Unlocking the Health Secrets of Onions: Investigating the Phytochemical Power and Beneficial Properties of Different Varieties and Their Parts

Onions (<i>Allium cepa</i> L.) are widely consumed worldwide and are recognized for their high content of bioactive compounds with potential health benefits. This study investigates the nutritional and phytochemical properties of three onion varieties-Tropea red onion, red onion, and yellow onion-analyzed in their whole form as well as in their peel and pulp. An innovative drying system was employed to assess its impact on the retention of bioactive compounds. The results highlight significant differences in nutrient composition among varieties and onion parts. The peel exhibited the highest concentrations of proteins, phenolic compounds, flavonoids, and antioxidants, followed by the whole onion and pulp. Tropea red onion stood out for its superior antioxidant capacity, vitamin C content, and phenolic acid levels, reinforcing its potential for functional food applications. This study also revealed that mineral content, particularly calcium, potassium, and sulfates, varied across onion varieties, influencing their nutritional and health-promoting properties. These findings support the valorization of onion byproducts for their bioactive potential and sustainability in the food industry. The data emphasize the need for further research on innovative processing techniques that enhance the bioavailability and effectiveness of onion-derived health-promoting compounds.