Physical characteristics and chemical compositions of local red onion cultivar grown in Kapıdağ, Turkey

Abstract

Preserving traditional cultures, promoting local and rural development, protecting small producers and improving product quality, the conservation and sustainable use of all plant genetic resources is essential for food security. The objective of this study was to determine the characteristics of landrace red onion (Allium cepa L.) in Southern Marmara Region in Turkey for measures of conservation. Red onions produced in the Kapıdağ Peninsula are called as “Kapıdağ purple onion”, "Kapıdağ red onion" or "Kapıdağ fish onion". Red onion is generally produced by small family farmers according to traditional methods. The red onion samples were taken from Doğanlar, Turanlar, Ormanlı, Ballıpınar and Çayağzı villages in Erdek district and investigated for various properties including information about the descriptions of red onions and ecology. In addition, various chemical (titratable acidity, pH and total soluble solid) and physical (weight, width length and color of onion bulbs) analyses were performed in red onion samples. In this study, titratable acidity and pH values of red onion bulbs were found to be between 0.146% - 0.194% and 5.36 – 5.59 respectively. Total soluble solids and total phenol of red onion bulbs were between 9.17% –10.23% and 58.69 mg GAE g dw-1 – 138.37 mg GAE g dw-1 respectively. Bulb weights of red onion were between 83.31-169.06 g. Bulb width (diameter) and length in red onion bulbs were 70.28 – 49.97 mm and 78.29 – 60.31 mm, respectively. Red onion bulbs, Ormanlı, Turan, Ballıpınar and Çayağzı areas had have elliptical shape, while Doğanlar area had have flattened shape. The tunic colors and flesh color of onion bulbs ranged from red to red dark violet. The obtained from our study will support the protection of genetic resources in their agro-ecosystems and development regional community.