The abomination of the Egyptians most probably was, that the Hebrews scrupled not to eat of those things which the Egyptians worshipped. 2 Kings 23:13.
Related Commentaries of Genesis 43:29
Genesis 43:29-32
29 And he lifted up his eyes, and saw his brother Benjamin, his mother's son, and said, Is this your younger brother, of whom ye spake unto me? And he said, God be gracious unto thee, my son.
30 And Joseph made haste; for his bowels did yearn upon his brother: and he sought where to weep; and he entered into his chamber, and wept there.
31 And he washed his face, and went out, and refrained himself, and said, Set on bread.
32 And they set on for him by himself, and for them by themselves, and for the Egyptians, which did eat with him, by themselves: because the Egyptians might not eat bread with the Hebrews; for that is an abomination unto the Egyptians.