Evaluation of curative and protective control of <I>Penicillium digitatum </I>following imazalil application in wax coating

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Effects of citrus wax coating and brush type on imazalil residue loading, green mould control and fruit quality retention of sweet oranges

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Imazalil resistance in Penicillium digitatum and P. italicum causing citrus postharvest green and blue mould: Impact and options

Citrus green and blue mould, caused by Penicillium digitatum (PD) and Penicillium italicum (PI), respectively, are mostly controlled by means of postharvest fungicide applications. Currently, IMZ is regarded as the most effective fungicide in use. Effective IMZ concentrations that inhibit 50% (EC50) growth of nine PD and five PI isolates were assessed in vitro and the various isolates categorized according to their resistance (R) factors. Effective residue levels that provided 50% curative (ER50C) and protective (ER50P) control of these isolates were determined in vivo. All the PI isolates were sensitive, having EC50 values of 0.005–0.050 mg mL 1. Three PD isolates were sensitive (0.027–0.038 mg mL 1), while one resistant isolate was categorized as low resistant (R-factor of 19), one as moderately resistant (R-factor of 33.2), three as resistant (R-factor of 50–57.6) and one as highly resistant (R-factor of 70.7). Sensitive PD isolates had mean ER50C and ER50P values on Valencia orange fruit of 0.29 and 0.20 mg g 1, and 0.33 and 0.32 mg g 1 on navel fruit, respectively. ER50 values for resistant isolates did not always correlate with EC50 values and ranged from 1.22 to 4.56 mg g 1 for ER50C and 1.00–6.62 mg g 1 for ER50P values. ER50P values for resistant isolates could not be obtained on navel orange fruit, but ER50C values (1.42– 1.65 mg g 1) were similar to those obtained on Valencia fruit. The PI isolates all behaved similar to the sensitive PD isolates with ER50C and ER50P values on navel and Valencia fruit <0.38 mg g 1. Alternative fungicides were assessed for the control of an IMZ sensitive, resistant and highly resistant PD isolate; these included sodium ortho-phenylpenate (SOPP), thiabendazole (TBZ), guazatine (GZT), imazalil (IMZ), pyrimethanil (PYR) and Philabuster1 (PLB; a combination of IMZ and PYR), fludioxonil (FLU), azoxystrobin (AZO), Graduate1A+ (GRA; a combination of FLU and AZO) and propiconazole (PPZ). Multiple fungicide resistance was shown to IMZ, GZT, TBZ and PPZ in both resistant isolates. For the sensitive isolates, IMZ, SOPP, TBZ, GZT and PLB provided best curative control, while IMZ, GZT and PLB provided best protective control. For the IMZ-resistant isolates, SOPP, PYR and PLB gave the best curative control, while none of the fungicides provided adequate protective control.Citrus Research International, Citrus Academy, Postharvest Innovation Fund (PHI) and Technology and Human Resources for Industry Programme (THRIP).http://www.elsevier.com/locate/postharvbio2016-09-30hb201

Optimization of Hemicellulose Coating as Applied to Apricot Drying and Comparison with Chitosan Coating and Sulfite Treatment

Drying of hemicellulose-coated apricots was compared to sulfuring and chitosan coating. Air velocity, temperature and hemicellulose concentration were optimized using the Box-Behnken response surface methodology against total color change (Delta E-star), yellowness (Delta b(star)) and final moisture content. Drying kinetics were evaluated by Newton, Page and Logarithmic models. Diffusion coefficient, activation energy and rehydration rate were calculated. The optimal drying conditions were found as 1 m/s of air velocity, 80C of air temperature and 3% (w/v) hemicellulose coating, which gave values of 15.2, -8.3 and 26% for Delta E-star, Delta b(star) and final moisture, respectively. The hemicellulose-coated apricots indicated better color values than the uncoated and chitosan-coated samples, while sulfuring still attained the best color values. Drying kinetics were best described by the Logarithmic model at 60 and 70C and Page model at 80C for 2% hemicellulose coating. Effective diffusion coefficients ranged from 2.499 to 5.742 x 10(-9) and the activation energy was calculated as 33.78 kJ/mol. The hemicellulose-coated apricots had slightly higher rehydration rate than the uncoated and sulfured samples. In conclusion, hemicellulose coating showed a promise for use in fruit drying