Mycological stability of minimally-processed young coconut (Cocos nucifera L.) as influenced by different chemical and physical treatments
2003
Waje, C.K.
Young coconut samples were minimally processed and subjected to five different treatments. These included dipping of the nuts in sodium metabisulfite (5% and 10%), citric acid (2.5% and 5%), oxalic acid (2.5% and 5%) and hydrochloric acid (0.01%) solutions, and in hot water (50 deg C, 70 deg C and 100 deg C). Samples were stored under ambient room (25 deg C) and refrigerated (13 deg C) temperatures. Results showed that among the treatments used, only the sodium metabisulfite was effective in prolonging the storage life of tender nuts in terms of preventing husk discoloration and surface mold growth. Under cold storage, surface mold growth was observed only after four weeks. At ambient room temperature, maximum shelf-life is four days and 2 weeks for the nuts treated with 5% and 10% sodium metabisulfite, respectively. Samples treated with citric acid exhibited peel discoloration after three days under ambient and cold storage. For the nuts treated with oxalic acid, browning occurred during the fourth and seventh day under ambient and refrigerated temperatures, respectively. Peeled nuts dipped in hot water and hydrochloric acid readily turned brown after dipping. Seven representative mold isolates were isolated from tender nut samples. Cultural and morphological characteristics showed the identity of the mold isolates as Aspergillus niger, Penicillium citrinum, Syncephalastrum racemosum, Geotrichum candidum, Penicillium funiculosum, P. islandicum, and Helmintosporium curvulum, wherein A. niger and P. citrinum are the most predominant molds in minimally-processed young coconut. The critical control points in the minimal processing steps for tender nuts where molds would likely to occur and/or proliferate on the surface peel were identified to be the dipping of the peeled nuts with the whitening agent, air drying and storage
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