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Caffeine extraction

When we used to live in Broad Ripple I would buy coffee beans from Hubbard & Cravens’ roasting plant on 52nd Street next to the Monon once in a while. Their roast was a little too dark for my preference, and their hours were such that we started calling them Hubbard & Closed, so it wasn’t always at the top of my list of places to buy beans back then.

I was in the neighborhood, loosely speaking, earlier this week to pick up this month’s Bacon of the Month Club treat from Goose the Market, and I was low on coffee, so I stopped in the Carrollton location to pick up some beans.

Caffeine does not usually have much effect on me, but last night I was awake until 2:00. What happened?

When I got home I eagerly flipped on Miss Silvia, the espresso machine, in anticipation of a rich, invigorating beverage. I was immediately distracted by the dog’s silliness and other chores that needed attention. Some time later, I got around to making the shot of espresso that I had been looking forward to. It was good, so maybe I am coming around on my opinion of Hubbard & Cravens’ roast level.

Fast forward to this morning when I was laying in bed, unable to sleep. I had plenty of time to think about the cause of my insomnia.

Silvia’s boiler temperature is controlled by two simple bimetallic thermostats, so temperature regulation is not very precise. Temperature swings of 40° are not unheard of with this type of thermostat. When I brewed my espresso yesterday evening, I noticed that it was extremely hot. The thermostat must have just cycled off at the very top of its 110°C (230°F) range. (I am certain that I had not left the steam switch on, which brings the boiler to 140°C [284°F].) The espresso even appeared to be boiling as it came out of the portafilter.

Wikipedia says that caffeine’s solubility in water increases dramatically with temperature.

Not being a chemist, I have to assume that caffeine’s solubility would continue to increase with temperature. So, it is definitely plausible that if the water was much hotter than normal for that fateful shot, the machine could have extracted much more caffeine than normal into my espresso.

If the solution to this is better temperature control, am I trying to talk myself into joining the ranks of people who have hacked their espresso machines to include a PID controller? Uh-oh.

coffee silvia

2010-02-17

Christopher

notes

2 comments

Brewing with Miss Silvia

Politics aside, one of the things I will give George W. Bush credit for is chipping in for my Rancilio Silvia espresso machine with that tax rebate back in 2001. I love this machine. It’s built like a tank and brews excellent coffee.

Looking back, it’s been a superb value, even at $395. Amortizing the cost of the machine over 8 years and adding the cost of ingredients, our latte habit has cost 65¢ per day. Compare this with a $3 latte at Starbuck’s, and there’s just no contest.

Today, the going rate for a Silvia is $595. Add in the essential accessories, and the price probably comes closer to $650. This sounds like an awfully large investment, but the break even point is just 275 lattes — less than a year for most folks. My advice for anyone looking for an espresso machine has always been to get a good one. If you don’t get a good one, then it you won’t enjoy using it, you won’t be as happy with what you make, and the result will be that you won’t get much use out of it. So you will have wasted your money.

I stumbled on a video made by Mark Prince of coffeegeek.com that shows how satisfying it is to make your own espresso based beverages. He published a detailed review of the most recent revision of the Silvia a while back. If I had to get another espresso machine today, I wouldn’t hesitate to replace ours with another Silvia.