Effectiveness of neutral electrolyzed water and copper oxychloride on fungi spores isolated from tropical fruits

The aim of this study was to assess the antifungal effectiveness of neutral electrolyzed water (NEW) to inhibit the spore germination of post-harvest fungi common in fruits, determine the required available chlorine concentration (ACC) of NEW and to compare it with copper oxychloride (CO) and sterile distilled water (SDW) in vitro. This study evaluated the biological effectiveness of NEW to inactivate pure cultures of 11 different fungi obtained from post-harvest tropical fruits with anthracnose, rottenness or necrosis symptoms. A conidial solution of 1 x 104 spores/mL per culture was prepared and treated with a low, medium and high ACC of NEW (pH 7.0 ± 0.05, 12, 33 and 53 mg/L of ACC and ORP of 850 mV), CO at 0.3 g/L, or sterile distilled water as a control, for 3-, 5 and 10-min contact time. Spore germination of Alternaria alternata, Botrytis cinerea, Cladosporium australiense, Colletotrichum gloeosporioides and C. siamense, Fusarium solani and F. oxysporum, and Lasiodiplodia theobromae was inhibited in 100% by NEW at 12, 33 and 53 ppm ACC; 3,5 and 10 min contact time. Aspergillus niger and A. tamarii required 53 mg/L ACC to inhibit 100% of spore germination. NEW at 33 and 12 mg/L inhibited around 50% and <25% of A. niger spore germination, respectively. NEW at 53 mg/L ACC was the most efficient treatment against Rhizopus stolonifer but only inhibited spore germination in ~25%. CO inhibited spore germination by 100% of A. alternata, B. cinerea, C. australiense, C. gloeosporioides, C. siamense and L. theobromae. However, CO inhibited <25% of spore germination of F. solani, F. oxysporum, A. niger, A. tamarii and R. stolonifer. NEW and CO had a significant effect on every fungus compared to a SDW treatment. SDW was the least effective treatment, followed by CO. NEW at 12 mg/L and 33 mg/L ACC were equally effective in eliminating the fungi, and more effective than CO. NEW at a concentration of 53 mg/L ACC was the most effective treatment. Results obtained in this study show that NEW has effectively inhibited spore germination of these species, and this treatment could be used as a substitute an ecological novel alternative to CO to avoid spore growth in the above-mentioned fruits.