Photo by Jong Marshes on Unsplash

We are mostly water. Arguably, we are ambulating water bottles. The food we cook is mostly made of water and we cook food in water. Nonetheless, like anything common, it can be taken for granted.

Plants are the ultimate water containers; nearly all vegetables and fruits have water content about 80% (by weight) or higher. The water content of carrots is equivalent to full cream milk, just bound rather than flowing. A zucchini is 95% water. An iceberg lettuce: 96%. Numbers to consider when estimating your daily water intake.

My estimate of the percentage water content in a 350ml plastic bottle of mineral water, taking into account the weight of the bottle (and ignoring mineral content that would further reduce water percentage) came to 96% — same as a lettuce and perhaps making lettuce a boutique water bottle.

Instead of carrying a water bottle around as a conspicuous health accessory, we could be carrying a lettuce. A lettuce contains the same amount of water, provides multiple additional nutrients and is better for the environment. Just tuck it under your arm.

Five random observations on water:

1. Water is a better conductor of heat than oil. Put your finger in 55C water and the pain would immediately make you take it out, but less so for 55C oil. Oil only seems to be better at conducting heat because it can be heated to above 100C. For a related reason, oil heats faster than water — water can take a long time to boil (100C), whereas oil can be brought up to deep-frying temperature (180C) quite quickly. The water needs to absorb a lot of heat energy for each 1° increase in temperature, hence for a given temperature it feels hotter than oil. Heat and temperature are not the same thing.

2. Water is much better at conducting heat than air. It is possible to put your hand in a 100C oven, but certainly not in 100C (boiling) water (not even 55C water). This property of water is exploited in sous vide cooking. It is also why defrosting in an ice-water bath is so effective.

3. Steam is not water vapour. Water vapour is a gas and it is invisible. Steam consists of water droplets suspended in air.

4. Cold water (below 4C) is less dense than warmer water and floats to the surface (which is why lakes freeze from the top down). This is a unique property of water: Any other substance (liquid, solid or gas) expands when it is heated, but water expands (becomes less dense) when it cools.

5. The taste of water comes from its dissolved impurities, not from the water itself. ‘Pure’ distilled water (or deionized water) tastes awful. Seriously, awful. In a way that is hard to describe without experiencing it. A non-taste. As well, our saliva is slightly acidic, and water with an acidity that matches our saliva is more agreeable to drink.

What we in developed countries take most for granted about water is that it is delivered to our homes by a tap and taken away by a drain. The infrastructure surrounding that is massively complex and creaking. Whether it will withstand the pressures of global heating we will find out soon enough.



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Science of cooking, eating and health. Retired neuroscientist.