Sure, but in a world dominated by the Christian church, isn't it possible that the discrimination was based more on religion than on race?

I don't remember where (help me, please!) but I read an account by a medieval European monk visiting monasteries and Christian communities in Africa. He described their religious practices, traditions, culture architecture and food in great detail, but mentioned their (certainly much darker) skin tones only in passing.

"Race" (boiled down to skin melanin contents) as a distinguishing point between groups of people is not a permanent fixture in human history. It is especially overwhelmed by religion, language and culture/tribal nationality in terms of its use as a dividing point between "us" and "them".

Depends on the place I suppose. In Portugal it was primarily because of religion (many time out of fear that they had secretly kept their Jewish religion, rather than actually converting to christianity).

It doesn't really make sense to talk about the expulsions in the 1500s as being motivated by race, given that there was no meaningful difference in race between the Jewish and Christian populations in the area, and they had widely intermingled.

While I have read plenty of accounts of riots and expulsions that either explicitly or implicitly state their reasons as being motivated by fears of new Christians still Secretly practicing Judaism, I haven't seen a single account naming race or some ethnic distinction as the cause.

First, I'm not discussing anti-Semitism in general. This is a discussion specifically focused on the idea of when and where Jews were considered a separate race. It's still quite possible for a group to be discriminated, and even persecuted, without them being classified as a separate race. Just ask the Irish.

Second, Oliver Cromwell readmitted the Jews to England, nearly 500 years ago. The Dutch readmitted Jews over 500 years ago. The Swedes 300 years ago. Over 200 years ago Napoleon's Western European armies emancipated Jews, primarily from Eastern Europe's absolute monarchies.

In contrast, Jews were never granted equal legal status in Russia until 1917. Pogroms were regular occurrences in Ukraine, Poland and Lithuania until the 1920s. The Romanian Iron Guard persecuted Jews with such brutality, that even the Nazis told them to dial it back. Contrast with Denmark, where the local populace refused to let the SS deport even a single Danish Jew.

Anyone with even a passing familiarity of Jewish history would tell you that while anti-semitism in the modern period isn't unheard of in Western Europe, its orders of magnitude worse in Eastern Europe.