Change of Citrus medica L. Var. Linetta volatile profile after three months storage

Abstract

© 2018 International Society for Horticultural Science. All rights reserved. Citrus medica L. var. linetta is commonly known as citron or Somsa in Thailand. It is a local fruit that can be grown in most parts of Thailand. Leaf and peel provide unique aroma oil. The taste of the juice is sour and sweet and it is used as a seasoning in Thai cuisine. In addition, Somsa is believed to have a medicinal effect on sore throat, cough and sputum. In contrast to its wide range of applications, Somsa is not commonly utilised due to limited availability, which has resulted in few studies of Somsa. The objective of this study is to identify the volatile compounds in fresh Somsa and Somsa stored for three months at 30°C. The information obtained could emphasise the importance of this plant and enhance usage options. The method of analysis was solid phase micro extraction (SPME). Volatile constituents were extracted from 1.5 g samples each of exocarp, mesocarp, endocarp, vesicle and seed with headspace of 4.5, 4.5, 2.5, 3 and 5 cm, respectively, in amber jar volume 31.4 cm3. The sample was placed in water bath at 70°C for 30 min to reach equilibrium. Absorption period was compared at 20 and 40 min. The volatile was injected into gas chromatography coupled with mass spectrometry. The results showed that the different absorption time did not affect percentage of peak area. Volatile profiles of five different parts of Somsa were similar. Main components in fresh and stored Somsa were D-limonene (4.63-39.85%), naphthalene (1.07-9.45%) and 3-cyclohexene-1-methanol (2.45-9.52%). Stored Somsa had overall lower concentrations compared to fresh. In addition, new volatile compounds were found in the stored sample including 9-octadecenoic acid and acetic acid. This indicated there was the formation of acid compounds during storage. Therefore, storage of Somsa at elevated temperature increases acidity through acid compounds generation and reduction of volatile concentration.