品味奇蹟：白葡萄酒結晶的故事與意義
每當選購白葡萄酒時，我們有時會在酒瓶底部發現一些白色結晶，甚至在晃動酒瓶時，這些結晶還會上升漂浮。雖然酒專家告訴我們這是正常現象，不會影響品質，但我們或許仍心存疑問：帶有結晶的白葡萄酒真的沒有變質嗎？現在，讓我們來探討這個問題，並確認我們能夠安心品味這樣的白葡萄酒。
首先, 白葡萄酒出現結晶是正常現象而且無害的，亦不會影響味道，可以放心飲用，就像果汁一樣，有時有渣的鮮榨果汁才是好東西～
酒中含有多種溶解物質，如酒石酸、糖分、蛋白質和礦物質。當這些物質的濃度超過其溶解度時，就會開始析出形成結晶。通常已較低溫度。當酒的溫度降低時，物質的溶解度就會減少，導致它們從液體中析出。所以酒石酸在低溫下很容易結晶。
A . 白葡萄酒結晶的成分是什麼？
白葡萄酒結晶成分通常是由酒石酸（tartaric acid）沉澱形成，有時也會伴隨著蛋白質（protein）沉澱和色素（pigment）沉澱。
葡萄酒（wine）中含有大量的酒石酸，它可以與酒中的鉀離子（potassium ion）和鈣離子（calcium ion）結合，形成酒石酸氫鉀（potassium bitartrate）和酒石酸鈣（calcium tartrate）。由於這兩種物質的溶解度都相對較低，因此容易聚合形成沉澱。酒石酸沉澱通常呈現晶瑩剔透的結晶狀，宛如白砂糖般美麗。葡萄酒是一種自然的產物，並且每一瓶都可能有獨特的特徵和驚喜。
蛋白質沉澱：
白葡萄酒中的蛋白質含量通常較高，它們可以與酒中釋放出的單寧（tannin）結合，形成白色絮狀物。在較高溫度下，葡萄酒中的蛋白質有時也會凝結，產生白色沉澱。蛋白質沉澱通常以絮狀懸浮於葡萄酒中。
色素沉澱：
葡萄酒中含有眾多的色素物質，屬於多酚類化合物。在常溫下，它們以溶解狀態存在，但當溫度下降時，這些色素物質會形成沉澱。在陳年過程中，色素物質會不斷發生聚合或縮合反應，膠體顆粒逐漸增大，因而產生沉澱。
B. 白葡萄酒結晶形成的原因是什麼？
白葡萄酒結晶形成的原因有多種，以下是其中幾種常見情況。
1. 樹齡較老：
樹齡較老的葡萄藤吸收的礦物元素含量較高，因此釀造的葡萄酒中鉀和鈣離子的含量也較高，這促進了結晶的形成。
2. 種植氣候較冷涼：
氣候較冷涼的種植環境下，白葡萄品種的果實酸度相對較高 （例如：法國 Alsace 產區），這間接導致酒中酒石酸的含量增加，進而促進酒石酸和鈣、鉀等離子結晶物質的形成。當酒液中的酒石酸濃度超過了其可溶解的限度時，酒石酸就可能結晶出來形成結晶物。
3. 冷浸漬發酵：
低溫下的發酵過程會降低酒中結晶物質（crystalline substances）的溶解度，進而促使酒石酸沉澱的生成。酒石酸是葡萄酒中常見的有機酸之一。
4. 陳年時間長：
葡萄酒在長時間的陳年過程中，酒石酸會與鈣、鉀等離子發生聚合反應，形成酒石酸沉澱。通常，陳年時間越長，酒石酸沉澱的量就越多。同時，葡萄酒中的色素也會進行聚合反應，形成色素沉澱。這就是為什麼一些經過長時間陳年的葡萄酒會有更多的結晶形成，比如著名的貴腐甜白葡萄酒(Noble Wine) 。（貴腐酒，法語：Trockenbeerenauslese，德語：Trockenbeerenauslese）
5. 儲藏溫度過低：
儲藏過程中，溫度過低會使酒石酸和鈣、鉀等離子的溶解度降低，進而析出形成沉澱。一般來說，溫度越低，酒石酸沉澱的概率相對越大。
在低溫情況下，酒石酸就可能結晶出來形成結晶物。這種現象通常發生在葡萄酒瓶中冷藏或運輸期間，當酒的溫度下降時，酒石酸就容易結晶。
三、有結晶的白葡萄酒是否安全飲用？
酒石酸沉澱、蛋白質沉澱和色素沉澱這些結晶物質都來自於葡萄果實本身，對人體並沒有任何的危害作用，不會影響健康。許多人認為酒石酸沉澱必然很酸，實際上葡萄酒口感並不具有明顯的酸味，只是在口感上帶有一種微細的沙沙感，不會影響口感。
市面上常見的白葡萄酒中的沉澱物基本上都是酒石酸沉澱，但也有極少一類懸浮物沉澱，它們以菌落狀懸浮於白葡萄酒中，導致葡萄酒顏色暗淡不純，失去光亮。這種情況通常是由微生物感染引起的，這類葡萄酒不建議飲用，因為可能對人體健康有害。
