The Milk Experiment (Doesn’t That Sound Nice): Part 1

This is the second post in a long series I’ve got planned about the history and culture of drinking tea (first post on Earl Grey here). In black tea drinking culture, milk and sugar are important elements. I’ll get into sugar eventually, but for now let’s focus on milk.

There are several ways to put milk in your tea. Every single person I know has a different way of doing it (and is convinced that they know the best way). The two major camps are Milk First™ and Tea First™. Theoretically, to put milk in first you warm the cup with hot water from the kettle, steep the tea in a pot, dump the water from the warmed cup and add milk, then pour the tea from the pot to the cup. To put tea in first, you steep the tea in the pot, pour it from the pot to the cup, and add the milk.

I started this experiment a little biased, to be honest. To me, putting milk in first seems ridiculous. I still think there are too many extra steps, but I’m trying to be more open minded.

As many ways as there are to put milk in your tea, there are even more reasons why you should do it a certain way. Here are the major reasons I’ve heard:

  • Milk First mixes the milk better (no need for spoon)
  • Tea First mixes the milk better (requires spoon)
  • Milk First prevents the milk from curdling
  • Tea First prevents the milk from curdling
  • Milk First is a remnant of an 18th century effort to protect the cup from the heat of the tea. The cup, and this is important, is either:
    • local earthenware/pottery used by the lower classes
    • or, various kinds of porcelain, either imported from China or made in Europe, and therefore very expensive, and only used by the upper classes.

You can see the problem here. As far as I know, it would be very hard to prove that either milk or tea first would mix better … so unless anyone has a suggestion I’m going to skip over that first set. And the last point? We’ll get to that, but not today.

It turns out that curdling milk is a very strange process, and it’s not all about heat. It’s actually about acidity. So meet my new friends, pH strips. pH, as you may remember from 7th grade science, is a scale that chemists use to determine the acidity or basicity of a water-based solution. I’m not a chemist, so that’s about as good as I can do. Basically, there are two ends on the scale: 1 is the most acidic, and 14 is the most basic. 7 is neutral. An example of an acid would be lemon juice, which is about 2. An example of a base is ammonia, which is about 11.

In this photo we have the pH packet with scale and strips of litmus paper, and a grapefruit, which according to the pinkish-red colour of the strip I tested, is probably in the 3-4 range.

Milk is close to neutral. It’s actually just a little bit acidic, which is probably why when you leave it in your fridge too long it starts to curdle (separate) on its own. The addition of more acidity to your milk will speed up that process, dividing the milk into curds (the clumps) and whey (the translucent watery stuff). By the way, forcing milk to curdle is how you make cheese and butter, so it’s not all bad stuff.

Now, there is some basis to trying to protect your milk from the heat of your tea water. Heat does speed up this process, but it isn’t the reason the process happens in the first place. The reason the process happens is the pH dropping – it becomes more acidic.

I haven’t met anyone who puts lemon in their black tea … I would imagine they usually do lemon + sugar or lemon + honey, not lemon + milk, which should definitely cause the milk to curdle.

I put together a science experiment to help set this straight. I even asked my mother for help. She’s a nurse practitioner with years of experience in clinical research, so she knew much more about what was going on than I did. A friend of Mom’s came along and helped as well, which was nice, because she doesn’t even drink milk.

Here’s the set up: we had four teas, and three milks. We brewed each kind of tea three different times (three different bags each time). With each brew, we added a set amount of one of the milks to all four teas. Every time we did anything, we took the pH. We also took the temperature.

For this experiment, we were testing Tea First™. We put the bag in, the water on top of the bag, brewed five minutes, took the bag out, took pH and temp, put milk in, took pH.

We were looking for the strange flecks (curds) and sheen (whey) that sometimes appear in black tea with milk. Of course, sometimes with tea there’s a similar strange phenomenon of a residue hanging in a ring around the edge of the cup. I have to admit I’m not entirely sure what that is, but I think it’s leftover from the washing. I could be wrong. Feel free to tell me so.

Sorry about the glare on this picture, but you can kind of see the flecky bits and the oily-looking sheen.

The teas: Red Rose Earl Grey, Lady Grey, London Tea (no idea what that is, but it was in my parent’s cabinet), Tazo English Breakfast. I made sure to have a non-Earl Grey, because Earl Grey is supposed to have citrus flavourings, which I thought would produce a result (see grapefruit test above).

The teas. I believe the Tazo is on the bottom right, above that is the London Tea, to the left (top) is the Red Rose, and then below, left is the Lady Grey.

The milks: Skim, expired 4/16, whole, expired 4/23, and whole, expired 5/7. The experiment was done on 4/27. The idea is that the older the milk, the more likely it is to begin the curdling process in your tea. In order to ensure we got the same amount of milk in each cup, we used pipettes!

Our three milks and the three pipettes. Each tea got four pipettes filled with milk up to the black line. Mom’s idea. Isn’t she clever!

These are the results:

pH @ 5 min Temp @ 5 min Skim exp. 4/16 pH after milk
Red Rose EG 7 158.3 flecking 6.5
Lady Grey 6.5 160.3 flecking 6.5
London Tea 6.5 163.3 flecking 6
Tazo EB 6.5 163 no flecking 6.5
pH @ 5 min Temp @ 5 min Whole exp. 4/23 pH after milk
Red Rose EG 7 157.6 flecking 6.5
Lady Grey 6.5 156 no flecking 7
London Tea 7 157.1 flecking 7
Tazo EB 7 158.7 flecking 7
pH @ 5 min Temp @ 5 min Whole exp. 5/7 pH after milk
Red Rose EG 6.5 157.1 flecking 6.5
Lady Grey 6.5 158.5 no flecking 6.5
London Tea 6 157.9 flecking 6.5
Tazo EB 6 157 no flecking 6.5

Essentially, they’re inconclusive. Not enough happened. There are far too many variables to account for what did happen. The first time the mugs had been through the diswasher, but the next two times they were washed by hand. The lighting changed. The pH paper was out on the counter too long. The teas were varying ages … I could go on and on. The only thing I can conclusively say is that putting your tea in first might cause your milk to curdle, and it might not. Also, science is hard.

BUT, before you get mad that I made you read all that for nothing, there is a way in which inconclusive results are still important. They still contribute to what we understand about milk and tea. They mean that we should do more experiments on this – will Milk First™ provide a different result? Maybe introducing tea to milk, instead of milk to tea, will actually help prevent milk from curdling. So stay tuned, Milk First-ers. Your time may have come.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: