| 25. And they sat down to eat a meal, and they lifted their eyes and saw, and behold, a caravan of Ishmaelites was coming from Gilead, and their camels were carrying spices, balm, and lotus, going to take [it] down to Egypt. | כה. וַיֵּשְׁבוּ לֶאֱכָל לֶחֶם וַיִּשְׂאוּ עֵינֵיהֶם וַיִּרְאוּ וְהִנֵּה אֹרְחַת יִשְׁמְעֵאלִים בָּאָה מִגִּלְעָד וּגְמַלֵּיהֶם נֹשְׂאִים נְכֹאת וּצְרִי וָלֹט הוֹלְכִים לְהוֹרִיד מִצְרָיְמָה: |
Rashi explains that caravans usually had bad smells, but Hashem made sure that this caravan in specific didn't smell bad because a tzadik would be inside of it. Therefore, the smell of the caravan did not bother Yosef.
The Zichron Meir comes to expand on Rashis answer and says that if Hashem wants a certain person to undergo suffering, once that suffering is complete he will suffer no more. Yosef needed to suffer through shame and slavery, but not that of a bad smell. Therefore Hashem made sure that the caravan did not smell.
What other possibilities are there as to why the small detail of a caravan is mentioned in the Pasuk?