Tea and Food Pairing

Micro Salad

Micro Salad (Source)

Last summer, I was lucky enough to meet one of the scientists behind molecular gastronomy, Hervé This. I also attended his session at the Euroscience Open Forum entitled “Science and the future of cuisine” where he (along with Mark Post and Bill Yosses) discussed molecular cuisine and the new trend in scientific cooking called note-by-note cuisine. The session was full of fascinating examples of this new cuisine but also covered the practicalities of sustaining the human race by “creating” vegetables and meat in the lab. It was an unforgettable session and tasting the chocolate mousse that was produced without cream or eggs sealed the deal!

In particular though, it drew my attention to the application of science for understanding taste and flavour so when I attended the World Tea Expo a few weeks ago, I was excited to hear Virginia Utermohlen (Cornell University) and Renée Senne talking about their scientific approach to pairing food with tea. Virginia started with the basics of taste and flavour and discussed how the chemicals in tea bind to receptors in our mouths and nose. The session then focussed on the effect that food has on the taste of tea – how some foods will mute the taste of tea while others will enhance it. I was expecting the session to be based around a molecular matching approach but Virginia’s approach was mostly based on trigeminal receptors (for heat and coolness). Cinnamon and mint were used to illustrate the power of these receptors. We were each given a cinnamon sweet which is considered to be “heat” on a taste/temperature scale so it gives a sense of warmth after binding to its receptors. After the taste had developed we took the sweet out of our mouth and replaced it with a mint. The “coolness” of the mint turns off the heat receptors and gives a sense of cold when it binds to its own receptors so the cinnamon taste was completely replaced with mint. After the mint was removed the heat receptors become active again and the heat of the cinnamon came back as residual cinnamon in the mouth was picked up.

Trigeminal Receptors

Thermal Nociceptors (Source)

From there, we went on to apply the model to Black (hot), Oolong (warm) and Green (cold) tea. The general premise was to use food of similar heat or coolness together to avoid unpleasant tastes and to allow the tea and the food to complement each other and enhance each others flavours. So Oolong (warm) could not be mixed with Cardamom (hot) because the hot spice would mute the taste of the warm drink. Crème fraiche going well with Mexican food is an example where flipping hot and cold can result in a positive effect. It makes sense to some extent but still didn’t clear up some of the well-known anomalies of molecular matching (e.g. strawberries clashing with black tea and sugar clashing with green tea). It is an interesting model to consider alongside other food pairing methods and certainly goes a long way to explaining why I like my chilli-chocolate with black tea.

Nepalese tea – First Flush SFTGFOP

Until 2000, Nepal’s tea exports accounted for only about 150,000 kg per annum. However, due to liberalisation, the Nepalese tea industry has witnessed an exponential rise in tea exports in the last ten years. At present, Nepal produces approximately 18 million kilograms of tea per annum on an area of 18,149 hectares. The climate, soil and unpolluted air in Nepal are said to be ideal for tea and production is incentivised through government subsidies for machinery. CTC manufacturing accounts for 87% of production. The remaining 13% of Nepalese orthodox tea has a reputation for being outstanding.

Nepal First Flush Side ViewI received some tea samples last week from a Nepalese colleague who was kind enough to bring some back from his travels. There were a number of samples but one in particular caught my eye: a first flush SFTGFOP Black tea. As a first flush it was probably picked sometime in March or April and these teas are generally a milder and gentler tea than the leaves that are plucked later in the year.

Nepal First Flush The leaves are short and wiry and although the leaves are mostly brown you can see from the photo the white buds and some partially oxidised green leaves. The smell of the dry tea is strong and grassy.

Preparation: To prepare this tea, I put 3g of the tea in a gaiwan. After rinsing the leaves, I add the boiling water for 30 seconds but I felt it needed a little longer so I left it for about 40 seconds.

First steepThe first cup is sweet-smelling, light yellow and the taste is crisp and light with that very distinctive musky taste. Pungent is a word that suits this tea well (especially the second and third steeping) but not pungent in the usual sense of overpowering sourness but softly pungent as an interesting background that deepens the taste. This tea held well for six steepings with increasing steeping durations each time.

Among the rest of the samples is an Autumn SFTGFOP and I’m looking forward doing a comparison taste in the coming days.

 

Oxidation

I briefly mentioned oxidation in my getting sorted post when I was talking about the different categories of tea and thought it might be worth talking about a little more.

Oxidation is basically what causes the leaves of the tea plant (that are green when they grow) to turn brown. It is a biochemical reaction which involves the absorption of oxygen (like when an apple is cut). Black tea is generally close to fully oxidised, Green teas are usually non-oxidised and Oolongs tend to be partially oxidised to varying degrees. Oxidation is pivotal to the processing of tea and will change its colour, smell and flavour.

