IFU (INTERNATIONAL FRUIT AND VEGETABLE JUICE ASSOCIATION)
As the trade of blood orange juice and concentrates depends on their colour intensity, a unique and internationally accepted method for measuring their total concentration has been developed by the IFU. It provides an analytical technique that can be used by both processors of blood orange juices and purchasers (such as bottlers) as a standard way of establishing specifications that does not rely on arbitrary visual appearance. It is a useful tool to avoid conflict between buyers and sellers.
Launched in February this year, IFU method #83 Colour measurement in blood orange juices has been developed in-house by its Methods of Analysis (MAC) laboratory.
The colour of pigmented “blood” oranges is caused by the presence of anthocyanins. Cyanidin-3-glucoside is the main anthocyanin pigment seen in oranges with lower concentrations of other mono- and di-glycosides anthocyanins. The total concentration of the anthocyanin pigments varies depending on the variety concerned and seasonal climatic influences.
The method works on the principle that anthocyanins pigments are completely extracted from the juice with a specified volume of acidified methanol. After centrifugation the pigment content is determined by measuring the extract’s absorbance at 530 nm against a solvent blank.
The method requires the use of a spectrophotometer capable of measuring at a wavelength of 530 nm, a centrifuge with sufficient speed to give a “g” force of 3000 g and other equipment and solutions typically found in a juice operational laboratory.
The method say the IFU has taken three years to develop and was validated in 2016 with 18 participating international laboratories using blood orange samples.