Thanks everyone. Based on the advice from this thread, I've elected to Ready an action to Sunder the spell component pouch when the sorceror goes to cast. The sorceror took a 5ft step and began to cast, which triggered the ready action, and the subsequent destruction of the pouch. The DM has ruled that this has disrupted the casting as he was not able to retrieve the required components. With the remaining move action, the sorceror sought to retrieve his emergency spell component pouch, which triggered an AOO.