EFFECT OF EXPOSURE TO RADIO-FREQUENCY ELECTRIC FIELDS ON SEED-BORNE MICROORGANISMS

Exposure of naturally infected and artificially inoculated seeds to radio-frequency (rf) electric waves of 59 to 64 Mc/sec was of varying effectiveness in eradicating internally borne fungi and bacteria. Diaporthe phaseolorum was eliminated from soybean seeds with little reduction in seed germination. Survival of Ascochyta pisi and A. pinodes (Mycosphaerella pinodes) in field pea seed was greatly reduced by similar treatment, but the fungi were not usually eradicated without appreciable reduction in germination. Germinability of pea seeds was unaffected by increasing the moisture content of the seed to 16% from 10.3%. The A. pinodes content of such seeds, however, was reduced by approximately 50%. Both seed and fungus were more susceptible to damage by rf treatment at the higher moisture level. Bean seed infected with Xanthomonas phaseoli var. fuscans and cabbage seed inoculated with X. campestris were killed by exposures which reduced but did not eradicate the bacteria. Colonies of both xanthomonads on nutrient agar media were destroyed by rf treatment.

Download Full-text

Numerical and experimental studies on a novel Steinmetz treatment chamber for inactivation of Escherichia coli by radio frequency electric fields

Innovative Food Science & Emerging Technologies ◽

10.1016/j.ifset.2017.04.009 ◽

2017 ◽

Vol 41 ◽

pp. 337-347 ◽

Cited By ~ 8

Author(s):

Hassan Masood ◽

Adel Razaeimotlagh ◽

Patrick J. Cullen ◽

Francisco J. Trujillo

Keyword(s):

Escherichia Coli ◽

Radio Frequency ◽

Electric Fields ◽

Experimental Studies ◽

Radio Frequency Electric Fields

Download Full-text

Inactivation of Lactobacillus plantarum in Apple Cider, Using Radio Frequency Electric Fields†

Journal of Food Protection ◽

10.4315/0362-028x-72.3.656 ◽

2009 ◽

Vol 72 (3) ◽

pp. 656-661 ◽

Cited By ~ 18

Author(s):

DAVID J. GEVEKE ◽

JOSHUA GURTLER ◽

HOWARD Q. ZHANG

Keyword(s):

Radio Frequency ◽

Lactobacillus Plantarum ◽

Electric Fields ◽

Treatment Time ◽

Hold Time ◽

Electrical Energy ◽

Gram Positive ◽

Apple Cider ◽

Gram Positive Bacteria ◽

Radio Frequency Electric Fields

Radio frequency electric fields (RFEF) nonthermal processing effectively inactivates gram-negative bacteria in juices, but has yet to be shown effective at reducing gram-positive bacteria. Apple cider containing Lactobacillus plantarum ATCC 49445, a gram-positive bacterium, was RFEF processed under the following conditions: field strength of 0.15 to 15 kV/cm, temperature of 45 to 55°C, frequency of 5 to 65 kHz, treatment time of 170 μs, and holding time of 5 to 50 s. The effect of refrigerating the inoculated cider prior to processing, the extent of sublethal injury, and the effect of storing the treated cider for 35 days were investigated. The population of L. plantarum was reduced by 1.0 log at 15 kV/cm, 20 kHz, and 50°C, with a 5-s hold time. There is a synergistic effect between RFEF and heat above 50°C. Inactivation significantly (P < 0.05) increased as frequency was decreased from 65 to 5 kHz. Inactivation increased linearly with field above 8 kV/cm. Holding cider at 55°C after RFEF treatment for 5 and 50 s resulted in 2.5- and 3.1-log reductions, respectively. The surviving population was composed of 1.4-log sublethally injured cells. Storing processed cider at 4°C for 35 days steadily and significantly (P < 0.05) reduced L. plantarum from 4.5 to 0.9 log CFU/ml. The electrical energy density was 51 J/ml. This provides the first evidence that nonthermal RFEF processing inactivates gram-positive bacteria, and that surviving cells may die off during refrigerated storage.

Download Full-text