For spinach, lay your spinach on paper towel before putting it in the fridge (or lay a piece of paper towel on top). The paper towel is there to absorb excess moisture. Pick out yellow or wilted leaves from the spinach and discard. Do not wash before refrigeration as the excess moisture will cause the spinach to wilt prematurely. Place spinach in a large plastic bag or a topless glass container. Do not pack the spinach tightly; the spinach should remain loose for ventilation and circulation. Refrigerate spinach at temperatures below 40 degrees; after seven days, the spinach will begin to significantly lose any amount of folate. Folate is a Vitamin B compound that promotes new cell growth in the body. So eat it up.