science

Lees (fermentation)

Lees (fermentation) is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lees (fermentation) rather than just read about it. In short: Lees are sedimentary deposits of dead yeast or residual yeast and other particles that precipitate, or are carried by the action of "fining", to the bottom of a vat of wine after fermentation and aging. When brewing beer, this sediment is known as trub, not lees.

Key takeaways

Lees (fermentation) belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lees (fermentation) to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lees (fermentation) from memory before moving on to harder problems.

Reference excerpt

Lees are sedimentary deposits of dead yeast or residual yeast and other particles that precipitate, or are carried by the action of "fining", to the bottom of a vat of wine after fermentation and aging. When brewing beer, this sediment is known as trub, not lees. However, when formed during secondary fermentation, yeast residual sediment is named lees for both wine and beer, or dregs for beer alone. This material is the source for most commercial tartaric acid, which is used in cooking and in organic chemistry. The term in English derives from Middle English lie, from Anglo-French, from Medieval Latin lia. Webster's Third International Dictionary shows from lia, "probably of Celtic origin, akin to Old Irish lige (bed), Gaulish legasit (he laid) and Welsh llaid (mud)." Normally, the wine is transferred to another container (racking), leaving this sediment behind. Some wines (notably Chardonnay, Champagne, and Muscadet) are sometimes aged for a time on the lees (a process known as sur lie), leading to a distinctive yeasty aroma and taste. The lees may be stirred (French: bâtonnage) for uptake of their flavour. The lees are an important component in the making of ripasso, where the leftover lees from Amarone are used to impart more flavour and colour to partially aged Valpolicella. Fujian red wine chicken is made from rice wine lees.

Sur lie

Sur lie literally translates from French as 'on lees'. Sur lie wines are bottled directly from the lees without racking (a process for filtering the wine). In the case of great Chardonnay, such as Montrachet, this adds a toasty, nutty "hazelnut" quality and additional depth and complexity. Chemically, this can alter the oak flavour molecules, increasing the integration, and making the oak seem less obtrusive to the palate. This is desirable because oak tannins are polyphenolic acids, and can be harsh. This process can also give an added freshness and creaminess to the wine, and improve color and clarity. Muscadet is made in this fashion. The effect of the lees during bottle fermentation for at least 18 months on Champagne is considerable. The "bready" toasty notes associated with some of the greatest sparkling wines made are the result of sur lie aging.

Other uses Beer on an element of lees (residual sediment) is also sold, such as many

Trappist beers Unibroue Quebec, Canada-based ales/beers Real ales of older styles (not India Pale Ale) Weissbiers Kombucha can also be brewed sur lie. Lees can also be distilled to produce Hefebrand, or "lees spirit", an alcoholic beverage containing a minimum of 38% alcohol by volume.

Light lees protocol In a process in which yeast is added to wine that has completed primary fermentation, this secondary yeast addition typically remains in the wine from 2–8 weeks, depending on the winemaker's goals. The yeast is stirred (bâtonage) frequently, and racked when the protocol is complete. Also known as secondary autolysis, a light lees protocol releases additional mannoproteins and polysaccharides that can influence the flavour, tannins, and acidity of the wine.

Illustrations

Worked examples

Example 1 — a first encounter with Lees (fermentation)

Start with the simplest possible case. Write down what Lees (fermentation) claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lees (fermentation) before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lees (fermentation) ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lees (fermentation)

In research: Lees (fermentation) appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lees (fermentation) in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lees (fermentation) is common in secondary-school and first-year university syllabi. It links to neighbouring topics By-products, Fermentation in food processing, Winemaking, so understanding it makes those chapters shorter.
In everyday life: Look for Lees (fermentation) outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lees (fermentation) in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lees (fermentation) means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lees (fermentation) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lees (fermentation) in simple terms?

Why does Lees (fermentation) matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lees (fermentation)?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lees (fermentation).