The sentence that best explains the significance of the novel's title, The Grapes of Wrath, is D. Steinbeck describes the migrants' anger as "fermenting".
The Grapes of Wrath (1939) tells the story of the Joads, a poor family of farmers that leave their home in Oklahoma in search for a better life. However, when they reach California, the Joads only encounter starvation and workers that are constantly exploited. The title of the novel is of great relevance since Steinbeck intends to underline the fact that the family's anger ripens very quickly due to the oppression they suffer. Furthermore, by using that title, the writer tries to remark that the family's feelings of frustation are ready to be harvested as the grapes are by the end of the novel. Therefore, the title refers to the Joads' growing anger and the need for revenge against the migrants' oppressors.