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Roasting Natural Process Coffee Beans

*Before 120°C: Open the air damper slightly (smaller than for washed beans). Natural process beans tend to be woody and dry, with silver skin that doesn't easily detach. Steam the beans to increase moisture content and promote ripening while reducing scorching. Maintain higher moisture content in beans at 150°C to prevent steaming the beans.

*120-168°C: Open air damper about 3/4 (washed beans about 1/2) to allow rapid evaporation of moisture from the beans. If temperature rises too quickly, adjust heat to delay the temperature increase.

*168-198°C: Maintain consistent heat increase, reaching about 198-200°C in approximately 12 minutes. Reduce heat about 30 seconds before first crack.

*215-222°C: During first crack period. After 30 seconds, assess the situation. If cracking sounds are too rapid and intense, immediately turn off heat and coast until the end of first crack. About 1 minute later, when cracking sounds become sparse, you can drop the beans.

*After dropping beans, place roasted beans in a mesh basket and rub gently to remove silver skin and carbon debris. Then pick out any white beans for cleaner flavor.

Natural process coffee beans, soft beans, or low-altitude beans show similar changes during roasting, so I classify them in the same group. Natural process beans undergo longer processing time than washed beans, so their moisture content is relatively lower, especially on the bean surface. Therefore, surface dehydration (the entire bean turning white) is easily achieved during roasting. The following photos feature Tchembe from Ninety Plus, a lightly fermented natural process bean. I won't elaborate on its flavor profile—this is a well-known bean that you can easily research online...

The characteristic of natural process coffee beans is that their surface moisture content is lower (at least) compared to washed beans. Therefore, white spots easily form on the surface during the steaming phase and spread throughout the entire bean. As shown in the picture—when the beans are at 127°C during the steaming phase, they turn completely white. From the cross-section, you can see that only the center core still retains higher moisture content and remains somewhat green.

After steaming is complete, the bean surface begins to enter the Maillard reaction phase. Initially, light yellow reactions start on the bean surface. Due to even surface dehydration, the entire bean colors quite uniformly. From the cross-section, you can still see some green areas.

When the bean temperature reaches 160°C, the surface Maillard reaction enters its vigorous phase. Due to proper steaming, the entire bean colors quite uniformly, and the previously green center core begins to turn yellow, indicating that the core is also undergoing Maillard reaction.

At 172°C, the browning reaction of the beans is quite even, and internal color gradually deepens. At this point, the beans emit popcorn or toast aromas, representing the peak of Maillard reaction, also known as dehydration completion or bean shrinkage point. However, natural process beans have more thorough dehydration, so dark wrinkles from insufficient dehydration are barely visible. For washed beans, surface wrinkles would be quite obvious at this stage. To avoid errors in the subsequent caramelization reaction, I reduce heat and air flow here to avoid "excessive" temperature increase (not temperature reduction), which could cause over-caramelization and burnt flavors. However, I believe that caramelization hasn't officially begun at this stage.

First Crack

First crack begins at 186°C. At this point, you're only hearing cracking sounds from a few beans among many. The remaining beans should still be in pre-first-crack state, their centers filled with water vapor ready to crack. The Maillard reaction is nearing completion. If you drop the beans at this point, you'll experience abundant aroma and sucrose sweetness (simple sweetness, not caramelized sweetness). However, poor processing can easily result in grassy and astringent flavors, and your mouth and stomach may feel heavy.

After Intense First Crack

More than half of the beans have developed first crack, and water accumulated in the bean core has been fully expelled. From the beginning of first crack to after intense first crack, about 1% of water can be expelled. This is the period of most vigorous water expulsion from beans. If moisture content is measured, only about 1% remains, with water activity aw=0.2. In short, the beans no longer have free water. However, be aware that if you want to continue roasting into second crack, you must find ways to retain some moisture, otherwise, without free water, bound water will suffer, and ultimately without water, the beans will burn. The consequences of reaching second crack would be disastrous.

So how do you retain water for second crack? Unfortunately, second crack is not currently my area of expertise, and I cannot answer this question. However, I can confirm that the entire technique should change. You absolutely cannot use the method I've described of extending time after first crack to roast beans to second crack—this would fail terribly because you would get intense burnt bitterness.

I know some experts roast beans to second crack, and their time is faster than roasting to first crack. Their techniques are naturally different. I believe they also consider moisture and burnt bitterness issues after entering first crack.

Additionally, there's a very obvious difference in internal bean changes from before to after first crack. At 186°C, the bean exterior is darker while the core is lighter. However, after first crack, the opposite occurs— the interior becomes darker. I'm still investigating this phenomenon, but I know that the bean core is undergoing caramelization reaction at this time.

My Discoveries

Whenever white spots appear on beans during the steaming phase, it indicates faster moisture loss in those areas. When I slice these areas, they are quite brittle and lighter in color.

Areas on beans without white spots during steaming are quite tough when I slice them, requiring some force to cut. During the Maillard reaction phase, these areas are also darker in color. After dehydration completion, these areas form strong contrast with faster-dehydrating areas, creating distinct wrinkles, commonly known as bean shrinkage points.

Therefore: White spot areas will become lighter in color and brittle in structure during the subsequent Maillard reaction phase. At this time, the Maillard reaction is incomplete. Why? Because excessive dehydration in white spot areas means that when temperature reaches the Maillard reaction phase, there isn't sufficient water available, so the reaction is incomplete, resulting in lighter color and weaker aroma.

Aren't White Spots Bad Then?

I believe that white spots on the bean surface, due to their brittle structure, can create ventilation channels to help release internal moisture from beans. The key to the entire roasting process is to ensure the entire bean is thoroughly cooked. The formation of white spots helps achieve thorough roasting because once drainage channels are formed, combined with appropriate temperature increase rates, it helps the bean internal moisture reach the appropriate aw=0.7 when temperature reaches the Maillard reaction phase.

Of course, internal moisture that is too high or too low will produce undesirable results. Therefore, balancing dehydration, internal bean temperature through damper and heat configuration, and temperature increase rate is an art.

What if Bean Surface Has Too Few White Spots?

This indicates that surface dehydration is appropriate or insufficient. When entering the Maillard reaction phase, because there's enough moisture, good Maillard reaction can form. However, due to the tough structure, brittle dehydration channels cannot form, so internal moisture accumulates and cannot be expelled. Once reaching Maillard reaction temperature with excessive moisture, chlorogenic acid hydrolysis reaction will activate, producing undesirable bitterness (vinyl catechol polymers). This is what people generally call insufficient dehydration.

Natural Process Coffee Bean Brand Recommendations

FrontStreet Coffee's freshly roasted single-origin natural process coffee beans—such as Natural Yirgacheffe and Natural Sidamo—offer full guarantees in both brand and quality, suitable for brewing with various equipment. More importantly, they offer extremely high value for money. A half-pound (227g) bag costs only about 70-90 RMB. Calculating at 200ml per cup with a 1:15 coffee-to-water ratio, one bag can make 15 cups of specialty coffee, with each cup costing only 5-6 RMB. Compared to cafés selling cups for dozens of RMB, this offers exceptional value for money.

FrontStreet Coffee: A Guangzhou-based roastery with a small storefront but diverse bean varieties, where you can find both famous and lesser-known beans. They also provide online shop services at https://shop104210103.taobao.com

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473