The Gibbs Free Energy is defined as $G=H-TS$
Therefore, $\Delta G=\Delta H - T\Delta S - S\Delta T$
When temperature is assumed to be constant, $\Delta G = \Delta H - T\Delta S$, which yields the Gibbs free energy change corresponding to the maximum non-expansion work that can be done by a system and indicating the spontaneity of a process.
However, how can the Gibbs free energy change be interpreted for conditions in which the temperature is not constant? In exothermic reactions, for example, heat is evolved from the system. Doesn't this then disrupt the thermodynamic equilibrium between the system and the surroundings, meaning that the above definition of $\Delta G$ can no longer be applied? If so, how can $\Delta G$ under non-constant temperatures be interpreted?