D. 如何品味帶有結晶的白葡萄酒?
結晶葡萄酒品味方法：
1. 在確定要飲用哪一瓶白葡萄酒之前，應該保持其酒瓶處於直立狀態數小時。
2. 醒酒前需準備好醒酒器、過濾器、濾布和一個光源。（如果沒有這麼多器具的話，其實有一個醒酒器就夠了，在將酒液倒入醒酒器時不要晃動酒瓶，倒到最尾有沉澱就不要再倒了。如果不介意的可以直接倒入酒杯，待其沉澱在杯底欣賞一番，也未嘗不是一種樂趣。）
3. 開瓶時，不要搖晃或轉動酒瓶。
4. 倒酒時，將目光與酒瓶保持90度角，緩慢地將白葡萄酒注入醒酒器中。
5. 注意將瓶中最後有沉澱的酒液留在瓶肩，不要倒入醒酒器中，以確保醒酒器中無沉澱。
這樣，我們就可以安心品味帶有結晶的白葡萄酒，享受其中的奇蹟與魅力。
The Story and Significance of Crystals in White Wine
When selecting a bottle of white wine, you may sometimes notice white crystals at the bottom of the bottle, which can even float when the bottle is shaken. While salespeople assure us that this is a normal phenomenon that doesn’t affect quality, we might still wonder: Is white wine with crystals truly safe? Let’s explore this question and confirm that we can enjoy such wines with peace of mind.
First and foremost, the presence of crystals in white wine is a normal and harmless occurrence that does not affect the taste. You can enjoy it just like freshly squeezed juice, which may sometimes contain pulp—often a sign of quality.
What Are the Components of White Wine Crystals?
The crystals in white wine are typically formed from tartaric acid precipitates, and they may also include protein and pigment precipitates.
Wine contains various dissolved substances, such as tartaric acid, sugars, proteins, and minerals. When the concentration of these substances exceeds their solubility, crystallization begins. Tartaric acid, a common organic acid in wine, can bond with potassium and calcium ions to form potassium bitartrate and calcium tartrate. Since the solubility of these two compounds is relatively low, they easily aggregate to form precipitates. Tartaric acid precipitates appear as translucent crystals, resembling beautiful grains of sugar. Wine is a natural product, and each bottle may have unique features and surprises.
Protein Precipitates
White wine often contains higher protein levels, which can combine with released tannins to form white, fluffy particles. At higher temperatures, proteins may sometimes coagulate, resulting in white precipitates that appear suspended in the wine.
Pigment Precipitates
Wine contains various pigment substances that belong to polyphenols. In a dissolved state at room temperature, these pigments can precipitate when temperatures drop. During the aging process, pigment substances undergo polymerization or condensation reactions, causing colloidal particles to increase in size and form precipitates.
Why Do Crystals Form in White Wine?
There are several common reasons for the formation of crystals in white wine:
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Older Vines:
Older grapevines absorb more mineral elements, leading to higher levels of potassium and calcium ions in the wine, promoting crystallization. -
Cooler Growing Climates:
In cooler climates, the acidity of white grape varieties is relatively high (e.g., the Alsace region in France), indirectly increasing tartaric acid levels and thus promoting the formation of crystallized substances when the concentration exceeds solubility limits. -
Cold Maceration Fermentation:
Low-temperature fermentation reduces the solubility of crystalline substances, encouraging the precipitation of tartaric acid, a common organic acid in wine. -
Extended Aging:
Over long aging periods, tartaric acid can polymerize with calcium and potassium ions to form precipitates. Generally, the longer the aging time, the greater the amount of tartaric acid sediment. Additionally, pigments in the wine also undergo polymerization, leading to pigment precipitates. This is why some aged wines, such as noble sweet white wines (e.g., Trockenbeerenauslese), exhibit more crystallization. -
Storage at Low Temperatures:
Storing wine at excessively low temperatures decreases the solubility of tartaric acid and calcium and potassium ions, resulting in precipitates. Typically, the lower the temperature, the higher the likelihood of tartaric acid crystallization, which often occurs during refrigeration or transport.
Is White Wine with Crystals Safe to Drink?
Tartaric acid, protein, and pigment precipitates are all derived from the grapes themselves and pose no health risks. Many believe tartaric acid sediment must be very acidic; however, the wine's taste does not exhibit a significant acidity, only a subtle sandy texture that does not detract from the overall experience.
Most sediment found in commercial white wines is tartaric acid precipitate, although there may be rare instances of suspended microbial colonies that can dull the wine’s appearance. Such wines are not recommended for consumption as they may pose health risks.
How to Enjoy White Wine with Crystals
Here’s how to properly enjoy crystallized white wine:
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Keep the Bottle Upright:
Prior to drinking, maintain the bottle in an upright position for several hours. -
Prepare for Decanting:
Gather a decanter, filter, cheesecloth, and a light source. If you have only a decanter, that suffices. When pouring, avoid shaking the bottle and stop pouring when you reach the sediment at the bottom. -
Avoid Shaking:
Do not shake or rotate the bottle when opening. -
Pouring Technique:
Maintain a 90-degree angle with the bottle while slowly pouring the wine into the decanter. -
Leave the Sediment Behind:
Ensure that the last bit containing sediment remains in the bottle to keep the decanter clear.
By following these steps, you can confidently enjoy white wine with crystals and appreciate its unique charm and wonder.