Effect of temperature on the cell wall composition of raisins during storage under a modified atmosphere.

摘要

Effect of temp. on cell walls of raisin tissues during modified (controlled) atmospheric storage was studied. Raisins obtained from seedless grapes (Flame var.) were kept under a modified atmosphere (MA) composed of CO2 (60) and N2 (40), and stored at 10 (10MA), 20 (20MA), 30 (30MA) and 40 degree C (40MA); an additional sample was stored under air at 20 degree C (20A). Colour and changes in cell wall components were monitored during storage. At the end of the storage period, the 40MA and 20Asamples showed a significant decrease (approx. 18-19) in yield of cell wall material (CWM), whereas less than 6 of CWM had been degraded in the 10MA sample. Decrease in CWM was mainly due to pectic polysaccharide degradation, although for 20A and 40MA samples, hemicelluloses were also affected. Throughout storage, 10MA, 20MA and 30MA samples exhibited similar CWM solubility; however, that of the 40MA sample underwent a significant decrease, from 10 to 4.5, probably due to formation of new pectic chains of higher mol. wt. In contrast, the CWM solubility of sample 20A increased from 10 to 15, suggesting that MA may have promoted inhibition of pectic-polysaccharide-degrading enzymes. In general, combined use of relatively low temp. and a MA helped to preserve raisin colour and maintain levels of their CWM at values similar to initial concn.