1. Introduction
Olive oil is nowadays widely appreciated by consumers all over the world due to its health protection and nutrition. Thus, olive (Olea europaea L.) is now planted in many non-Mediterranean regions across continents under diverse environmental conditions (Vossen, 2007). As a new fast-developing producer country, olive introduction and cultivation in China have been supported by government strongly. Although the scale of olive cultivation in China cannot compare with that in Mediterranean countries, it is growing at an amazing rate over the past few years. There were only 25,300 hectares of olive trees planted around in 2009, and the area rapidly increased to 65,600 hectares in 2015 (Su et al., 2018). Furthermore, the planned area of olive cultivation was about 200,000 hectares, and the main planned area is located in the hot valley zone of the Jinsha River (Su et al., 2018). Therefore, millions of seedlings will be planted in the future.
As a non-Mediterranean country, the climate feature in China is quite different from that in traditionally olive growing regions. The most distinguished feature between China and Mediterranean country is the different timings of rainfall. There is a strong possibility that the trees cultivated in this region encounter rainfall more frequently in anthesis and fruiting periods. It is widely known that environment conditions have great effect on the chemical composition of olive oils (Ceci, Mattar, & Carelli, 2017; Deiana et al., 2019; Fuentes et al., 2018). Though previous studies showed that tree age may affect fatty acid profile, tocopherols, squalene, phytosterol and phenolic compounds in olive oils, much more attention was paid on the influences of environment conditions than tree age (Chtourou et al., 2017a, 2017b). In general, olive has the same growth pattern of the other stone fruits. Several researches have demonstrated that tree age also have effects on the chemical composition of stone fruits, such as Amrapali mango (Meena & Asrey, 2018). Therefore, the influence of tree age on the characterization of olive oils deserves greater attention.
‘Coratina’ and ‘Koroneiki’ are two of the main olive cultivars planted in China which is famous on their high oil contents and good contents of phenolic compounds. However, there is a little information available on comprehensive features of olive oils in China. Therefore, the differences between Coratina and Koroneiki oils produced from trees of different ages were evaluated. The evaluation of the characteristics of oils produced from olive trees with different ages has many values for developing Chinese olive industry.