El alimento no perecedero está junto a la manta térmica.

Because Spanish normally uses estar for the location of people and things.

• está junto a... = is next to...
• es would be used for identity, category, or essential characteristics.

So here, since the sentence tells you where the food is, está is the correct verb.

Perecedero means perishable. Adding no in front makes it non-perishable.

So:

• alimento perecedero = perishable food
• alimento no perecedero = non-perishable food

In Spanish, this kind of negative description is often formed simply with no + adjective.

In Spanish, descriptive adjectives usually come after the noun.

So:

• alimento no perecedero
• manta térmica

This is the most normal word order. English often puts adjectives before the noun, but Spanish usually puts them after.

Because adjectives must agree with the noun they describe in gender and number.

• alimento is masculine singular, so the adjective is perecedero
• manta is feminine singular, so the adjective is térmica

Compare:

• el alimento no perecedero
• la comida no perecedera
• la manta térmica
• las mantas térmicas

Junto a means next to, beside, or right by.

Yes, al lado de is also very common and usually means almost the same thing.

So these are both natural:

• El alimento no perecedero está junto a la manta térmica.
• El alimento no perecedero está al lado de la manta térmica.

Junto a can sound a little more compact or slightly more formal, but both are standard.

The accent marks show which syllable is stressed.

• está stresses the last syllable: es-TÁ
• térmica stresses the first syllable: TÉR-mi-ca

In está, the accent is also important because it distinguishes the verb form from esta, which can be a demonstrative adjective meaning this.

So:

• está = is
• esta manta = this blanket

Both can refer to food, but they are not always used in exactly the same way.

• alimento is a bit more general or technical: food item, nourishment, provisions
• comida often means food in everyday speech, and it can also mean meal

In a context like supplies, emergency kits, or storage, alimento no perecedero sounds very natural.

Yes, in this sentence they are the normal choice.

Spanish uses definite articles very often, especially when talking about specific things already identified in the situation.

So:

• el alimento no perecedero
• la manta térmica

Leaving them out would usually sound incomplete or unnatural here.

It can be understood either way depending on context, but grammatically it is singular.

Here, el alimento no perecedero could mean:

• one specific non-perishable food item, or
• non-perishable food as a category or supply item

If you wanted to make it clearly plural, you would say:

• Los alimentos no perecederos están junto a la manta térmica.

That means The non-perishable foods are next to the thermal blanket.

A manta térmica is a thermal blanket, often the thin metallic emergency blanket used to keep someone warm.

In Spain, manta térmica is a normal and clear term for that kind of blanket, especially in first aid, camping, or emergency contexts.