Ultrasound and Antimicrobial Compounds: A Suitable Way to Control Fusarium oxysporum in Juices

This paper reports on the use of ultrasound, combined with either Na-benzoate or citrus extract, to inhibit Fusarium oxysporum in orange juice. In a preliminary step, spores of F. oxysporum were inoculated into distilled water and treated through an ultrasound equipment; the treatments differed for acoustic energy (the maximum power attained by the equipment was 130-W frequency, 20 kHz; the energy was reported as percentage of the maximum power, from 40% to 100%), pulse (2 and 10 s), and duration of the treatment (from 2 to 10 min).Then, the treatment was validated in orange juice, in combination with either benzoate (0-100 ppm) or citrus extract (0-1,800 ppm), using a mixture design called centroid. The most significant effects were time, as single term, and the interaction energy/time/pulse; concerning the possibility of extending juice shelf life, the use of benzoate and citrus extract controlled F. oxysporum growth in orange juice and achieved a reduction of 5 log cfu/ml for at least 14 days.