What is the importance of the juxtaposition of water and fire? And what do these things help foreshadow?

Fire represents heat in this novel and heat symbolizes
love and passion. The title, "Like Water for Chocolate" refers to the fact that water
must be boiled (heated to a very high temperature) before it can be used to melt the
chocolate for hot chocolate, a popular drink in Mexico. When water is not
exposed to heat, it becomes a symbol of sadness. For example, when Tita cries
into the cake batter and the wedding guests eat the cake, they all undergo a magical
spell in which they cry over their own lost loves, just like Tita is crying over Pedro.
When Tita peels onions, she sheds tears but unless she can transform her tears into her
food, they remain symbols of sadness. Gertrudis tries to extinguish the heat she feels
after eating the quail prepared with the rose petals that Pedro gave Tita with water
outside in the watercloset, but the heat emanating from her body turns the water into a
steam that emits a fragrance that attracts the revolutionary soldier. The other
instances of fire and heat help foreshadow the way Tita and Pedro die, consumed by the
fire of their passion.