm

  6. As I understand it, cafestol and kauhweol (sp?) have very low water solubility and are found in grounds (including fines) and oil after brewing. Percolators push the coffee to the top where the fines are trapped by the compacted grounds.

    You can see the oil on top and the fines in your coffee, so removing cafestol is a matter of getting rid of these things.

    Comment by Peter Ross — January 10, 2018 @ 5:01 am

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