The stability of retinol, α-tocopherol, trans-lycopene, and trans--carotene in liquid-frozen and lyophilized serum (original) (raw)

The concentrations of retinol, a-tocopherol, and trans-b-carotene in lyophilized serum stored at 2 258C and 2 808C have been monitored for 10 years. There was no evidence of degradation of any of these compounds over the 10-year period. Retinol, a-tocopherol, and trans-b-carotene were less stable at 2 258C in liquid-frozen serum than they were in lyophilized serum. At 2 808C, trans-b-carotene levels were stable for up to 3 years of storage in liquid-frozen serum. Both retinol and a-tocopherol appeared stable in liquid-frozen serum for at least 5 years at 2 808C. The effect of repeated freeze / thaw cycles on retinol, a-tocopherol, trans-lycopene, and trans-bcarotene in liquid-frozen and reconstituted lyophilized serum both stored at 2 208C was also studied. Retinol, a-tocopherol, trans-lycopene, and trans-b-carotene in reconstituted lyophilized serum stored at 2 208C were stable for at least 3 days with minimal ( , 5) freeze / thaw cycles.