Does our sense of smell favor processed foods?

Was fascinated to read an article based on a review paper published in the journal Science about the human sense of smell:

https://www.vox.com/science-and-health/2017/5/11/15614748/human-smell-good-science

The Science paper's author, John P. McGann contends, I think successfully, that the human sense of smell is demonstrably better than we have believed.*

What struck me, though, was not that we have a good sense of smell—think of all the perfumes that have been created, each subtly different from the next, and you realize how important smell is to humans and how exquisitely sensitive we can be. 

Rather I was intrigued to learn that we are superior to other animals in smelling components of food, but not just any food: human food that requires processing like cheese and coffee and roasted meats and beer and wine (no data on tea as yet, though).

Here is a picture of a dog following the scent trail of a pheasant and one of a human following the scent trail of chocolate oil, from the vox.com article. Clearly the human goes less astray! Of course you could always argue motivation: the human may have been more motivated and the dog occasionally distracted. The fact remains, nevertheless, that the human does a pretty good job!

So what components of food are humans able to smell at lower concentrations than can other mammals? This question has NOT been studied extensively, but the Science article cites three compounds: 

• n-pentanoic acid, also called valeric acid, which has a dairy, slightly fruity quality, and is found in milk, cheese, yogurt, coffee, as well as some fruits, including bergamot (Earl Grey, anyone?);**
• n-octanoic acid, aka caprylic acid, that has a waxy, fatty, rancid, oily, vegetable, cheesy quality, and is found in a host of foods, notably (for my thesis) beer and wine;** 
• 3-mercapto-3-methylbutyl formate, which has a sulfurous (that's the mercapto-) aroma, mixed with a caramellic, onion, coffee, roasted meat quality, and is found in beer and coffee.***

Laska and his colleagues suggest that perhaps each species' smell capacity is adapted to their dietary niche. 

It is interesting to contemplate that humans have developed a repertoire of olfactory receptors that are particularly attuned to the uniquely human foods that require processing for their development, like dairy products, and beverages, and possibly tea. Awaiting further studies!

* John P. McGann. Poor human olfaction is a 19th-century myth. Science 12 May 2017:
Vol. 356, Issue 6338, eaam7263. DOI: 10.1126/science.aam7263

** Selçuk Can Güven and Matthias Laska. Olfactory Sensitivity and Odor Structure-Activity Relationships for Aliphatic Carboxylic Acids in CD-1 Mice. PLoS One. 2012; 7(3): e34301.
Published online 2012 Mar 30. doi:  10.1371/journal.pone.0034301.

*** Sarrafchi A, Odhammer AM, Hernandez Salazar LT, Laska M. Olfactory sensitivity for six predator odorants in CD-1 mice, human subjects, and spider monkeys. PLoS One. 2013 Nov 20;8(11):e80621. doi: 10.1371/journal.pone.0080621. eCollection 2013.

Memorial Day Barbecue? Here's the sauce!

It's barbecue time again, so I'm proposing my Carolina-style sauce with Lapsang Souchong — it's my take on a super delicious way to have pork or chicken...or tofu!

Why choose a mustard-and-vinegar-based barbecue sauce to make with the Lapsang Souchong? Because the chemicals in LS hit the cool to cold receptors in the mouth, as do those in mustard, onions, garlic, and thyme. So rather than getting the kick from something like a chili pepper, this sauce gives you a kick from hitting the cold receptors, along with the tang of the vinegar.

Of course you can add a pinch of chili pepper if you like (and my daughter likes...) — just that it tastes less...how can  I put it...like Lapsang Souchong and more like something you would expect, with slightly muddled flavors due to the activation of TRPV1, the capsaicin receptor.

Here are the ingredients:
1 cup prepared mustard (a grainy kind)
1/2 cup apple cider vinegar
1/2 cup of Lapsang Souchong tea
2 tbsp. butter
1/2 Vidalia onion, chopped
1 tbsp chopped garlic
A couple of sprigs of thyme
Juice of 1/2 lemon
1/2 cup brown sugar

Here's how I made it:

Boil a cup of water, add 2 tablespoons of Lapsang Souchong tea, and let brew for 6 to 7 minutes, to get all the smoky pine flavors out of the leaves. 

In a small saucepan, sautée chopped onion and garlic in butter until onion is translucent. Add mustard, vinegar, sugar, lemon, and thyme to the onion garlic mix. Add a quarter of the tea. Bring to a simmer, stirring, for 5 minutes. Taste. If not smoky enough, add a little more tea, stir and taste again. 

At this point you may want to add a little more sugar to balance the acidity that is highlighted by the tea. If you add too much sugar, then add a little more tea to get back the smoky tangy flavor. In fact, you should play with the proportions of this sauce to make it just right for you. 

Note that I didn't add any salt — the mustard I used had enough, but you may want to. No pepper either, but you may want to "kick it up a notch" as Emeril used to say, by adding some fresh ground pepper. My thought is that the meat or tofu should already have enough pepper.

