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Why Coffee Roasters Need Quality Assurance: What You Don’t Want in Your Morning Cup

August 2, 2018

Why Coffee Roasters Need Quality Assurance: What You Don’t Want in Your Morning Cup

| By Greg Luli |

Coffee drinkers all have their own very unique preferences when it comes to determining how they experience a great cup of coffee. For some, it’s the bright acidity and full-bodied fruity flavor, or it could be the subtle chocolatey hints coupled with the natural sweetness of steamed whole milk. For others, it may not really be the taste, but rather simply the powerful punch this caffeinated beverage provides to help them get through the day.

Whether you’re on a quest for the perfect morning cup of coffee, something that will enhance a meal, or to enjoy on a leisurely afternoon, you expect that when you purchase coffee from your favorite specialty coffee roaster that you will have high-quality coffee beans roasted just how you like and brewed using your preferred method. It also goes without saying that you also expect this coffee to be free of contamination and taste how its supposed to. But, how can you be sure that it is? After all, the majority of coffee comes from third-world countries, goes through many steps in processing, including being processed in open areas, often on the ground; even the most expensive and best quality coffee beans.

This is where the coffee roaster steps in. The coffee roaster plays two very important roles in that journey a green coffee bean makes from the fruitlet to your cup. The first is the one in which we are most familiar: roasting coffee in just the right way to bring out the flavors we’ve come to know and love. The second key role is in quality assurance and quality control. This ensures that your cup of joe is not contaminated by various things that you really don’t want to find or taste.

Green vs roasted coffee

Coffee is an agricultural product that makes a very long journey from the shrub from which its picked all the way to your cup. Along the way, there are many things that can go wrong (physically and chemically) that could end up producing a less than joyful experience. Even when we raise the quality bar by only considering specialty Arabica coffee, several key points to watch out for and processes to follow in coffee quality assurance and coffee quality control that are essential to ensure the pleasant experience we seek. These points start with the farmer, pass on to the export/import agents, to the roaster, and finally to the barista.

Because coffee beans are actually the seeds of the coffee fruit known as the “cherry”—due to the likeness of actual cherries—they can be damaged by pests and microbes while still on the branch. The integrity of the beans can also be damaged during processing or they can even be spoiled by microbes during this process, which can result in very off-putting and undesirable flavor characteristics. One example of this is from poorly-fermented coffee beans known as “full blacks”. This can happen even to the very best coffee beans out there. These damaged beans can impart grassy, musty, sour, earthy, phenolic, or disagreeable fermented flavors. They look very different than your typical green coffee bean and take on either a reddish, purple or black tone.

(Full black coffee beans due to poor fermentation)


Another common form of damage is from insects that attack the coffee cherries while still on the branch. The “berry borer beetle” is a serious pest in many countries, including Hawaii, where top quality Kona coffee is grown. The beetle bores a small hole into the soft portion of the bean. These chewed-up beans can expose them to microbe spoilage also resulting in very undesirable flavors.

Coffee beans with Insect Damage

(Coffee beans with severe insect damage)


The Specialty Coffee Association (SCA) has set very specific coffee standards for judging the quality of coffee, both green and roasted. These standards set limits to the number of defective beans that are permitted in green coffee to qualify as “specialty grade”. However, it is the job of the coffee buyers (importer and roaster) to examine green coffee and determine if it meets these standards. Most of these defects can be avoided with improved farming and processing practices, but ultimately it is the coffee buyer that must grade the green coffee and determine that its quality is high enough for specialty coffee products.

As mentioned already, because coffee is processed in open areas and on the ground, foreign objects can be introduced during processing and packaging. It is not uncommon to find rocks, nails, screws, other types of beans, and even broken glass in green coffee. Specialty grade coffee should have zero foreign objects per standard sample of 300 grams. However, with such a small sample size, it is not uncommon for specialty coffee to have a rock here or there.

Therefore, many of the best specialty coffee roasters in the business use the proper and most up-to-date equipment to assure that if any of these foreign objects do get into the green coffee that they are removed before they end up in your favorite roast.

Foreign objects removed from coffee beans

(A collection of foreign objects that have been removed from green or roasted coffee, including metal, glass, and wood)


Additionally, in order to prevent metal objects from getting through the roaster, metal detectors or strong magnets can be used. Here at Café Virtuoso, the main production roaster utilizes magnets in the green bean cart to remove all sorts of metal. These magnets are powerful enough to remove even the smallest of stones that may have a high iron content.

Loring Coffee Roaster Magnets

loring coffee roaster magnets

(Loring green bean cart showing magnets in the bottom of the cone. The magnets attract stones that have a high mineral content)


The second line of defense is a piece of equipment called a “destoner”. This device separates roasted coffee from any objects that are more dense by the use of a vacuum cyclone. Dense materials (rocks, glass, metal) are trapped below while the lighter coffee is conveyed up into a finished product hopper.

Loring coffee roaster and destoner

(A Loring destoner attached to Café Virtuoso’s 70lb roaster)


So, the next time you head out to grab coffee from your favorite coffee roaster, it might be a good idea to ask them what quality assurance processes and steps for quality control that they have implemented to make sure that you get all that you want in your favorite coffee, and none of what you don’t.

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Greg Luli

General Manager
An industrial microbiologist—both by education and for 30 years by trade—Greg is intrigued and challenged by the endless intricate nuances, methods and scientific knowledge needed to roast and brew specialty coffee. If he’s not outdoors hiking with his dogs, he can most certainly be found helping to perfect the roast levels of the newest coffee bean varieties to arrive.

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