Thermocouple Thermometer in Coffee Making

August 27, 2020

Thermocouple Thermometer in Coffee Making

Unless a thermocouple thermometer is employed in your coffee-making, arriving at a cup of coffee that opens the day like a breath of fresh morning air could be highly improbable. If at all. You see, the best coffee beans are just half of the story; the other half is making sure you get to process them right. And no probe comes closer in this department than a thermocouple thermometer.

Many, if not most, of the billions of people worldwide who make coffee-drinking a habit daily, are not aware of how meticulous and exacting the process is to get each cup right. But make no mistake about it. Part of keeping a chock full of taste in each cup is keeping temperatures all throughout the process consistent.  A job that under scrutiny would fall to a thermocouple thermometer. More often than not.

 

Coffee-making: The Art of Keeping Temperatures Consistent

It’s true. To say coffee-making isn’t temperature-dependent is anomalous. Among other things in an expert’s coffee-making handbook, of course.

For starters, it wouldn’t sit well with coffee-lovers all over America who gobble up over 400 million coffee cups a day.

Then again, if thinking of 400 million cups of coffee daily overwhelms you, think again. America may be getting the biggest piece of the pie, but the superpower nation is not alone. Refer to the two images below to see how much coffee is produced and consumed internationally. 

 Coffee consumed in the USA Coffee industry in Brazil

Indeed, coffee beans and the right temperature come a long way. Just a look at how the 15th-century Ottoman Empire and Greater Persia used crude big-spoon-looking dished pan with extra long handles to roast coffee beans to a consistent taste will tell you how lucky we are to have the technology now on our side.

From the onset, know that coffee as an aqueous extract is a combination of several solids and yes, oils. As such, the coffee-making process has a lot of variables that can affect the final product. Eliminating as many of these variables as possible is the art of coffee-making.

Let’s take a look at how today’s coffee arrived at your morning table with one key variable in the picture sought always: the right temperature. In the age-old 4-stage process that makes coffee happen:

 Roasting, Grinding, Brewing, Extraction 4 stage process

  • Roasting

Roasting green coffee beans bring out the taste of coffee by removing chlorogenic acid. The temperature has a lot to do with the right roast. And each coffee expert has his own coffee profile to follow to get to the consistency in taste.

This is where a thermometer must come in to keep temperatures in check. To keep the RoR stick to the profile as much as possible.

In fact, this is where it gets really tricky. Roasting changes the bean externally: its size nearly doubles while its color shifts from yellow to brown. Crackling sounds are triggered as cell walls of each bean bursts and oil gets released.

Moreover, for the connoisseur in you, roasting sets off a chemical reaction that changes the insides of the bean. For one, the longer one single bean gets roasted, the more sugar is burnt off leading to bitter tastes. Reason enough why more often than not, probes are set all over the place (e.g., inside the drum, while cooling) to monitor the roasting process.

Know that each coffee bean type requires a distinct charge temperature, the temp of your drum right before you add the beans. Each expert may have different takes on the number but it’s not unusual for charging temperature to be between 375ºF(191ºC) and 425ºF(218ºC). Really hot!

 

  • Grinding

To make brewing a walk in the park, roasted beans must be ground. Again, methodology matters here as grounding affects the quality of brewing. The most common methods are burr-grinding and your home blender which is actually a blade grinder.

 

  • Brewing   

This when the ground coffee meets screaming hot water. Steeping, or separating the flavor from the beans, then follows which can be done via filters. Or a simpler method via pour-over.

The right temperature must be once again observed here. For many baristas all over the world, their lucky number is 205. And that represents 205 °F or 96 °C as the perfect temperature for brewing coffee. A temperature slightly below boiling water.

Brew it too hot and you run the risk of drinking bitter coffee; brew it too cold and you have a watery liquid that tastes flat. Devoid of flavor.

 

  • Extraction

The part where you separate the ground beans from the liquid using filters.

All these steps are time-sensitive. Fact is the moment a coffee bean is picked from the cherry, you are running against time. To note, the longer it takes for fresh beans to be roasted the lesser the chances of arriving at a consistent well-loved cup of coffee.

And yet, of all the steps, roasting plays a most pivotal role. It’s also where you’d need to keep a real close eye on changes in temperature in your journey towards a doable cup of coffee. One you can concoct right away with confidence when you need to.

