Ascorbic acid and mineral composition of longan (Dimocarpus longan), lychee (Litchi chinensis) and rambutan (Nephelium lappaceum) cultivars grown in Hawaii

Longan (Dimocarpus longan), lychee (Litchi chinensis), and rambutan (Nephelium lappaceum) cultivars were harvested from different locations in Hawaii and analyzed for vitamin C (ascorbic acid) and mineral content. Longan fruit had the highest vitamin C content (60.1 mg/100 g fresh weight) among the three specialty fruits tested. Average ascorbic acid content was 27.6 mg/100 g for lychees and 36.4 mg/100 g for rambutans. Vitamin C content was 63.3 and 55.3 mg/100 g for the longan cultivars, Biew Kiew and Sri Chompoo, respectively. For rambutans, vitamin C content ranged from 22.047.8 mg/100 g for the six cultivars tested. The early maturing lychee cultivar, Kaimana, had an average ascorbic acid content of 33.2 mg/100 g, and the later maturing Groff and Bosworth-3 cultivars had 21.2 and 22.5 mg/100 g, respectively. No correlation was found between ascorbic acid and total soluble solids (TSS) content. Longans were a good source of K (324.9 mg/100 g) and Cu (0.26 mg/100 g). Consumption of lychee fruit (100 g) would meet 2–4% of the daily recommended intake (DRI) for six minerals (P, K, Mg, Fe, Zn, Mn), and 22% of the DRI for Cu. Rambutan fruit had 20% of the DRI for Cu and 8–10% of the DRI for Mn. In general, fruit mineral content was not associated with soil mineral content.