oxidization levels of Oolongs

Theoretically any tea can be made at any oxidation level. But traditionally Pouchong/baozhong is made at light oxidation level. Tie Guan Yin was made at higher oxidation level than modern day’s green style Tie Guan Yin, and lower oxidation level than Wuyi yan cha most of the times.

Also some oolong can be made with medium/high oxidation but light roasting. But low oxidation with heavy roasting is not commonly seen.

I’ve had tieguanyins that are lighter and some that are darker. I guess it all depends on the producer. You can usually tell by the color of the leaves whether it will be light or dark. I don’t know if I said anything useful at all…

Tie Guan Yin is a kind of Oolong tea, which sits between the full oxidized black teas and un-oxidized green teas. At present, Tie Guan Yin Oolong tea can divide into light oxidization and moderate oxidization.

The characteristics of light oxidization one: its brewed tea leaves is green, and many of the brewed tea leaves are broken. While the brewed tea color is also green, to some degree, it like the soup of mung bean, and the dry tea has a distinct orchid fragrance as well.

The main character of moderate oxidization Tie Guan Yin: it was made through a traditional way, so when compared it to light oxidization one, the latter has golden tea color, mellow taste, also the leaves are very complete after brewing.

Hi BubbleDrae and others, an old thread but I thought the answers above were pretty inaccurate, so here’s a better (and long!) answer:

So firstly, oxidisation does very little to the colour of the leaves. Almost NOTHING. If anyone tells you that their tea is dark because of the long oxidisation, stop buying tea from them. Here’s two pictures I took myself – the first is a Wuyi Yan Cha after 18 hours of oxidisation (still very green) and the second is a Tie Guan Yin after about 12 hours of oxidisation (again, only slight discolouration on the edges of the leaves):

http://imgur.com/zjstW10,dIRGJj6

Try this experiment – pluck a healthy leaf from a nice evergreen tree, and put it in your house for 12-18 hours (at around 25 degrees celsius). Check the colour at the end – I very much doubt it will change colour at all.

Colour in oolong teas (the dark colour) comes from the post-oxidisation baking, drying and roasting. Oolong teas all experience different processing, but all will go through some phase of “sha qing” to stop oxidisation, which involves a short, extremely high heat (around 300 degrees). This still doesn’t necessarily change the colour much. Here’s a Tie Guan Yin leaf after the “sha qing” and a round of bruising unique to TGY processing:

http://imgur.com/nGbTDtI

Still green….

Most darker oolongs like Wuyi Yan Cha will go through multiple very light roastings and then drying phases, which is where the leaves turn from 95% green to perhaps 30% green. When a Yan Cha (or Dan Cong for example) is finished and ready to drink, it will still be fairly green – see this picture:

http://imgur.com/zxWrLAs

Sorry for the crappy picture – the leaves are quite brown, but still with strong green parts and definitely not the deep chocolate associated with most dark oolongs.

The dark, chocolate colour only comes from roasting. Red/black teas are completely dark because of their long and full roast, and Da Hong Pao (a Wuyi Oolong) is chocolate brown because of the roast. Generally the roast is lowish temperature, maybe 80-100 degrees for 1-2 hours.

So….

If you’re a newbie I would recommend you to mostly ignore the oxidisation level as an indicator of taste, and focus on the roast level, if that oolong is roasted. Most of the time you won’t taste the relative oxidisation levels, but you will taste the roast levels. “Light”, “medium” and “dark” should normally refer the roast of the tea, which corresponds to the colour and taste very closely.

Normal Tie Guan Yin (Iron Buddha) is NOT roasted. Different TGY varieties are distinguished by the oxidisation period and farm location, but not by the roast level. Generally you have ‘pure’ TGY which has about 8 hours of oxidisation and a buttery taste, a ‘tuo suan’ which has a longer oxidisation and a sour and tingly taste, and then a variety in the middle. However, lots of farms also like to subsequently roast a TGY many weeks after it’s finished processing, but then it should be clearly labelled as “roasted TGY” or sometimes 浓香 nong xiang / 老铁 lao tie. You’ll see the difference in these two pictures between a medium-roasted TGY and a normal non-roasted TGY (these are the same teas, the only difference is the roasting):

http://imgur.com/xbR38Oz,F2J6Efz

I must confess I label my normal TGY as a “green oolong” but that’s mostly for marketing purposes – green teas sell better, and it’s a keyword that many of my customers are looking for, so I abuse it a bit :)

@Will – the proper bruising of any TGY happens after the long oxidisation has been stopped by the ‘sha qing’ (very high heat quick fire). Same for other oolongs – any unintentional ‘bruising’ that happens during the rolling and shaping of the leaves happens after oxidisation has stopped. There’s a small amount of discolouration in leaves sometimes, but I’d say 95-99% of the finished red/brown colour comes from the baking and roasting.

