Опара перекисла вплоть до того, что потеряла объём.

Опара is a baking term. It means a pre-ferment, starter mixture, or sponge made from flour, water (or milk), and yeast before the final dough is mixed.

In everyday Russian, this is a fairly specific word mostly used in cooking and baking contexts.

Перекисла comes from the verb перекиснуть, which means to become too sour, to over-ferment, or to go past the proper stage of fermentation.

In this sentence, it means the sponge/pre-ferment fermented too long and became overly acidic.

The prefix пере- often adds the idea of too much or over-:

• переварить = overcook
• пересолить = oversalt
• перекиснуть = become too sour / over-ferment

Because опара is a feminine singular noun.

In the past tense, Russian verbs agree with the subject in gender and number:

• masculine: перекис
• feminine: перекисла
• neuter: перекисло
• plural: перекисли

So:

• опара перекисла = the sponge over-fermented

Вплоть до того, что means something like:

• to the point that
• so much so that
• to such an extent that
• even to the extent that

It introduces the extreme result of the situation.

So in this sentence, it shows that the over-fermentation became so severe that the sponge even lost volume.

You can think of the structure as:

• X happened to such a degree that Y happened

Того is the genitive singular form of то.

That is because the preposition до normally requires the genitive case:

• до дома
• до утра
• до того

So вплоть до того, что... is a fixed expression built around до + genitive.

You do not need to translate того very literally every time. The whole phrase functions idiomatically as to the point that or so much so that.

Literally, it means lost volume.

Here потеряла is the past tense of потерять = to lose, and объём means volume.

In baking, this means the sponge stopped being airy or puffed up and began to collapse or deflate.

So the phrase suggests that instead of rising well, it went too far and lost its structure.

Объём is the direct object of потеряла, so it must be in the accusative case.

However, for many inanimate masculine nouns, the accusative singular looks exactly the same as the nominative singular.

So:

• nominative: объём
• accusative: объём

That is completely normal in Russian.

Often, yes — depending on context.

A more literal translation is lost volume, but in natural English baking language, that may mean:

• collapsed
• deflated
• lost its rise

So collapsed can be a good natural translation if that fits the context, even though the Russian wording is more literally about losing volume.

No, the subject is not repeated, because Russian often leaves it out when it is already clear.

In Опара перекисла вплоть до того, что потеряла объём, the subject of потеряла is understood to be the same as before: опара.

English often prefers to repeat it:

• The sponge over-fermented to the point that it lost volume.

Russian does not need the equivalent of it here.

The sentence has a neutral, natural word order:

• Опара перекисла вплоть до того, что потеряла объём.

Russian word order is flexible, but changes usually affect emphasis more than basic meaning.

For example, moving parts around may sound more literary, emphatic, or less natural depending on context. The given version is a standard way to say it.

It is generally neutral to slightly bookish. It is not extremely formal, but it is a bit more structured than very casual speech.

In conversation, people might also use simpler phrasing such as:

• так, что
• до того, что
• настолько, что

But вплоть до того, что is perfectly normal and understandable in standard Russian.

Both verbs here are perfective:

• перекисла ← перекиснуть
• потеряла ← потерять

Perfective aspect is used because the sentence describes completed results:

• the sponge ended up over-fermented
• it ended up losing volume

The focus is on what happened as a result, not on the ongoing process.

If the speaker wanted to emphasize process rather than result, different wording might be used.