When you want your RoR (Rate of Rise), the speed at which the temperature of your coffee beans changes while roasting, to be optimal ultimately you will have to know the temperature details. To do that requires the utility of a sensor probe.

Not only will probes help you use reading data as you roast, but it also gives you a profile of the roast allowing you to replicate what worked well. In short, you eliminate errors as you have numbers to guide you. Arriving at that distinctive taste more consistently.

 

Thermocouple Thermometer: King of the Hill

How thermocouple thermometers can help with coffee making

For the most part, two commercial temperature probes have risen to the challenge posed by the rigors of coffee making; the rest have simply fallen short. One is the resistance temperature detector or RTD and the other is the thermocouple thermometer.

RTDs probes have a simple basic principle: the higher the temperature applied to a metal, the higher the resistance to the flow of electricity. Measured in Ohms, the resistance value is converted to temperature readings.

On the other hand, a thermocouple makes the most on the thermoelectric effect - churning up temperature readings by measuring the voltage produced when a distinct temperature is applied to two dissimilar metal alloys joined together.

Of course, it all boils down to performance. Here’s how the thermocouple thermometer fares against its closest competition in the coffee making:

 

  • TEMPERATURE RANGE

When temperatures are seething hot, the thermocouple is at the top of its game. And it’s not even close.

It’s true. New manufacturing techniques have stretched the capacity of RTDs to measure high temperatures. But the majority of RTDs, a little over 90% of them, are built to work below 400 °F. Beyond that is considered an uphill climb.

However, thermocouples live up to the game. They are designed to withstand volcanic temperatures. Some have been used up to 2500 °F.  And this is one obvious reason why thermocouples as a thermometer have become a household word in coffee making more than the resistance-based RTDs.

You wouldn’t want to stop your roasting just because you’re afraid your RTD probe will break, right?

 

  • SENSIBILITY

The ability to sense the temperature isn’t an advantage in making coffee if it takes you forever to get to the readings. Of course, speed is of the essence. The faster, the better.

And speed is what you get with a thermocouple doing your bidding. While both RTDs and thermocouples are quick enough to respond to changes in the temperature, thermocouples are way faster leaving the competition eating dust.

For the record, a thermocouple’s ability to detect temperature changes is thrice faster than the popular PT100 RTD, a leading design. And if you want to capitalize on the speed of discovery, relying on an exposed-tip thermocouple is your best bet.

Certainly, RTDs have come a long way as manufacturers have managed to improve its performance over time; but even its fastest variety, the thin-filmed PT100, is nowhere near the speed of the slowest thermocouple.

 

  • PRICE

In many industries wanting to cut costs, relying on the thermocouple thermometer probe makes a sound decision. Simply put, of all the probes out there that can be manufactured en masse, thermocouples are the cheapest.

There are ways you can save on RTDs but overall one RTD will cost twice or thrice more when put side-by-side a thermocouple that can deliver the same results. Manufacturers can mass-produce the two-metal thermometer gauge at a lesser cost.

If you’re an avid coffee-maker who is keen about cutting your expense (as most would) then a couple or two of thermocouple thermometers won’t hurt your budget as much as RTDs. For one, you can save on RTD by using cheap copper wire but even that would fail miserably when compensating for its higher cost.

For the most part, coffee roasters have relied on Type J or Type K thermocouples for ages. You’d be wise to check their specifics if you’re new to the venture.

Then again, don’t throw away other probes just yet. Even when thermocouples are superior in a lot of ways, other commercially-available probes - RTDs and thermistors specifically - can hold their own in other industries. Each probe type has its own distinct advantages over the other.

For instance, RTDs are generally more accurate in zeroing in on the exact temperature. It’s not unusual for RTDs as fine as 0.1°C, a seemingly-impossible feat that would make a thermocouple squirm. The two-distinct-metal probe clocks in a range of ± 0.2 to ± 0.5 °C accuracy.

Your job, therefore, is to consider the nature of the job and find the best probe-type to serve your needs.

 

In short, due diligence is a must. The tool must fit the job. And not the other way around.

It just so happens that when it comes to producing a perfect cup of coffee, putting faith in a thermocouple thermometer is spot on.

Check out PerfectPrime’s collection of thermocouple thermometers here to see which one would be suitable for your coffee needs.



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