I have found conflicting evidence to this claim, I know that Aranha was very active and fought to pass the resolution, but as far as casting the tie-breaking vote, I found a lot of controversial sources to this popular anecdote here in Brazil.
Just a quick point in that I don't think it's fair to say that the passage of resolution 181 is what created the state of Israel. It was more probably more accurate to say that the ensuing Israeli Declaration of Independence and then war of independence are what created the modern state of Israel. It also appears that the vote was not close enough to require a tiebreaking vote.
The other user is correct that the UN vote did not create Israel. It was a nonbinding proposal. It passed in November 1947, but Israel was founded May 1948.
The vote passed with more than one vote over the required number. 56 member states voted, with 10 abstaining/absent. That meant to pass, it needed 31 votes in favor (2/3 majority), and it got 33.
I doubt Brazil was even number 31 or 32, since I'm fairly sure they voted alphabetically.