Eiruvin 1:9

In order to establish a shittuf, one requires a volume of food equal in size to a dried fig for each resident of the alley or the city, up to a maximum of 18 people. After 18 people, the requisite volume is enough food for two meals, which is equal to 18 dried figs or six medium-sized eggs. Even if thousands upon thousands of people want to rely upon a shittuf, food for two meals is all that is required.

Eiruvin 1:10

If a shittuf is made using a food that is eaten “as is,” like a loaf of bread, certain grains or raw meat, the necessary volume is enough for two meals. If one uses a side dish that is normally eaten with bread, like cooked wine, roasted meat, vinegar, fish brine, olives and onions, the volume needed is enough to accompany two meals.