Canned Spinach | Fresh Spinach in a Pressure Canner

This amount is for 2 500 ml jars; a 1 L jar may also be used. Do not use a larger jar, because no processing time has been tested for it. Wash the jars in hot, soapy water and rinse them. Keep them hot until filling; pressure processing heats the jars, so they do not need to be sterilized by boiling first. Prepare the lids according to the manufacturer’s instructions; do not reuse lids. Place the rack in the pressure canner, add 5–8 cm of hot water, and keep it warm over low heat.

Use only freshly picked spinach; discard wilted, discolored, diseased, or insect-damaged leaves. Wash in small batches and keep rinsing until the water runs clear and no grit remains at the bottom. Trim off thick stems and center ribs. The USDA average is 907 g of spinach per 500 ml jar.

Place the spinach in batches of 454 g in a cheesecloth bag or steamer basket and steam over boiling water for 3–5 minutes, until thoroughly wilted.

Loosely pack the wilted spinach into the jars without pressing it down. If desired, add a quarter of a 4 ml measure of salt to each 500 ml jar; salt is for flavor only. Add freshly boiled water, not the blanching water, leaving 2.5 cm of headspace. Remove air bubbles with a plastic spatula, restore the 2.5 cm headspace, wipe the rims with a clean, damp cloth, and close the lids.

Place the jars upright on the rack, spaced apart, lock the canner lid, and turn up the heat with the vent pipe open. Once a steady stream of steam escapes from the vent, vent for 10 minutes; air left in the canner keeps the temperature low even if the gauge shows pressure. Then add the weight or close the valve and let the pressure rise.

Set the pressure according to altitude. For a weighted-gauge canner: 10 psi at 0–305 m and 15 psi above 305 m. For a dial-gauge canner: 11 psi at 0–610 m, 12 psi at 610–1,219 m, 13 psi at 1,219–1,829 m, and 14 psi at 1,829–2,438 m. Istanbul and Izmir are in the first band (10 psi weighted gauge, 11 psi dial gauge); Ankara is at 938 m (15 psi weighted gauge, 12 psi dial gauge); central Erzurum is above 1,829 m (15 psi weighted gauge, 14 psi dial gauge). Have a dial gauge tested for accuracy every year before use. Start timing when the gauge reaches the pressure for your altitude: process spinach for 70 minutes in 500 ml jars or 90 minutes in 1 L jars. Adjust the heat to maintain steady pressure; if pressure drops below the target at any point, bring the canner back to pressure and restart the processing time.

When processing is complete, turn off the heat and let the pressure return to zero naturally without moving the canner. Do not cool it with cold water or open the valve early, because cooling is part of the tested process and a sudden pressure drop can cause liquid to siphon from the jars. When the gauge reads zero, remove the weight or open the valve, wait 10 minutes, then open the lid away from you so steam does not hit your face.

Use a jar lifter to remove the jars upright and place them 2.5 cm apart on a towel or wire rack. Let them cool undisturbed for 12–24 hours; do not tighten the lids. Once cool, press the center of each lid: it is vacuum-sealed if the center stays concave and does not flex when pressed. If it springs back or clicks up and down, it is not sealed. Refrigerate unsealed jars and use them soon, as you would a cooked dish. Label sealed jars with the product name and date.

Store sealed jars in a cool, dry place away from direct light. Before opening, inspect the lid: if it is bulging, the jar is leaking, liquid spurts or foams when opened, or the contents are moldy or smell bad, the food has spoiled. Do not taste questionable canned food; if unopened, place it in a thick bag, seal it tightly, and discard it. Botulinum toxin does not always cause visible signs, so following the processing time and pressure exactly is the only safeguard.