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Abstract
The present investigation was carried out in an effort to open a new research area for the possibility of making use of some essential oils to prepare natural biocides. For this purpose, 6 essential oils (fennel, peppermint, caraway, eucalyptus, geranium and lemon) were tested for their antimicrobial activity against some postharvest pathogens. The most effective oils were selected for the preparation of the biocides. In addition, the prepared biocides were tested in vitro and in vivo against the tested pathogens attack some horticulture crops. Finally, the formulated biocides were interacted with some recommended doses of gamma radiation to extend the shelf life of potato tubers and orange fruits. Biological and biochemical changes in the tubers and fruits were examined. The obtained data could be summarized in the following:
6.1. Antimicrobial activity of essential oils:
Results showed that fennel, peppermint and caraway oils gave a complete inhibition for the growth of Alternaria alternata, Penicillium italicum, Penicillium digitatum and Botrytis cinerea. On the other hand, eucalyptus, geranium and lemon oils were less effective in controlling the growth of the same microorganisms with exception of the activity of geranium oil against Alternaria alternata as it completely inhibit its growth.
6.2. Preparation of biocides:
Fennel, peppermint and caraway oils were selected for the preparing of biocides. It was obvious that emulgator B.L.M., emulgator B.L.M. + tween 20 or tween 80 were the most successful emulsifiers for the formulation of essential oils after mixing with different fixed oils i.e., sesame, olive, cotton and soybean oils as additives.
The results of physico-chemical properties indicated that oils alone did not gave any emulsion in water. While, the formulated oils passed successfully through emulsion stability tests (spontaneous emulsification, cold stability and heat stability) and did not show any oily separation. Also, viscosity, surface tension and pH were determined for more characterization of the prepared biocides.