TDS不等於濃感：為什麼中焙0.95喝起來比極淺焙1.25更濃？ TDS ≠ Perceived Strength: Why a Medium Roast at 0.95 Can Taste Stronger Than an Ultra-Light Roast at 1.25
目錄：
1. 為什麼中焙較容易被感覺「濃」？
2. 濃度是數字，濃感是結構
量到的TDS(總溶解固形物)是「杯中溶了多少東西」，但嘴巴感覺到的「濃」，其實是大腦把多個線索綁在一起的結果：甜感與苦感的重量、口感的黏稠度、微粉與膠體帶來的厚度、香氣的調性與酸感的亮度。於是就會出現看似反直覺的情況：中焙 TDS 0.95，喝起來反而比極淺焙 1.25 更濃。
先把觀念釐清：TDS 只回答「量」，不回答「內容」。兩杯就算數字差很多，若溶解物的組成不同、口感結構不同，濃感會完全反轉。極淺焙常被形容「清、亮、解析高」，中焙則常是「厚、甜、重」。這些形容大多不是在講濃度，而是在講風味與觸感的結構。
Measured TDS (Total Dissolved Solids) tells us how much material is dissolved in the cup. But what we perceive as “strength” is the brain integrating multiple cues at once: the weight of sweetness and bitterness, mouthfeel viscosity, thickness contributed by fines and colloids, aroma character, and the brightness of acidity. That’s why a seemingly counterintuitive result can occur—a medium roast at 0.95 TDS can taste stronger than an ultra-light roast at 1.25 TDS.
Let’s clarify the concept first: TDS answers quantity, not content. Even if two cups differ significantly in numbers, differences in the composition of dissolved materials and mouthfeel structure can completely reverse perceived strength. Ultra-light roasts are often described as clean, bright, high-definition, while medium roasts are described as thick, sweet, weighty. These descriptors usually refer not to concentration, but to flavor structure and tactile sensation.
為什麼中焙較容易被感覺「濃」？
● 第一個原因是褐變反應帶來的烘焙甜香與厚度。
中焙的梅納反應與焦糖化產物更明顯，帶來焦糖、堅果、可可、烘焙甜香等訊號。這些味道的「重量感」很強，會讓你覺得咖啡更厚、更有存在感。相反地，極淺焙即使 TDS 高，常見主軸是柑橘、花香、茶感與明亮酸質，大腦會把它解讀成「清爽、輕盈」，而不是「濃稠、厚重」。
● 第二個原因是微顆粒(細粉)造成的稠感。
你喝到的「厚」不一定都來自溶解物，有時反而是過濾系統帶進杯中的細粉、膠體顆粒，讓口感變得黏、滑、稠，甚至帶一點粉感。VST 量到的是溶解固形物的比例，但杯中如果混入較多微粒，嘴巴仍會明顯感到更濃、更厚。中焙通常比較好磨也比較好沖：沖起來水路穩、味道集中，常常更容易讓這類「厚度線索」出現；極淺焙則可能呈現更乾淨、輕薄的觸感，即便 TDS 偏高也不一定有厚重感。
● 第三個原因是萃取段落與感官錯覺。
很多人把「苦」與「烘焙感」直接聯想到「濃」。當一杯咖啡中，苦甜與烘焙香更集中、更靠前，你會覺得它更強、更重。極淺焙就算溶解量高，若酸質更突出、甜感還沒堆疊出厚度，甚至出現局部欠萃與局部過萃的不均，整體印象反而會變成「亮但薄」「香但不厚」。換句話說，量到 1.25 可能代表溶解物多，但那些溶解物不一定是讓人覺得厚重的那一類。
Why Medium Roasts Are More Often Perceived as “Stronger”
1. Browning reactions add sweetness, roast aroma, and weight
Medium roasts show more pronounced Maillard reactions and caramelization products, contributing caramel, nutty, cocoa, and roasted sweetness notes. These flavors carry a strong sense of flavor weight, making the coffee feel fuller and more present. By contrast, even with higher TDS, ultra-light roasts often center on citrus, florals, tea-like notes, and bright acidity. The brain tends to interpret these as refreshing and light rather than dense and heavy.
2. Fines and micro-particles increase perceived viscosity
Not all perceived “thickness” comes from dissolved solids. Fine particles and colloids that pass through the filter can add viscosity—creating a slick, dense, even slightly powdery mouthfeel. VST measures dissolved solids, but if more micro-particles are present in the cup, the coffee can still feel noticeably thicker and stronger. Medium roasts are generally easier to grind and brew consistently, producing steadier flow paths and more concentrated flavor—conditions that often allow these thickness cues to appear. Ultra-light roasts, on the other hand, tend to brew cleaner and lighter in texture; even with higher TDS, they may not feel heavy.
3. Extraction phases and sensory bias
Many people subconsciously associate bitterness and roast character with “strength.” When bitterness, sweetness, and roasted aromas are more concentrated and forward, the coffee feels stronger and heavier. With ultra-light roasts, even if the total dissolved amount is high, prominent acidity and underdeveloped sweetness—or uneven extraction with both under- and over-extracted zones—can create an overall impression of bright but thin or aromatic but light. In other words, a TDS of 1.25 may indicate more dissolved material, but not necessarily the kind that reads as weighty or dense to our senses.
濃度是數字，濃感是結構
TDS 呈現杯中有多少溶解物，但喝到的「濃感」，更像是「風味重量+口感厚度+香氣調性」的合成。理解這點之後，就能更精準地用沖煮去控制：想要更「厚」就往褐變甜感與口感結構走；想要更「清亮高解析」就把乾淨度、流速與酸甜平衡放在第一位。
Concentration Is a Number, Perceived Strength is a Structure
TDS shows how much is dissolved in the cup, but perceived strength is the combined result of flavor weight, mouthfeel thickness, and aroma character. Once this distinction is clear, brewing becomes more intentional: If you want more body, lean into browning-derived sweetness and mouthfeel structure. If you want clarity and high-definition brightness, prioritize cleanliness, flow rate, and acid-sweet balance.
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