Oxidation Chart

Oxidation Chart (Source)

Oxidised teas, are bruised (from lightly to extensively)  to break the  cell walls and allow the enzymes in the leaves to cause natural oxidation reactions. Heating the leaves stops oxidation by deactivating the enzymes. In this way the tea producer can decide on the extent of oxidation by introducing heat. Green teas are non-oxidised and so are heated early in the production process so that the oxidation process is skipped.

Sometimes tea-oxidation is called fermentation but no microorganisms are used so this is a misnomer. Generally when people talk about tea-fermentation they are talking about oxidation.

However, just to complicate matters, the proper micororganism fermentation does take place with pu-erhs.

There are exceptions to this, but here are the usual oxidation and fermentation levels:

Black tea – almost fully oxidised

Oolong tea – partialy oxidised (ranging from 12% – 80%)

White tea – minimal oxidation

Green tea – No oxidation

Yellow tea – No oxidation

Pu-erh – fermented (sheng pu-erh is not oxidised but shou pu-erh is)

Caffeine

I was reading an old article from Bord Bia that said that tea consumption was on the rise at night-time. The reason given was that “people are at home more often and tea is a comforting affordable reliable beverage”.

There have been several papers written on the effect of caffeine on sleep disruption and even more papers written on effect of caffeine on other health issues (good and bad). A major problem in this type of research is that all the papers tend to use very different values for the caffeine content in beverages and foods.

There are plenty of reasons for the variations. Preparation plays a large role and differences in the time and temperature of steeping, the size of the tea leaf and the type of tea used will all influence the caffeine content of tea. The variety of plant, care of the plants, soil nutrients, picking season and the part of plant used will also play a role.

Caffeine Crystals under the microscope

Caffeine Crystals under the microscope (Source)

Caffeine is a white, odourless crystal that occurs naturally in coffee, tea and chocolate and is added to colas and energy drinks. After a lot of reading, here is a summary of caffeine content in tea from sources that seems reliable:

Tea (~200ml after one steeping of three minutes)

Chinese white tea – 75mg

Darjeeling white – 56mg

Indian Green – 59mg

Kenyan Green – 58 mg

Chinese Oolong (Ti Kwan Yin) – 37mg

Assam (FTGFOP) – 86mg

Darjeeling Black (SFTGFOP1) – 54mg

 

For comparison here are some for coffee and other beverages:

Coffee (~200ml)

Coffee (ground roasted) – 115mg

Coffee (instant) – 80mg

Cola – 20mg

Decaffeinated coffee – 4mg

Espresso, single shot – 75mg

Espresso, double shot – 150mg

Red Bull (250ml can) – 80mg

 

Chocolate

It seems to be generally accepted that there are 6mg of caffeine per 30g serving. But it seems to vary a lot:

70% Green and Black dark Chocolate (30g) – 4.5mg

Green and Black milk chocolate (30g) – 2mg

White chocolate (30g) – 0mg

Cadbury dairy milk (28g) – 15mg

Herbal tea

Herbal tea – 0mg

(Note: other substances like theobromine, tanninic acid, caffeol also play a role)

 

I found it surprising how high the caffeine content of green tea is. Many claim that green and white tea have less caffeine than oolong or black tea because of the minimal oxidation. It seems to be well-proven now that this is not the case. White tea in particular uses the bud of the plant which has been shown to have a higher caffeine content that the leaf. I guess most people wouldn’t have a can of coke before bed but I wonder if they know that a Chinese white tea has three times as much caffeine?

With a few exceptions, herbal tea or tisanes have no caffeine at all. That includes Rooibos so there is a huge selection of tea alternatives for night-time. I’ve been going through a rough time with sleep lately so now I only drink tea up to about 3pm and right before bed I drink hops tea. It seems to really help. And no, by hops tea I don’t mean beer though sometimes that helps too :-).

 

Main Sources:

Barone JJ, Roberts, H.R. (1996), Caffeine consumption, Food and Chemical Toxicology, Volume 34, Issue 1, January 1996, Pages 119–129.

Richardson, B. (2009), De-bunking the At-Home Decaffeination Myth Story, Fresh Cup January 2009

Chin JM, Merves ML, Goldberger BA, Sampson-Cone A, Cone EJ. (2008), Caffeine content of brewed teas. J Anal Toxicol. 2008 Oct;32(8):702-4.

 

Steeping tea

I realise that my last post where I describe the preparation of Tieguanyin was probably confusing (my readership of two lodged their complaints!) so I’m going to try to clear things up today. The preparation of tea is called steeping and involves soaking the tea leaves in water to extract the flavour.

