Evaluation of food additives and low-toxicity compounds as alternative chemicals for the control of Penicillium digitatum and Penicillium italicum on citrus fruit.
The effectiveness of low-toxicity chemicals as possible alternatives to synthetic fungicides for the control of post-harvest green and blue moulds of citrus was evaluated. A preliminary selection of chemicals, mostly common food additives, was made through in vivo primary screenings with oranges artificially inoculated with Penicillium digitatum or P italicum. Selected compounds and mixtures were tested as heated solutions in small-scale trials. Immersion of artificially inoculated oranges or lemons for 120 s in solutions at 40.6 degrees C and natural pH of potassium sorbate (0.2 M), sodium benzoate (0.2 M) or mixtures (0.1 + 0.1 M) of potassium sorbate with sodium benzoate, sodium propionate or sodium acetate were the most effective organic acid salts tested and reduced green mould by 70-80% after 7 days of storage at 20 degrees C. The mixtures did not significantly enhance the effectiveness of potassium sorbate or sodium benzoate alone. These solutions were as effective as sodium carbonate or calcium polysulphide treatments and, in general, they were more effective on lemons than on oranges. Satisfactory control of green and blue moulds was obtained by dipping oranges for 150 s in solutions of sodium molybdate (24.2 mM) or ammonium molybdate (1.0 mM) at 48 or 53 degrees C, but not at 20 degrees C. At 53 degrees C, however, the effectiveness of hot water was not enhanced by either molybdate. Molybdenum salts at higher concentrations were phytotoxic and stained the fruit. At non-phytotoxic concentrations, the effectiveness of these solutions was more influenced by temperature than by concentration. In general, the inhibitory effects of all compounds tested were not fungicidal but fungistatic and not very persistent. In conclusion, potassium sorbate, sodium benzoate and ammonium molybdate, among the wide range of chemicals tested, were superior for the control of post-harvest Penicillium decay of citrus fruit.
Palou
Lluís
L
Area de Postcollita, CeRTA, Centre UdL-IRTA, Av Rovira Roure 177, 25198 Lleida, Catalonia, Spain. lluis@uckac.edu
Usall
Josep
J
Smilanick
Joseph L
JL
Aguilar
Maria-José
MJ
Viñas
Inmaculada
I
D002957:Citrus / Q000382:microbiology*; D004347:Drug Interactions; D005503:Food Additives / Q000494:pharmacology*; D005638:Fruit / Q000382:microbiology*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008982:Molybdenum / Q000494:pharmacology; D009930:Organic Chemicals / Q000494:pharmacology*; D010407:Penicillium / Q000187:drug effects* / Q000254:growth & development; D011422:Propionates / Q000494:pharmacology; D019346:Sodium Acetate / Q000494:pharmacology; D020160:Sodium Benzoate / Q000494:pharmacology; D013011:Sorbic Acid / Q000494:pharmacology
D005503:Food Additives; D009930:Organic Chemicals; D011422:Propionates; D019346:Sodium Acetate; D008982:Molybdenum; C024687:sodium molybdate(VI); C514135:sodium propionate; C029658:propionic acid; C022175:ammonium molybdate; D020160:Sodium Benzoate; D013011:Sorbic Acid