Capsicums, commonly referred to as bell peppers, are a culinary staple found in a variety of dishes worldwide. Known for their crisp texture, vibrant colors, and versatile flavor profiles, capsicums are as fascinating scientifically as they are delicious. The chemistry behind these capsicums explains everything from their rainbow-like hues to their unique taste and nutritional benefits.

The Various Colors of Capsicums

The striking colors of capsicums, from green, yellow, orange, to red, is due to the result of specific pigments produced during the ripening process:

Green Capsicums:

Green capsicums are unripe capsicums rich in chlorophyll, the pigment responsible for their green hue. Chlorophyll is also a key molecule in photosynthesis, enabling the plant to capture sunlight and convert it into energy. Chlorophylls are complex macrocyclic compounds with an extensive system of conjugated double bonds, responsible in turn for conferring upon the molecule its color. It is anchored in the thylakoid membranes of the chloroplasts.

Yellow Capsicums:

Yellow capsicums contain carotenoids such as lutein and zeaxanthin, which are known for their role in eye health. Carotenoids include carotenes and their oxygenated derivatives, the xanthophylls. The variation in pigment composition during ripening gives capsicums their signature color spectrum, making them visually appealing and nutritionally diverse. Some of the compounds contributing to the yellow pigment include β and α-carotene, β-cryptoxanthin, zeaxanthin, curcubitaxanthin A, and violaxanthin.

Orange and Red Capsicums:

As capsicums ripen, chlorophyll breaks down, revealing carotenoid pigments that were previously masked. Compounds like chlorophyll and lutein degrades, and red compounds like capsanthin, anthin-5,6-epoxide, and capsorubin are synthesized. Likewise, beta-carotene, abundant in orange and red capsicums, is a precursor to vitamin A and contributes to their vibrant tones.

Flavor and Aroma of Capsicums

Capsicums have a distinctive flavor that evolves as they ripen:

Green Capsicums:

These unripe capsicums are slightly bitter due to the presence of alkaloids and fewer sugars. The bitterness is complemented by a crisp texture, making them ideal for savory dishes. The aroma of a green bell pepper is mainly due to 2-methoxy-3-isobutylpyrazine.

Red, Yellow, and Orange Capsicums:

As capsicums ripen, their sugar content increases, while bitterness decreases. This sweetness comes from the accumulation of simple sugars like glucose and fructose. Ripened capsicums also contain more aromatic compounds, enhancing their fruity and sweet notes. Their pungent oral sensation is induced by capsaicin, dihydrocapsaicin, homodihydrocapsaicin, and nordihydrocapsaicin.

Nutritional Chemistry of Capsicums

Capsicums are packed with essential nutrients and bioactive compounds that make them a powerhouse of health benefits.

They are one of the richest natural sources of vitamin C, with red capsicums containing up to three times more vitamin C than oranges. Vitamin C is a potent antioxidant that supports the immune system and promotes healthy skin.

Likewise, beta-carotene in red and orange capsicums contributes to eye health and skin regeneration. Other carotenoids act as antioxidants, protecting cells from oxidative stress.

In medicine, capsaicinoids have been used for the treatment of gastritis, arthritis, toothache, musculoskeletal and neuropathic pain, chronic indigestion, other pharmacological disorders and also microbial infections.

Unlike their spicy relatives, capsicums lack significant amounts of capsaicinoids, the compounds responsible for heat in chili peppers. This makes them mild and suitable for all palates.

Cooking with Capsicums

Cooking capsicums can alter their texture, flavor, and nutritional content.

High temperatures soften capsicums by breaking down their cell walls, making them tender and releasing their natural juices. Cooking enhances sweetness by concentrating sugars and caramelizing them. Roasting capsicums can produce smoky, complex flavors due to Maillard reactions and sugar caramelization. Capsicums lose some water-soluble vitamins, like vitamin C, during prolonged cooking, but lightly steaming or stir-frying can help preserve these nutrients.

Capsicums: A Chemical Perspective on Ripening

The transformation from green to red capsicum is a chemical journey. It is not just a process of ripening, it is the beauty of chemistry in nature.

During ripening, carotenoids are synthesized and esterified with saturated or unsaturated fatty acids. Chloroplast pigments, lutein, neoxanthin and β-carotene, mainly present in the vegetative stage gradually decrease in concentration during ripening. This is due to their use in the biosynthesis of chromoplast pigments and the inhibition of their synthesis to increase the production of the chromoplast pigments.

Like many fruits, capsicums produce ethylene gas, a hormone that accelerates ripening. Exposure to ethylene triggers the breakdown of chlorophyll and the synthesis of carotenoids.

Additionally, enzymes such as pectinase and cellulase degrade the cell walls, softening the pepper as it ripens. Amylase converts starches into sugars, increasing sweetness.

Conclusion

The chemistry behind capsicums is a testament to the wonders of nature. From the pigments that paint them in vivid colors to the sugars and nutrients that make them delicious and healthy, every aspect of a capsicum’s life is guided by chemical processes.

Whether you’re enjoying them raw in a salad, roasted on a pizza, or sautéed in a stir-fry, take a moment to appreciate the intricate chemistry behind these vibrant, versatile vegetables. They’re not just food—they’re science on your plate!

References:

·        Rudrapal, Mithun & Sarwa, Khomendra. (2020). Capsicum : Chemistry and Medicinal Properties of Indigenous Indian Varieties. 10.5772/intechopen.92241.

·        Antonio, A. S., Wiedemann, L. S. M., & Veiga Junior, V. F. (2018). The genus Capsicum: a phytochemical review of bioactive secondary metabolites. RSC Advances, 8(45), 25767-25784.

·        Roth, K. (2014). The biochemistry of peppers. ChemistryViews. 

·        Antonio, A. S., Wiedemann, L. S. M., & Veiga Junior, V. F. (2022). Origin and evolution of Capsicum. In V. F. Veiga Junior, L. S. M. Wiedemann, C. P. de Araujo Junior, & A. da S. Antonio (Eds.), Chemistry and Nutritional Effects of Capsicum (pp. 1–14). Royal Society of Chemistry.