El yogur está tan agrio que mi madre le pone miel, pero mi abuelo dice que así pierde su sabor.

Because estar is usually used for a temporary state or condition, while ser is used for more permanent characteristics.

Here, the yogurt has become sour or is sour right now, so está agrio is the natural choice.

• está agrio = it tastes sour / it has gone sour
• es agrio would sound more like sourness is an inherent characteristic, which is not the usual idea with yogurt in this context

So Spanish treats this as a condition, not an essential quality.

Tan ... que means so ... that.

It works just like in English:

• Está tan agrio que... = It is so sour that...

Structure:

• tan
  • adjective/adverb + que

Examples:

• Está tan frío que no quiero salir. = It’s so cold that I don’t want to go out.
• Habla tan rápido que no le entiendo. = He speaks so fast that I don’t understand him.

Agrio means sour. It agrees with yogur, which is masculine singular, so it stays agrio.

Agreement:

• masculine singular: agrio
• feminine singular: agria
• masculine plural: agrios
• feminine plural: agrias

So:

• el yogur agrio
• la leche agria

Not exactly.

These words are related, but they are not interchangeable in every context:

• agrio = sour, tart, gone sour
• ácido = acidic; sometimes also sour, but often more technical or literal
• amargo = bitter

For yogurt, agrio is very natural.
If you said amargo, that would mean bitter, which is a different taste.

Yes. In standard Spanish, yogur is masculine, so we say el yogur.

You may also see spelling variants such as:

• yogur
• yoghur
• yoghurt
• yogurt

But yogur is the most common simplified spelling in Spanish, and it is masculine:

• el yogur está agrio

Le refers to el yogur.

In Spanish, with poner, it is very common to use an indirect object pronoun to show to what something is added.

So:

• mi madre le pone miel = my mother puts honey in/on it
• le = to it / on it / into it, referring to the yogurt

Even though English would often just say puts honey in it, Spanish often includes this pronoun.

Because le is not replacing miel. It refers to the yogurt, as the thing receiving the honey.

Think of it like this:

• poner algo a algo / poner algo en algo
• miel is the thing being added
• yogur is what receives it

So:

• le pone miel = she adds honey to it

Using lo or la here would suggest a direct object pronoun, which is not what Spanish normally uses for the receiving thing in this structure.

Because miel is being used as an uncountable substance, like honey in English.

So pone miel means adds honey.

This is similar to:

• pone azúcar
• pone sal
• pone agua

If you used an article, the meaning would change slightly:

• pone la miel = she puts the honey (a specific honey already known in context)

But here the general substance is meant, so no article is needed.

Because possessives like mi, tu, su, nuestro, etc. normally replace the article.

So you say:

• mi madre
• mi abuelo
• mi casa

Not:

• la mi madre
  in standard modern Spanish

This is very normal and directly comparable to English my mother, my grandfather.

That que is different from the que in tan ... que.

There are two separate uses here:

1. tan agrio que...

   • que = that
   • part of the result structure so ... that

2. dice que...

   • que introduces what someone says
   • dice que así pierde su sabor = he says that this way it loses its flavour

So both are common, but they belong to different structures.

Because decir que followed by a statement normally takes the indicative, not the subjunctive.

Here the grandfather is simply stating an opinion:

• dice que así pierde su sabor

So:

• pierde is present indicative

The subjunctive is usually triggered by things like doubt, emotion, denial, influence, or certain set expressions—not by a straightforward he says that... sentence.

Here así means like that, that way, or in that manner.

So:

• mi abuelo dice que así pierde su sabor means:
• my grandfather says that like that / that way, it loses its flavour

In context, así refers to putting honey in the yogurt.

In context, su refers to the yogurt.

So pierde su sabor means it loses its flavour—that is, the yogurt loses its own natural taste.

Spanish su can sometimes be ambiguous because it can mean:

• his
• her
• its
• your (formal)
• their

But here context makes it clear that it means its.

Because su sabor emphasizes its own flavour—the yogurt’s flavour.

Both could be understandable in some contexts, but su sabor is more natural here because the speaker is talking about the yogurt losing its characteristic taste after honey is added.

So:

• pierde su sabor = it loses its flavour / its own taste

Because the subject is still el yogur.

In the second clause:

• mi abuelo dice que así pierde su sabor

the thing that loses its flavour is the yogurt, so the verb is third person singular:

• pierde

Even though mi abuelo is the person speaking, he is not the one losing flavour.

The present tense here describes a general or habitual situation.

It suggests something like:

• the yogurt is sour
• my mother adds honey
• my grandfather says that this makes it lose its flavour

Spanish present tense is often used for:

• current situations
• habits
• general opinions

So this sounds very natural.

Yes. That is another very natural way to say it.

Compare:

• Mi madre le pone miel.
• Mi madre pone miel al yogur.

Both are correct.

You can even combine them:

• Mi madre le pone miel al yogur.

Spanish often likes this kind of pronoun doubling, especially when the indirect object is mentioned explicitly.

The sentence follows a very normal Spanish order:

• El yogur = subject
• está tan agrio = verb + adjective phrase
• que mi madre le pone miel = result clause
• pero mi abuelo dice = contrasting clause
• que así pierde su sabor = content clause

So the full structure is roughly:

[Subject] + [verb/state] + tan + adjective + que + [result], pero + [new subject] + dice que + [statement]

Spanish word order is fairly similar to English here, which makes this sentence quite approachable.

A broad Spain pronunciation would sound roughly like this:

• El yogur está tan agrio que mi madre le pone miel, pero mi abuelo dice que así pierde su sabor.

A few points:

• yogur: the y sounds like the English y in yes
• g in agrio is a hard g, like in go
• h in miel does not exist, so nothing special there
• c in dice in most of Spain sounds like the th in think
• z in sabor is not present, so nothing unusual there
• r in agrio and pierde is a tapped Spanish r

If you are learning Spain Spanish, dice would usually sound like di-the.

Yes: yogures.

If you made the subject plural, the agreement would change:

• Los yogures están tan agrios que mi madre les pone miel...

Changes:

• el → los
• está → están
• agrio → agrios
• le → les

This is a good example of how Spanish agreement works across the sentence.