The effects of frozen storage conditions on lycopene stability in watermelon tissue

The purpose of this investigation was to evaluate the rate of deterioration of lycopene in watermelon tissue during frozen storage, because little is known about the stability of watermelon tissue lycopene under cold storage conditions. Heart tissue from each of nine individual watermelons was stored at -20 or -80 degreesC as either small chunks or puree and periodically sampled over a year's time. Initial freeze-thaw experiments indicated that a small percentage of lycopene, similar to4-6%, degraded during an initial freeze-thaw. Analyses of the samples showed a loss of similar to30-40% lycopene over a year's storage at -20 degreesC and a loss of similar to5-10% over the same period at -80 degreesC. Lycopene was slightly more stable in pureed compared with diced watermelon tissue at -20 degreesC, but not at -80 degreesC. The kinetic data were best fitted by application of two simultaneous, first-order decay processes. HPLC analysis of the samples after a year's storage suggested that beta-carotene was more stable during storage at -20 degreesC than was lycopene.