Dynamic high pressure is one the most promising alternative to traditional thermal treatments for fluid food decontamination and diversification. Its effectiveness in the deactivation of pathogenic and spoilage microorganisms in model and real systems is well documented. Moreover, continuous or semi-continuous application of this technique to improve safety and microbiological quality of milk and whole liquid eggs has been proposed. Cavitation and viscous shares have been identified as the primary mechanisms of microbial cell disruption during high pressure homogenisation (HPH). In addition to the effects on microbial cells, the HPH treatment acts on food constituents, especially proteins including enzymes, leading to modification in their functional properties or activities. To evaluate the effects of HPH on the milk microbial ecology, several microbial species were inoculated in UHT whole milk and subjected to a treatment of 1000 bar. The comparison of the cell loads recorded after the high pressure treatment indicated that the most pressure resistant species were Lb. helveticus, E. coli, Lb. plantarum, E.coli, and L. monocytogenes, whereas Ps. cepacia, Ps. fluorescens, , S. aureus, Klebsiella oxytoca, and Enterococcus faecium were most sensitive to the treatment. The ability of the survivors to start the growth was evaluated monitoring their cell loads after an incubation at 15°C for 24 h. Almost all the considered species, except E. coli, L. monocytogenes, S. aureus and Y. lipolytica were able to increase their cell loads under the adopted experimental conditions. Moreover, in order to evaluate the effect of HPH treatment on the activity of antimicrobial enzymes on L. monocytogenes, the strain Scott A was inoculated in homogenised (1000 bar) and pasteurised (70°C for 30’’) milk previously added with lysozyme. The samples were incubated at 37°C for 12 hours. The data obtained showed the HPH treatment was more effective on L. monocytogenes deactivation, in respect with pasteurised and not treated milk. Results of this work suggest that HPH can represent a useful tool for microbial deactivation and for enzyme activity enhancing without detrimental effects on shelf-life and safety of treated food.
Pathogenic species deactivation by high pressare homogenization
GUERZONI, MARIA ELISABETTA;LANCIOTTI, ROSALBA;VANNINI, LUCIA;PATRIGNANI, FRANCESCA;IUCCI, LUCIANA
2004
Abstract
Dynamic high pressure is one the most promising alternative to traditional thermal treatments for fluid food decontamination and diversification. Its effectiveness in the deactivation of pathogenic and spoilage microorganisms in model and real systems is well documented. Moreover, continuous or semi-continuous application of this technique to improve safety and microbiological quality of milk and whole liquid eggs has been proposed. Cavitation and viscous shares have been identified as the primary mechanisms of microbial cell disruption during high pressure homogenisation (HPH). In addition to the effects on microbial cells, the HPH treatment acts on food constituents, especially proteins including enzymes, leading to modification in their functional properties or activities. To evaluate the effects of HPH on the milk microbial ecology, several microbial species were inoculated in UHT whole milk and subjected to a treatment of 1000 bar. The comparison of the cell loads recorded after the high pressure treatment indicated that the most pressure resistant species were Lb. helveticus, E. coli, Lb. plantarum, E.coli, and L. monocytogenes, whereas Ps. cepacia, Ps. fluorescens, , S. aureus, Klebsiella oxytoca, and Enterococcus faecium were most sensitive to the treatment. The ability of the survivors to start the growth was evaluated monitoring their cell loads after an incubation at 15°C for 24 h. Almost all the considered species, except E. coli, L. monocytogenes, S. aureus and Y. lipolytica were able to increase their cell loads under the adopted experimental conditions. Moreover, in order to evaluate the effect of HPH treatment on the activity of antimicrobial enzymes on L. monocytogenes, the strain Scott A was inoculated in homogenised (1000 bar) and pasteurised (70°C for 30’’) milk previously added with lysozyme. The samples were incubated at 37°C for 12 hours. The data obtained showed the HPH treatment was more effective on L. monocytogenes deactivation, in respect with pasteurised and not treated milk. Results of this work suggest that HPH can represent a useful tool for microbial deactivation and for enzyme activity enhancing without detrimental effects on shelf-life and safety of treated food.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
