itigo to mikan ha hiyasu to motto oisii desu.

They are doing two different jobs.

• いちご と みかん: here と means and.
• 冷やす と: here と marks a conditional/result relationship, often translated as when, if, or once.

So:

• いちご と みかん = strawberries and oranges/mandarins
• 冷やす と = when you chill them / if you chill them

Japanese often reuses the same sound/word for different grammar functions, so this is very normal.

は marks the topic of the sentence.

So いちご と みかん は means:

• As for strawberries and mandarins...
• Strawberries and mandarins, ...

The speaker is introducing those fruits as the topic, and then saying something about them.

Even though there are two nouns, they are joined into one topic:

• いちご と みかん = one combined noun phrase
• は = marks that whole phrase as the topic

Because in this sentence, 冷やす と is using the conditional と pattern.

Verb + と often expresses a result that naturally happens when something is done.

So:

• 冷やすともっとおいしいです = If/when you chill them, they taste even better

This pattern can sound like a general truth or tendency.

Compare:

• 冷やして = chill them, and... / te-form connection
• 冷やしたら = if you chill them... more conversational and flexible
• 冷やすとき = when chilling them / at the time of chilling them

So 冷やすと is correct because the sentence is talking about the result of chilling them.

Because clauses before particles like と normally use the plain form, even in polite sentences.

So this is completely normal:

• 冷やす = plain form inside the conditional clause
• おいしいです = polite ending for the whole sentence

Japanese often mixes:

• plain form inside subordinate clauses
• polite form at the end of the sentence

That does not make the sentence inconsistent.

Japanese often leaves out information that is obvious from context.

In English, we might say:

• If you chill strawberries and mandarins, they taste even better.

In Japanese, the sentence does not need to explicitly say:

• who chills them
• what exactly is being chilled

because いちご と みかん is already the topic, so it is easy to understand that those are the things being chilled.

A more literal breakdown is something like:

• As for strawberries and mandarins, if (someone) chills (them), they are even more delicious.

This kind of omission is extremely common in Japanese.

もっと means more.

In this sentence, it means:

• more delicious
• even better
• tastier

So:

• おいしい = delicious
• もっとおいしい = more delicious / even more delicious

In natural English, even better often sounds smoother than more delicious, but grammatically もっと is simply more.

Because おいしい is an い-adjective, not a verb.

Japanese adjectives can act like predicates by themselves.

So:

• おいしい = is delicious
• おいしいです = is delicious (polite)

The です here adds politeness. It does not turn おいしい into a verb; it just makes the sentence sound polite.

Yes. 冷やす usually means to chill/cool something.

That is different from:

• 冷える = to become cold / to get chilled

So here, 冷やす suggests an action done to the fruit:

• chill the strawberries and mandarins

Because Japanese omits obvious objects, the sentence does not explicitly say them, but that is understood.

Using は makes the sentence sound like a general statement about those fruits as a topic.

• いちごとみかんは... = As for strawberries and mandarins...

If you used が, the nuance would shift more toward identifying them specifically or emphasizing them in context.

For a general statement like strawberries and mandarins are better chilled, は is very natural.

It can be understood as either, depending on context.

In this sentence, it has the feel of a general truth or usual result, so English translations like these all work:

• If you chill them, they are even more delicious.
• When chilled, they taste even better.
• They taste even better when you chill them.

So と here is not a strong uncertainty kind of if. It often describes what normally happens.

Yes, it is natural and understandable.

It sounds like a simple statement such as:

• Strawberries and mandarins are even tastier when chilled.

A native speaker might also say similar versions like:

• いちごとみかんは、冷やすともっとおいしいです。
• いちごとみかんは、冷やしたほうがおいしいです。

The original sentence is perfectly fine, and it is a good example of:

• X と Y は for a combined topic
• verb + と for a result/conditional
• もっと for more/even more
• い-adjective + です for a polite ending