What Can’t You Boil Down?

Last updated: 05.01.2025

Reading time: 3 minutes

As it's easier to list what you can't preserve rather than what you can, I've created a list of foods that can't be preserved. This post was written by Dietl Stefan Markus Bastian (SMBD) from the Fryd community.

This Article Contains:

What Cannot Be Boiled down or Only to a Limited Extent?
What Can Be Used Instead?
Frequently Asked Questions About Preserving

Quick Overview

What Can’t I Boil Down?

Products containing gluten
Fresh or freeze-dried parsley
Dairy products and milk
Seafood
nuts
pectin
oil
Bay leaves (only cook with, then remove)

Exception: Milk and dairy products as well as flour can be cooked into solid masses such as cakes or bread.

What Cannot Be Boiled down or Only to a Limited Extent?

Walnuts cannot be boiled down — Nuts such as walnuts are not suitable for preserving.

Products containing gluten, as it would otherwise ferment (e.g. wheat, spelt, oats)
Vegetable broth containing gluten
Fresh parsley and freeze-dried parsley. Both still contain bitter substances. This makes the food bitter
Vegetable stock with parsley (if not powdered)
Milk and dairy products (including butter)
Seafood
nuts
Products containing carboxymethyl cellulose (methyl cellulose can be boiled down, but carboxymethyl cellulose cannot)
Tying aids for roulades etc. such as yarn, clips or needles
Bay leaves can be cooked, but must be removed from liquid dishes before cooking. (otherwise everything will taste extremely like bay leaf afterwards). For solid dishes (e.g. pork in its own juice), the bay leaf can be placed at the bottom of the jar.
Oil (becomes rancid over time)
Bones and cartilage (remove before cooking)
Smoked over coniferous wood
Pectin, as it becomes liquid again
E466 (obtained from coniferous wood)

Exception:

Milk and dairy products as well as flour can be cooked in solid masses (e.g. cakes) (1.5% UHT milk). Gluten can also be boiled down in solid baked masses, such as in a cake. It is then inactivated (baked to death, so to speak) and does not ferment. Cakes can therefore be cooked (30 minutes at 100 degrees).

What Can Be Used Instead?

Gluten-free starches (based on corn, rice, potato or manioc starch)
Dried parsley
Iodized salt (note, some people don't like the taste afterwards, others don't notice any difference) (only not usable during fermentation)
Stock cubes (without barley malt extract)
Cereal-based flavorings (e.g. wheat flavoring, yeast extract)
"may contain traces of..."
clarified butter
Gluten-free vegetable stock (if it is not a powder, then without parsley)

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Cover picture by Alexei on Pixabay.

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