The oxidation of reducing sugars by metal ions is discussed in Chapter 3,
and an experiment using the Fehlings test for qualitative determination of
reducing sugars is included in the Appendix. The Lane–Eynon Method
is an extension of the Fehlings reaction to determine the quantity of
reducing sugars by titration. It is commonly used in wineries to measure
total reducing sugars. A standard glucose solution is reacted with alkaline
copper sulfate under specified heating conditions. One milliliter of wine
is added to a second standard glucose solution, and the amount of sugar
required for reduction is determined titrametrically using methylene blue
as an endpoint indicator (Zoecklein et al. 1995; Boulton et al. 1996). The
difference between the two solutions is the reducing sugar content of
the wine.