What is borscht? What's symbolically significant about this being Zaroff's meal when we first meet him in The Most Dangerous Game?

Borscht is a Russian soup made with beets that is blood red, symbolizing Zaroff’s bloodlust. 

Borscht is popular in the Ukraine and Russia, and other Eastern European countries.  It is traditionally made with beetroots, which makes it blood read.  Hot, red, liquid brings to mind blood.  In fact, borscht is sometimes even made with blood as an ingredient. 

General Zaroff prides himself on bringing civilization to his island.  This means he built a great...

Borscht is a Russian soup made with beets that is blood red, symbolizing Zaroff’s bloodlust. 

Borscht is popular in the Ukraine and Russia, and other Eastern European countries.  It is traditionally made with beetroots, which makes it blood read.  Hot, red, liquid brings to mind blood.  In fact, borscht is sometimes even made with blood as an ingredient. 

General Zaroff prides himself on bringing civilization to his island.  This means he built a great big, fancy house.  He has electricity and wine, and imports his food.  The borscht is more than him showing off.  It makes him seem all the more bloodthirsty.  A man who loves to hunt humans eats blood-red soup. 

Rainsford notices the color of the soup.

They were eating borsch, the rich, red soup with whipped cream so dear to Russian palates. Half apologetically General Zaroff said, "We do our best to preserve the amenities of civilization here. Please forgive any lapses. We are well off the beaten track, you know. Do you think the champagne has suffered from its long ocean trip?"

Zaroff brags about importing the champagne by ship.  He is demonstrating to Rainsford that he gets whatever he wants.  This is the attitude he has toward life, and the reason why he thinks that it is acceptable to kidnap sailors and hunt, then kill them.  Rainsford accepts Zaroff’s quirks and even thinks he is being a good host, but the man makes him uncomfortable.

"Not in the least," declared Rainsford. He was finding the general a most thoughtful and affable host, a true cosmopolite. But there was one small trait of the general's that made Rainsford uncomfortable. Whenever he looked up from his plate he found the general studying him, appraising him narrowly.

Zaroff knows who Rainsford is already.  He has read his books.  He is likely studying him to see if he is willing to hunt people, and if not, if he will be good prey.  Of course, Rainsford does not approve of hunting men.  He also has no choice but to play Zaroff’s game, because he will be killed by Ivan if he doesn’t.