Oil your plastic container first

A thin coat of oil before you pack tomato sauce is the easiest way to keep your plastic lunch box from turning red.

Plastic is porous. Tomato sauce is acidic, and that acid etches tiny pits where the red pigment and the smell can settle in. Rub a few drops of cooking oil around the inside before you add the sauce — cooking spray works too. The oil fills those pores, so the sauce slides off instead of bonding.

Rinse the box right after lunch, then wash it normally. If a smell still lingers, scrub it with baking soda and cold water. But the oil barrier usually does the job.

If it still stains, the plastic is already scratched up. That’s when you switch to glass.