Effect of High Intensity Ultrasound Treatment on the Growth of Food Spoilage Bacteria

The aim of this study is to determine the effect of high intensity ultrasound (amplitude, temperature and treatment time) on the inactivation of food spoilage bacteria Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064, Listeria monocytogenes ATCC 23074 and Bacillus cereus 30. The model suspensions of bacteria were treated with 12.7-mm ultrasonic probe operated at 600 W nominal power (ultrasonic treatment implemented at 20 kHz) and at amplitudes of 60, 90 and 120 µm. Also, treatment time of 3, 6 and 9 min and temperature of 20, 40 and 60 °C were used. The results were statistically processed with STATGRAPHICS Centurion computer program and response surface methodology. All three parameters studied seem to substantially affect the inactivation of bacteria in pure culture. The results also indicate increased inactivation of microorganisms under longer period of treatments, particularly in combination with higher temperature and/or amplitude. After ultrasonic treatment at 60 °C, 9 min and 120 μm, the viability of cells was not confirmed for Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064 and Listeria monocytogenes ATCC 23074. Under the mentioned conditions the highest inactivation (3.48 log CFU/mL) of Bacillus cereus 30 was obtained

Utjecaj ultrazvuka visokog intenziteta na rast bakterija uzročnika kvarenja hrane

The aim of this study is to determine the effect of high intensity ultrasound (amplitude, temperature and treatment time) on the inactivation of food spoilage bacteria Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064, Listeria monocytogenes ATCC 23074 and Bacillus cereus 30. The model suspensions of bacteria were treated with 12.7-mm ultrasonic probe operated at 600 W nominal power (ultrasonic treatment implemented at 20 kHz) and at amplitudes of 60, 90 and 120 µm. Also, treatment time of 3, 6 and 9 min and temperature of 20, 40 and 60 °C were used. The results were statistically processed with STATGRAPHICS Centurion computer program and response surface methodology. All three parameters studied seem to substantially affect the inactivation of bacteria in pure culture. The results also indicate increased inactivation of microorganisms under longer period of treatments, particularly in combination with higher temperature and/or amplitude. After ultrasonic treatment at 60 °C, 9 min and 120 μm, the viability of cells was not confirmed for Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064 and Listeria monocytogenes ATCC 23074. Under the mentioned conditions the highest inactivation (3.48 log CFU/mL) of Bacillus cereus 30 was obtained.Svrha je ovoga rada bila utvrditi utjecaj ultrazvuka visokog intenziteta (velike amplitude, te pri višoj temperaturi i duljem vremenu obrade) na inaktivaciju bakterija što uzrokuju kvarenje hrane, i to: Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064, Listeria monocytogenes ATCC 23074 i Bacillus cereus 30. Suspenzije bakterija tretirane su pomoću sonde promjera 12,7 mm, nominalne snage od 600 W (ultrazvučna je obrada provedena pri 20 kHz) sa tri amplitude (60, 90 i 120 µm), na temperaturi od 20, 40 i 60 °C, tijekom 3, 6 i 9 min. Rezultati su obrađeni programom STATGRAPHICS Centurion, pri čemu je korištena metoda odzivne površine, a utvrđeno je da sva tri ispitana parametra bitno utječu na inaktivaciju bakterija u čistoj kulturi. Rezultati pokazuju da je bolja inaktivacija mikroorganizama postignuta s duljim vremenom obrade ultrazvukom pri višim temperaturama i/ili većim amplitudama. Nakon ultrazvučne obrade na 60 °C i 120 µm tijekom 9 min potpuno su inaktivirane stanice bakterija Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella spp. 3064 i Listeria monocytogenes ATCC 23074. Pri tim je uvjetima postignuta najveća inaktivacija bakterija Bacillus cereus 30 (3,48 log CFU/mL)