咖啡烘焙

 

Coffee Roasting Stages: 起 (Equilibration), 承 (BT Delta Accelerating), 轉 (BT Delta Descending), 合 (Flavor Development Finishing)

1. 起 (Equilibration Stage)

   • Purpose: This stage is about evenly distributing heat within the beans as they enter the roaster. The goal is to ensure that all beans start with a uniform heat level, creating a consistent baseline for the rest of the roast.
   • Soak Method: In this stage, some roasters use the "soak" technique, which involves starting with low or no heat right after charging the beans. This pause allows the beans to stabilize and gradually acclimate to the roasting environment, minimizing any initial temperature shock.
   • Impact: A proper equilibration helps ensure that beans are evenly heated, setting the foundation for balanced flavor development in later stages.

2. 承 (BT Delta Accelerating Stage)

   • Purpose: In this stage, the beans experience their fastest rate of temperature rise. The internal and external temperature difference (D) of the beans increases, pushing the beans toward an accelerated chemical reaction phase.
   • Impact: A higher rate of temperature increase in this stage helps develop the initial flavors. Adjusting the heating rate can either widen or narrow the internal-external temperature difference, affecting how uniformly the beans develop their initial flavors. For example, a faster heating rate might intensify specific flavors, while a slower rate could provide a more balanced flavor profile.

3. 轉 (BT Delta Descending Stage)

   • Purpose: Here, the temperature rise slows as the beans’ internal temperature nears the surrounding environment. This phase focuses on the Maillard reaction and caramelization, creating complex flavor compounds.
   • Impact: Slowing down the rate of temperature rise (narrowing the temperature differential) helps the beans develop a balance of acidity and sweetness. By adjusting this stage, roasters can influence the production of small and medium-sized aromatic molecules, enhancing the coffee’s complexity. This phase is crucial for achieving flavor depth and is particularly impactful for balancing fruity and sweet notes.

4. 合 (Flavor Development Finishing Stage)

   • Purpose: Starting at the first crack, this stage is the final refinement, where flavors are locked in and nuances are fine-tuned. Maillard and caramelization reactions peak, with pyrolysis (dry distillation) further enhancing roasted flavors.
   • Impact: This stage is crucial for the final flavor profile. Carefully managing the heat ensures that the beans are neither underdeveloped (green or grassy flavors) nor overdeveloped (bitter or charred). Especially in light roasts, selecting the right drop point (end of roast) requires skill to balance the flavors without losing the desired acidity and sweetness.
     
     

     階段	目的	手法	評論	建議	風味影響

     起 (均熱階段)

     均勻加熱，準備豆子進入烘焙

     可用靜置手法（低火或暫停加熱）

     這個階段的「靜置手法（soak）」強調豆子的均熱，減少內外溫差，這對於豆子的穩定性非常重要。透過靜置讓豆子逐步升溫，可以避免溫度衝擊帶來的過早反應。然而，靜置的時間和火力控制很考驗烘焙師的經驗，特別是對不同豆種的適應性。例如，水分含量高的豆子可能需要更長的靜置時間，反之則可以縮短。

     這一階段尤其適合小批量或手工烘焙中使用，因為在工業烘焙中或多鍋次烘焙中靜置時間過長可能會降低烘焙效率。

     建立一致的溫度基礎，確保後續烘焙的穩定性

     承 (升溫加速階段)

     快速升溫，加大內外溫差

     高升溫速率

     「承」階段的重點在於快速提升溫度，拉大豆子的內外溫差，這為之後的風味發展打下基礎。高升溫速率不僅加強豆子的內外溫差，還有助於提高豆子表面化學反應速率，但也會產生高風險。若升溫過快，可能會導致外部過度焦糖化而內部未熟，影響整體風味的一致性。

     在這個階段，可以考慮根據豆子的特性（例如硬度、密度）來微調升溫速率。例如，高密度的豆子可以承受更快的升溫，而低密度豆子則可能需要稍微緩和的升溫速率，以保持內外溫度的平衡。

     發展初始風味，升溫速率決定風味的強烈或平衡

     轉 (升溫趨緩階段)

     放緩升溫，縮小內外溫差

     控制升溫逐漸放緩

     「轉」階段是這個理論的核心，因為此階段是風味構築的關鍵。梅納反應和焦糖化反應在此階段持續進行，並隨著升溫趨緩，內外溫差逐步縮小。這個階段的控制直接影響咖啡的酸甜平衡和香氣複雜度。然而，這一階段的操作難度較高，特別是當升溫速率調整不當時，會導致酸度過高或甜味不足。

     此階段可以考慮採用更精細的溫度管理，適時調整火力。對於想要增加果香的淺焙，可以延長轉階段的時間，而對於希望突顯堅果或巧克力風味的中深焙，則可以加快升溫速率以增強焦糖化效果。

     平衡酸甜，構築風味的複雜性，增強果酸和甜感的層次

     合 (風味收斂階段)

     最終風味定型，鎖定風味層次

     精細控制溫度，選擇適當的下豆點

     合階段的難度在於如何找到完美的下豆點。在淺焙中，一爆之後的熱控制需特別精確，避免過焙影響到原本的酸甜平衡；而在深焙中，適度延長合階段的時間則能增強苦韻和濃郁感，為風味增添層次感。合階段還引入了乾餾作用（pyrolysis），這對於增添深層香氣至關重要，但若處理不當會導致豆子過於呆板、喪失甜感。

     這個階段的控制應根據預期的最終風味目標調整下豆點。對於希望保持清新酸質的淺焙，應迅速出豆；而對於中深焙，可以在保持溫度的前提下適度延長，鎖定豐富的風味層次

     決定最終風味，平衡酸甜苦，增添層次感