Color and Chlorophyll

• Jalapenos are the fruits of the same species -- Capsicum annuum -- as sweet bell peppers. Like them, they start out life as green chilies. This is because of the presence of the plant pigment chlorophyll B, which helps the peppers absorb the energy from sunlight they need to grow and mature. As jalapenos ripen, their changing colors reflect diminishing amounts of chlorophyll, which they gradually convert into another form of pigment, called carotenoids. At full maturity, jalapenos are bright red, although some pass through other color transitions along the way. These include purple, dark brown and black, indicating the presence of the blue-black pigment chlorophyll A.

Carotenoids

• Carotenoids give yellow, orange and red fruits and vegetables their vivid hues. According to research cited by the Linus Pauling Institute, the ease with which the body converts carotenoids into vitamin A makes these chemicals especially beneficial to human health. We don't find many red jalapenos in stores because they require need a longer growing season to mature to that stage, which would make them significantly more expensive.

Harvesting and Ripening

• Tomatoes, like peppers, are members of the nightshade family, yet tomatoes can be harvested when green and will continue to ripen off the vine until red and fully mature. Sellers hasten this process along by spritzing unripe tomatoes with the plant hormone ethylene. Ethylene doesn't have the same effect on peppers, however, so when you buy a green jalapeno, nothing can make it turn red. Also, because the food industry believes that consumers prefer uniformity of color, peppers in the process of turning red are deemed to have no commercial value.

Taste Differences and Color

• As jalapenos ripen, sugar content increases, so the red ones are sweeter than the green. As for pungency, a study published in the October 2000 issue of "HortScience" suggests that color plays little or no role. After measuring the capsaicin content of chilies, researchers from New Mexico's Chile Institute concluded that it varied widely among those on the same plant and appeared to be determined by position. Those closest to the bottom of the plant were hottest.