96-2 |
Inactivation efficiency of UV treatment of juices |
T. KOUTCHMA1, C. Adhikari1, and E. G. Murakami2. (1) National Center for Food Safety and Technology, Illinois Institute of Technology, 6502 S. Archer Road, Moffett Campus, Summit-Argo, IL 60501, (2) National Center for Food Safety and Technology, FDA, 6502 S. Archer Road, Summit-Argo, IL 60501 Efficiency of UV reactors decreases when solutions with high absorbance and solid particles such as apple juice (cider) are processed. There are no data available on quantitative impact of product/process parameters such as dissolved and suspended solids content, flow rate/regime on dosage delivery that can alter UV inactivation efficiency. Heterogeneity of flow pattern and irradiation field can also affect UV disinfection rate. To evaluate critical product/process parameters that affect inactivation efficiency of continuous UV treatment of apple juice. E. coli K12 was chosen as a target microorganism for dose-response calibration in static conditions and biodosimetry in a thin-film UV reactor using apple juice and a model system. Malate buffer and caramel (0.13 and 0.6 %) were used to simulate the effects of juice parameters such as pH, oBrix and color/absorbance on inactivation rates. Solid-liquid flows and Residence Time Distribution (RTD) were analyzed using the Dispersed Phase Model (DPM) approach. A 5-log reduction of E. coli K 12 was obtained after one pass at the slowest flow rate of 57 ml/s in 0.13% caramel. Higher absorbance or less residence time decreased bacterial inactivation. Nevertheless, an increase of flow rate to 160 ml/s caused an increase of inactivation reaction rates from 0.74 to 1.12 and from 0.24 to 0.5 1/s in 0.13 and 0.6% caramel. A higher inactivation rate was observed in model with particulates compared to transparent caramel solutions of identical absorbance. It was concluded that absorbance of a solute determined the magnitude of absorbed dose in liquids with particles. There was no consistent effect of pH /Brix. DPM provided a representation of the transport of particle-associated microorganisms in the reactor for rational design of UV process. Absorbances of solution and flow rate are the critical parameters of UV treatment of juices that should be controlled to achieve the performance standard of a 5-log reduction.
Session 96, Nonthermal Processing: Food safety and quality of nonthermal processed foods
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