THE STABILITY OF RETINOL, ALPHA-TOCOPHEROL, TRANS-LYCOPENE, AND TRANS-BETA-CAROTENE IN LIQUID-FROZEN AND LYOPHILIZED SERUM

The concentrations of retinol, alpha-tocopherol, and trans-beta-carote ne in lyophilized serum stored at - 25 degrees C and - 80 degrees C ha ve been monitored for 10 years. There was no evidence of degradation o f any of these compounds over the 10-year period. Retinol, alpha-tocop herol, and trans-beta-carotene were less stable at - 25 degrees C in l iquid-frozen serum than they were in lyophilized serum. At - 80 degree s C, trans-beta-carotene levels were stable for up to 3 years of stora ge in liquid-frozen serum. Both retinol and alpha-tocopherol appeared stable in liquid-frozen serum for at least 5 years at - 80 degrees C. The effect of repeated freeze/thaw cycles on retinol, alpha-tocopherol , trans-lycopene, and trans-beta-carotene in liquid-frozen and reconst ituted lyophilized serum both stored at - 20 degrees C was also studie d. Retinol, alpha-tocopherol, trans-lycopene, and trans-beta-carotene in reconstituted lyophilized serum stored at - 20 degrees C were stabl e for at least 3 days with minimal ( < 5) freeze/thaw cycles. (C) 1998 Elsevier Science B.V. All rights reserved.