014
Cru Speech
Acidity &Wine Part 1:
the chemistry and microbiology 酸度與葡萄酒 第一部份：化學與微生物學 English Text : Han Tao Lau Translation : Joe Lo
A few months ago, the Australian wine industry mourned the passing of one of
幾個月前，澳洲葡萄酒界為一位偉大葡萄酒先驅Ray Beckwith博士的離世
its greatest pioneers – Dr Ray Beckwith. One of Dr Beckwith’s most important
作出了沉痛的哀悼。 Beckwith 博士其中一項最重要的發現，是關於葡萄酒
discoveries was the link between acidity and microbial stability in wines. What
酸度與細菌穩定性的研究。在這裡就讓我們把他的對葡萄酒細菌與微生物
better way therefore to celebrate his life than to explore the concept of acidity in
關係的研究傳揚開去吧，我想這應該是悼念他的最好方法了。今期就讓我
wine? What exactly is the role of acidity in preventing wine spoilage, and apart
來們一起探討酸度如何防止酒質變壞，以及酸度經常在葡萄酒話題之間被
from this, why is acidity so often talked about in wine?
提及的原因。
While I have no wish to make this article seem like a high school chemistry
我並不希望把這篇文章寫成一篇像化學科的論文般，可是，我仍然要略為
lesson, nonetheless, it is important to clarify some of the key concepts
解釋一下其中關係到葡萄酒與酸度的主要概念。在釀酒師的工作範疇裡，
relating to acidity in wines.
其中有兩項數據是我們必須注意的—酸鹼值（ pH ）及可滴定酸度／總酸
There are two measurements related to acidity that winemakers look at in
度（TA）。
particular – pH and titratable / total acidity (TA). pH是一種用作量度氫離子（H+）的數值，亦可以粗略解釋為溶液之中氫離子 pH is a measurement of the activity of the hydrogen ion (H+). It can be
的濃度指數。pH的讀數由0至14，低pH值代表酸性較高、接近7代表中性、
roughly defined as as the power or concentration of H+ in a solution.
而高pH值則代表鹼性較高。以葡萄酒而論，普遍的pH值大約為3至4左右。
Values for pH range from 0 to 14, with low pH values being acidic, values near 7 being neutral, while higher pH values are described as being alkaline
可滴定酸度和總酸度一般來說可以算是差不多意思，兩者都是用來量度葡
or basic. In wine, pH values usually range from 3-4.
萄酒或葡萄汁之中含有的酸性高低。在歐洲地區 TA 是以每公升所含多少克 硫酸作計算單位（ g/L ）；通常在新世界，包括澳洲則多數會以酒石酸作
Titratable acidity and total acidity are roughly interchangeable terms, used
計算。對我來說，把這些酸性物質稱作酒石酸似乎更加合理，不只是因為
to give a measurement of the acids present in grape juice or wine. In most
身在澳洲的關係，而是因為酒石酸在葡萄酒和葡萄果實之中更加普遍地存
of Europe, TA is expressed in grams per litre (g/L) as sulfuric acid. In much
在。硫酸比酒石酸的酸度強烈得多， TA 值為 4.2g/L 的硫酸已經相等於 TA 值
of the new world, including Australia, it is expressed as tartaric acid. To
7g/L的酒石酸。一般葡萄酒的TA值以酒石酸計算約為5-10g/L左右。
me, expressing this value in tartaric acid really makes a lot more sense, not just because I work in Australia, but because tartaric acid is the most
那為甚麼 pH 和 TA 兩者的量度同樣需要呢？為甚麼不只用其中一種？首先，
common acid found in grapes and wine. Sulfuric acid is a stronger acid
在釀酒學上， pH 和 TA 是葡萄酒味道中兩種完全不同的量度法， TA 可以被
than tartaric, so a TA of 4.2g/L expressed as sulfuric acid would equate
視為一種直接量度酒中實際酸度或酸性味道的方法。當酒的 pH 值低時，酒
roughly to a TA of 7g/L expressed as tartaric acid. In wines, TA is usually in
的味道會較酸；但事實上若其 pH 高、同時 TA 亦高的話，酒的味道同樣會偏
the range of 5-10 g/L expressed as tartaric acid.
酸。另一方面，pH亦是影響口感的重要因素，擁有高pH值的酒，口感會較
So why is it important to measure both pH and TA? Would it not suffice to
，這酒的味道便會變得像肥皂一般、或者不夠結實而顯得平淡。
圓潤和黏口，但若果酒在這個情況下沒有足夠的實際酸度時（也就是 TA ）
use just one of these measurements? Firstly, from an organoleptic point of view, pH and TA are very different indicators of how a wine tastes. TA can
另外， pH 亦會影響紅酒的酒色。低 pH 值會令酒偏向深紅色；而高 pH 值則
be seen as a more direct indicator of the actual acid taste, or sourness, of
會令酒色帶藍紫。
wine. While wines with a low pH tend to taste more acidic, in actual fact, wines with a high pH can still taste quite acidic if they have a high TA. The
Cru Speech_HanTao.indd 1
最重要的一點是，pH在穩定微生物中所擔當的角色，這亦是Beckwith博士
28/3/13 6:07 PM