PODcast Newsletter, Issue 17

What it all boils down to...

There are three basic ways of constructing the heating portion of an espresso machine: boiler, thermoblock, and heat-exchanger boiler. Let's start with the construction most likely to be used by PODcast readers.

Boiler machines are the typical home or office espresso machine. Water is pumped into a heated chamber where it is raised to around 203 F. When the user switches on the pump, cold water is pumped into the chamber forcing hot water out of the chamber and then through the pod or ground coffee. This is basically like the water heater in your home. And like a water heater, it can easily run short on hot water if you try to use too much too quickly — that is, it has a definite recovery time between shots which should be heeded. When the user wants steam for frothing milk, the boiler is heated to a higher temperature (above 212 F). When the valve is opened steam issues from the steam wand. To make coffee again, the boiler must cool back down to coffee brewing temperature. Attempts to pull shots when it is still too hot will result in sputtering and burned coffee. Temperature gauges or indicator lights are useful on such machines that must change their boiler temperature. The above photo shows the brass boiler in a FrancisFrancis! X6.

Thermoblock machines work by having a heat-exchanger made from a block of brass with a serpentine path cut into it through which the water flows. By the time the water exits the block its temperature should be the same as the block. The block should have enough thermal mass to prevent the flow of water from decreasing the block's temperature. This system is also used to heat water in homes. You may have seen under-sink hot water heaters — this is generally how they work. I've heard some negative attitudes towards this system as though it was somehow inferior to a boiler. I disagree. In my experience this system is has better thermal stability and has a much better recovery time than a boiler machine. The Ascaso Dream with Fixed Filter Holder (which we used to sell but is no longer available) is such a machine and one that I can recommend highly. The Grimac Nuvola Terry and its cousins also use thermoblocks and there are few espresso machines that make better espresso from pods. Actually, the Terry has two thermoblocks — one for coffee and one for steam. That's the way to do it — no temperature swings and restabilization. In the photo above you can see the two thermoblocks in a Nuvola Terry.

Lastly, there is the heat-exchanger boiler system. It's sort a of combination of the above two methods and is the method employed in commercial espresso machines and a few prosumer machines. The boiler is quite large in these machines and is not for making coffee at all — its purpose it to provide a nearly endless supply of steam for frothing. A pipe carrying water from the pump to the brewhead runs through the boiler, picking up heat from the surrounding hot water. This is the heat-exchanger. The boiler acts like the above-mentioned thermoblock to heat the water in the pipe. The water in the pipe and the water in the boiler do not intermingle. This system is generally quite expensive as it requires a lot of hand work in brazing and bending the copper tubing. Shown above is the heat-exchanger boiler in an Elektra A3.

The Astra Pro is the least expensive machine that I know of with a heat-exchanger boiler. The Astra is also designed with pods in mind (both E.S.E. (single) and double shot) and is made in America. I have a lot of personal experience with the Astra Pro. Astra machines are a good choice for commercial establishments, offices, and serious espresso hobbyists. If you are interested, please call Astra for pricing and tell them PodMerchant sent you.
 

Chosen from our enormous selection of espresso pods, this issue's Featured Product is Lucaffe Mr. Exclusive 100% Arabica pods. Mr. Exclusive is a 100% Arabica coffee, meaning that only Arabica beans are used. It is not blended with Robusta beans (see our Coffee Primer). It is, however, a blend of various Arabica beans — as opposed to beans from a single country or growing region. This allows for producing a more well-rounded cup as well as ameliorating issues with poor growing seasons in a particular locale. Lucaffe describes Mr. Exclusive as a "blend coming from Arabica coffee from South America, Asia and a small percentage from the central Africa."

Starting with the pod itself, Lucaffe has improved the construction recently, adding on the bottom a circle of small bumps which indicate the downward facing side of the pod. (See Tip #6 in Issue 5 for more information on pod orientation). The crema is dark tan, substantial, and long lasting. The aroma reveals hints of toasted cereal, vanilla, and custard. It has a very neutral, well-rounded, classic coffee flavor without any substantial competing notes of other flavors. The body is medium — not heavy, grainy, or oily. I personally prefer the heavier body of a blend with Robusta, but at least the body is not thin or wimpy as can be the case with some Arabica blends. The aftertaste is minimal and not objectionable. This is a coffee best consumed straight, but it should hold up alright in a cappuccino or latte. Mr. Exclusive is one of my personal favorite espressos.

Note: The results above are as generated from a FrancisFrancis X6 espresso machine. The judgments of crema, aroma, taste, etc. are somewhat subjective and are the opinions of PodMerchant.com and not advertising claims.
 

We've got a very large shipment coming by sea due in the middle of April (just about the time I should be writing the next issue...) Blucaffe will be back in stock and we will also be stocking Lucaffe's Messico (Mexico) pod.
 

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