54F-7 |
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O. MARTÍN, A. Sobrino, and C. Carnice. Dept. of Food Technology, Univ. of Lleida, UTPV-CeRTA, Av. Alcalde Rovira Roure, 191, Lleida, 25198, Spain Non-thermal treatments such as High Intensity Pulsed Electric Fields (HIPEF) are being developed in order to achieve processed foods with minimal loses of bioactive compounds. HIPEF represents one of the most promising minimal processing technologies and have been proved to inactivate microorganisms under nonthermal conditions. The objective of this study was to investigate Staphylococcus aureus inactivation by HIPEF in milk by applying a factorial design methodology, in which HIPEF effect on S. aureus could be evaluated taking as treatment variables field intensity, number of pulses, pulse width, fat content of milk and pulse polarity. S. aureus CECT 240 was used as the target microorganism and inoculated into milk (approximately 107 ufc/ml). A five level factorial design on survival rate was performed and samples were treated according to the factor combination by a continuous HIPEF treatment. The results obtained showed that the model applied was significant at 95% confidence interval and the curvature test was also revealed as significant. In this case, number of pulses, fat content and pulse polarity were pointed out as main significant factors, while field intensityxpulse width and number of pulsesxpulse polarity were main interactions. Maximal inactivation of S. aureus (3.3 log reduction) was achieved when bipolar pulses at 8ms pulse width, 300 pulses and 35 kV/cm were applied and when whole milk were considered. These results suggest that a later response surface fitting should consider a second order model due to the significant curvature test. So, survival rate can be modeled by considering the main factors number of pulses, fat content and pulse polarity, and field intensityxpulse width and number of pulsesxpulse polarity as main interactions, what represents an advantage with respect to the total number of experiments performed and the statistical analysis approach.
Session 54F, Nonthermal Processing: General I
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |