The jalapeño pepper (Capsicum annuum) is typically harvested and consumed when its skin is a firm, glossy green. This green stage represents an immature state of the fruit. A red jalapeño is simply a green jalapeño that has been allowed to fully ripen on the plant. This natural maturation cycle results in significant changes to the pepper’s chemical composition, flavor, and heat level.
The Science Behind Jalapeño Color
The initial green coloration is due to the high concentration of chlorophyll, the pigment responsible for photosynthesis. As the fruit matures, the plant triggers the breakdown of this chlorophyll, allowing previously masked pigments to become visible.
The red color emerges as carotenoid pigments, particularly capsanthin, are synthesized and accumulate within the fruit cells. Capsanthin provides the vibrant red hue seen in fully ripened peppers. This transformation from chlorophyll-dominated green to carotenoid-dominated red indicates the fruit has reached full maturity.
Maximizing Ripening While Still on the Plant
Allowing the jalapeño to remain on the plant until it turns red is the best way to achieve maximum flavor and heat. Ripening requires consistent, warm temperatures, ideally between 65 and 85 degrees Fahrenheit during the day. Consistent exposure to full sun (at least six to eight hours daily) is also necessary for the plant to develop the fruit’s color and capsaicin content.
Gardeners can encourage the final stages of ripening by slightly stressing the plant as the season nears its end. Reducing the frequency of watering helps signal the plant to finish its reproductive cycle by ripening the remaining fruit. This slight reduction in moisture can also increase the concentration of capsaicin, leading to a hotter pepper.
Removing any late-season flowers or small fruit redirects the plant’s energy toward ripening the existing, full-sized peppers. Ripening on the plant often requires an additional three to four weeks after the pepper has reached its full green size. Premature picking should be avoided if the goal is a fully red pepper.
Turning Green Jalapeños Red After Picking
If environmental factors like an early frost force a premature harvest, methods exist to encourage color change off the plant. The most effective technique involves placing the peppers in a warm, bright location, maintaining a temperature around 70 degrees Fahrenheit or higher. Jalapeños are considered non-climacteric, meaning they do not ripen significantly in response to ethylene gas, the primary agent used to ripen fruits like bananas and tomatoes.
While some attempt the paper bag method with a ripe apple or banana, this practice often proves ineffective for peppers and can lead to spoilage if the environment is too humid or sealed. The best approach for off-plant ripening is to keep the peppers in a single layer in a warm, well-ventilated spot away from direct sunlight, which can cause sunscald. The color change will be slower than on the plant, sometimes taking one to two weeks, and the resulting flavor may not be as robust.
Flavor and Heat Changes in Red Jalapeños
The shift from green to red is accompanied by noticeable changes in culinary properties. Green jalapeños possess a fresh, grassy, and slightly bitter flavor profile, contrasting sharply with the mature red version. Red jalapeños develop a higher sugar content, resulting in a distinctly sweeter and fruitier taste that adds complexity to dishes.
The capsaicin concentration tends to increase as the fruit matures. Green jalapeños typically register between 2,500 and 5,000 Scoville Heat Units (SHU), while fully ripened red jalapeños often fall within the 5,000 to 8,000 SHU range. This increase in heat and sweetness makes the red peppers desirable for making specialized sauces, drying, or smoking into chipotle peppers.