After riding the train in today with the two people in the world who haven't learned how to cover their mouths when they sneeze and cough, it's time to fortify my immune system to fight through the winter cold and flu season. In today's Food Section, we talk about the very trendy blood orange juice. High in Vitamin C and antioxidants, the blood orange juice is slightly thicker with a flavor that blends the nice dry citrus of the grapefruit with only the slightest hints of sweetness in an orange. At Ina's, 1235 W. Randolph, the restaurant serves the Sicilian brand juice Aliseo. Word is that the best blood oranges come from Sicily. The story goes that volcano ash from Mt. Etna has made the soil a perfect spot for growing the lushest blood orange trees, says Sal Russo, owner of Amici Italian Deli, 1149 Fairview in Westmont. While the oranges are in season in December and January, Russo says he sells the juice year-round: "A lot of it."