Determination of organic acids and carbohydrates in ‘Salustiana’ orange fruit from different rootstocks

Abstract This study aimed to determine carbohydrates and organic acids in fruit from ‘Salustiana’ orange tree [Citrus sinensis (L.) Osb.] grafted onto different rootstocks using the HPLC technique, as well as to evaluate their physicochemical properties. As rootstocks, we tested ‘Rangpur’ lime, ‘Cleopatra’ mandarin, ‘Sunki’ mandarin, ‘Swingle’ citrumelo, and ‘C-13’ citrange. Fully mature fruit was first characterized according to their physicochemical parameters as fruit mass, longitudinal and equatorial diameters, peel color, juice yield, soluble solids, titratable acidity, and ratio. Then, freshly squeezed juice was used to determine and to quantify organic acids and carbohydrates by the HPLC system. All analyses were performed in triplicate complete randomized with five treatments (rootstocks). Fruit from all evaluated rootstocks presented adequate physicochemical attributes, meeting the quality standards of the citrus industry. ‘C-13’ citrange induced in a production of large-sized fruit whereas ‘Rangpur’ lime promoted higher soluble solids content in its juice. Significant differences were not observed between the treatments with regards to organic acids and carbohydrates concentrations. Citric and ascorbic acids were identified and quantified in the juice samples. The sugars identified were sucrose, glucose, and fructose. Organic acids and carbohydrates concentrations are consistent with those reported in the literature for citrus juice, providing information about nutrition and quality of ‘Salustiana’ sweet orange produced onto different rootstocks.摘要 本研究旨在采用高效液相色谱法（High Performance Liquid Chromatography，HPLC），测定嫁接于不同砧木的‘Salustiana’甜橙（*Citrus sinensis* (L.) Osb.）果实中的碳水化合物与有机酸含量，并评价其理化性状。供试砧木包括‘Rangpur’酸橙、‘Cleopatra’曼达林橘、‘Sunki’曼达林橘、‘Swingle’枳柚以及‘C-13’枳橙。首先，依据果实质量、纵径与横径、果皮色泽、出汁率、可溶性固形物、可滴定酸度及固酸比等理化参数，对完全成熟的果实进行品质表征；随后，以鲜榨果汁为材料，通过高效液相色谱系统对其中的有机酸与碳水化合物进行定性与定量分析。所有分析均设置三次重复，采用完全随机设计，共包含5个砧木处理组。所有供试砧木所结果实的理化性状均表现优良，符合柑橘产业的质量标准。其中，‘C-13’枳橙砧可诱导结出大规格果实，而‘Rangpur’酸橙砧的果汁可溶性固形物含量更高。各处理组间的有机酸与碳水化合物浓度未表现出显著差异。果汁样品中可检出并定量柠檬酸与抗坏血酸，检出的糖类包括蔗糖、葡萄糖与果糖。本研究测得的有机酸与碳水化合物浓度与已有文献中柑橘果汁的相关报道一致，可为不同砧木嫁接的‘Salustiana’甜橙的营养品质与商品品质提供参考数据。