Revisamos el encurtido y la fermentación.

Revisamos comes from revisar, which usually means to review, to check, to inspect, or to go over.

In this sentence, it most naturally means something like we review/check the pickling and the fermentation. The best English choice depends on context:

• in a class: we review
• in a lab or workshop: we check or we inspect

It can be either one.

For -ar verbs, the nosotros form is the same in:

• the present: we review / we check
• the preterite: we reviewed / we checked

So revisamos could mean:

• we review
• we reviewed

You need context to know which one is meant. Written by itself, the form is ambiguous.

Because Spanish often leaves out subject pronouns when they are not needed.

The ending -amos already tells you the subject is we (nosotros/nosotras), so saying the pronoun is usually unnecessary.

• Revisamos el encurtido y la fermentación. = normal, natural
• Nosotros revisamos el encurtido y la fermentación. = possible, but more emphatic, as in we are the ones who review it

Spanish uses definite articles more often than English does.

Here, el encurtido and la fermentación can refer to:

• the processes as topics being discussed
• specific things already known from context

So Spanish naturally says:

• el encurtido
• la fermentación

Even when English might say just pickling and fermentation, Spanish often keeps the article.

Encurtido can refer to:

• pickling as a process
• a pickle / pickled product
• pickled vegetables in some contexts

In this sentence, since it appears next to la fermentación, it most likely refers to pickling as a process or topic, not just one individual pickle.

So the pair el encurtido y la fermentación sounds like two techniques, methods, or subjects being reviewed.

Because the sentence is talking about them as general processes or categories, not as several separate items.

Compare:

• el encurtido y la fermentación = pickling and fermentation, in general
• los encurtidos = pickles / pickled foods
• las fermentaciones = different fermentations or fermentation processes

Using the singular here is very natural when naming topics.

Because fermentación is a feminine noun.

A very useful pattern is that nouns ending in -ción are usually feminine:

• la fermentación
• la información
• la conversación
• la producción

So it takes the article la.

The accent mark shows where the stress goes: fer-men-ta-CIÓN.

Without the accent, Spanish stress rules would make you expect the stress somewhere else, so the written accent is needed.

In Spain, the ci in -ción is usually pronounced with the th sound of think in most regions, so roughly:

• fer-men-ta-THYON

In Latin American Spanish, it is usually more like:

• fer-men-ta-SYON

So for Spain Spanish, the final part sounds like -thión.