Metabolite Composition of Grapefruit (<i>Citrus paradisi</i>) Grown in Japan Depends on the Growing Environment and Harvest Period

Abstract

'Sagan-Ruby' is the first grapefruit (Citrus paradisi) cultivar to be developed in Japan and is used for food, cosmetics, and other purposes owing to its favorable characteristics, such as the absence of harmful pesticides and its long shelf life. The desired qualities of grapefruit depend on the specific use, and these qualities are influenced by the metabolite composition of the fruits. However, little is known about the influence of the growing environment or harvest period on the metabolite composition of the 'Sagan-Ruby' grapefruit. Therefore, we harvested fruits that were grown either in a plastic house without artificial heating or outdoors with rain cover from December, 2014 to April, 2015, on a monthly basis, and we investigated the composition of the primary metabolites such as sugars, organic acids, and amino acids, in the juice and peel of the fruit using gas chromatography mass spectrometry (GC/MS). We detected a total of 53 and 68 compounds in the juice and peel, respectively, and the first and second components of the principal component analyses of the detected metabolites of both juice and peel were associated with the growing environment and harvest period, respectively. Since we observed that glucose, fructose, sucrose, and citric acid were more concentrated in the juice of outdoor-grown fruits than in that of the house-grown fruits, especially in March and April, it is likely that the sweetness and acidity of the fruits are dependent on the growing environment. Similarly, the primary metabolite contents, including succinic acid and other organic acids, were higher in peels from outdoor-grown fruits. In addition, we also observed that the contents of proline, phenylalanine, and other amino acids in the juice increased continuously from December to April, and many sugars, including glucose and fructose, gradually decreased in peels from December to February and were lower from February to April. These results indicated that quality of the 'Sagan-Ruby' grapefruit varies with the harvest period.

Primary Metabolism in Citrus Fruit as Affected by Its Unique Structure

“…A gradual increase in most of the free amino acids was detected during fruit development and toward maturation of Valencia orange (Sinclair, 1984). This increase is associated with citrate decline and it is common to all citrus cultivars (Kimura et al, 2017). However, different trends were detected in Navel oranges ( Citrus × sinensis ), with most amino acids and their metabolites decreasing from stage II to III of fruit development (Katz et al, 2011).…”

Influence of Excessively High Temperatures on the Fruit Growth and Physicochemical Properties of Shiranuhi Mandarin in Plastic-Film Greenhouse Cultivation

“…The composition of secondary metabolites in grapefruits ( C. paradise ) is affected by the cultivation environment and harvest time [ 8 ]. Additionally, heat treatment affects phenolic compounds and the antioxidant capacity of citrus peel extracts [ 9 ].…”

Comparative Metabolomics Analysis of Citrus Varieties

“…Moreover, primary and secondary metabolites in citrus varieties are strongly associated with their unique qualities, such as taste, flavor, and appearance, as well as health benefits. The contents of these metabolites are generally affected by the cultivation environment, harvest period [6], and citrus variety [7]. Although there is a wide variety of citrus fruits, and these varieties have been extensively hybridized to improve their quality and to protect them against the effects of climate change [8,9], comparative analysis of metabolite profiles according citrus varieties has been limited.…”

“…Among these, nuclear magnetic resonance (NMR) and mass spectrometry (MS) have been used to compare the metabolite profiles of citrus varieties. Several metabolomic studies have been conducted on citrus varieties such as tangerines [12], grapefruits [6], mandarins, and oranges [7]. However, to date, the primary and secondary metabolites of kumquat, mandarin, and their hybrid varieties, which are cultivated as the major citrus varieties in East Asia [13], have not been compared, and the correlation between these metabolites and the quality characteristics of citrus fruits has not been investigated.…”