Refrigeramos los recipientes herméticos para mantener la cadena de frío.

It can be either:

• present: we refrigerate / we keep refrigerated
• preterite: we refrigerated

Spanish has some forms that look the same in both tenses, and refrigeramos is one of them. In this sentence, it most naturally sounds like the present, especially if it is describing a procedure, routine, or instruction: We refrigerate the airtight containers to maintain the cold chain.

Because Spanish usually drops subject pronouns when the verb ending already makes the subject clear. The ending -amos tells you the subject is we.

So Refrigeramos... already means We refrigerate.... You could say Nosotros refrigeramos..., but that would usually add emphasis or contrast.

Spanish uses definite articles more often than English.

So los recipientes herméticos does not necessarily mean some very specific containers already mentioned; it can simply mean the airtight containers as the relevant ones in this context. Likewise, la cadena de frío is a standard concept, so Spanish naturally uses la.

In Spanish, descriptive adjectives usually come after the noun. So recipientes herméticos is the normal word order for airtight containers.

Putting the adjective before the noun is much less common here and can sound literary, emphatic, or unnatural in ordinary technical language.

Here herméticos means airtight, sealed, or tightly closed. It is related to English hermetic, but in everyday Spanish it is much more common than hermetic is in everyday English.

So in natural English, you would usually translate recipientes herméticos as airtight containers rather than hermetic containers.

Para followed by an infinitive expresses purpose: to, in order to. So para mantener means to maintain or in order to maintain.

This is very common in Spanish:

• Estudiamos para aprender = We study to learn
• Cierro la puerta para evitar ruido = I close the door to avoid noise

After a preposition like para, Spanish normally uses the infinitive form of the verb, not a conjugated form. That is why you get para mantener.

A conjugated verb would need a different structure, for example para que mantengamos..., but that would mean something slightly different and would require que plus the subjunctive.

La cadena de frío is the standard term for the cold chain: the system of keeping food, medicine, or other products at the correct low temperature during storage and transport.

The structure noun + de + noun is very common in Spanish. Here, de frío means something like of cold or involving refrigeration. It is a fixed expression, so learners should treat la cadena de frío as one unit of meaning.

Refrigerar and enfriar are related, but not identical.

• Refrigerar = to keep something at a refrigerated temperature, or to place it under refrigeration
• Enfriar = to cool something down in a more general sense

In a food-safety context, refrigerar is more precise because it suggests proper refrigerated storage, which fits well with la cadena de frío.

In Spain, a rough guide would be reh-free-kheh-RA-mos, with the stress on ra.

A few useful pronunciation points:

• the g before e sounds like the Spanish j, a throaty sound
• the r here is a light Spanish r, not a strong English r
• the stress falls on -ra-: re-fri-ge-RA-mos

The accent mark shows that frío is pronounced in two syllables: frí-o. Without the accent, Spanish spelling rules would tend to suggest a different vowel grouping.

So the written accent helps show the correct pronunciation and stress. This is why you write frío, día, río, and similar words with an accented í.