Seedless Berry Syrup, Jam and Coulis: Which Strainer Actually Stops the Seeds

The short answer: raspberry and blackberry seeds are about 1 mm across, blueberry seeds smaller still. A normal kitchen strainer has openings close to that size, so seeds slide straight through. You need a 60-mesh screen (openings around 0.25 mm), and you need to work the fruit through it while it is warm, with the back of a spoon, in small batches. No cheesecloth, no jelly bag, no chinois required.

Why your strainer let the seeds through

Most all-purpose strainers sit somewhere between 12 and 20 mesh. That is perfect for pasta and rinsing rice, and useless against seeds. Then people go to the other extreme, coffee filters or several layers of cheesecloth, and thick syrup simply refuses to pass. The right tool is in the middle: fine enough to hold a seed, open enough to let syrup, purée or juice drain with a little help.

Step by step: syrup or coulis

1. Cook the berries with sugar (and a splash of water or lemon juice) until they collapse, about 5 to 8 minutes. 2. While still hot, set a 60-mesh strainer over a bowl that is taller than the strainer is deep, so the rim rests on the bowl and both hands are free. 3. Ladle in a cup at a time. Push and scrape with the back of a spoon or a silicone spatula in slow circles. Warm fruit flows; cold fruit sets and fights you. 4. Scrape the underside of the mesh into the bowl every batch, that is where the thickest purée collects. 5. Discard the seeds, or fold them into muffins.

Step by step: jam

Strain the cooked fruit before adding pectin or the final boil, when it is thinnest. For seedless raspberry jam, strain everything; for a lightly seeded jam, strain half and stir it back in. Weigh the purée after straining and adjust sugar to the new weight.

Three mistakes that make it slow

Straining cold fruit. Loading the whole pot at once so the mesh blinds over. Pressing with a metal spoon edge hard enough to dent the weave; use the rounded back and steady pressure instead.

What about the fine mesh clogging?

It will, a little, and the fix is the scrape: every 30 seconds, scrape the top of the mesh to move the seed cake aside, and the underside to release the purée. Rinse the mesh from the back under hot water as soon as you are done and nothing dries in the weave.

One strainer for the whole recipe

With COLAROA you rinse the berries in the 20-mesh cup, then swap to the 60-mesh cup to strain the seeds out, on the same solid 304 stainless handle. There is no weld between handle and cup, so pushing purée through with a spoon does not stress the joint that fails on ordinary strainers. The mesh numbers are explained in 20 vs 40 vs 60 mesh, sizes are on the FAQ page, and the launch list gets 15% off during Amazon launch week.