How does the Vessyl "smart cup" recognize any beverage?

Every now and then you read about a product that seems a bit magical (The Verge article):

"The result is Vessyl, a 13-ounce cup that recognizes any beverage you pour into it, displays its nutritional content, and syncs all your drinking habits to your smartphone."

Wow pour in a mystery liquid, and the Vessyl smart cup can identify the beverage. Apparently the cup is indeed pretty smart:

"I tried nearly a dozen beverages in it — and it successfully identified all of them. Within 10 seconds, the device, which currently resembles more of a Thermos than a finished product, recognized Crush orange soda, Vitamin Water XXX, Tropicana orange juice, Gatorade Cool Blue, plain-old water, and a few other beverages, all by name. Yes, this cup knows the difference between Gatorade Cool Blue and Glacier Freeze."

Presumably Vessyl is measuring the amounts of different chemicals in the liquid. It can then compare the resulting chemical profile against a database of beverage ingredients and make a prediction. For example, a beer contains ethanol (alcohol), whereas a Coke has lots of sugar and caffeine. The company is being secretive about which chemicals the cup is measuring, but it is probably quite a few.

How does this measurement work? This question was posed on reddit. One possibility is that Vessyl uses infrared (IR) spectroscopy, a technique I described earlier on how the iWatch could non-invasively measure blood glucose levels:

"Over the last 25 years, there has been extensive work on non-invasive blood glucose monitoring. The research has coalesced around several basic technologies but the most popular is to use near-infrared spectroscopy (NIRS). The near IR refers to the light that illuminates the sample; near infrared wavelengths (800 nm to 2500 nm) are just above the visible spectrum (390 nm to 700 nm). The key concept is that different molecules (e.g. glucose, insulin, hemoglobin) will absorb light at different wavelengths, letting a specific pattern of wavelength intensities to be transmitted through the sample. In other words, different compounds will absorb different wavelengths of light to different extents creating a distinctive spectroscopic "fingerprint." Using this technique one can identify and quantitate a specific compound. The challenge is that blood is a complex mixture of compounds. However, one can determine the spectrum of blood without glucose and then subtract this from a sample of blood with glucose to create the glucose "difference spectrum" which can be quantitated against some standard."

An alternative to IR spectroscopy would be to use Raman spectroscopy, which measures (inelastic) scattering of light rather than the absorption of light. Basically a monochromatic source (i.e. laser) shines light on a sample, and the photons are absorbed and then reemitted at a different frequency (Raman effect). Different parts of the sample molecule produce different wavelength shifts and the resulting spectral pattern ("fingerprint") provides information about the identity of the compound, while the peak sizes give information about the amount.

Some compounds are more easily measured by IR spectroscopy, others by Raman spectroscopy. A combination of the two is the most effective, but also more expensive. My guess is that Vessyl uses the Raman technique because water gives a high background IR signal that can mask the true signal from other compounds dissolved in the water. For example, it is easier to measure ethanol in water with Raman than IR spectroscopy, and ethanol is undoubtedly one of the chemicals that Vessyl measures in order to distinguish the various alcoholic beverages.

An alternative to Vessyl would be to simply record manually or electronically what you drink. For example, there are calorie counting food apps in which you take a picture of your meal, and then the app identifies each food item and the amount on your plate, and then uses its database of food information to calculate the total calories of the meal.

The advantage of Vessyl is that it makes the process of collecting data a lot easier; the disadvantage is that you have to carry around an expensive cup with you. I can envision some compelling use-cases especially if Vessyl can "learn" to identify new drinks or correct its mistakes. I am eager to test Vessyl out when it is released.

Figure 1. Vessyl a smart cup that recognizes and records what you are drinking.