What is the fine-grained topic of the following text: Profits at their delightful Zibbibo plunged after the national chain arrived with low prices and oversize portions that in no way resemble Nino’s so-good Sicilian fare—rigatoni with homemade sausage, the layered eggplant “tower,” shrimp with artichoke hearts. Only return the topic.
Impact of national chain on local Sicilian restaurant profits