Yellow teapot

Traditional style teapot used here in Ireland

Here in Ireland (and in all Western countries that I have been to) steeping involves putting tea leaves (or tea bag) into a large teapot and then adding in boiling water. The tea is served from the teapot into cups after around two minutes if you like ‘weak’ tea and or after several minutes if you like ‘strong’ tea. After about five minutes, the tea leaves and the liquid need to be separated or it will over-steep and becomes bitter. If this happens, it is usually addressed by either adding more water to dilute or starting over and making a ‘fresh pot’. I’ve seen variations on this process where people add the tea leaves, add the water and then heat up the teapot on a gas hob. The teabag-in-a-cup is a another variation – the teabag  is put in the cup, water is added and the teabag is removed and discarded once the tea looks strong enough.  There are lots of variations but the basic process is consistent – the flavour of the tea is extracted by steeping the tea once (i.e single steeping).

Yixing Clay Teapot [Source]

Yixing clay teapot [Source]

However, in China, Taiwan and other parts of Asia, there is a different way to prepare good quality tea that involves several short steepings rather than one long steeping. To do this we add the tea to the teapot (usually a very small teapot) and add the water but instead of steeping for ~five minutes, we steep for maybe 30 seconds (it depends on the tea). After the 30 seconds, we separate completely the leaves and the water by pouring off all the tea from the tea pot into cups. It may seem like a short time at first but don’t worry, it works. When we are ready for more tea, we re-steep the tea by adding water to the teapot again (with the same leaves). This time we will wait a little longer – maybe 40 seconds before pouring off all the tea. This is the second steeping and will taste and look different to the first steeping. We can repeat this several times, increasing the duration of steeping each time. During each steeping the water opens the leaf a little more and the colour, smell and taste of the tea will vary. Eventually, it will start to loose taste and colour and then we know to stop. Using this method we get smaller cups of tea but more of them with a variety of flavours and the tea does not over-steep. It is not unusual for a good quality Pu-erh to have ten steepings and it can go to 20 steepings or more.

Brew basket

Brew basket

The re-steeping technique does not need a teapot. The same result can be achieved if we put a brew basket in a cup, add the leaves and water and then wait thirty seconds before removing the brew basket. When we are finished drinking the first cup we put brew basket back in the cup, add water again and wait say 40 seconds for the second steeping. Again, this can continue for multiple steepings, increasing the duration with each steeping.

I hope that helps to clear up the difference between single-steeping and re-steeping. When I post about individual teas I’ll describe the steeping preparation that I’ve used, including timings. I have deliberately left out factors like water-type, temperature, rinsing, utensils and volume of tea. I’ll come back to those in future posts.With all that said, tea is meant to be enjoyed so don’t feel under pressure to prepare your tea a certain way. Experiment and see what you think!

Getting sorted

I was setting up the categories for this tea blog and it got me thinking about the neatness of the tea classes. There are six classes or categories of tea (green, white, yellow, oolong, black and pu-erh) and I still find it fascinating (and handy now) that each of the thousands of different teas that are out there can fit into one of those six categories. Better again, all tea comes from the leaves of a single species of plant: Camellia sinensis.

Camellia sinensis

Camellia sinensis

Here are the categories that I have for the blog so far:

  • Tea:
    1. Black – almost fully-oxidised and mostly produced in India (Assam and Darjeeling), Kenya, Sri Lanka and China. E.g. Keemun, Zhenshan Xiaochung (lapsang souchong).
    2. Green – teas such as sencha, Matcha, Gunpowder, Longjing, Taiping Houkui that have had minimal oxidation and kept the green color of the leaves. Predominantly from China, Japan and Korea.
    3. Oolong – partially oxidised and complicated in production, this type includes Da Hong Pao (red robe) and Tieguanyin. Produced in China and Taiwan.
    4. Pu-erh – post-fermented tea from China and called ‘black tea’ in China. Comes as sheng (raw) or shou (cooked). My favourite!
    5. White – made from the buds of the Camellia sinensis and very lightly processed it includes bai mudan (white peony) and Baiho Yinzhen (silver needles).
    6. Yellow – these teas are not easy to find here so this category won’t be used too much to start with but it didn’t seem right to leave it out.
  • Buying tea & storage: looking at where to get good tea and how to store it or age it.
  • Tisanes: This will cover all the herbal drinks that are sometimes referred to as tea but are herbal infusions or herbal teas. This covers peppermint, chamomile, ginger, fennel etc.
  • Rooibos & Honeybush: Technically these are tisanes but they get their own category because I love them so much!
  • Out and About: This is where I post about going for afternoon tea or lunch to see what the tea is like out there.

I’m sure there are plenty more categories that I’ll need to add as I go along but theses will do for a starting point.