Khymos » DIY

DIY mineral water

Martin Lersch — Sun, 30 Jan 2011 21:00:14 +0000

I’m quite fond of carbonated water, and last summer I bought a water carbonator so I wouldn’t have to carry all the water home from the shop. The working principle of the carbonater is very simple – a bottle filled with cold tap water is subjected to a pressure of carbon dioxide for a couple of seconds, allowing some of it to dissolved in the water. The result is an instant sparkling water. But even with the carbonation there is something missing. The big difference between my homemade instant carbonated water and bottled mineral water is the mineral content. True, tap water may also contain a number of minerals, but this varies and there are huge regional differences. In Norway most water is very soft (i.e. low in calcium and magnesium) and has a very low mineral content. But tap water rarely has a desirable mix of minerals compared with the really good tasting mineral waters.

Beeing a chemist I started pondering about whether it would be possible to mimic natural mineral waters by adding a clever cocktail of salts before carbonating the water. A real DIY mineral water if you like. The first thing a scientist does these days when a new idea strikes is to google it. I found simple instructions calling for addition of sodium bicarbonate, more elaborate recipes with magnesium sulfate, calcium chloride, potassium bicarbonate and sodium bicarbonate and a recipe for magnesium bicarbonate water where magnesium hydroxide is neutralized by the carbonic acid. But none of these were replicas of actual mineral waters. What I really was looking for was a calculator that would tell me which salts to add in order to clone a specific natural mineral water. But since I couldn’t find this I figured I would have to make my own.

Pure carbon dioxide added to water under pressure

Websites such as Mineral waters have comprehensive listings of mineral contents of several hundred commercially available natural mineral waters from around the world. Major cations are calcium, magnesium, sodium and potassium. Major anions are bicarbonate, chloride and sulfate. In addition a number of trace minerals are present at lower concentrations. One thing I’ve wondered about is which ions contribute most to the taste. The fact that even low concentrations of manganese or iron give an unpleasant metallic taste suggests that the taste of cations is a function of concentration as well as their individual taste thresholds (just like with odorants!). But things are complicated by the fact that iron salts can induce olfactory sensations as well, possibly due to catalytic lipid oxidation. Unfortunately I haven’t found scientific papers on which cations/anions contribute to the desirable taste of mineral water (but please let me know if you know any!). Therefore, as a starting point I decided to begin with some well known mineral waters and assume that their mineral content is quite close to an “optimum”. Furthermore I decided to only focus on the the major cations and anions.

Carbonation equipment from the book Vollständige Anleitung zur Fabrikation künstlicher Mineralwässer

When searching I got a number of hits in old German books such as Über die Nachbildung der natürlichen Heilquellen (1824) and Vollständige Anleitung zur Fabrikation künstlicher Mineralwässer (1860) which discuss how to prepare artificial mineral waters with elaborate descriptions of the the carbonation equipment. Sub sole nihil novi est. Germany has numerous spa towns (Ger.: Kurorte) were the local mineral water was (and is) claimed to have health benefits. In the 19th century some spa towns would evaporate their mineral water to yield the contained mineral salts as a dry residuce for the visitors to bring back home. There they could redissolve the minerals in water and enjoy the health benefits in the comfort of their own home.

One of the books had a recipe for “Selterswasser” (Selters water, named after the town Selters):

This recipe corresponds approximately to a water with the following mineral content (all numbers are mg/L): calcium 58, magnesium 32, sodium 232, bicarbonate 603, chloride 195, sulfate 11. The recipe specifically mentions that iron salts and silicates have been left out, and that the total salt concentration has been somewhat reduced compared to the actual mineral water in Selters. We can compare this with a contemporary analysis of Selters water (mg/L): calcium 110, magnesium 38, sodium 299, bicarbonate 850, chloride 269, sulfate 20. We see that the lower salt concentration claimed in the recipe above is actually true. Not bad considering that the recipe was from 1860!

