Oxalate content of New Zealand grown and imported fruits

• Oxalate contents determined in 21 local and 9 imported fruits consumed in New Zealand.
• Local fruits contain low but variable amounts of total and soluble oxalates.
• All fruits studied are low in oxalate, except for the following five.
• Feijoa, Indian gooseberry, carambola, rhubarb and goji berry contain high oxalate.
• Rhubarb contained the highest levels of oxalates of locally grown fruits.

Total and soluble oxalate contents of 21 locally grown and 9 imported fruits commonly consumed in New Zealand were determined by extracting total oxalates with 2 M HCL for 20 min and soluble oxalates with nanopure water for 20 min at room temperature (21 °C). The extracted oxalates were analysed by ion exchange HPLC. Total oxalate content of locally grown fruit ranged from 2.0 to 640.2 mg/100 g fresh weight (FW) while the soluble oxalate ranged from not detected to 431.3 mg/100 g FW. The total oxalate content of a selection of imported fruits ranged from 2.9 to 7566.5 mg/100 g FW and the soluble oxalate content ranged from 1.2 to 3855.4 mg/100 g FW. Very high levels of total oxalates were measured in 2 imported fruits, Indian gooseberry (Phyllanthus emblica L.) and carambola (Averrhoa carambola L., star fruit), and in New Zealand-grown rhubarb (Rheum rhabarbarum L.), at 7566.5, 436.1 and 640.2 mg/100 g FW, respectively, and their soluble oxalates were also the highest measured of all the fruits.