Introducing coffee roasting

Roasting is an important and integral step for coffee beans towards becoming a delightful cup of coffee. Roasting is necessary for two reasons - firstly, green coffee beans are very dense, making it impossible to grind green beans, thus, roasting is necessary to make coffee more soluble. Secondly, coffee has a complex chemical structure with over 1000 different compounds. Roasting develops and transforms these compounds into nuanced flavors and aromas that characterize coffee.

In this blog entry KALVE head production roaster Alina Sinkevych introduces the roasting process, how KALVE roast its coffee and how roasts differ.

How does KALVE roast its coffee?

KALVE Coffee Roastery's philosophy is that coffee is perfect in its cherry and our primary goal is to highlight the natural flavors, sweetness and balance of coffee.

In KALVE Coffee Roastery we use three gas-powered roasters BESCA with capacities of 2kg, 15kg, and 120kg respectively. We also have a small electric sample roaster, IKAWA. A sample roast is usually used when we receive farm samples before contracting and buying coffee in bulk. This means that we already know what quality coffee can offer before we buy it. This allows us to start working on coffee's roast profile as soon as we receive a fresh batch of green coffee.

Each coffee has its unique roasting profile with specific roast curve, time and set maximum temperature. While each coffee is unique and asks for a tailored roast profile, coffee's regional origins offer certain similar characteristics in chemical composition of the coffee. For determining the first roast profile, we usually use our 2kg roaster, so we can roast less amounts to determine the right roast profile for a new coffee. We use a special computer program which monitors the conditions in the roaster and records the roast profile's curve and settings. Additionally KALVE keeps all its previous coffee roast profiles, so whenever we receive a new coffee we can much easier pinpoint a starting point based on coffee region, variety and used processing method. 

Quality controls are an important and crucial part of the roasting process. KALVE conducts quality control for their entire coffee portfolio weekly. We ensure not only high-quality coffee but also consistency of high-quality. Weekly quality controls allow us to monitor both the quality and consistency of our roasts and adjust the roast profile as needed to maintain the desired quality and balance, and do it consistently. Additionally, we freeze the first roast samples of every coffee each month, to do a quarterly cupping of all the coffees, that way ensuring that our profiles remain consistent in extended periods of time.

Each coffee also undergoes a 3 month aging quality check after coffee has arrived at the roastery. Three months after the initial Q scoring of the coffee, we do another Q scoring to re-evaluate the coffee’s sensory quality.  If quality diminishes, which is a normal and natural process for green coffee, the price is adjusted to maintain a fair and appropriate balance between price and quality.

How is coffee roasted and what happens to coffee during the roasting process? 

A coffee roasting machine is equipped with a large rotating drum, which is heated by a gas flame. Coffee beans are placed inside the drum, which rotates and ensures continuous rotation and mixing. The coffee is heated or roasted by  circulating hot air and the drum's walls.  

There are four main variables - air flow, drum speed, flame and roasting time -  which can be individually or jointly changed to adjust roasting and the quality of the end roast. 

Coffee consists of more than 1000 chemical compounds including salts, minerals, fats, acids, sugars etc.;  and many of them are developed and changed during the roasting process.  Important point of reference during the roast is what in industry is called - first crack. It happens when the coffee bean heats up to the level where moisture and carbon dioxide, formed from the chemical reactions, escapes the bean. First crack is indicated by a cracking or popping sound, similar to when making popcorn. 

To put simply, the roasting process is divided into two parts - before and after the first crack. During the first part, coffee develops the enzymatic compounds which make up floral, berry, fruity and herby flavors. Enzymatic compounds are formed and evolve in coffee during time while coffee is in the farm and growing conditions and processing will affect and shape enzymatic composition of the coffee bean.
Together with enzymatic compounds, also salts, minerals and  acids evolve till the first crack. The phase needs to be long enough to evenly develop all the characteristics, otherwise coffee will taste salty, sour and sharp.
Second part of the roasting process develops flavors like chocolate, caramel and nuts and those are known as sugar browning compounds and they occur because of the caramelisation process which is caused by high levels of sugars in the coffee and the heat produced by roasting. Our task with roasting is to find the right settings and roast profile to emphasize coffee's characteristics in a good and balanced way. For example, our natural coffee from Finca La Palma has a high level of natural sweetness and flavors of very ripe tropicals and citrus. We want to emphasize the good and mouth watering characteristics of lime candy, sweet tropicals and vanilla during the first  phase and during the second phase we bring out the natural sweetness and compliment it with a silky texture. 

Roasting process can also include the second crack. The second crack develops full-bodied, creamy texture and taste notes of intense chocolate and sweet caramel. Our espresso blend Toffee is roasted with the second crack to have a full-bodied, thick and creamy texture. Thanks to well developed and adjusted roast profile we can offer a consistent taste profile all year round, while the coffees making up the blend change seasonally. 

FUN FACT! Roasting process involves Maillard reaction which is a fascinating and complex chemical reaction between amino acids and reducing sugars, responsible for changing coffee's color from green to brown and developing aromas and flavors. Same reaction happens when making a bread toast or grilled meat and briefly speaking, thanks to Maillard reaction our foods taste more tasty.

What's the difference between espresso and filter roast? 

Espresso roasts are roasted for a longer time and results in a darker color and less dense beans. As a result, when brewing you need less extraction or brewing time, but higher temperature and pressure(temp. - 94-960 ; pressure 6 - 9 bar). Coffee roasted as an espresso will offer a full-bodied, more intense cup.

On the other hand, filter roasts are roasted for a shorter time and have a lighter color, but more dense beans. Filter roast aims to develop the enzymatic or natural occurring compounds of the coffee and has more developed acids. Filter roasts technically develop less sugar browning or caramelization compounds. Therefore filter roasts tend to have more nuanced flavors than espresso roasts. Our suggestion for filter coffees is to use coarser grind size, lower water temperature (90-950) and longer brewing time. But it is not a rule, it is a recommendation for making a perfect, balanced cup with your comfort brewing method. In professional coffee competitions, it is a lot about experimentation. Using very light roasted coffee in an espresso machine or experimenting with different funky brew ratios. 

Fact! In  KALVE we classify our coffees as espresso, filter or omni roast. Omni roast is a compromise roast and means coffee will be suitable for any preparation method, however only few coffees are suitable for omni roast.
Technically, any coffee can taste good as an espresso or filter roast, but usually that asks for two different roast profiles.

However, the in-cup method is the safest and most versatile coffee preparation method that is fit for any roast. Coffee professionals all around the world use in-cup or cupping methods to taste, evaluate and control the quality of the coffee. 

In the following KALVE Blog series we will look at the final stage of coffee's journey to tasty and flavourful cup. That is - understanding the science behind brewing and tips and tricks of brewing the perfect cup! 

Read the previous blog entry of how KALVE sources and buys its green coffee - HERE.