Purple tomatoes present a unique challenge because their deep coloration develops well before the fruit is fully mature. These varieties do not follow the familiar green-to-red color change seen in traditional tomatoes. Since the purple pigment is present from an early stage, relying on visual color alone often leads to premature harvesting and a lack of flavor development. Understanding the specific biology of these fruits and focusing on alternative sensory cues is necessary to pick them at the peak of their flavor.
Why Color Alone is Misleading
The deep, nearly black color of purple tomatoes is due to high concentrations of anthocyanins, which are potent antioxidant pigments. Unlike the lycopene that gives red tomatoes their final color, anthocyanins in these varieties often begin to accumulate in the skin early in the fruit’s development. This pigment production is triggered by direct sunlight exposure, acting like a natural sunscreen for the developing fruit.
This light dependency means that the purple coloring develops unevenly across the fruit’s surface. The parts of the tomato that are shaded by leaves or the stem end, known as the shoulders, may remain green or a lighter color, even as the exposed parts darken significantly. The purple coloration simply signals the presence of the pigment, not the internal balance of sugars and acids that define ripeness.
The Key Indicators of Peak Ripeness
The most reliable indicator is the tactile test, which assesses the fruit’s texture. An unripe tomato will feel rock-hard, but as it ripens, the fruit softens and develops a slight, noticeable “give” when gently pressed with a thumb. This pressure should be applied carefully, particularly near the blossom end, which often ripens slightly ahead of the stem end.
Visual cues beyond the initial purple hue also provide important clues. As the fruit fully matures, the initially glossy, highly reflective sheen on the skin transforms into a slightly duller or matte appearance. This subtle shift indicates a change in the skin’s structure that accompanies the final stages of internal ripening.
Focusing on the under-color, or the areas less exposed to the sun, is also effective. The light-colored areas near the stem and the bottom of the tomato that were initially green will begin to change color as the fruit reaches maturity. For many purple varieties, this shift involves the green turning to warmer tones like olive green, brick-red, or a muddy purple-brown, signaling that the interior carotenoids have developed.
A final, highly accurate sign of readiness is the development of a distinct, sweet, and earthy aroma near the stem end of the fruit. When a tomato is truly ripe, the volatile compounds responsible for its flavor are fully formed, and this aroma is easily detected right where the fruit attaches to the vine. If the tomato is visually and texturally ready, a strong, pleasant smell confirms that the internal flavor profile is at its peak.
Proper Harvesting Techniques and Storage
Once ripeness is confirmed by tactile, visual, and aroma tests, harvesting should be done with care to prevent damage. Instead of pulling the fruit, which can cause bruising or tear the plant tissue, use sharp, clean shears or clippers. Make a clean cut just above the calyx, which is the small green cap attached to the fruit.
Leaving the calyx and a small piece of the stem attached helps slow moisture loss and prolongs the fruit’s freshness. After picking, avoid stacking the tomatoes in deep containers, as this can cause the delicate, ripened fruit to bruise under its own weight; instead, use shallow baskets or single layers.
Ripe purple tomatoes should be stored at room temperature, ideally between 65°F and 70°F, away from direct sunlight. Refrigeration should be avoided, as temperatures below 55°F cause flavor compounds to break down and can result in a mealy texture. If a tomato is picked when slightly under-ripe—for instance, due to a forecast of heavy rain—it can be placed indoors at room temperature to finish ripening, as tomatoes continue this process off the vine.