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L.J. von Mollendorff, G. Jacobs, and O.T. de Villiers

`Flavortop' nectarines [Prunus persica (L.) Batsch] were stored at -0.5C or 3C for 0, 1, 2, 3, or 4 weeks, after which the fruit was ripened at 15C. After ripening, fruit samples were tested daily or every second day for extractable juice, internal conductivity, and woolliness. The change in the percentage of extractable juice during ripening differed very little among the five storage periods. A rapid increase in internal conductivity occurred during ripening in fruit with or without cold storage, but the onset of the increase was advanced with longer cold-storage periods. No woolliness developed in fruit not placed in cold storage or in fruit cold-stored for 1 or 2 weeks at - 0.5C or 3C. Woolliness only developed during ripening of fruit cold-stored for 3 or 4 weeks at -0.5C or 3C. Incidence of woolliness increased to high levels during ripening and decreased thereafter to no woolly fruit by the 11th day. The lowest values for extractable juice coincided with the highest incidence of woolly fruit. Fruit stored for 4 weeks took longer to pass the woolliness stage. At the end of the ripening. period, cold-stored fruit were similar in appearance and juiciness to those ripened without cold storage. Nectarines stored at 3C generally developed woolliness earlier, had a lower incidence of woolliness, and took longer to overcome the problem than fruit stored at -0.5C. Incidence of browning of the mesocarp tissue was greater at 3C than at -0.5C.

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L.J. von Mollendorff, O.T. de Villiers, G. Jacobs, and I. Westraad

`Flavortop' nectarines [Prunus persica (L.) Batsch] were either stored for 4 weeks at -0.5C or not subjected to cold storage before being ripened at 15C. The differences in extractable juice, woolliness, composition, and gelling characteristics of extracted pectins between the two treatments were determined during ripening. As ripening progressed, the extractable juice in both treatments decreased to low values after which it increased with further ripening. Woolliness only occurred in fruit that was cold stored. Nectarines became woolly from the 2nd day and peaked on the 6th day of ripening in fruit cold stored for 4 weeks. As fruit firmness decreased, the soluble pectin concentration increased to the same extent in both treatments at the expense of insoluble pectin. In cold-stored fruit, the viscosity of pectin increased gradually until the 6th day of ripening, while in noncold-stored fruit maximum viscosity was higher and occurred between the 4th and 6th day of ripening. From the 6th day, the viscosity decreased in both treatments to levels lower than the initial viscosity. The extractable juice was lowest when the viscosity of soluble pectins and percentage of woolly fruit were highest. Molecular mass distribution of soluble pectins decreased considerably during ripening at 15C.