Impact of type of microorganism and different intrinsic and extrinsic factors on the high-pressure carbon dioxide inactivation of microorganisms.
Special Symposium - Innovations in Food Technology (LMC Congress)
Innovations in Food Technology - Poster Session (Food - P2)
Keywords: high-pressure carbon dioxide; non-thermal pasteurization; inactivation; microorganisms
Thermal food preservation is a well known and old technique for reducing the microbial count of foods. For heat sensitive food products, however, thermal pasteurization can impart undesirable organoleptic changes in addition to some detrimental affects to the nutritional quality of the food. Due to the increased consumer demand for nutritious, fresh-like food products with a high organoleptical quality and an extended shelf life, non-thermal processing alternatives have been proposed. For almost two decades now, the use of high-pressure carbon dioxide (HPCD) has been proposed as an alternative cold pasteurization technique for foods.
The first objective of this study was to screen for the susceptibility of different food pathogens and spoilage organisms towards a HPCD treatment. For this purpose, the different microorganisms, suspended in brain heart infusion (BHI) broth, were HPCD-treated at 105 bar, 35°C, 20 min, and 400 rpm with 70% liquid in the reactor volume. Our results showed that HCPD is effective in deactivating microorganisms in their vegetative form. Although often stated that gram-positive bacteria are more difficult to deactivate than gram-negative bacteria, we could not observe any difference in susceptibility. However, yeasts were found to be more resistant towards HPCD than bacteria. Among the tested vegetative cells, Alicyclobacillus acditoterristris and Zygosaccharomyces bailii were most resistant, probably due to their ability to grow under acidic conditions. As suspected, bacterial and fungal spores displayed the highest resistance towards HPCD treatments and were hardly reduced under the treatment conditions.
Secondly, the influence of different food components and the effect of intrinsic properties on the inactivation of Pseudomonas fluorescens, suspended in BHI-broth, by HPCD (105 bar, 35°C, 5 or 20 min, 400 rpm, 70% liquid in the reactor volume) were investigated separately. The presence of water soluble starch (1% and 10% (w/v)) did not influence the antimicrobial activity of HPCD. The inactivation of P. fluorescens was positively influenced by the addition of NaCl (2% and 8% (w/v)) and Tween 80 (0.5% (v/v)). On the contrary, sunflower oil (10% and 30% (v/v)) and whey protein (10% (w/v)) reduced the antimicrobial efficiency of HPCD. An enhanced microbial reduction was observed with lowering pH and viscosity of suspending medium. Lowered water activity of the suspension (aw = 0.95) due to the addition of both glycerol and NaCl did not influence the inactivation of P. fluorescens. However, when the water activity was lowered with glucose, an antagonistic effect was observed.
