Utilizing hydrodynamic cavitation and ultraviolet irradiation to improve the saftey of minimally processed fluid food
Milly, Paul Jesse
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TM A Shockwave Power Reactor (SPR) was utilized to induce hydrodynamic cavitation and increase mass transfer of fluid from bulk fluid to an ultraviolet irradiated surface for minimally processing fluid food. Hydrodynamic cavitation is the formation of gas bubbles in a fluid due to pressure fluctuations induced by mechanical means. Details of the novel equipment design are presented and energy consumption was compared to conventional thermal food processing technologies. Energy input was less than 220 kJ/kg and conversion efficiency from electrical to thermal was 55 to 85%. Calcium-fortified apple juice processed at 3000 rpm and 3600 rpm rotor speed on the reactor went through a transient temperature change from 20ûC to 65.6ûC or 76.7ûC and the total process lethality exceeded 5-log reduction of Lactobacillus plantarum, Lactobacillus sakei and Zygosaccharomyces bailii vegetative cells and ascospores. Tomato juice inoculated with Bacillus coagulans spores and processed at 3000 rpm and 3600 rpm had transient temperature from 37.8ûC to 93.3ûC or 104.4ûC had viable CFU reduced 0.88 and 3.10 log cycles, respectively. Skim milk inoculated with P.A. 3679 spores and processed at 3000 rpm or 3600 rpm had transient temperature from 48.9ûC to 104.4ûC or 115.6ûC had CFU reduced 0.69 and 2.84 log cycles, respectively. A KI to I3¯ chemical dosimeter for UV was used 2to quantify photons received by fluid in the annular space of the SPR. UV dose (J/m) increased 22from 97 J/m at 0 rpm to over 700 J/m for SPR speeds above 2400 rpm. Inactivation of E. coli 25922 in apple juice and skim milk in the UV-SPR at exit temperatures below 45ûC was greater than 4.5 and 3 logs, respectively. Utilizing hydrodynamic cavitation and ultraviolet radiation to obtain minimally processed pasteurized low acid and commercially sterilized high acid fluid foods is possible with appropriate process considerations for different products.