Simmer some more, say 5 to 10 minutes, with stirring, then use or refrigerate. I expect that the sauce will get better after a night or two in the refrigerator, but I wouldn't keep it longer than 5 days. With luck you shouldn't have any left by that time! Note that you probably will have made more LS tea than needed for the sauce — enjoy it!

Here's the sauce in my saucepan — was stirring it with my rice paddle…

Making your tea less bitter

In the Wednesday post, I mentioned that as the ratio of amino acids to polyphenols in oolongs increases, the value of the tea increases, and suggested that the reason is that polyphenols are bitter, so potentially aversive, while most of the amino acids in tea are sweet and savory (umami), giving the tea a delicious flavor.

The question is then, how can you make a lower grade oolong taste more delicious?

One way, as I will explain in my talk about cold versus hot brewed tea at World Tea Expo 2017* is to brew the tea cold, because much less polyphenol gets into the cup.

The other way is to inhibit the bitter message, which can be done with a tiny amount of salt. We will try this experiment in my other session at World Tea Expo, a focussed tasting called "Pairing with Tea: the Science of Flavors and How to Enjoy Them!" Wednesday  June 14th. Here is a diagram of taste bud cells you may have seen on this blog before:

The X from the salt-sensing cell to the bitter-sensing cell indicates inhibition. There is an X from the sweet-sensing cell to the bitter sensing cell as well, but you need relatively more sweet than salt to sense the effect.

Hope we will be to carry out this and other experiments together at WTE!


* What's in the Cup & Why You Like It: Hot Brewed vs Cold Brewed - CS49
Tuesday, 06/13/2017: 8:30 am - 10:00 am
Room: N237
Session Number:  CS49

Oolong quality and amino acid/polyphenol ratio

One of my two talks at World Tea Expo 2017 will be on cold- versus hot-brewed teas.* (The other will be about pairing with teas, about which more in my next post.)

One of the most important conclusions we will reach is that the quality of a tea depends on the ratio of amino acids to polyphenols. Here is a result from a paper on oolongs: the more prized the oolongs — and the more costly — the higher the ratio.**

Looking forward to seeing you at WTE 2017! 


* What's in the Cup & Why You Like It: Hot Brewed vs Cold Brewed - CS49
Tuesday, 06/13/2017: 8:30 am - 10:00 am
Room: N237
Session Number:  CS49

** Yueh-Tzu Hung, Po-Chung Chen, Richie L.C. Chen, Tzong-Jih Cheng. Sequential determination of tannin and total amino acid contents in tea for taste assessment by a fluorescent flow-injection analytical system. Food Chemistry 118 (2010) 876–881.

How much theanine in your cup?

When I was looking for information to share with you all at World Tea Expo come June, found a fascinating paper about L-theanine content of different teas available in England. L-theanine is a compound found in young tea leaves that may (or may not) have worthwhile effects on your mood and sleep.*

You may have heard that green tea has more L-theanine than does black tea. However, as the authors indicate, the studies providing these measures extracted total theanine from the leaf—they didn't measure the amount of L-theanine that gets into the cup you actually drink.

That's why the authors of the paper measured extracted L-theanine, namely the amount in a cup of 200ml, with the tea brewed with water at 80ºC for 2 minutes.

Under these circumstances the results were reversed, as the graph below shows. For the sake of simplicity, all of the teas I included in the graph were Twinings teas—several other brands of teas were tested, with the same results. 

Average theanine content of different Twining's teas.

The "Everyday" tea was a bag tea, while all the rest were loose leaf. The first difference is that the loose leaf teas released significantly less theanine than the bagged tea. The second difference is that the green and white teas released less than some, but not all, of the Twinings black teas. 

When all of the teas tested (including teas produced by other companies) were taken together, however, black bagged teas released significantly more theanine than did the loose leaf black teas and the loose leaf green and white teas. It is likely that the leaf particles in bagged teas offer more surface area to the water for extraction. With respect to the difference between some black teas and other teas, the difference may come from the more extensive processing of black teas, which may release more theanine.

Incidentally, for most of these teas, the maximum theanine was released at 2 minutes of brewing; and lemon, sugar, or small amounts of milk had no effect on theanine release.

Bottom line: enjoy your specialty loose leaf teas for their exquisite flavor, but if you just need a theanine "hit," go for a bagged tea!

* Emma K. Keenan, Mike D.A. Finnie, Paul S. Jones, Peter J. Rogers, Caroline M. Priestley. How much theanine in a cup of tea? Effects of tea type and method of preparation. Food Chemistry 125 (2011) 588–594.

Mango green tea and dirty socks

The other day, friend of Pairteas and tea connoisseur Marzi Pecen (www.pecen.net) asked me why her mango-flavored green tea had a smell of dirty socks, and why she couldn't taste the mango at all. Here's the (longish) answer — it has to do with the odorants in dried mango and how they interact with those in green tea.

