勃艮第冷門知識—酒精發酵後“死酵母”培養法

死酵母培養法

酒精發酵結束之後，已無糖分供酵母存活，死去的酵母菌會逐漸沉積到酒槽或橡木桶底部，堆積成泥狀，這些物質稱為lies。這些無生命的死酵母在培養的過程中會影響葡萄酒的風味，因此常被釀酒師利用。

不過，這些物質也有可能為葡萄酒帶來怪味，所以通常人們會先去除其中的雜質，透過換桶保留比較健康、沉澱在上層的較細的lies，也可先處理過後再將一部分放回酒中和葡萄酒一起培養。

泡在酒中的死酵母在酵素的作用下，會水解成許多不同的物質，包括蛋白質、氮、有機酸、香氣物質和甘油。和lies一起培養的葡萄酒，在乳酸發酵的過程中會比較順利，其產生的甘油也會讓酒的口感變得更為圓潤，在香氣上，常會讓白酒產生燻烤與烘焙麵包的香氣。

攪桶

為了讓死酵母菌的水解更有效地進行，很多酒莊會進行攪桶來加速水解。在發酵控制不太發達的時代，為讓酒中殘餘的糖分全部發酵成酒精，葡萄農常在發酵末期用一根棒子攪拌桶內的葡萄酒。現在，釀酒師也會在白酒培養的階段進行攪桶，目的在於讓沉澱的死酵母和葡萄酒充分混合，加快水解。

通常用頂端呈長鉤狀的金屬棒伸進橡木桶內攪動，大多一週攪桶一兩次，但也有酒莊在最頻繁時會一天多次。攪桶的方法又分兩種，一種是溫和地攪動沉澱物，另一種是當遇到有還原問題時，要由上往下攪，順便將空氣打入酒中，透過適度的氧化減少還原的怪味。

攪桶常要貫穿整個培養的階段，但後期次數會減少，約一個月一次。攪桶過度可能引發氧化的問題，也可能讓酒變得過於肥膩而失去均衡，有些酒莊僅在前幾個月進行低頻率的攪桶，有時甚至完全不做。在發酵之前沒有進行沉澱去酒渣的酒莊，為避免產生怪味，通常很少進行攪桶。

非木桶培養的白酒同樣可利用死酵母來提升香氣與圓潤感，現在也有一些不鏽鋼桶內部具備旋轉扇葉，可定時旋轉，讓沉澱的酵母與酒充分混合。培養黑皮諾紅酒時很少採用攪桶的方式，不過，還是會有酒莊偶爾採用滾動木桶的方式。

換桶

自然沉澱是讓培養階段的葡萄酒變得更乾淨、澄清的最簡易方法。只要一段時間靜止不動，酒中較大的懸浮物就會沉澱到酒槽或橡木桶底。這些混合著死酵母和其他沉澱物的酒渣，有時會讓封存在桶中的葡萄酒因為缺乏氧氣而產生類似臭雞蛋氣味的還原怪味。

有些酒莊在培養階段每隔一段時間就會進行換桶，例如在乳酸發酵完成後，葡萄酒由原來的桶中流到清洗乾淨的橡木桶中，以去掉桶中沉澱的酒渣，同時，在換桶的過程中，也可以讓酒與空氣接觸，降低出現還原氣味的風險，若是紅酒則可以藉此柔化單寧。換桶通常需要用泵抽送，對比較敏感的葡萄酒可能產生傷害，在勃艮第，現在更常用利用重力作用的虹吸法或氣壓法來進行換桶，以減少對葡萄酒的影響。

不過，現在勃艮第堅持不換桶的酒莊也相當多，大部分釀酒師認為，釀造黑皮諾時多一事不如少一事，培養時除非必要，最好不要去驚動正在熟成的黑皮諾，培養時不換桶除酒渣的做法相當盛行。在釀造霞多麗時，有的酒莊從發酵前將葡萄汁注入橡木桶，一直到裝瓶之前，都使用同一個橡木桶，讓葡萄酒和原來的酵母與酒渣泡在一起。

人們也相信霞多麗在培養的階段最好不要過多打擾，做越多事反而越有害。也許因為lies的作用，完全不換桶的酒莊常能保留飽滿濃厚的味道。有些酵素可以保證死酵母不會產生異變，不一定非換桶不可。

