Thirty-four-year-old Brigitta Jansen, a statuesque brunette with radiant skin, is no stranger to unpasteurized milk. She grew up in a tiny German village, where she and her grandmother, pails in hand, would fetch milk fresh from a neighbor’s farm. But over the years, after moving to a bigger town and then, ultimately, to New York City, she unthinkingly switched to pasteurized milk, which was more convenient and easier to find.