New IFU Method of analysis #17 has been listed on the IFU website under Methods of Analysis and then Chemical Methods.
It is the Determination of the ascorbic acid content of juice products using titrimetric procedures.
There are many different approaches available to measure ascorbic acid (Vitamin C) in beverages (fruit juices and drinks) and this topic is reviewed in IFU recommendation No 5 which was published some years ago.
Although it would be recommended to use IFU 17a, which is an HPLC method, to measure this compound in fruit juices/purées and nectars, there are times that a quicker method is required. This compound can be estimated using a simple redox based titration, which is suitable for a juice QA/QC type environment. Here either iodine or dichlorophenol indophenol (DCPIP) can be used as a titrant. Both these materials (I2 & DCPIP) will oxidise ascorbic acid, and the titration end point is detected by a noticeable colour change in the solution. The volume of titrant at this end point is then used to calculate the level of ascorbic acid in the sample.