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Ahmed El Ghaouth, Rathy Ponnampalam and Joseph Arul

The effect of chitosan coating on the respiration rate, ethylene production and quality attributes of tomatoes stored at 20°C under high humidity-regular atmosphere was investigated. Chitosan coating reduced significantly the respiration rate and ethylene production of tomatoes, with a greater effect at higher concentration. In addition coating modified the internal microatmoaphere of fruits. Furthermore, coated fruits were firmer, higher in titratable acidity, less decayed and their change in color proceeded at a slower rate than the control.

In conclusion chitosan coating delayed senescence and prolonged storage life of tomatoes, without affecting their market quality by acting as diffusion barrier for gases.

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Ahmed El Ghaouth, Joseph Arul, Rathy Ponnampalam and Francois Castaigne

The effect of chitosan coating on green peppers and cucumbers stored at 13°C and 85% R.H. on weight loss, quality and respiration was assessed. Chitosan coating markedly reduced the weight loss of both green peppers and cucumbers, with greater effect at higher concentration. In addition, color loss, wilting, decay and respiration was significantly lower in coated fruits than in the control.

The results of this study indicate that the mechanism by which chitosan coating delay senescence in green peppers and cucumbers is more likely due to its ability to alleviate water stress than to modify the internal microatmosphere.

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Ahmed El Ghaouth, Rathy Ponnampalam, François Castaigne and Joseph Arul

The effect of chitosan on respiration, ethylene production, and quality attributes of tomato (Lycopersicon esculentum Mill.) fruit stored at 20C was investigated. Coating the fruit with chitosan solutions reduced the respiration rate and ethylene production, with greater effect at 2% than 1% chitosan. Coating increased the internal CO, and decreased the internal O2 levels of the tomatoes. Chitosan-coated tomatoes were firmer, higher in titratable acidity, less decayed, and exhibited less red pigmentation than the control fruit at the end of storage. Chemical name used: 2-amino-2- deoxy-p-D)-glucan (chitosan).

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Charles L. Wilson, Jose M. Solar, Ahmed El Ghaouth and Deborah R. Fravel

An apparatus was developed for the rapid and facile evaluation of soil fumigants in a controlled manner using small volumes of soil. The apparatus consisted of a manifold to which were attached six canisters containing a loamy sand soil (adjusted to –100 kPa soil water potential). The soil was infested with either conidia of Fusarium oxysporum or Trichoderma harzianum; sclerotia of Sclerotinia minor; ascospores of Talaromyces flavus; vermiculite colonized with Pythium aphanidermatum; or beet (Beta vulgaris L., cv. Detroit Red) seed colonized with Rhizoctonia solani. Using nitrogen gas (N2) as a carrier gas, either N2 or N2 plus benzaldehyde was passed continuously through the soil for 24, 48, or 72 hours. At all three exposure times, benzaldehyde + N2 reduced viability of R. solani and S. minor, and reduced populations of P. aphanidermatum and T. harzianum. Populations of F. oxysporum were reduced after 48 and 72 hours of exposure to benzaldehyde, whereas populations of T. flavus were reduced only after 72 hours of exposure. Fumigation with benzaldehyde + N2 for 24 hours did not affect soil pH 1 week after exposure, but fumigation for 48 or 72 hours temporarily lowered pH from an average of 6.86 to 5.57 and 5.32, respectively. The biocontrol fungus, T. flavus, was less sensitive to benzaldehyde than the pathogens or the biocontrol fungus, T. harzianum. Thus, combining T. flavus with benzaldehyde to enhance biocontrol may be possible.