First, what is the difference in odor profile between fresh and dried mango? 

Mango is highly perishable when fresh. By contrast dried mango is quite stable, and can readily be added to tea to create a flavorful blend. 

When I smell or taste dried mango by itself, I get a two step effect. The first effect is cool and slightly lemony, then a warm orange-like tropical fruit aspect quickly kicks in.

This two step effect can be explained from the data obtained by Bonneau and her colleagues, in which they compared fresh and dried versions of the most commonly cultivated mango, Mangifera indica L. cv. Kent.*

Fresh and dried mangoes differ dramatically in their aroma chemistry, though two compounds present in both fresh and dried mangoes — β-myrcene and 3-methylbutyl butanoate — together contribute strongly to the "mango" sensation.  Both of these compounds activate warm receptors.

The lemony sensation from dried mangoes comes from the presence of limonene and a small number of other terpenes with a citrusy flavor. Limonene in particular activates the cold receptor, which is why the first fleeting sensation is cool — cool receptors turn on quickly and turn off quickly, especially when turned off through activation of warm receptors, including sweet receptors. 

That's why the sensations quickly becomes warm: the "mango" compounds start activating the slow-responding warm receptors, and the flavor becomes intensely mango-y.

Next, what happens when you add dried mango to green tea?

Here's where we run into flavor problems! The process of drying mangoes leads to the production of hexanal and heptanal, and the disappearance of mesifuran. Hexanal and heptanal both activate the cool/cold receptors, while mesifuran is a major contributor to the sweetness and warm flavor of fresh mangoes. 

When dried mango is added to green tea (which itself activates cool/cold receptors) the balance of flavors shifts from warm to cool/cold. As a consequence, the major mango flavor compounds — β-myrcene and 3-methylbutyl butanoate — cannot be sensed => no mango flavor!

At the same time, the cool/cold activating aromas are exaggerated...and heptanal has a smell of dirty socks...

The following chart shows the relative odor activity values (OAVs) of these compounds in fresh and dried mango, according to the data from Bonneau et al.:

Odor activity values of selected compounds in fresh and dried mangoes. Data from Bonneau and her colleagues.*

As you can see, drying increases the OAVs of the two characteristic mango compounds, and completely eliminates mesifuran. The cool/cold-receptor-activating limonene increases slightly, while hexanal and heptanal make an appearance, so heptanal can offer its dirty odor.

Just thinking it would be very interesting to contrast mango-infused green tea with a mango-infused oolong. My guess is that the mango-ness would be enhanced and the dirty-sock effect diminished when you pair dried mango with a warm receptor activating oolong such as Tie Guan Yin. Give it a try?


* Bonneau, A., Boulanger, R., Lebrun, M., Maraval, I. and Gunata, Z. (2016), Aroma compounds in fresh and dried mango fruit (Mangifera indica L. cv. Kent): impact of drying on volatile composition. Int J Food Sci Technol, 51: 789–800. doi:10.1111/ijfs.13038

Why do tea and books go so well together?

A fascinating article in The Guardian, based on research presented by Cecilia Bembibre and Matija Strlič,* may well have given the answer...

https://www.theguardian.com/books/2017/apr/07/the-smell-of-old-books-science-libraries

As you may know I have been hard at work clearing out my home of nearly thirty years (anniversary in August) in preparation for moving to be near my daughters and grandchildren. One of the difficult tasks has been to triage my many thousand volumes, each of which holds a special message for me -- books I read as a child, books that once belonged to my grandparents and even greatgrandparents, medical books, science books, math books, history books, school books, and especially books that my children loved to look at as toddlers and from which my parents and I read to them...

So I have been surrounded by that rich old book smell, and memories of curling up with a good book, cup of tea at hand, immersed another world.

Turns out that old book smell is made up of a number of compounds that are also contained in tea. The Historic Book Odor Wheel from the article (below) was created to show the different characteristic odors of an historic book and to indicate the corresponding compounds the authors were able to identify. I added red stars for compounds that are also present in tea, and a yellow arrow for limonene, which is present in bergamot and therefore in Earl Grey tea.

As you can appreciate, pleasant odors in the historic book are also present in tea, particularly in black tea (furfural and benzaldehyde). The "-al's" — hexanal, heptanal, and to a variable extent undecanal, are more characteristic of green teas, where they contribute to the grassy green flavors; and benzaldehyde is found in oolongs, too.

As I think about it, it's the lack of book smell that explains why I can't curl up with a good computer or Kindle.

* Cecilia Bembibre and Matija Strlič. Smell of heritage: a framework for the identification, analysis and archival of historic odours. Heritage Science20175:2
DOI: 10.1186/s40494-016-0114-1.
By the way, this article is open source so you can go on line to read it in its entirety, an exciting and worthwhile exercise because of the elegant discussion of smell as heritage:
https://heritagesciencejournal.springeropen.com/articles/10.1186/s40494-016-0114-1