Learn Dutch: Het aroma ontwikkelt zich tijdens het rijpen.

In Dutch, the verb ontwikkelen (to develop) requires a direct object. If something is developing on its own (like an aroma), you must use the reflexive pronoun zich (literally "develops itself"). Leaving it out would make the sentence feel incomplete to a Dutch speaker.

Why is the verb rijpen used with the article het?

Adding het in front of an infinitive turns the verb into a neuter noun. This is called a nominalized infinitive. It functions exactly like an English gerund ending in "-ing" (in this case, "aging" or "ripening") and is extremely common after prepositions like tijdens.

I usually translate "aging" as ouder worden. Why is rijpen used here?

While ouder worden literally means "getting older" and is used for people or animals, rijpen refers to a maturing process. It literally translates to "to ripen" (like fruit) but is the standard Dutch term for the "aging" of wine, cheese, and flavors.

Does the diminutive of aroma undergo the short-to-long vowel shift we are studying in this lesson?

No, because the final vowel in aroma is already long. However, its diminutive does have a spelling quirk: it becomes aromaatje. You have to double the a to ensure the pronunciation remains long when the -tje suffix is attached!