Las albóndigas quedaron más sabrosas porque mi madre puso un poco de chorizo en la salsa.

Here quedar means something like to turn out or to end up being.

So Las albóndigas quedaron más sabrosas means the meatballs turned out tastier or ended up tasting better.

This is a very common Spanish pattern:

• La sopa quedó muy buena. = The soup turned out very good.
• El pastel quedó seco. = The cake turned out dry.

It does not mean they stayed or they remained here, even though quedar can mean that in other contexts.

Because the subject is Las albóndigas, which is plural.

So the verb must also be plural:

• La albóndiga quedó... = singular
• Las albóndigas quedaron... = plural

The ending -aron is the third person plural preterite ending for many -ar verbs.

Because it agrees with albóndigas, which is a feminine plural noun.

In Spanish, adjectives usually agree in gender and number with the noun they describe:

• la albóndiga sabrosa = feminine singular
• las albóndigas sabrosas = feminine plural

The same thing happens with más sabrosas: más stays the same, but sabrosas changes to match the noun.

Más sabrosas specifically means tastier or more flavorful.

• sabroso = tasty, flavorful
• más sabroso/a = tastier, more flavorful

You could sometimes use mejores for better, but más sabrosas is more precise because it talks specifically about flavour.

So:

• quedaron mejores = they turned out better
• quedaron más sabrosas = they turned out tastier

Because this is an implicit comparison, not an explicit one.

Here más sabrosas means something like tastier than before or tastier than they otherwise would have been, but Spanish does not need to say the second part if it is understood from context.

Compare:

• Las albóndigas quedaron más sabrosas.
  = The meatballs turned out tastier.

• Las albóndigas quedaron más sabrosas que las de ayer.
  = The meatballs turned out tastier than yesterday’s.

You only need que when you actually say what you are comparing them to.

Because porque here means because and introduces the reason.

• porque = because
• por qué = why

Examples:

• Quedaron más sabrosas porque mi madre puso chorizo.
  = They turned out tastier because my mother added chorizo.

• ¿Por qué quedaron más sabrosas?
  = Why did they turn out tastier?

This is a very common spelling distinction in Spanish.

Puso is the preterite form of poner and means put / added.

• infinitive: poner
• preterite, él/ella/usted: puso

So:

• mi madre puso un poco de chorizo = my mother put / added a bit of chorizo

It is irregular, so it does not become ponió.

Other forms of the same tense are:

• puse = I put
• pusiste = you put
• puso = he/she put
• pusimos = we put
• pusieron = they put

The preterite is used because the sentence describes completed past events.

• mi madre puso... = your mother added it at a specific moment in the past
• las albóndigas quedaron... = the result happened and was completed

This sentence tells a finished little story: your mother added chorizo, and as a result the meatballs turned out tastier.

If you used the imperfect, it would suggest a habitual action or background description instead, which would not fit as well here.

Un poco de means a little bit of or some.

• un poco de chorizo = a little bit of chorizo

The de is required after un poco when it is followed by a noun.

Compare:

• un poco de chorizo
• un poco de sal
• un poco de agua

But if there is no noun after it, you can just say:

• Quiero un poco. = I want a little.

In Spanish, the definite article is used more often than in English.

Las albóndigas can mean:

• the meatballs in a specific context, or
• meatballs already known to the speaker and listener

In English, we sometimes drop the article more easily, but Spanish often keeps it.

Here it sounds natural because the sentence is talking about a specific batch of meatballs.

Not always exactly.

In Spain, chorizo usually refers to a cured or semi-cured pork sausage with paprika, very common in cooking. In this sentence, adding a bit of chorizo to the sauce would give it a richer, smokier flavour.

English speakers may know the word chorizo, but the exact type can vary by country. Spanish chorizo from Spain is often different from Mexican chorizo.

So in this sentence, think of Spanish chorizo.

En la salsa means in the sauce.

Spanish commonly uses en for something placed inside a mixture, container, or substance:

• poner sal en la sopa = to put salt in the soup
• poner azúcar en el café = to put sugar in the coffee
• poner chorizo en la salsa = to put chorizo in the sauce

So en is the natural choice here.

Yes. Puso is completely natural, but añadió would also work.

• mi madre puso un poco de chorizo en la salsa
• mi madre añadió un poco de chorizo a la salsa

Both mean your mother added some chorizo, but they are structured slightly differently:

• poner algo en... = put something in...
• añadir algo a... = add something to...

So the original sentence is perfectly idiomatic, but learners may also hear the second version.