Chang94598 Senior Member Joined: 24 Oct 2007 Posts: 207 Location: SF Bay Area
Posted Thu May 3, 2012, 1:16pm Subject: Re: Musings On Coffee Extraction, and measuring it:
My guess is, when Dr Lockhart did the research in the 50's and 60's, he probably summoned people around him and did a blind taste preference and published his result. His papers were published in the 50's and 60's, and it seems only the SCAA office in Long Beach has readily available copies. Eventually in my search for the information perhaps I'll find someway to the SCAA library.
Fast forward several decades, with advancement in molecular biology and physiology. Since in the extraction measurement we are concerned mainly about taste, let's go through the taste pathway.
From the taste cells on the taste buds, the electrical signal travels via the facial, glossopharyngeal, and vagus cranial nerves to the solitary nucleus of the brain stem. From the brain stem, it travels to the ventral posterior medial nucleus in the thalamus, then to the frontal lobe, where we interpret "taste".
The genes that encode these receptors have different expression in different individuals, therefore the "super-taster" that are commonly mentioned in coffee forums. I tend not to emphasize the "super" excessively, as it really denotes ability to taste bitterness, not necessarily "increased" ability to taste.
Taste can be trained, and is profoundly affected by culture and smell. The fifth taste, umami, typically associated with MSG, is a basic taste in Asian cooking that was not truly recognized until the receptor and associated genes were discovered. Cats, for example, lack the genes, and therefore receptors, for sweetness.
The typical taste receptor has a life span of about 10 days. As we age, the ability to replenish these receptors decreases. Furthermore, we also gradually lose the receptors for smell. To compound the problem further, more plaques build up in our blood vessels and brain, so our nervous system cannot interpret the signal well both in the peripheral and central nervous system. Typically, as we lose senses of smell and taste, we tend to add more condiments, like salts, to our food, to make up for the loss in our senses.
My suspicion is, someone more mature tend to enjoy the coffee with higher extraction rate, and vice versa. Because our taste and smell change as we age, and a lot of other variables, as long as the coffee is extracted within certain range, repeatable, and enjoyable, the extraction numbers are FYI's only.
Posted Thu May 3, 2012, 2:46pm Subject: Re: Musings On Coffee Extraction, and measuring it:
Chang94598 Said:
...
The typical taste receptor has a life span of about 10 days. As we age, the ability to replenish these receptors decreases. Furthermore, we also gradually lose the receptors for smell. To compound the problem further, more plaques build up in our blood vessels and brain, so our nervous system cannot interpret the signal well both in the peripheral and central nervous system. Typically, as we lose senses of smell and taste, we tend to add more condiments, like salts, to our food, to make up for the loss in our senses. ....
And something as simple as water-brushing one's teeth and scraping one's tongue before tasting allow one to taste...more.
Chang94598 Said:
... My suspicion is, someone more mature tend to enjoy the coffee with higher extraction rate, and vice versa. Because our taste and smell change as we age, and a lot of other variables, as long as the coffee is extracted within certain range, repeatable, and enjoyable, the extraction numbers are FYI's only.
I used to think this - I don't anymore. Too many conflicts with simple observation.
If I do a decent heavy-strength coffee (around 1.4% - like Starbucks strength when they brew Pike Place) - my father thinks it's fine, his wife thinks you can stand a spoon up in it. On a light roast coffee.
On a darker roast at 1.15% - many people find it too much, even my father. And many times, I can sneak up to 1.7% strength with a Yemen or Yirg or the occasional Costa Rica with no complaints. I just don't think I see the correlation with age - but it is interesting that I wasn't the only one to think that.
(the above examples are "technically" in the extraction range of 18%-22%, the strength is adjusted by changing the brew ratio).
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Chang94598 Senior Member Joined: 24 Oct 2007 Posts: 207 Location: SF Bay Area
Posted Thu May 3, 2012, 5:15pm Subject: Re: Musings On Coffee Extraction, and measuring it:
Netphilosopher Said:
And something as simple as water-brushing one's teeth and scraping one's tongue before tasting allow one to taste...more.
I used to think this - I don't anymore. Too many conflicts with simple observation.
If I do a decent heavy-strength coffee (around 1.4% - like Starbucks strength when they brew Pike Place) - my father thinks it's fine, his wife thinks you can stand a spoon up in it. On a light roast coffee.
On a darker roast at 1.15% - many people find it too much, even my father. And many times, I can sneak up to 1.7% strength with a Yemen or Yirg or the occasional Costa Rica with no complaints. I just don't think I see the correlation with age - but it is interesting that I wasn't the only one to think that.
(the above examples are "technically" in the extraction range of 18%-22%, the strength is adjusted by changing the brew ratio).
You just confirmed my observation that different people interpret the same drink differently, due to experience and different taste and smell gene expression. Incidence wise, women tend to have higher expressed receptors for bitterness, therefore the wife can't stand a spoon up in it. The expression of the allele of bitterness gene T2R is different among different people, therefore it adds another variable to "extraction" rate. Imagine if these two individuals were in Dr Lockhart's group.....which extraction rate would they prefer?
Many people used to think coffee's bitterness is mostly due to caffeine. While caffeine is certainly bitter, the melanoidins are now thought to be responsible for the majority of bitterness.
There are several printed and electronic atlases to identify the GC/MS fingerprints, which generally run in the thousands, so the machine itself while helpful, will need additional information to be useful.
By age 50, about 50% of the smell receptors are gone. I don't have the approximate rate for taste receptors, but these phenomenons are well documented in medical texts and reports.
Addendum: water and brushing will stimulate the nerve endings and transmitt signals via the cranial nerves. Ions in water can activate the taste receptors, via ion gated channels to traverse through cell membranes, without binding of the actual receptor. Brushing obviously is a tactile stimulus which also activate the cranial nerves.
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