Genesis 43:32

‘And they set on for him by himself, and for them by themselves, and for the Egyptians who ate with them by themselves, because the Egyptians are not allowed to eat bread with Hebrews, for that is an abomination to them.'

Joseph, as vizier and lord of Egypt eats at his own table. None may share with him for they are not of sufficient rank. The Egyptians who have been invited also sit at their own table. It would be ceremonially improper for them to mix with ‘foreigners'. Egyptians looked down on non-Egyptians, especially until they could speak Egyptian. They looked on them as not really human. And the brothers sat at their own table, separate from both.