Burgundy Unpopular Knowledge - “Dead Yeast” Culture Method after Alcohol Fermentation

Dead yeast culture

After the end of the alcoholic fermentation， there is no sugar for the yeast to survive， and the dead yeast will gradually deposit into the bottom of the tank or oak barrel and pile up into a mud。 These substances are called lies。 These inanimate dead yeasts affect the flavor of the wine during the cultivation process and are often used by winemakers。However， these substances may also bring strange taste to the wine， so usually people will remove the impurities first， and retain the healthier， finer layers deposited on the upper layer by changing the barrel， or they can be processed before returning the wine to the wine。 Neutralize with wine。

The dead yeast soaked in wine is hydrolyzed into many different substances， including proteins， nitrogen， organic acids， aroma substances and glycerin。 The wine cultivated with the lies will be smoother in the process of lactic acid fermentation。 The glycerin produced will make the taste of the wine more round。 In the aroma， the white wine will often produce the aroma of baking and baking bread。

Stirring bucket

In order to allow the hydrolysis of the dead yeast to proceed more efficiently， many wineries will perform a mixing tank to accelerate the hydrolysis。 In an era when fermentation control is not well developed， in order to ferment all the sugar remaining in the wine into alcohol， the grape farmers often use a stick to stir the wine in the barrel at the end of the fermentation。 Now， the winemakers will also stir the barrels in the stage of liquor culture， in order to mix the dead yeast and wine that are precipitated and accelerate the hydrolysis。

Usually， the metal rod with a long hook at the top is inserted into the oak barrel to stir， and the barrel is stirred once or twice a week， but there are also many times when the winery is most frequently。 There are two ways to stir the bucket。 One is to gently agitate the sediment， and the other is to stir up from top to bottom when there is a problem of reduction。 By the way， the air is blown into the wine and reduced by moderate oxidation。 Restore the strange smell。

Stirring buckets often run through the entire culture phase， but the number of later passes is reduced， about once a month。 Excessive barreling may cause oxidation problems， and may make the wine too fatty and unbalanced。 Some wineries only perform low-frequency mixing barrels in the first few months， sometimes not at all。 In the winery where no slag is precipitated before fermentation， in order to avoid the strange smell， it is usually rare to stir the barrel。

Non-wooden cultured white spirits can also use dead yeast to enhance aroma and roundness。 Now there are some stainless steel barrels with rotating blades inside， which can be rotated regularly to allow the precipitated yeast to mix well with the wine。 It is rare to use a bucket when cultivating Pinot Noir， but there are still occasions when the winery uses rolling wooden barrels。

Change bucket

Natural sedimentation is the easiest way to make the wine in the culture stage cleaner and clearer。 As long as it does not move for a while， the larger suspended matter in the wine will settle to the bottom of the tank or oak barrel。 These slags， which are mixed with dead yeast and other sediments， sometimes cause the wines that are contained in the barrel to produce a similar smell of rotten egg odor due to lack of oxygen。

Some wineries change barrels at regular intervals during the cultivation period。 For example， after the lactic acid fermentation is completed， the wine flows from the original barrel to the cleaned oak barrel to remove the precipitated slag from the barrel。 In the process of the barrel， the wine can also be brought into contact with the air to reduce the risk of reducing the odor。 If it is red wine， it can soften the tannin。 Changing barrels usually requires pumping， which can cause damage to sensitive wines。 In Burgundy， it is now more common to use gravity-based siphoning or barometric pressure to change barrels to reduce the impact on wine。

However， there are quite a lot of wineries that Burgundy insists on not changing barrels。 Most winemakers think that it is better to do more when brewing Pinot Noir。 It is better not to disturb the ripe Pinot Noir unless it is necessary。 It is quite popular not to change the barrels of wine residue during cultivation。 When brewing Chardonnay， some wineries inject the grape juice into the oak barrels before fermentation， until the bottling， using the same oak barrel to make the wine and the original yeast and slag together。

People also believe that Chardonnay should not be bothered at the stage of cultivation。 The more things you do， the more harmful it is。 Perhaps because of the role of the lies， the winery that does not change the barrel at all can always retain a full and rich taste。 Some enzymes can ensure that dead yeast does not change， and it is not necessary to change the barrel。