In a large bowl, dissolve yeast in warm water. Add the sugar, milk, butter, eggs, lemon zest, salt, mace and 3 cups flour. Beat on medium speed for 2 minutes or until smooth. Stir in enough remaining flour to form a soft dough (dough will be sticky).
Turn onto a lightly floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease top. Cover and let rise in a warm place until doubled, about 1 hour.
Punch dough down. Turn onto a lightly floured surface; knead in raisins. Divide dough into six equal portions. Shape each into a 20-in. rope. Place three ropes on a greased baking sheet; braid. Pinch ends to seal and tuck under. Repeat with remaining ropes.
Cover and let rise in a warm place until doubled, about 45 minutes. Beat egg yolk and water; brush over loaves. Bake at 350° for 25-30 minutes or until golden brown. Cool on wire racks.
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