STORAGE PERFORMANCE OF FORTUNE MANDARINS FOLLOWING HOT-WATER DIPS

Commercially ripe 'Fortune' mandarins were dipped in water at 50 degre es C (Dip50), 52 degrees C (Dip52), 54 degrees C (Dip54), 56 degrees C (Dip56), or 58 degrees C (Dip58) for 3 min before storage at 6 degree s C for 30 days and 3 additional days at 20 degrees C (simulated shelf -life). Untreated fruits were used as control. Scanning electron micro scopy of untreated fruit revealed rough and granular wax surface struc tures with a number of deep surface cracks. II? contrast, fruits dippe d at 50-54 degrees C did not exhibit similar fractures and the fruit s urface appeared relatively homogeneous. Dip56 resulted in parts of the surface with no apparent epicuticular wax and zones with an accumulat ion of waxy deposits. With Dip58, the fruit surface appeared as if the treatment had melted and completely removed epicuticular waxes. Dip50 -54 reduced chilling injury and levels of decay, both during cold stor age and simulated shelf-life. Dip56-58 showed no advantages compared w ith untreated fruit. Neither Dip50 nor Dip52 causec adverse effects to rind surface, either during or after simulated shelf-life. Conversely , higher dip temperatures induced heat damage in the form of rind brow ning, the extent and number of fruits affected increasing as bath temp erature increased. Water loss was consistently lower in untreated frui t. Peel water loss was consistently higher in Dip56 and Dip58 fruit. D ifferences in external appearance, physiological behaviour and interna l quality attributes between untreated and Dip50-54 fruit were minimal . Dip56 and especially Dip58 had negative effects on the external appe arance of fruits. The off-flavour found in Dip58 was probably due to i ncreased levels of ethanol in the juice. (C) 1997 Elsevier Science B.V .