Anthocyanin Content, Peroxidase and Polyphenol Oxidase Activities in Relation to Browning Potential of Celebration, Sapphire and Santa Rosa Plum Fruits During Cold Storage

Document Type : Original Article

Authors

1 Mamouraa Bot. Garden, Alexandria, Hort. Res. Inst., Agric. Res. Center, Giza. Egypt.

2 Dep. Plant Prod. (Pomology), Institute of Efficient Productivity, Zagazig Univ. Egypt.

Abstract

The present study was carried out during 2007 and 2008 seasons on fruits of the newly introduced plum cvs. Celebration and Sapphire (from South Africa) in comparison with the local cv. Santa Rosa. The fruits were stored at 0°C and 85 - 90 % relative humidity. The physio-chemical properties of the stored fruits were followed up in 4 days intervals during the storage period and a sample was transferred to 20°C for observation after 2, 4 and 6 days (shelf life sample to simulate the marketability period). Fruits cooled at 0˚C can be stored for 28 days with good firmness but they lost their firmness and became dull in shelf life store. Chilling injury (CI) symptoms as flesh browning, translucency and bleeding appeared in the last two cold storage intervals (24 and 28 days) when the fruits were transferred to 20˚C. During cold storage period at 0˚C, Celebration had the highest significant weight loss percentages. In all cvs., weight loss averages of shelf life fruits were less than 1 % after 2 days and Sapphire fruits had the lowest percentages of weight loss. After 8 days at 0˚C then storage at 20˚C, Sapphire cv. had the lowest firmness loss percent. After 16 days of cold storage, the three cvs. had good firmness values but when the fruits were transferred to 20˚C, those values decreased significantly after 2 and 4 days. After cold storage, fruits of Santa Rosa cv. lost the highest percent of soluble solids content (SSC) compared with Celebration and Sapphire fruits. For shelf life fruits, there were no significant changes in SSC for the three cvs. in most intervals. Celebration fruits had the lowest initial acidity values and during the first cold storage periods (4 and 8 days) the acidity values of all cvs. decreased slightly but they increased when the fruits were transferred to 20˚C. With the progress of cold storage, the fruits of the three cvs. had less acidity content compared with the initial values and those values declined during the subsequent shelf life period. Peel anthocyanin content of Santa Rosa fruits (red cv.) decreased with the advancing of cold storage while that content of Celebration fruits (red cv.) increased slightly. On the other hand, the yellow Sapphire cv. showed the greatest increase in peel anthocyanin content. Santa Rosa flesh had the highest initial content of anthocyanin compared with the other two cvs. The flesh anthocyanin contents increased during the first 12 days of cold storage then decreased with the advancing of cold storage. During cold storage, peroxidase (POD) activity of all cvs. decreased then increased again during the last intervals. There was general trend of decreasing POD activity in shelf life fruits of all cvs. in the first 12 days of the experiment then it increased during the last 16 days. On the other hand, Sapphire fruits significantly had the highest initial values of polyphenol oxidase (PPO) activity and those values decreased sharply by the end of cold storage period. Celebration and Santa Rosa cvs. showed contrast trend where the PPO activities showed an increasing trend with the progress of cold storage. 

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