But back to my calculations: As mentioned I decided to make a spreadsheet that would calculate the amounts of salts to mix in order to replicate a mineral water to be chosen from a list. The salts I settled with are sodium chloride (aka table salt), sodium bicarbonate (aka baking soda), magnesium sulfate (aka as Epsom salt), calcium sulfate (aka gypsum), magnesium hydroxide (a suspension of this in water is often referred to as “milk of magnesia”) and calcium hydroxide (aka slaked lime or pickling lime). The sulfates are available as anhydrous salts, but to avoid any problems with moisture and storage I’ve only used the hydrated salts in the calculator. You can download the spreadsheet for Excel: mineral_water_calculator.xlsx (17 kB). There are five simple steps to use it:

Choose which mineral water you want to recreate (click to show drop down list)
Selected cations (calcium, magnesium, sodium) and anions (sulfate, chloride, bicarbonate) are shown
Compare original with composition of the artificial mineral water
Carbonate water and add the calculated amounts of salt
If known, please enter the composition of your tapwater here and the recipe will be adjusted according to this

So far I’ve only added the composition of 10 mineral waters to the lookup list. If anyone should have an extensive list of mineral water compositions available in excel readable format I’d be happy to include it in an update

Screen view of my mineral water calculator

Oh – you may wonder if I’ve tried this? No – not yet. I’ve spent my time researching this, not testing it yet. But I will buy the required salts and report back! If you happen to have the pure salts available, why not give it a try?

Perfect steak with DIY “sous vide” cooking

Martin Lersch — Sun, 21 Jan 2007 12:20:03 +0000

One important aspect of molecular gastronomy is the application of scientific principles to food preparation in a normal kitchen. This can very well be illustrated by discussing the preparation of a steak. The surface of the meat needs to be heated to > 120 °C (250 F) for the Maillard reaction to take place at a reasonable rate. This gives meat much of it’s characteristic aroma. The interior of the meat however should not be heated to more than 50-65 °C (120-150 F) for a rare or a medium rare appearance. If the heat is provided by a frying pan with a temperature typically in the range 120-160 °C (250-320 F), the different temperature required for the interior and the surface of the meat can actually be quite difficult to achieve. Bringing the meat to room temperature before cooking by taking it out of the fridge 1-2 hours in advance helps. Also, half way through the cooking it’s advisable to let the meat rest on a plate to allow the heat to diffuse into the interior and to let the surface cool down a little.

There is however an easier way to make a perfect steak! In restaurants the method has been around since the 70′s and is known under the name sous vide (fr. under vacuum, more info on history of sous vide in this NY Times article). The meat is packed in plastic bags, vacuumed and put into thermostated water baths. This equipment is not (yet?) found in the average kitchen. So here is a simple DIY procedure. You just use a normal plastic bag, leave the meat in the water bath for 30 min (or longer) and then quickly fry both sides to generate the products of the Maillard reaction. You do need a thermometer though to control the temperature of the water bath, preferably one with a dip in probe.

1. Put the meat (I used a rib eye steak for this experiment) in a thick plastic bag. Only put one or two pieces of meat in each plastic bag – this ensures a greater contact surface with the water.

2. Add any spices you like (salt and pepper always works well – for the experiment shown I used curry paste, soy sauce and chili sauce in stead), press (or suck) out the air and close the plastic bag tightly by tying a knot (or use a zip-lock bag). You don’t want any water to enter the bag!

3. Heat a pot of water to the desired temperature (or use hot tap water) and place the plastic bag with meat in the water. Cover with a lid (not shown in the picture) to reduce heat loss. If you use a large pot of water it’s easier to keep the temperature constant. Also, it’s easier to control the temperature with an induction or gas stove top than with an electric plate since there is no additional heating once you turn them off. Regarding the temperature, start with 60 °C (140 F) and experiment from there (or check this table at Wikipedia for doneness temperatures of meat). You should leave the meat in the water for at least 30 minutes – more for a thicker cut. But the good thing is you can leave it for much longer (several hours) provided the temperature does not come above 60 °C (or whatever temperature you decided on). A convenient way to keep the temperature constant for a long time is to put the pan with water into the oven and use the thermostat of the oven.

4. Heat a frying pan, add a fat of you choice, remove meat from plastic bag and brown both sides of the meat. Since you take the meat directly from the water bath it’s already at about 60 °C. Therefore the browning is very fast.

5. A temperature of 60 °C (140 F) gives the meat a pink interior. It’s succulent and juicy. The short frying gives it a nice browned crust and the chewing resistance is perfect. All in all a wonderful combination of taste, aroma, texture and mouth feel!

Note added January 2009:
Since I published this procedure the first time I’ve learnt a lot more about sous vide. The procedure above is a rather crude procedure, but it works. If the meat turns out grey you’ll need to turn the temperature somewhat down. If you’re interested in reading more about sous vide, the best discussion I know of which also includes important safety aspects is Douglas Baldwin’s “A Practical Guide to Sous Vide Cooking”.