January 29, 2012
Spherification and Alcohol
Spherification is a "Molecular Gastronomy" technique for making small edible spheres out of just about anything. Since my first flavor sphere experience I've wanted to learn more and make my own.
I had the Willpowder kit for basic spherification. The process sounds straightforward:
- Stir a quantity of Sodium Alginate into the target mixture for your spheres.
- Fill a dropper or small squeeze bottle with the alginate mixture.
- Drip drops of the mixture into a bath of calcium chloride in water.
Well it's not that easy. I chose to start with alcohol and I had a hard time blending the sodium alginate into amaretto. They just didn't want to mix and my repeated attempts to blend them resulted in lots of air bubbles in the mixture. Worse, when I dropped the amaretto/alginate mixture into my chloride bath it splattered on the surface and spread out into a thin film. Fail :(.
I had read that others had more luck using "Reverse Spherification" with alcohol. I gave this a try but I could only produce large amorphous non-spheres by dunking a spoon of the mixture in the bath. Dropping from any height had the same issue as above. Also note, reverse spherification is done with calcium lactate gluconate and NOT calcium chloride. I tried. You don't want the taste of calcium chloride in your spheres!
After some trial and error, I came across an article in Make Magazine that saved the day. The key was to first blend a mixture of sodium alginate and water first. Here's a short recipe:
Amaretto Spheres
Ingredients:
- 2g sodium alginate
- 3g calcium chloride
- 1 1/2 C water
- 1/2 C amaretto
Tools:
- An immersion blender.
- A slotted spoon (with slots small enough to pick up spheres).
- A squeeze bottle or plastic syringe.
Steps:
- Blend sodium alginate and 125g (about 1/2 C) of water with an immersion blender.
- Set aside for a couple of hours to let bubbles disperse.
- Meanwhile, make a calcium chloride bath, with 1.5g calcium chloride to 1C water*. I usually make 2 cups to fill a medium bowl.
- After most of the bubbles have dispersed, add a small quantity (perhaps 1/8th) of the sodium alginate / water mixture to the amaretto. Mix with a spoon or small wisk. Load some of the amaretto mixture into a dropper or squeeze bottle and test.
- If the drop disperses on the surface of the bath, clean it off the surface, add more of the alginate mixture to the amaretto and try again.
- Once the spheres start to hold together, you're all set. The longer the sphere sits in the bath, the more the alginate and calcium will react so you'll get thicker walls.
- Remove spheres from the bath as quickly as you feel appropriate. Dip in a water bath. Slosh around. Remove and use.
I've found that the contents of the spheres leach out if they're left to sit for some time. You want to use them as soon as you can to preserve color and flavor.
* Some people insist on using distilled water for the bath, since impurities in tap water might prevent the alginate and calcium from bonding. I took this suggestion and haven't yet experimented with tap water.
Some other things I learned while spherificating:
- Sodium Alginate is useful both for creating the bonds that form a membrane around your spheres and for thickening your target mixture. Your mixture will need to be thick enough to break the surface tension of the calcium chloride bath.
- Dropping height matters. Again, it's all about breaking the surface tension. Experiment by dropping from different heights. Dropping height can determine whether you break the surface and also dictate the shape of your spheres.
Now to find something useful to do with these spheres ...
August 24, 2011
Moisture Sensor: Calibration Round 1
I grow plants. For a time, I've wanted a low-cost sensor that can live in my plants and broadcast information about temperature, light, water, and drainage that I can compare to ideal growing conditions. I've set out to build such a device. This post focuses exclusively on the moisture sensor component.
Commercial grade soil moisture sensors are available, but they are cost-prohibitive for placing in dozens of plants, rather large, and sometimes have very high power requirements for a small device. I'll need to make this component myself.
I have a handful of designs in mind for the sensor. A couple of other hobbyist projects use a variation on the gypsum block sensor:
I've elected for a different design because plaster is quick to absorb moisture and slow to dry. As a result, gypsum block sensors may provide a less granular measure and can inaccurately represent the wetness of the surrounding soil (perhaps I should prove this assertion?).
The designs I'm considering generally share a common component: The sensor is a simple design involving a pair of concentric electrodes, sand as a neutral moisture medium, and a plaster disk to filter out salts or impurities that may cause errors in measurement. These parts are assembled inside a 1/2" plastic tube cap.
This is a resistive sensor that works when an external device applies a voltage across the electrodes. The medium between the electrodes (in this case, sand) acts as a resistor. As the moisture in the medium varies, the voltage carried across the electrodes varies. This voltage can be measured to determine how wet the medium is.
At the start of the test, I arranged the sensors in a pot of sand, then fully saturated the sand with water. The test ran for about three days, sampling (excessively) once every 30 seconds. Below is a plot of the measure taken by the four devices at 15-minute granularity.
While the measurements from the four devices are relatively consistent, there's room for improvement in both precision (note the poor measurement granularity and flapping) and consistency across devices (I seem to have one "wet" sensor and one "dry" sensor). A few adjustments should offer an improvement.