Why is the boiling point of sugarcane juice lower than the boiling point of water?
A more plausible explanation is that it is not water that is boiling.  The  &quot;organic substances&quot; and maybe the &quot;nitrogenous substances&quot; in the juice could include some more volatile components that may pass selectively into the gas phase at a lower temperature than most of the solution.  Such a vapor would not be the pure organic or nitrogenous substance; it would carry off some water vapor as the vapor pressure of the water is a large fraction of an atmosphere.  The temperature at which such selective vapor begins to form is properly called the bubble point.
Of some relevance is the effect of the sugar itself on the boiling point.  In the absence of other solutes this effect is very small, cfailing to reach $5°C$ boiling point elevation until we have nearly 80% sucrose in the solution (by mass).  Sucrose has a large molar mass smd water has a high heat if vaporization, both of which factors attenuate the boiling point rise at concentrations relevant to sugar cane juice.  This lack of an effect from the main nonvolatile solute would enable small amounts of more volatile components to yield a bubble point lower than the boiling point of pure water.

From Ref. [1]
Reference
1.
Willism Heffner and Hinanshi Jin, &quot;Building a Low Cost, Hands-on Learning Curriculum on Glass Science and Engineering using Candy Glass&quot;, MRS Online Proceeding Library Archive (January 2009) 1233,
https://www.researchgate.net/deref/http%3A%2F%2Fdx.doi.org%2F10.1557%2FPROC-1233-PP03-06.