PRESERVATION FACTORS AND PROCESSING EFFECTS ON ANTHOCYANIN PIGMENTS IN PLUMS

The use of a combination of preservation factors has been suggested as a viable alternative to minimally process fruits and preserve them fo r practical periods of time. Although microbiological stability is the main goal, in the case of prunes color preservation is also of great concern. Prunes (Prunus domestica L.) of the 'Angeleno' variety were e mployed. The fruits were cut in half and the seeds removed. A treatmen t of 150 s under steam resulted in the permanent inactivation of brown ing enzymes. The treated fruit was stored for 90 days in systems (a(w) = 0.98 with sucrose and 0.1% benzoate) at three different pH values: 2.95, 3.45 and 3.95. After 90 days of storage at room temperature, 77% of the original anthocyanin remained at pH 2.95, but only 29% at pH 3 .45 and 8% at pH 3.95. There was also an increase in the degradation i ndex with time and with increasing storage pH. Color density values de creased as a result of anthocyanin degradation and not because of brow ning reactions. A marmalade prepared using the pH 2.95 preserved prune s was stored at room temperature for 90 days. An additional 27% of the original anthocyanin was destroyed, but the degradation index increas ed only slightly and remained constant throughout the storage period. Color density values remained very low. No microbial growth occurred i n the stored prunes or marmalade, and the marmalade was classified org anoleptically as good. Copyright (C) 1996 Elsevier Science Ltd