Here’s a picture of a handful of highly oxidised 60-70% (脱酸, tuo suan) TGY from Gan De (感德) last year about midway through the bruising/shaping process (about 2 hours after oxidisation has stopped):

http://imgur.com/itC0qb3

No visible brown other than the stems. This is a closeup of a single leaf from the same stage of processing:

http://imgur.com/oNH2u3T

Now you can see two places – on the right hand side and on the bottom edge – where there’s a tiny bit of red.

Finally, here’s the same tea I brewed while I write this :)

http://imgur.com/5dKeaRo

This is a finished tea and no red/brown on the leaf.

When you see lots of red/brown in teas occuring during oxidisation, it’s probably because the leaves have been treated poorly before oxidisation (ie. machine harvested, accidentally broken, crushed in transit). The oxidisation process for TGY is basically just placing intact, freshly picked leaves on trays in @23 degree Celsius rooms for 6-18 hours. It shouldn’t change the colour.

Regarding tearing edges off – whatever tearing of leaves happens can only be accidental/incidental and isn’t done to specifically remove brown edges. A farm processing maybe millions of leaves over a 10-12 day harvesting period simply doesn’t have the man-power or time to carefully tear edges off individual leaves. I’ve only seen that level of care given to competition grade teas, in which case, if they’re having to tear brown edges off, they’ve already lost :)

Regarding roasting – I guess it depends what you mean by roasting. TGY is heat treated in three places: sha qing (to stop oxidisating, high heat), during the shaping and bruising (it’s rolled multiple times for a 30-60 seconds in about 180 degrees C and then bruised again) and then finally it goes through a very light drying at the end (this turns the leaves completely dry and brittle). “Roasting” or “baking” for TGY specifically refers to putting the completely finished TGY in an oven again specifically to give it another different flavour, but then it’s not pure TGY any more.

@Will – my point is that a Da Hong Pao and a TGY undergo extremely similar oxidisation periods, but one of them is chocolate brown and the other is bright green. When does the massive colour change happen? Not during the formal oxidisation stage.

When the DHP and TGY leaves come out of the oxidisation stage, they look pretty much identical (ie. the vast majority of the leaf is green). Yes, there’s some discolouration to differing degrees, and yes, Wuyi teas often start to have a red edge because they’re rolled around and tumbled more, but the huge colour change appears in the later stages of processing. I’ve been to Anxi and Wuyi every May/October for the last 3-4 years and I’ve seen these all directly myself, not books or internet. Maybe we’ve had different experiences at different farms or different regions…

The other point was to try help the original poster, because terms used to describe oolongs are often vague. Light/medium/dark could point to colour, oxidisation or roast level. Tea retailers should do better – if someone is saying that their oolong tea is chocolate coloured because of the long oxidisation period, it’s nonsense.

The TGY I posted a picture of was a batch I literally watched being processed last May. The leaves didn’t have any red edge before oxidisation, or before bruising, or after bruising, and it wasn’t roasted. There was no red edge to rip off in the first place. The tea gets ripped and beaten up during the bruising/shaping, but you can see there’s still green edges left to the leaf – there’s just no physical way the tea master has enough control during the bruising/shaping to tear the brown bits off and leave the green bits.

By “pure TGY” I mean 正味 (zheng wei) which is what’s used as the standard TGY here in FZ. The finished leaves are 95-100% green.

Someone else might have to weigh in here, but I’m fairly sure that the name “TGY” does indicates the processing method?

This is a great discussion, thanks guys! I have always believed that TGY was a reference to the varietal of the tea plant, but often find that distinguishing between “pure TGY” and something other than such is a subjective debate. I have friends in Fujian and I have heard differing accounts, which leads me to believe that the answer lies somewhere ambiguously between science and tradition…