Re: How can I measure the sugar content in different colored bananas?

The sugar content of most fruits is measured easily by using a hand 
refractometer, which measures in Brix units. One brix unit is approximately one 
percent sugar. I've never measured a banana but you would need to squeeze some 
juice out to get a sample for the refractometer. There are also chemical 
methods for sugar analysis. The major sugars will be fructose, glucose and 
sucrose. The book cited lists a ripe banana as containing 6 grams glucose, 4 
grams fructose and 7 grams sucrose per 100 grams fresh weight. The Brix chart 
webpage indicates a Brix number of 16 corresponds to an excellent banana.

References


Using a Refractometer to Measure Sugar

Wills, R.B.H. et al. 1989. Postharvest: An Introduction to the Physiology and 
Handling of Fruits and Vegetables. London: BSP Professional Books.


Brix Table for Fruits