Contents of Flavor Components in Newhall Navel Oranges (Citrus sinensis) Harvested from Eleven Production Areas of China

Gas chromatography (GC) was applied to evaluate the contents of soluble sugars and organic acids in the juice sacs of mature Newhall navel orange fruits from 11 production areas of China in 2011 and 2012. The main bitter compounds, nomilin and limonin, were determined using high performance liquid chromatography (HPLC) in samples harvested in 2012. Results showed that fructose, glucose and sucrose were the three main soluble sugars. Among total soluble sugars, the content of sucrose accounted for 51.01% - 60.19%, ranking the highest, while the content of inositol accounted for 1.61% - 2.14%, ranking the lowest. Generally, the contents of soluble sugars in the juice sacs differed significantly between 2011 and 2012 in Danjiangkou, Guilin and Quzhou production areas. Citrate and malate were the two most abundant organic acids detected. Organic acid content in many production areas, including Danjiangkou, changed significantly between 2011 and 2012. The contents of limonin in the two most abundant production areas, Jishou and Ya'an, were 670.0±293.2 μg/g and 652.1±217.0 μg/g, respectively. The content of nomilin (789.7±38.9 μg/g) in Quzhou was significantly higher than that in the other production areas. Partial correlation analysis showed that the contents of fructose and glucose, malate acid and quinic acid, and nomilin and inositol were positively correlated (P < 0.05), with correlation coefficients of 0.98, 0.43 and 0.48, respectively; while the content of sucrose and quinic acid was negatively correlated, with r=-0.39 (P < 0.05). Our results showed differences between the quality of sugars, organic acids and bitter compounds in mature Newhall navel oranges in different production areas, with climate among the main determinants of organic acid and bitter compound content.