Kapıdağ Purple Onion

Kapıdağ Purple Onion is a variety of onion produced within the geographical boundaries of the Kapıdağ Peninsula, located in the Erdek district of Balıkesir province, and distinguished by its unique characteristics. The product’s defining qualities originate from the soil and climatic structure of its growing region. This special onion has been cultivated by the local population for many years, preserving its distinctive traits. It has been officially registered by the Turkish Patent and Trademark Office as a geographical indication.

The Kapıdağ purple onion is a cultivated plant species of Allium cepa. The onion bulbs have a dark purple outer skin and deep red flesh. The skin color is notably darker than that of other red onion varieties and may leave a red stain when peeled. The flesh is juicy and sweet in texture. Physically, the average width of the bulb is approximately 78.6 mm and the average length is approximately 61.7 mm. Its chemical composition includes approximately 7.90% total sugars and 10.51% dry matter. The onion has a skin structure consisting of at least three layers.

Cultivation takes place in sandy-loamy and alluvial soils found in the valley floors of the Kapıdağ Peninsula. The seeds used in production have been propagated within the same geographical boundaries for nearly a century without genetic contamination. This practice is essential to prevent cross-pollination and preserve the product’s original qualities.

• Seeds are sown in seedbeds during the planting season.
• Seedlings grown in the seedbeds are transplanted to main fields in March or April. Planting density is set at 5–10 cm between plants and 10–15 cm between rows.
• All necessary agricultural practices—including irrigation, weeding, and weed control—are carried out by local farmers using their knowledge and experience.
• The optimal harvest period is the end of June to the beginning of July.
• Harvested onions are left to dry in the field for 7 to 10 days.
• Some of the dried onions are braided into triple or quintuple plaits and hung for storage. Under suitable conditions (cool and dry), their shelf life is 4 to 5 months.

The registered geographical boundary of the Kapıdağ Purple Onion is limited to the Kapıdağ Peninsula. Located in the northwest of Türkiye, south of the Sea of Marmara, the peninsula has a triangular morphology connected to the mainland by a tombolo. Covering an area of approximately 300 km², it lies within the administrative boundaries of the Erdek district of Balıkesir province. The region’s maximum elevation is 633 meters. The soils of the peninsula generally reflect the characteristics of the underlying bedrock, exhibiting a sandy, well-aerated, and skeletal-rich structure. The climate of the region displays a transitional character, influenced by Mediterranean, Black Sea, and Central Anatolian climatic types.

A monitoring authority has been established to verify compliance with the registered characteristics of the product. The authority consists of five members, coordinated by the Erdek Chamber of Commerce, with one representative each from the Erdek District Governorate, Erdek Chamber of Agriculture, Erdek Municipality, and Erdek Directorate of Food, Agriculture and Livestock. Monitoring is carried out periodically, upon complaint, when suspicion arises, or as needed.Monitoring includes:

• Identification and registration of producers within the geographical boundary,
• Verification of seed production procedures and the absence of foreign varieties near seed plots,
• Inspection of the morphological characteristics and production methods during harvest,
• Compliance of marketing companies with registered characteristics (at least twice annually),
• Sampling and independent laboratory analysis where necessary.